What a fan has is a static pressure/volume curve. It can product a different amounts of air volumes per given pressure resistance. The goal is controlled mass air flow. Restrictions in a system are measured as "differential pressure drop" per volume of air movement. Fans can be optimized for pressure (vs volume) to combat things like dirty filters. EMC motors are electronically torque controlled to attempt to move a constant mass of air -- so when the air is hot it spin faster then when the air is cold. Thus with an EMC motor and proper fan and ducts, the motor current will be higher with a dirty filter, but only up to a point : If air movement is blocked the fan is unable to do work and the fan speeds up full because it becomes unloaded. Hopefully the pressure resistance of duct work, was a little less then the the mid point of the pressure volume curve of the fan, per intended volume of air movement. Pressure resistance of duct work can be pre-calculated per a given volume to see if it is within the preferred performance curve of the air handler. Static pressure measurements are merely a tool to determine if mass air flow is within spec or expectations : In the real world things like doors, exhaust fans and chimney effect have to be accounted for.
Counter-intuitive. I upgraded my furnace filter and was concerned that the reduced flow may add stress to my blower motor, but based on your explanation, it actually reduces stress on the blower. I just need to look at how it effects air flow at the vents, which I assume will impact my HVAC efficiency and may cause my system to run longer.
It decreases the stress, but if the airflow is nearly blocked, it also massively decreases cooling. So the ratio between power/cooling becomes worse (bigger), the more restricted (even blocked) the airflow is. Thus the motor can be damaged with restricted airflow, even if the power draw is decreased.
As a inspector...I see this every single day...on improper installed systems ( Returns at 1 wc and a-lot higher @.5 wc rated)...it's sad on how many HVAC contractors don't understand the fundamentals in there own field....
thanks i should know that i dont remember making a comment or being at this video:? and of course you cant just click on your notifications to bring you back to where we may have been in case we dont remember where we have been etc etc etc ,,,,, @@capitolrefrigerationheatin7501
Hi, may i ask.. I have 2 blowers, centrifugal type: 1 is rated at 1.5sp and the other is 2.5sp.. Both are rated at 20000cfm,same motor. Which one pushes "stronger"? (i mean that i can feel the air in the end of the vent with ~100m length)..
Thanks for the video it was very educational and helpful. I have a Carrier 58mca-060-16110 furnace with air conditioning installed in a small room at the center of the house with grates in all the walls to the surrounding rooms(house is on a slab and doesn't have return ducting). The filter is mounted on the side of the furnace(one side exposed to the room) and sucks the air directly from the room.I have a digital manometer and want to check pressures on the furnace. I have a few questions if you don't mind. 1. Does the one probe need to be held in front of the filter or just anywhere near the furnace. Or is it needed at all, at least for the filter drop. 2. Does the probe inserted above the heat exchanger and below the evaporator coil need to be anywhere specific in the space. My coil is offset to the left side directly over the heat exchanger (no room to insert it) but there is a lot of open space to the right of it that's probably not directly in the airflow. Thanks
Please follow the instructions that the manometer manufacturer recommends in order to obtain accurate measurement. I would suspect that your 1. measurement will be near zero in that it sounds as if there is very little static, having no returns. It seems appropriate to hold the probe in the front center of the filter. It would be normal in measurement 2. to insert the probe through a small hole in the duct and position the nosepiece in the center, and parallel to the sides, of the duct.
I fail to see how this is relevant sorry. It may be just me but i would have liked to have seen some static pressure readings to go along with this. Because as far as i can tell you really only raised the static pressure on the return side of the fan. And left the cardboard in the top as well as the bottom at the end of the video. And it seems like you are saying a high static pressure is a good thing because we have a lower current draw, but the evap will freeze over? Again sorry if I failed to see the real world point to this.
Absolutely fascinating information! Counter intuitive as you mentioned. But I imagine at some point with enough restriction wouldn't there be an increase in amps similar to locked rotor of a compressor? I mean, hypothetically if all inlets were completely sealed off tight aside from the need for motor cooling by passing air?
With an air-over induction motor in a blower application, the motor is dependent upon the right amount of air flowing over the motor to keep it cool. The actual load that the motor will see is based upon the amount of air the blower is working. If all air is restricted, there is no air for the blower to pressurize. This lack of work can be seen by a drop in the motor operating amps. As a result, the Watts being supplied to the motor are not being converted into work effectively and the winding temperature of the motor will increase. With less air moving over the motor for heat removal and an increase in winding temperature, the motor will overheat. But the amps will be below nameplate or FLA.
So essentially .... if i apply this logic to a squirrel cage blower to exhaust paint fumes, i can enclose the fan in a "restrictive casing" (5-6 inches for the side walls and casing ... but not block the outlet, correct ? This way, the fan will work less hard but displace enough air (pull) through a filter at the source (paint table) ? Thanks
The restrictive casing and filter will create static pressure, reducing airflow. How much will it restrict? I don’t know. If the amps are more than 25% below nameplate amps there is too much restriction and not enough air to keep the motor from overheating. The motor will fail prematurely. Thanks for the good question!
you say that it doesn't matter which the outlet or inlet get blocked and the current goes down. i don't see how that adds up. if the inlet if blocked yes the current should go down because it's creating a vacuum meaning the mass of the air should go down thus less friction on the impeller. if you block the outlet the current should go up because you pressurize the chamber around the impeller meaning the mass of the air goes up and the friction on the impeller goes up. hope not i am internally wrong. do not know very much about this and have never tested it, but that would be my logical explanation.
