How To Measure or Check for 3 Phase Voltage
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- Опубліковано 21 сер 2024
- how to measure 3-phase voltage on 3 phase Square D panel
going to each phase A phase to neutral measure B phase to neutral
C phase to neutral then measure phase to phase
this is a 3 Phase balance system
known as open Delta this is a 120-240 volts 3 phase system
you will have 120 volts on each leg 240 volts phase to phase
on B phase ( high leg) 208 volts to neutral
Thanks for watching!
- David
David@DavidJonesAC.com
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I hope you find this video helpful...thanks for watching from Jones Air Conditioning & Electric in Naples, FL!
Hi David i find that all of your videos very help full. What is your opinion on using acid away after a compressor burn out
This is a Delta system the center phase or high leg always has higher voltage providing by the power company for commercial business to operate large equipment at lower power rate to save power, also you will have 120 power for office equipment. Hope this helped. Thanks or asking.
David, thanks for posting this video. THIS is what I am talking about, straight to the point and you stayed on target with your video. All these other folks recording themselves with sticks and getting off track is just taking too much bandwidth., Thanks again for your video. :-)
You are 100% correct, I did not install this panel or have any red tape. Just trying to give a little explanation of how to measure 3 Phase voltage. I appreciate your comment, take care my friend.
PROTIP: The National Electrical Code requires all high leg conductors to be marked orange.
I'd go as far as tossing a roll of Scotch #34 orange tape in my tool bag, to mark them as I came across them, as a courtesy and to meet a very easily (inexpensively) achieved part of the NEC.
See NEC article 110.15, which started requiring the identification as early as the 1975 edition. The high leg wire is to be durably marked orange or by other effective means. Also it's required to be marked anywhere the high leg and Grounded Conductor [Neutral/mid point/0v] is also present, such as at a panel, or a motor starter, etc
Before 1975, common practice was to mark the wire on the high leg red, stemming the nick-name "Red-Leg Delta".
thank you Jones for sharing knowledge is power,have a nice weekend!!!
Well, here in California, this is called 240 DELTA with high leg. That center power lnput (B) should have RED tape on it. That's 208 to neutral. Neutral is center-tapped between A and C at the transformer on the pole. There's NO high leg on a WYE (or sometimes called STAR) system, all phases are 208 to each other, 120 to neutral.
I thought the high leg always had to be marked orange.
From what he said and showed,this is Delta with one coil center tapped. This type of Delta does have a high leg.
one of the best well explained tutorial out there on this subject ...thanks
hi! David! you explained very well and easy to understand, this is very valuable for my future career, thanks you.
I built a rotary phase converter and was testing between the leads to find one hot relative to neutral (the manufactured leg), thanks to this video I can see that this is a duplication of the normal measurements with "real" three phase supply.
In most cases with 480 there is always 277 for lighting. Unless power design calls for it other wise. Thanks for comment.
It can be it. All depend on the power company, you must always check for high leg in order to hook up your Phases correctly. Thanks for asking.
This was just a quick explanation, you have to listen to it close to get the understanding. I am going to do another one and explain it much better. Thanks for watching, and your comment.
Thanks for uploading, this answers a few fundamental questions that I have in mind.
Just a simple explanation of, how to for the beginner electrician. Thanks for your comment.
Thanks for the quick and simple demonstration.
I just thought of this question and you answered it!
Thanks Dave, for sharing with us.
This 120/208 3 phase Delta system which is typical for little strip shop type businesses. With this you have more choices. Thanks for asking.
Interesting. I've never come across this set up before so I was wondering initially how you got the 240v across the poles especially after you said that there was a neutral. I pretty much assumed that if it had a neutral it was bonded to ground in a star configuration. Apparently I have been living a sheltered life and I will be keeping my eye out for this configuration.
You can't do everything with one hand, you have to be on non conductive surface and how to place probes, and yes to some extend we are trusting the probes. Always be careful no guarantees with electric. Thanks for your comment.
