How to Measure Total External Static Pressure (TESP)
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- Опубліковано 7 лип 2024
- In this brief video Bryan explains How to Measure Total External Static Pressure (TESP) with a manometer as well as some of the things to look for when diagnosing high static pressure.
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this was probably the best video explaining it so far
A gifted teacher
Great video this has been very helpful
Great information
Awesome brother
Insane how much to hvac there actually is
👍thanks
Good
Great
Thanks Bryan. Question: Why do you not take the reading at the inlet of blower after the coil on the air handler system? Wouldn’t the coil count as a pressure drop in the return side?
Because it's "in the box" as rated - meaning it is shipped with the coil so the manufacturer accounts for it
@@bryanorr8818 that makes sense! Thank you!
How do you know if the filter is included in the box? It takes way too long too find it in the manuals
How do you tell it’s not a blockage in the furnace like a plugged heat exchanger or coil ?
Does the furnace motor matter? Will ECM motor increase static and PSC decrease from lack of airflow?
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I have been told that psc blowers tend to “slip” at higher static pressures, which I take to mean that they don’t spin as fast. EC motors will hit their rpm target if they have any enough horsepower to get their working against higher duct static.
This is is the explanation I’ve received for why psc motors draw fewer amps when they are starved for air and ec motors draw more.
I’d love for somebody to verify that.
@@paulgaras2606 I've been told the same thing. Thanks.
@@paulgaras2606 Some Lennox furnaces with ECMs will actually throw an error code to let you know that they are not moving the cfm that they were programmed to deliver. This is on the newer furnaces. The old ECMs would just destroy themselves trying to produce the cfm that they were programmed to deliver. Of coarse, the programming is done by adjusting the dip switches on the IFC. Psc motors will over amp if there is no load on them so it would only seem reasonable that the amp draw would be lower if airflow is restricted. Take a psc in the housing out of a furnace going to the scrapyard, power it up and check amp draw. Slowly start to cover the outlet of the blower housing with cardboard and the amp draw will go down.
This is awesome, however I would disagree w/ the AH / Fan-Coil section... Most units include / come w/ a factory filter, however the docs are typically horrible or never mention what the drop is for said filter (and they're typically way to small for anything but a rock catcher)... This is why I prefer static mapping on new equipment (although I know that's beyond the scope of what this video is going for).
You are correct usually when dealing with Carrier fan coil the external static chart includes a factory filter, As an example for a 3 ton Fancoil I found carrier data published as a .09 static pressure drop for factory filter. Therefore when measuring out in the field more than likely the factory filter was replaced with a pleated filter which now may have a .4 static filter pressure drop. From here is simple , measure external pressure including filter , obtain that measurement and then take the difference of the replaced filter vs factory filter reading and add to external measurement then go to chart. For example you read .3 on fancoil , then filter difference (.4 -.09=.31 ) , then add .31 to your external measurement and now your actual static is .61 , now that’s the number you plot on chart, you must always adjust from factory readings , most people miss this and it’s never taught.
Trane manual specifies no filter with wet coil and dry coil (heating and cooling modes). But it does have TESP ranges which COULD include a filter. So It effectively takes filter variance out of the spec.
In a perfect world, the return and supply will be the same?
Not necessarily. Your return might be intentionally lower if, for example, a central return is used (with transfer grills) or a plenum return in a commercial building. Obviously the supply ducts run to each room/zone so the supply static would be higher because the return is so much shorter. It would not have to mean that there is any problem with the design
Yes.. the static of return is lower than suply but depend on what the lenght of return duct.
What about a Trane hyperion a/h with coil on top
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What about a unit with electric heat strip. Where do you place probe before or after Strip..
If you want to know what the static pressure of a unit with heat strips, first, turn the unit on Heat, and make sure that the indoor blower motor's fan speed is on High (turn the Fan Select switch from 'Auto' to 'On'). Then, simply place your negative probe IN THE AIR STREAM before the heat strip(s), and place the positive probe IN THE AIR STREAM after the strip(s).
The difference is your pressure drop.