Interesting video. I agree the fan motor power will decrease when blocking airflow, but the overall system power will increase since the compressor will consume more power due to decreased efficiency.
compressor may be damaged due to liquid flooding and oil dilution in the compressor. Causing excess friction due to lack of proper lubrication in the compressor. it all goes downhill from there.
So I've got Feildpiece SC56 clamp meter and want to check running amps of an ECM motor on a heat pump to calculate CFM using the heat-rise method but need to have all doors closed and I don't have access to wiring outside the cabinet. My meter has inrush feature but no hold for regular tests. I'd greatly appreciate any advice on how I might perform this and also consider the fact that it's ECM? One idea I'm considering is to place my phone inside compartment to record video.
Is the airflow(cfm) the same in the cooling mode as the Heat mode? I have original manuals for my carrier 58mca-060-16110 furnace but there are no Airflow tables in it and I can't locate them on the internet. Thanks
Depends on the unit! Most gas furnaces use a lower cfm for heating, but it's not definite. You might look at your blower motor. 3 wires means it only runs at one speed, and so does 4 if 2 of them are brown (usually that's on a replacement part), and more than that means the motor is capable of multiple speeds. But just because it's capable, doesn't mean they're hooked up. Generally, if they're plugged in, they're in use, otherwise they'll be taped off.
Always love the counter-intuitive stuff . Stumps even the engineers . By the same principle then using bypass to dump air to the return in a zoning system will make the motor run harder as it has to deal with more air?
So is this good or bad? If I add a cold air return from the basement am I merely adding cost of oil burning? Is it worth it? Will it help warm the basement? So confused now.
The most important thing is to follow the manufacturer’s guide for static pressure for the specific piece of equipment. When the system is installed according to the manufacturer’s recommendations the static should be fine. If the static is not correct, then look at the filters and coils to make certain that they are clean and not blocked. If they are in good order, then look at the installation to see if it meets the manufacturer’s specifications. If not, then a change to the system may need to occur that would bring the system within the manufacturer’s specifications. There may be other considerations that could result in changes other than just adding a cold air return.
If I use a belt driven blower, with an external motor mounted on top, and I restrict he airflow with a filter at the source (paint fumes) and a reduction to 5 inches at the outlet, how will this affect it ? The motor is NOT inside the blower wheel
If you use a belt drive/general purpose motor (not an air over motor) and do not exceed the load rating of the motor, the motor should be fine. The amps should never exceed the full load amps (FLA) or service factor amps (SFA) on the motor nameplate. The more static pressure or restriction on the blower, the less air.
Thank you sir Sir please explain the effect of duct work size and amps as the air volume is same but size of duct varing like( 1 st case 8" 2 nd case 10" etc)
By reducing the duct size, which increases static pressure, the amount of air is restricted. This results in a reduction of air available for the blower to work. If it is a PSC motor operating the blower, this results in lower amps during motor operation. If duct size is increased, this reduces static pressure, resulting in less restriction of air. More air is available for the blower to work. If it is a PSC motor operating the blower, higher amps will be seen during motor operation.
thank u sir thank u lady may you provide us the Detailed explanation as it is in the wonderful video about the relation between static and dynamic converting when the flow pass the different duct size
its only talk about the air and pressure around the motor, so not concern about the input air (fresh air + return air) that flow into furnace to burning, so don't confuse.
Great videos. Q: If amp draw is reduced as static pressure is increased, obviously, watts will also go down reducing the amount of energy consumed. Why then, do I read elsewhere reducing static pressure will save on electricity bills? Thus, won't more flow filters, increased return sizes, etc actually make the electric bill go up? With ECM motors does this relationships change?
As static pressure is increased the amount of air being worked by the blower is restricted, that is, less air is available in the system. Because less air is being delivered not as much power is required. Hence, less energy is consumed. Which is good, unless you’re concerned about not having as much air volume which may be necessary for comfort. Yes, having more flow filters and increased return sizes will cause energy consumption to go up but it may result in having more air flow, which could result in better cooling or heating of those back bedrooms. Always remember that the motor has to have the proper amount of air flowing over it otherwise it will overheat. This will result in reduced motor life. Even if the full load amps are well below nameplate it doesn’t mean that the motor is operating more efficiently. If the amps are more than 25% below nameplate amps the motor probably does not have the proper amount of air flowing over it and it will overheat. Static pressure also impacts ECMs. Some ECMs are designed to compensate for changes in static pressure by varying their speed (constant air flow) while others provide a constant amount of power (constant torque) and are not as responsive to the static pressure changes as is the constant air flow design. Excessive static pressure will kill the ECM. One advantage of the ECM over the PSC motor is that the ECM is capable of operating at a low RPM on constant fan. This can help eliminate the stratification of air (hot spots and cold spots) that might be experienced with a PSC. By operating at a low RPM power consumption is reduced greatly.