Never had arcflash training... Never measure at the feeds. measure at breakers.
very helpful and thanks for giving code on B phase
What about how to properly ground the 120/240 3 phase panel?
tHANK YOU
You are very welcome my friend.
You can't unless the heat is design for 3 phase. Thanks for asking.
It really doesn't matter it will work either way. Thanks for asking.
you dont ALWAYS have a high leg in three phase system.....example...480v three phase
were is your safety equit, according to osha
almost tripped on the phases head first, going down
A-leg should be high, but for sure hi has to be marked as such so it's not introduced directly into the system
Dudes gonna get zapped one day by where he is hanging and grabbing the meter and not wearing arc flash gloves.
thank you for the Explanation.
Thanks for watching
Thanks for telling me this.
Dave, Good Stuff
You don’t always have a high leg on a 3 phase system
Ryan Gaines correct, he is getting power from a Wye-Delta transformer which will always have a 240V phase to phase and if done correctly L1 and L3 to ground/neutral will be 120 with L2 to ground/neutral at 208V.
Delta-Wye would be a balanced load with equal reading across the board.
Excellent video. Do you like the Fieldpiece meter?
Star is a 4 wire system 3 hots or live, and neutral and earth.Neutral is center tapped to earth so they become at the same potietial this means you could touch a neutral without getting a shock.Delta how ever has 3 wire's hot or live as known,and no neutral.this is because due to the cycle one phase overlaps the other phases in one cycle which in simple terms means that one phase is all ways in the negative cycle while 2 phases are in the positive.the negaive overlap acts as a neutral
Square D the best breakers on the planet.
Jolyon Welsh Why???
Do HVAC technicians have to be licensed electricians as well? Because typically you're not supposed to be messing around with any electrical equipment unless you're a licensed electrician?
What do you with 208 single pole? Btw most panels that dont have a high leg here in california.
This 1:33 minute video on “How to Measure or Check for 3 Phase Voltage” is provided by someone who, from his numerous other videos, is probably an expert in the field of HVAC/R (heating, ventilation, air conditioning and refrigeration). However, regrettably, he seems not to be an expert in explaining what is actually being measured in this situation. Also, it is doubtful that this could properly be explained in the very brief time taken.
I assume that electrical practitioners who are familiar with North American (and related) electrical practice will understand what is being measured and how it is derived. However, those of us who are more familiar with electrical practice in Europe and the rest of the world may benefit from a little more information.
After calling out only one of the three measured Phase to Phase voltages (all roughly 240 V), the presenter has not helped by failing to “call out” the three "Neutral" to Phase voltages, thus making it necessary for you to make 5 out of 6 readings from his meter - which he calls a "Fieldpiece".. This meter is a device manufactured by “Fieldpiece Instruments”, which is much more than a “multimeter” and is designed for use by HVAC/R personnel.
Some clues which may lead to further understanding of the electrical situation are contained in an earlier brief comment by “dougspair” who wrote:- “This is called 240 DELTA with high leg. ….. That's 208 to neutral. Neutral is center-tapped between A and C at the transformer on the pole.”
(He also wrote “There's NO high leg on a WYE [Y] (or sometimes called STAR) system, all phases are 208 to each other, 120 to neutral.” - but that is not quite relevant to this situation.)
Also, David Jones posted a comment shortly after this in which he stated “This is a Delta system the center phase or high leg always has higher voltage providing by the power company for commercial business to operate large equipment at lower power rate to save power, also you will have 120 power for office equipment. However, while a "Delta" system has no need of a "Neutral", (and really has no "center" phase) he has not chosen to explain either the existence of a "Neutral" and its derivation (or much else), in spite of various requests.
Be that as it may, I will now attempt to fill in some of the above omissions.