The problem with this scenario is that you are not measuring the pressure drop of the heat strips themselves. You are measuring the drop in pressure ACROSS THE UNIT, with the heat strips being the only means of providing heat, and the indoor blower facilitating the pressure drop and circulating that heated air into the conditioned space. Obviously, if you have a heat pump or a gas/electric furnace, then the heat strips are not going to be your primary source of heat, as the strips are for emergency, or backup heat.
You would have to disable everything but the indoor blower motor and the heat strips in order to determine the calculation you are inquiring about.
In my opinion, that's just not very practical. Instead, it would be more practical to determine the pressure drop across each individual component (i.e., the air filter, evaporator coil, and even the blower itself). Then measure the TESP (Total External Static Pressure) across the entire assembly as a whole.
Read the handler manual. In some units, it's not practical to measure before a heating strip, but the handler manual or heater manual should specify a static pressure drop which you could then subtract from the high side reading if you probe after the strip. However... strips are like .01 or .02 inches of pressure... so it's not much of a factor.
Could you please explain to me why the blower is on the supply side of a residential air handler. I've been looking for the answer to this for weeks. I keep getting conflicting answers. Thanks
Because an air-conditioning system's job is to 'supply' a space with conditioned air. That air then eventually 'returns' back to the unit due to various factors, including velocity, pressure, temperature, etc.
@@ParabellumX I don't think that's this person's question. He's probably asking why the blower is after the evaporator coil versus before. It doesn't matter what side the blower is on as it'll still move air in the same direction...
The question is better asked as why some configurations have the evap coils before or after the blower. I believe HVAC's with gas furnaces may have the evap coils after the blower.
Why don’t you put the probe next to the blower on the fan coil??? Instead of before the coil? It would add more resistance, or is it because you’re measuring “External” static pressure and not “total” static pressure?
Total external static pressure of the whole air handler is being measured and the coil is part of that piece of equipment. On a furnace, the probe is inserted before the coil because we are measuring the TESP of the furnace. Also, when measuring TESP, check manufactures instructions to see if the coil should be dry.
@@bill944 Thanks, I guess that makes sense. And what does a dry coil mean? Not running I’m AC or HP?
Yep. Just pull the o/d disconnect. Most important thing, always read instructions for that specific piece of equipment.
I do not understand the placement of the probe on the fan coil unit. If the probe is placed before the coil and the coil is blocked with dirt and crud you will get a low reading but if you place the probe after the coil you will get a high negative reading because that fan is really sucking trying to move that air and when this is added to the supply probe static you will get a very high TESP which means you will be moving less CFM’s. Somebody please help explain the placement of the probe on the return. If I want to check static on an old unit I will not get a correct TESP if my return probe is before the dirty coil. Thanks.
That's the whole point to find an issue as to WHY the airflow is obstructed. Recommend Cleaning the coil and then check it .
@@Progress24.7 My whole point is that they say you place the probes here and here to get the TESP. That is only true on a new unit. If you are servicing an old unit you will not get a true TESP if the coil is blocked, you will get a low TESP meaning you should have more airflow. Probes placed on the discharged of the fan and the incoming or return side of the coil will read low TESP if the coil is blocked, which means more airflow and actually it is complete opposite.
You say to point the probe into the air stream then you say you are trying notto get air directly into the probe . How is it that you can avoid velocity pressure when you point the probe directly into the air stream. You said point it opposite of the air flow (not with the air flow) I think you are measure ing velocity pressure id you do that.
The answer to that is : the probes don't have an open ended tip like a plain tube that is bent 90 degrees. the openings are on the sides of the tip. check out some close up pictures of the products out there for a better view than i describe. hope this helps
@@googleprivacy2829 Yes this. Static pressure is the pressure NOT associated with changing the velocity of the air, so the airflow must be perpendicular to the actual openings on the probe.
DF make up air specifically. Zero ISP or... take the intake SP "AFTER" the mesh filter. No one seems to know the answer to that one. Not even the manufacturers reps. I always just take the discharge SP as TESP on a DF MUA. Intake? Zero.
3:15 the words aren't clear to me here. And the picture also appears to be opposite of what you're saying.
You say the probe needs to be "pointed opposite of the airflow". Which would mean away from the airstream. But then you say "pointed INTO the airstream" which sounds like you want the probe pointed against the airstream as shown in the picture...
Total external static.... No presidence
That video sucked