Now I see the tradeoff between energy consumption, air flow and heat dissipation. I see so much incorrect information about these relationships. Many articles claim high efficiency (high MERV) filters will increase energy usage. What they really mean to say is energy usage will declinel however, with a hit on system performance due to reduced flow and longevity due to heat and motor wear. I have an ECM (not sure which kind, but it has fixed speed taps and isn't variable speed) in my Trane XT80 and measured TESP at .6 (.45 on the return and .15 to the supply). I don't see a maximum TESP on any of my labels or manuals. I know traditionally, maximum TESP is measured at .5 but am I within range?
Motors are designed to operate at a specified rpm, and current. Motors create heat while also moving air. If you increase static pressure on a centrifugal type blower, you will also increase rpms of the psc motor, this is proven by reading counter emf across the blower capacitor. When a motor is running out of it's designed range the actual efficiency of the motor decreases. So, even though your energy consumption may be reduced while operating under greater static pressure, the energy reduction is not linear to the air flow performance reduction, meaning "you're getting less bang for your buck". You're moving a lot less air for a little less energy consumption. The heat being created by the motor is slightly less, but the air flow being much less reduces the self cooling capability. The rpm increase, and excessive emf can cause shortened blower capacitor life. When static pressure increases on a "variable speed" ECM type motor, the motor has the ability to sense the air flow reduction, or static pressure increase, and will automatically increase torque in attempts to achieve proper air flow. The ECM does have a rev limiter, at which point it will intermittently cut out, sounding like a washing machine. I believe it's a voltage sensing limiter. When the variable speed motor has to increase torque to achieve the proper cfm, it may actually be consuming more energy than a less efficient PSC motor operating under normal static pressure. Other ECM motors like the X13 will behave similarly to the PSC.I believe it's voltage sensing limiter.
When you add static pressure at outlet, the pressure will increase after the blower as it is running and supplying air continuously. It may cause blower to surge and consume more power. How it shows decrease in amps?
As the static increases on the outlet side of the blower, the air volume (CFM) decreases. This results in less load on the blower. Less load results in lower amps and higher RPM with an induction motor.
so can you size a return too large? I have a 3 ton unit with a 2 ton grill can I simply add another 2 ton grill? I have plenty of room but don't want to reduce SP too much if its really required
Too much air can overwork the blower. If the blower is properly sized to the system and the static pressure is appropriate the full load apps of a PSC motor should be no greater than 10% above or 25% below nameplate amps.
Help Me, Amps go down, blower slow down, Does that mean system will not cool or heat correctly. I own same air handler in video. I upgraded blower that is 4 speed. So what more AMPS if it needs more power, give it. What is the issue?
When the amps go down, the blower is not slowing down, it is going faster because there is less load on the blower. Remember, the real load on the blower is the amount of air that it is working. Less load means less air in the system. Less air in the system and the system is not performing properly. The issue is not that the motor is incorrect, the issue is that the motor and blower are not working properly because the static pressure is incorrect. Perhaps undersized duct work, not enough return air, dirty coils, dirty filters, too many bends in ducts, improperly sealed ducts and the like all lead to incorrect static pressure. This will then lead to improper airflow in the system.
@@packardonline Thanks, more power / blower speed will not help when static pressure is incorrect. I have 3/4" suction line (20') on my 4 ton A/C that should be 7/8" line. Seems to work ok with a -25 temp drop out of ducts, but A-Coil drips a lot of condensation (2 qt per hr). Should suction line be replaced with correct size or am I in grey area for 3/8" velocity flow?
@@sunnysacto I would not want to make that call in a chat, but it can make a difference. The smaller line will restrict flow of refrigerant. Make certain that superheat and subcooling are to the manufacturer’s specs.
@@packardonline The last few HVAC tech did poor work. I'm learning all I can before I get next HVAC service. My blower motor runs hot on higher settings, putting heat into duct flow. I assume this is normal. I set blower on lowest speed, making less heat, seems to cool better with lower fan motor heat and less amps. Thanks for help
At 2:15 in the video, the amp draw is 7.08. At 4.20 in the video, the amp draw is 5.78. In both instances the situation is the same (lid of and no cardboard)Why are the amp readings different??
The conditions are NOT the same at 2:15 vs 4:20. The furnace door is off in both but at 4:20 there is cardboard over the blower inlet which is creating additional static pressure. This restricts air which unloads the blower. The blower is not working as hard and the amps are lower. - Rick Streacker, National Trainer. If you have any further questions do not hesitate to ask. Thank you for reaching out to Packard.
From Rick Streacker, National Training Coordinator - With a blower, when you reduce static pressure you reduce the restriction on air flow. When you reduce restriction, you have more air that the blower can “work”. When you have more air that the blower can work you have a greater load on the motor, if a PSC motor. With a PSC motor you do not lower the amperage when you lower the static pressure. The motor operating temperature is based upon load and ambient temperature. If the motor is not operating within it’s design parameters, that is, there is either too much load or not enough load, the winding temperature increases.
Packard Academy. Are you telling me that if this same test was done with a three phase motor in the blower fan that that adding air on the inlet would lower or flatline the amps but that on a permanant split capacitor motor adding air on the inlet will raise the amps.