In North America, most domestic and commercial "low voltage" lighting and appliances are operated on 120 V AC. Most premises in which such lighting and appliances are used are actually supplied with a 240 V AC single phase supply of a 3 phase system, via the secondary of a transformer. HOWEVER, this single phase secondary is also “center tapped” and the center tap is "Earthed" to become the "Neutral”, with most premises supplied via THREE conductors - two “Live” conductors, each supplying 120 V with respect to the third (Earthed) Neutral conductor. Should it be required to operate a large (high wattage) domestic single phase appliance requiring 240 V, this voltage is available by connecting the appliance across the two “live” conductors, which are 180 degrees “out of phase” with each other. (In this 240 V operation case, the “Neutral” can be ignored BUT the “frame” of any such appliance MUST still be earthed.)
(Please note that these 120 V AC 180 degrees "out of phase" components have no direct relationship with the 120 degrees "out of phase" components of any 3 phase transmission.)
The situation being described in this video is NOT the normal North American domestic/commercial situation. Here a (Delta connected) 3 Phase supply exists to power some quite heavy electrical motors (presumably associated with an air conditioning system) which require the rotating field from the 3 phase power supply. The power supply company must use three conductors to supply this heavy power requirement. However, the premises will also require the “Normal” (two) 120 V AC supplies, used for appliances and lighting in North America (and [possibly] a 240 V AC single phase supply). Here these two out of phase 120 V AC supplies are derived by providing an Earthed “center tapped” “Neutral” on the A Phase to C Phase winding of the Delta connected 3 phase supply and this "Neutral" is fed by the power company to the distribution board as a fourth conductor.
The voltage “read” between the “Neutral” so derived and both the A and C phase points will be 120 V AC. However, the voltage “read” between this “Neutral” and the B phase point will be the sum of the 120 degree “out of phase” voltages involved (120 V + 240 V). While the arithmetic sum of these voltages is 360 V, because the voltages are “out of phase” by 120 degrees, we must divide this arithmetic sum by the square root of 3 (1.732051) to obtain the correct AC result of (approximately) 208 Volts.
In contrast to this arrangement, should a 3 phase supply be required in European countries (and most of the rest of the world), the supply would normally be via a Wye (or Star) connected 3 Phase supply, with 230 V available between each “Phase” and the (Earthed) “Neutral” point. The voltage between any two Phases is then 230 V * 1.732051 = 400 V, but this is NOT a matter of any great moment - except for some small insulation considerations.
In the European (or "Most of the World") case, for single phase appliances and lighting purposes, 230 V is available from any single Wye/Star connected Phase point and the (Earthed) Neutral of the 3 phase Low Voltage supply.
(Please permit me to observe that, when any individual posts something as being "Normal", he should consider that what is "Normal" in his small area of experience may NOT be "Normal" in many other places in the world.)
very good explanation!
Uptight viewer...make your own channel
I appreciate the detailed explanantion
What Phase and line voltage physically mean, what is their role in life.. I know the line voltage is the voltage between two lines and the phase voltage is the voltage between the neutral and a line, that is only important for the calculations, however
You mean 240 from Negative to any of the Phases and 380-400 between any of the phases.
David what if your b phase bus bar isn’t producing voltage in a 3 phase main panel?
where is your arc flash ppe?
+wile coyote open air is a great insulator, standing on the ground on like this is perfectly safe as long as you take proper care.
listen to this man an arc flash can happen on a live circuit with faulty equipment , just his leads are enough to create an arc flash alone and he has both hands in the box to near the end of leads - no gloves ffs , you can get away with this but if you dont you will regret it for ever , watch videos of 480v arc flashes and come back and say real world .
Heyy nice video. but i just cant figure out why "phase B to neutral" is higher than the other two in the delta confinguration. Can you enlighten further please.. thnks
NO GLOVES?
If you're using good quality test leads like Fluke TL71, you don't need gloves.
LIKE
+DZEyoyo123 Uh. The test leads don't mean shit when it comes to the question of PPE or no PPE. Always have gloves
3 phase is always less expensive to operate..
Sir I have a 3 phase AC generator with no neutral wire and I have measured its AC voltage through multimeter by connecting red and black probes to its two phase wires. So the voltage that I have obtained is the two phase voltage or someone else plz explain . thank you
Ain't the black prong suppose to be on the neutral terminal when checking each phase
When I check these can I check them with the power on???