Freddy McIntire. So why did he bring up the fact that the example is with a PSC motor. If the blower fan doesn't know the difference then why bring up wether it's a PSC, synchrounus, PM, or 3 phase motor if the amps are going to do the same thing anyways.
I am completely lost now. I thought if you added air return ducts or even put a hole in the cold air before the filter that the furnace operated more easily, you cooled rooms more effectively, and you save money on heating and cooling..
For maximum comfort in our living areas we need proper airflow. The air is generally provided by blowers through ducts. The amount of that airflow, measured in cubic feet per minute (CFM), is impacted by restrictions in the system such as dirty filters, dirty coils, undersized ducts, lots of bends and curves in the ductwork, closed registers, and the like. These restrictions increase the static pressure, measured in inches of water column or water gauge (WG). As the static pressure increases, less air is available. As the static pressure declines, more air is available. This can be achieved by changing filters, cleaning coils, adding more air returns or increasing duct size. More air can be good, as long as I don’t overload the blower motor. Most residential systems should operate within .5”WG to .8”WG. The lower the static pressure, the more air, and the more load on the blower, and consequently the blower motor. The longest operating life of the motor is achieved when it is loaded properly (loaded with the right amount of air) operating at its highest efficiency. That results in the minimum amount of heat in the winding. When operating at it’s rated nameplate amps it’s at its highest efficiency. If operating at lower than nameplate amps, it’s not loaded at its optimal point and will operate less efficiently developing more heat in the winding, resulting in lower motor life. This occurs when static is too high and there is not enough air loading the blower. If operating at higher than nameplate amps, again, it is not loaded at its optimal point, it will operate less efficiently resulting in more heat in the motor winding and have a reduced life. This occurs if there is not enough static pressure. With permanent split capacitor (PSC) motors, if the motor does not exceed +10/-25% of the nameplate amps, it’s loaded and operating OK. When measuring amps, always make certain that all doors, panels, filters, and guards are in place. If this is not done, inaccurate measurements will occur.
@@packardonline Is there a simple way to decide if opening the cold air return directly one foot, say, in front of the filter will help warm my basement apartment? There are no air return vents and only one supply to the living area. Also, would ADDING a supply line from the plenum upset the balance in the 2-story house?
@@lvvry1855 Either of the actions you mention would have an effect on static pressure and airflow. The way that I’m interpreting what you say is that you would be increasing return air by enlarging the return area. This would reduce static and increase air availability and airflow. By adding another supply line, the static pressure would be increased, resulting in less airflow. My recommendation would be to have a licensed professional measure the load characteristics and review possible solutions.
If you are referring to the meter in the video there wouldn't have been any reason for the true meter reading not to have been read out loud. I assume the meter had to be positioned there for practicality. Mr. Streacker is our National Trainer and he would not allow the dissemination of false information. Thank you for your interest in the video.
you say that it doesn't matter which the outlet or inlet get blocked and the current goes down. i don't see how that adds up. if the inlet if blocked yes the current should go down because it's creating a vacuum meaning the mass of the air should go down thus less friction on the impeller. if you block the outlet the current should go up because you pressurize the chamber around the impeller meaning the mass of the air goes up and the friction on the impeller goes up. you blocked the inlet and outlet meaning the reading was false for the outlet test.. hope not i am internally wrong. do not know very much about this and have never tested it, but that would be my logical explanation.
When the amps go down, the blower is not slowing down, it is going faster because there is less load on the blower. Remember, the real load on the blower is the amount of air that it is working. Less load means less air in the system. Less air in the system and the system is not performing properly.
That was rather counterintuitive, i was surprised. I thought it would be the other way around. Thanks for this info.
What a fan has is a static pressure/volume curve. It can product a different amounts of air volumes per given pressure resistance. The goal is controlled mass air flow. Restrictions in a system are measured as "differential pressure drop" per volume of air movement. Fans can be optimized for pressure (vs volume) to combat things like dirty filters. EMC motors are electronically torque controlled to attempt to move a constant mass of air -- so when the air is hot it spin faster then when the air is cold. Thus with an EMC motor and proper fan and ducts, the motor current will be higher with a dirty filter, but only up to a point : If air movement is blocked the fan is unable to do work and the fan speeds up full because it becomes unloaded. Hopefully the pressure resistance of duct work, was a little less then the the mid point of the pressure volume curve of the fan, per intended volume of air movement. Pressure resistance of duct work can be pre-calculated per a given volume to see if it is within the preferred performance curve of the air handler. Static pressure measurements are merely a tool to determine if mass air flow is within spec or expectations : In the real world things like doors, exhaust fans and chimney effect have to be accounted for.
Counter-intuitive. I upgraded my furnace filter and was concerned that the reduced flow may add stress to my blower motor, but based on your explanation, it actually reduces stress on the blower. I just need to look at how it effects air flow at the vents, which I assume will impact my HVAC efficiency and may cause my system to run longer.
It decreases the stress, but if the airflow is nearly blocked, it also massively decreases cooling. So the ratio between power/cooling becomes worse (bigger), the more restricted (even blocked) the airflow is. Thus the motor can be damaged with restricted airflow, even if the power draw is decreased.
Thanks. I used this information to help me design a Fan for my shop.
Never ever had a blower go out. I’ve used all sorts of filters. Very reliable little motors.
thanks this is the info i was looking for
What do you think of the K and N washable filter that is Merv 11? I don't know what the pressure drop is?
As a inspector...I see this every single day...on improper installed systems ( Returns at 1 wc and a-lot higher @.5 wc rated)...it's sad on how many HVAC contractors don't understand the fundamentals in there own field....
so more static is less amps ? so its GOOD ?,,,is this correct ? then the CFM are comprimised as i see it ?
@@MrGarcon98 more static, you move less air and causes problems,ac coil freeze in ac mode or high limit trip in heating
thanks i should know that i dont remember making a comment or being at this video:? and of course you cant just click on your notifications to bring you back to where we may have been in case we dont remember where we have been etc etc etc ,,,,,
@@capitolrefrigerationheatin7501
It's sad that you don't understand how English works.
Hi, may i ask.. I have 2 blowers, centrifugal type: 1 is rated at 1.5sp and the other is 2.5sp.. Both are rated at 20000cfm,same motor. Which one pushes "stronger"? (i mean that i can feel the air in the end of the vent with ~100m length)..
This gave me a great deal of knowledge thank you for sharing...
Thanks for the video it was very educational and helpful. I have a
Carrier 58mca-060-16110 furnace with air conditioning installed in a
small room at the center of the house with grates in all the walls to
the surrounding rooms(house is on a slab and doesn't have return
ducting). The filter is mounted on the side of the furnace(one side
exposed to the room) and sucks the air directly from the room.I have a
digital manometer and want to check pressures on the furnace. I have a
few questions if you don't mind.
1. Does the one probe need to
be held in front of the filter or just anywhere near the furnace. Or is
it needed at all, at least for the filter drop.
2. Does the
probe inserted above the heat exchanger and below the evaporator coil
need to be anywhere specific in the space. My coil is offset to the left
side directly over the heat exchanger (no room to insert it) but there
is a lot of open space to the right of it that's probably not directly
in the airflow.
Thanks
Please follow the instructions that the manometer manufacturer recommends in order to obtain accurate measurement. I would suspect that your 1. measurement will be near zero in that it sounds as if there is very little static, having no returns. It seems appropriate to hold the probe in the front center of the filter. It would be normal in measurement 2. to insert the probe through a small hole in the duct and position the nosepiece in the center, and parallel to the sides, of the duct.
I fail to see how this is relevant sorry. It may be just me but i would have liked to have seen some static pressure readings to go along with this. Because as far as i can tell you really only raised the static pressure on the return side of the fan. And left the cardboard in the top as well as the bottom at the end of the video. And it seems like you are saying a high static pressure is a good thing because we have a lower current draw, but the evap will freeze over? Again sorry if I failed to see the real world point to this.
Absolutely fascinating information! Counter intuitive as you mentioned. But I imagine at some point with enough restriction wouldn't there be an increase in amps similar to locked rotor of a compressor? I mean, hypothetically if all inlets were completely sealed off tight aside from the need for motor cooling by passing air?
With an air-over induction motor in a blower application, the motor is dependent upon the right amount of air flowing over the motor to keep it cool. The actual load that the motor will see is based upon the amount of air the blower is working. If all air is restricted, there is no air for the blower to pressurize. This lack of work can be seen by a drop in the motor operating amps. As a result, the Watts being supplied to the motor are not being converted into work effectively and the winding temperature of the motor will increase. With less air moving over the motor for heat removal and an increase in winding temperature, the motor will overheat. But the amps will be below nameplate or FLA.
Logical explanations. Thanks for the demo! Subbing this just fmi.
So essentially .... if i apply this logic to a squirrel cage blower to exhaust paint fumes, i can enclose the fan in a "restrictive casing" (5-6 inches for the side walls and casing ... but not block the outlet, correct ? This way, the fan will work less hard but displace enough air (pull) through a filter at the source (paint table) ?
Thanks
The restrictive casing and filter will create static pressure, reducing airflow. How much will it restrict? I don’t know. If the amps are more than 25% below nameplate amps there is too much restriction and not enough air to keep the motor from overheating. The motor will fail prematurely.
Thanks for the good question!
you say that it doesn't matter which the outlet or inlet get blocked and the current goes down. i don't see how that adds up. if the inlet if blocked yes the current should go down because it's creating a vacuum meaning the mass of the air should go down thus less friction on the impeller. if you block the outlet the current should go up because you pressurize the chamber around the impeller meaning the mass of the air goes up and the friction on the impeller goes up. hope not i am internally wrong. do not know very much about this and have never tested it, but that would be my logical explanation.
Interesting video. I agree the fan motor power will decrease when blocking airflow, but the overall system power will increase since the compressor will consume more power due to decreased efficiency.
Perry schmidt. which compresor.
compressor may be damaged due to liquid flooding and oil dilution in the compressor. Causing excess friction due to lack of proper lubrication in the compressor. it all goes downhill from there.
Perry schmidt. Everything you just said is OPPOSITE of this video.