Can I use single phase motor on 3 phase system? No earthing provide from transformer...
Why between B connection and N is 220v?
0:54
i have a 460 compressor is there a way to run it ? i have a 240 three phase
+Luis Gaytan you can most likely wire it to run on 240 three phase current. from factory they come with a main plate that tells you how to wire it in low voltage(240). If the main plate is missing you can also identify the wires and wire it correctly.
What was the measurement from neutral to high leg?
You don’t get a hi leg in all 3ph
what are the 460 volt wires I have found that thay are brown orange yellow but my panel.has brown purple yellow what is wright
How would I wire a 3 phase ct meter on single phase?
Hi
Can anyone tell me why are those measures 220v between each line and not 440v
Why does three phase always have one line higher than the rest?why can't it be balance?
Wye 3 phase will read 120-125 each leg. No wild leg in this case.
No arc flash protection?
Worry about the facts not things that tell everyone else you don't know anything.
how do you determine single phase operation?
Can you check 3-phase with a Fluke 177?
Please don't try to do this if you don't even know what you are doing. If you would know it, you'd know if it's possible or not.
***** Too late. I already did. I posted this question a month ago.
Oooooooh be fuckin careful. Something as simple as hooking the probes to the wrong inputs on the meter can result in a flashover and extreme damage.
What i know delta systems dont have any neutral.. is that correct? thanks
Delta connection is every phase voltage is the same
Star?? I have heard of Detla and Wye or "Y"
3 phase = 3 hots one neutral ???
This connection cannot be three phase system. Because in a 3-phase "Y" connection, the voltage to neutral = line voltage / 1.732. Threrefore , your phase B to neutral reading should be 141 volts , not 208 V. Moreover, Delta system doe not have a neutral in it , unless it is centered-tapped.
It's not a "Y" connection.
It is a 3 phase system, looks like a 120/240 volt delta 4 wire configuration, with one phase being the wild leg at 208 volts phase to neutral.
In USA How many three-phase voltage values?
+王俊 Not to much for peoples houses. But it's very common in industry.
+eline65 TY 谢谢
If you want to build it yourself just google for 'inplix' . I know you will find good solutions for your idea.
PPE? No arc flash protection?
+Tim Gomes What is it on all of these videos with peolple asking about PPE. It is pretty rare to see people wearing PPE in the field.
+daniel goulet Just because it's rare, doesn't mean it shouldn't be done. You are right that it's not common. And pre-2008 electrical stnadard, it would fall under the old method of
If I want to wire a three phase 230volt hydraulic motor from this system do I still use the neutral or just the three phase wire with no neutral.
It is a Lincoln welder and generator.
Three phase delta
Instead of having three hot legs you will only have two.
Show what you got.
you should always have proper safety equipment on gloves glasses flash protection OK kids
messy wiring. zip ties are cheap
This is why you don't hire HVAC tech's as electricians. 😅
My God... so much misinformation here.
3-phase does NOT "always" have a high leg. If this were a 3-phase 120/208-volt Y system, there is no high-leg (all three phases will give 120v to neutral & 208v ph-ph). Same with 277/480v systems... there is no "high-leg". There is no high-leg on a 240v corner-grounded Delta either.
On 120/240v 3-phase systems (as shown in the vid), one of the three transformer windings is center-tapped and grounded, thus deriving the neutral leg (grounded conductor). Phase-phase will be 240v, and two phases will be 120v to neutral, with the third "high leg" being approx. 208v to neutral (this phase is NEVER utilized as a phase-to-neutral supply).
Lastly, the NEC does NOT "require" the B-phase to be the "high-leg". It recommends it, but any phase may be high-leg, as long as it is properly identified (typically with orange, or other differentiating/unique color). And, in any panel where the neutral is present/available, the panel must be marked to indicate the high-leg, e.g., "240v 3ph, High leg on C" (or whichever phase it is).
Don't hire this guy to do your electrical work! 😅😅
Wear gloves so you don't look like a bozoo.
really waste of time
bad explanation