Max R Nope. The system runs less efficiently, and thus needs to run longer to get to the temperature set point, which increases overall energy usage.
Alexander Riccio. No what.
So I've got Feildpiece SC56 clamp meter and want to check running amps of an ECM motor on a heat pump to calculate CFM using the heat-rise method but need to have all doors closed and I don't have access to wiring outside the cabinet. My meter has inrush feature but no hold for regular tests. I'd greatly appreciate any advice on how I might perform this and also consider the fact that it's ECM? One idea I'm considering is to place my phone inside compartment to record video.
Great Video....
Can you explain, "How i calculate static pressure for my duct for exhaust blower."
Is the airflow(cfm) the same in the cooling mode as the Heat mode? I have original manuals for my carrier 58mca-060-16110 furnace but there are no Airflow tables in it and I can't locate them on the internet. Thanks
Depends on the unit! Most gas furnaces use a lower cfm for heating, but it's not definite. You might look at your blower motor. 3 wires means it only runs at one speed, and so does 4 if 2 of them are brown (usually that's on a replacement part), and more than that means the motor is capable of multiple speeds. But just because it's capable, doesn't mean they're hooked up. Generally, if they're plugged in, they're in use, otherwise they'll be taped off.
Always love the counter-intuitive stuff . Stumps even the engineers . By the same principle then using bypass to dump air to the return in a zoning system will make the motor run harder as it has to deal with more air?
On a PSC motor, correct.
So is this good or bad? If I add a cold air return from the basement am I merely adding cost of oil burning? Is it worth it? Will it help warm the basement? So confused now.
The most important thing is to follow the manufacturer’s guide for static pressure for the specific piece of equipment. When the system is installed according to the manufacturer’s recommendations the static should be fine. If the static is not correct, then look at the filters and coils to make certain that they are clean and not blocked. If they are in good order, then look at the installation to see if it meets the manufacturer’s specifications. If not, then a change to the system may need to occur that would bring the system within the manufacturer’s specifications. There may be other considerations that could result in changes other than just adding a cold air return.
If I use a belt driven blower, with an external motor mounted on top, and I restrict he airflow with a filter at the source (paint fumes) and a reduction to 5 inches at the outlet, how will this affect it ? The motor is NOT inside the blower wheel
If you use a belt drive/general purpose motor (not an air over motor) and do not exceed the load rating of the motor, the motor should be fine. The amps should never exceed the full load amps (FLA) or service factor amps (SFA) on the motor nameplate. The more static pressure or restriction on the blower, the less air.
Thank you sir
Sir please explain the effect of duct work size and amps as the air volume is same but size of duct varing like( 1 st case 8" 2 nd case 10" etc)
By reducing the duct size, which increases static pressure, the amount of air is restricted. This results in a reduction of air available for the blower to work. If it is a PSC motor operating the blower, this results in lower amps during motor operation. If duct size is increased, this reduces static pressure, resulting in less restriction of air. More air is available for the blower to work. If it is a PSC motor operating the blower, higher amps will be seen during motor operation.
thank u sir thank u lady
may you provide us the Detailed explanation as it is in the wonderful video about the relation between static and dynamic converting when the flow pass the different duct size
its only talk about the air and pressure around the motor, so not concern about the input air (fresh air + return air) that flow into furnace to burning, so don't confuse.
Great videos. Q: If amp draw is reduced as static pressure is increased, obviously, watts will also go down reducing the amount of energy consumed. Why then, do I read elsewhere reducing static pressure will save on electricity bills? Thus, won't more flow filters, increased return sizes, etc actually make the electric bill go up? With ECM motors does this relationships change?
As static pressure is increased the amount of air being worked by the blower is restricted, that is, less air is available in the system. Because less air is being delivered not as much power is required. Hence, less energy is consumed. Which is good, unless you’re concerned about not having as much air volume which may be necessary for comfort. Yes, having more flow filters and increased return sizes will cause energy consumption to go up but it may result in having more air flow, which could result in better cooling or heating of those back bedrooms. Always remember that the motor has to have the proper amount of air flowing over it otherwise it will overheat. This will result in reduced motor life. Even if the full load amps are well below nameplate it doesn’t mean that the motor is operating more efficiently. If the amps are more than 25% below nameplate amps the motor probably does not have the proper amount of air flowing over it and it will overheat.
Static pressure also impacts ECMs. Some ECMs are designed to compensate for changes in static pressure by varying their speed (constant air flow) while others provide a constant amount of power (constant torque) and are not as responsive to the static pressure changes as is the constant air flow design. Excessive static pressure will kill the ECM. One advantage of the ECM over the PSC motor is that the ECM is capable of operating at a low RPM on constant fan. This can help eliminate the stratification of air (hot spots and cold spots) that might be experienced with a PSC. By operating at a low RPM power consumption is reduced greatly.
Now I see the tradeoff between energy consumption, air flow and heat dissipation. I see so much incorrect information about these relationships. Many articles claim high efficiency (high MERV) filters will increase energy usage. What they really mean to say is energy usage will declinel however, with a hit on system performance due to reduced flow and longevity due to heat and motor wear. I have an ECM (not sure which kind, but it has fixed speed taps and isn't variable speed) in my Trane XT80 and measured TESP at .6 (.45 on the return and .15 to the supply). I don't see a maximum TESP on any of my labels or manuals. I know traditionally, maximum TESP is measured at .5 but am I within range?
Motors are designed to operate at a specified rpm, and current. Motors create heat while also moving air. If you increase static pressure on a centrifugal type blower, you will also increase rpms of the psc motor, this is proven by reading counter emf across the blower capacitor. When a motor is running out of it's designed range the actual efficiency of the motor decreases.
So, even though your energy consumption may be reduced while operating under greater static pressure, the energy reduction is not linear to the air flow performance reduction, meaning "you're getting less bang for your buck". You're moving a lot less air for a little less energy consumption.
The heat being created by the motor is slightly less, but the air flow being much less reduces the self cooling capability. The rpm increase, and excessive emf can cause shortened blower capacitor life.
When static pressure increases on a "variable speed" ECM type motor, the motor has the ability to sense the air flow reduction, or static pressure increase, and will automatically increase torque in attempts to achieve proper air flow. The ECM does have a rev limiter, at which point it will intermittently cut out, sounding like a washing machine. I believe it's a voltage sensing limiter. When the variable speed motor has to increase torque to achieve the proper cfm, it may actually be consuming more energy than a less efficient PSC motor operating under normal static pressure.
Other ECM motors like the X13 will behave similarly to the PSC.I believe it's voltage sensing limiter.
Very informative but Mr. Streacker failed to mention PSC motor earlier in the video or in the title.
Ohhhh that makes Sense, is that why everything is Opposite compared to a ECM or X-13 Motor?
Amps would be higher as static increases
When you add static pressure at outlet, the pressure will increase after the blower as it is running and supplying air continuously. It may cause blower to surge and consume more power.
How it shows decrease in amps?
As the static increases on the outlet side of the blower, the air volume (CFM) decreases. This results in less load on the blower. Less load results in lower amps and higher RPM with an induction motor.
so can you size a return too large? I have a 3 ton unit with a 2 ton grill can I simply add another 2 ton grill? I have plenty of room but don't want to reduce SP too much if its really required
Too much air can overwork the blower. If the blower is properly sized to the system and the static pressure is appropriate the full load apps of a PSC motor should be no greater than 10% above or 25% below nameplate amps.
Help Me, Amps go down, blower slow down, Does that mean system will not cool or heat correctly. I own same air handler in video. I upgraded blower that is 4 speed. So what more AMPS if it needs more power, give it. What is the issue?
When the amps go down, the blower is not slowing down, it is going faster because there is less load on the blower. Remember, the real load on the blower is the amount of air that it is working. Less load means less air in the system. Less air in the system and the system is not performing properly.
The issue is not that the motor is incorrect, the issue is that the motor and blower are not working properly because the static pressure is incorrect. Perhaps undersized duct work, not enough return air, dirty coils, dirty filters, too many bends in ducts, improperly sealed ducts and the like all lead to incorrect static pressure. This will then lead to improper airflow in the system.
@@packardonline Thanks, more power / blower speed will not help when static pressure is incorrect. I have 3/4" suction line (20') on my 4 ton A/C that should be 7/8" line. Seems to work ok with a -25 temp drop out of ducts, but A-Coil drips a lot of condensation (2 qt per hr). Should suction line be replaced with correct size or am I in grey area for 3/8" velocity flow?
@@sunnysacto I would not want to make that call in a chat, but it can make a difference. The smaller line will restrict flow of refrigerant. Make certain that superheat and subcooling are to the manufacturer’s specs.
@@packardonline The last few HVAC tech did poor work. I'm learning all I can before I get next HVAC service. My blower motor runs hot on higher settings, putting heat into duct flow. I assume this is normal. I set blower on lowest speed, making less heat, seems to cool better with lower fan motor heat and less amps. Thanks for help
@@packardonline Gas Suction line is cool and liquid line is warm, but not hot.
Excellent great video!
You make it sound like the motor working hard is a bad thing. If its working hard then it moving air. Correct or not?
At 2:15 in the video, the amp draw is 7.08. At 4.20 in the video, the amp draw is 5.78. In both instances the situation is the same (lid of and no cardboard)Why are the amp readings different??
The conditions are NOT the same at 2:15 vs 4:20. The furnace door is off in both but at 4:20 there is cardboard over the blower inlet which is creating additional static pressure. This restricts air which unloads the blower. The blower is not working as hard and the amps are lower. - Rick Streacker, National Trainer. If you have any further questions do not hesitate to ask. Thank you for reaching out to Packard.
Thank you for the quick reply.. I somehow had missed that he left the cardboard in.
Great video and simple (but effective) demonstration!!
You are very welcome. Glad Packard could help!
why doesnt the blower use less amps... so it can get some rest?
Thanks so much.
Need to define static pressure, show the cfm vs static pressure table, sh I w how to measure static.
So this Proves that Dirty Air filters DO NOT put additional strain on Blower Motors. How can this be so?
Seriously what's the explanation?
how do you lower static pressure (i.e. lower the amperage) while lowering the temperature?
From Rick Streacker, National Training Coordinator - With a blower, when you reduce static pressure you reduce the restriction on air flow. When you reduce restriction, you have more air that the blower can “work”. When you have more air that the blower can work you have a greater load on the motor, if a PSC motor. With a PSC motor you do not lower the amperage when you lower the static pressure.
The motor operating temperature is based upon load and ambient temperature. If the motor is not operating within it’s design parameters, that is, there is either too much load or not enough load, the winding temperature increases.
Packard Academy thanks!
using the thick milk shake thru a skinny straw concept helps put these concepts into easy to grasp ideas.
Packard Academy. Are you telling me that if this same test was done with a three phase motor in the blower fan that that adding air on the inlet would lower or flatline the amps but that on a permanant split capacitor motor adding air on the inlet will raise the amps.
Freddy McIntire. So why did he bring up the fact that the example is with a PSC motor. If the blower fan doesn't know the difference then why bring up wether it's a PSC, synchrounus, PM, or 3 phase motor if the amps are going to do the same thing anyways.
hold the phone, you never took the cardboard off the inlet side near the end. What kind of test/demonstration is that.
I noticed that too and i also noticed he didnt address your comment.
I am completely lost now. I thought if you added air return ducts or even put a hole in the cold air before the filter that the furnace operated more easily, you cooled rooms more effectively, and you save money on heating and cooling..
For maximum comfort in our living areas we need proper airflow. The air is generally provided by blowers through ducts. The amount of that airflow, measured in cubic feet per minute (CFM), is impacted by restrictions in the system such as dirty filters, dirty coils, undersized ducts, lots of bends and curves in the ductwork, closed registers, and the like. These restrictions increase the static pressure, measured in inches of water column or water gauge (WG). As the static pressure increases, less air is available. As the static pressure declines, more air is available. This can be achieved by changing filters, cleaning coils, adding more air returns or increasing duct size. More air can be good, as long as I don’t overload the blower motor.
Most residential systems should operate within .5”WG to .8”WG. The lower the static pressure, the more air, and the more load on the blower, and consequently the blower motor. The longest operating life of the motor is achieved when it is loaded properly (loaded with the right amount of air) operating at its highest efficiency. That results in the minimum amount of heat in the winding. When operating at it’s rated nameplate amps it’s at its highest efficiency. If operating at lower than nameplate amps, it’s not loaded at its optimal point and will operate less efficiently developing more heat in the winding, resulting in lower motor life. This occurs when static is too high and there is not enough air loading the blower. If operating at higher than nameplate amps, again, it is not loaded at its optimal point, it will operate less efficiently resulting in more heat in the motor winding and have a reduced life. This occurs if there is not enough static pressure.
With permanent split capacitor (PSC) motors, if the motor does not exceed +10/-25% of the nameplate amps, it’s loaded and operating OK. When measuring amps, always make certain that all doors, panels, filters, and guards are in place. If this is not done, inaccurate measurements will occur.
@@packardonline Is there a simple way to decide if opening the cold air return directly one foot, say, in front of the filter will help warm my basement apartment? There are no air return vents and only one supply to the living area. Also, would ADDING a supply line from the plenum upset the balance in the 2-story house?
@@lvvry1855 Either of the actions you mention would have an effect on static pressure and airflow. The way that I’m interpreting what you say is that you would be increasing return air by enlarging the return area. This would reduce static and increase air availability and airflow. By adding another supply line, the static pressure would be increased, resulting in less airflow. My recommendation would be to have a licensed professional measure the load characteristics and review possible solutions.
5:01 got me nervous
James H it had a sheet of cardboard between his fingers and the blower inlet.
So block it all off and it's as efficient as ever huh may not be comfortable but it'll be efficient
Whole different ball game with DC blowers
Interesting that a Google search of this topic gives the wrong answer.
why we can't see the meter? just to make sure the lady is telling us the true..
If you are referring to the meter in the video there wouldn't have been any reason for the true meter reading not to have been read out loud. I assume the meter had to be positioned there for practicality. Mr. Streacker is our National Trainer and he would not allow the dissemination of false information. Thank you for your interest in the video.
Obvious false flag.
you say that it doesn't matter which the outlet or inlet get blocked and the current goes down. i don't see how that adds up. if the inlet if blocked yes the current should go down because it's creating a vacuum meaning the mass of the air should go down thus less friction on the impeller. if you block the outlet the current should go up because you pressurize the chamber around the impeller meaning the mass of the air goes up and the friction on the impeller goes up. you blocked the inlet and outlet meaning the reading was false for the outlet test.. hope not i am internally wrong. do not know very much about this and have never tested it, but that would be my logical explanation.
What the fuck! I'm tryna find out what those things that you press on with your foot to blow out air are called and I keep finding this crap!
🤯
Dude you're NOT adding static pressure you are adding and reducing friction loss!!! Pressure is on the positive side of the fan!!!
*static pressure differential
bro.
Filters reduce static pressure. More air flow means more static = more amp draw.
This doesn’t make any sense
When the amps go down, the blower is not slowing down, it is going faster because there is less load on the blower. Remember, the real load on the blower is the amount of air that it is working. Less load means less air in the system. Less air in the system and the system is not performing properly.
@@onenikkione Thanks! Perfect for explanation
Mansplaining..