Markings on Panel Boards, are they right?

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reyamkram

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Hanover park, il
I have 3 panel boards, marked 208/120, when I measure voltage with my meter, it reads P-P 220, P-N or G, 128 v. is the marking wrong, or is there a problem. the transformer that feeds the panel boards, is a square D cat# 225t3hf. and has 480 v coming in, it also said connected to tap 6 and tap 6 said 444v,

should It be connected to tap 3, which said 480v. any information would help a lot

Thank You, All
 
This should be the nameplate

img0759_600.jpg


Yes I would change the tap setting.
 
The 444V tap was probably used either due to low incoming voltage, a high load on the panel causing voltage drop, or 230V motor loads being used on a 208V supply, thus the primary side was overdriven (lower voltage tap) to boost the secondary side closer to 230V. My guess is the latter of the three. 128V L-N is 6.7% over a nominal 120V, tho if the panel is at the far end of the building, and the average 120V load is hundreds of feet away, that receptacle/outlet may be seeing closer to 120V.

Are there any 230V motor loads on the panel? Did you check it loaded or unloaded?
 
reyamkram said:
I have 3 panel boards, marked 208/120, when I measure voltage with my meter, it reads P-P 220, P-N or G, 128 v. is the marking wrong, or is there a problem. the transformer that feeds the panel boards, is a square D cat# 225t3hf. and has 480 v coming in, it also said connected to tap 6 and tap 6 said 444v,

should It be connected to tap 3, which said 480v. any information would help a lot

Thank You, All
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There is something wrong as that combination of voltages is not possible with a correctly installed and functioning wye system.
 
don_resqcapt19 said:
There is something wrong as that combination of voltages is not possible with a correctly installed and functioning wye system.
Click to expand...
You are correct, if incredibly picky.

If the transformer secondary were actually 208Y/120, then with the 120 raised to 128 the phase voltage should be (128/120)(208). And that would be approximately 222, not 220.
That seems to me to be consistent within calculation and measurement error though. :)

Sent from my XT1585 using Tapatalk
 
don_resqcapt19 said:
There is something wrong as that combination of voltages is not possible with a correctly installed and functioning wye system.
Click to expand...

:?

128 x 1.73 is indeed 221.44

Granted its about 1 1/2 volt off, but keep in mind that:

1) load can cause uneven voltages on each phase where on L1=N reads lower and L2=N reads higher than what the normal P-P/1.73 reads.

2) Loads switching on/off in real time can cause voltages to bounce up and down by the second.
 
I wouldnt touch the primary taps unless there was a problem or equipment change. The odds of the original electrician using the 444V taps by accident is in the seven zero range.

Dont assume it's wrong; figure out why the original EC wired it that way.
 
JFletcher said:
I wouldnt touch the primary taps unless there was a problem or equipment change. The odds of the original electrician using the 444V taps by accident is in the seven zero range.

Dont assume it's wrong; figure out why the original EC wired it that way.
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We are all so different. To me the fact the 120 is running so high is enough reason to change it.

If there is equipment that really needs 230 that should be addressed on its own.
 
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reyamkram said:
I have 3 panel boards, marked 208/120, when I measure voltage with my meter, it reads P-P 220, P-N or G, 128 v. is the marking wrong, or is there a problem. the transformer that feeds the panel boards, is a square D cat# 225t3hf. and has 480 v coming in, it also said connected to tap 6 and tap 6 said 444v,

should It be connected to tap 3, which said 480v. any information would help a lot

Thank You, All
Click to expand...

If it's your responsibility to get the transformer voltage down to 208/120 then like Bob I would change the taps too.
 
mbrooke said:
:?

128 x 1.73 is indeed 221.44

Granted its about 1 1/2 volt off, but keep in mind that:

1) load can cause uneven voltages on each phase where on L1=N reads lower and L2=N reads higher than what the normal P-P/1.73 reads.

2) Loads switching on/off in real time can cause voltages to bounce up and down by the second.
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220, 221, whatever it takes...

I agree though, there may be a REASON why the taps were used that way. For all we know, all 3 panels feed nothing but 230V motor loads, and the OP is simply reporting his Line to Neutral voltage readings, even though that is not actually being used anywhere.
 
Jraef said:
220, 221, whatever it takes...

I agree though, there may be a REASON why the taps were used that way. For all we know, all 3 panels feed nothing but 230V motor loads, and the OP is simply reporting his Line to Neutral voltage readings, even though that is not actually being used anywhere.
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:lol: Is that show from the US or Europe btw? :dunce:


If the panel is serving 230 volt loads with the intent to deliver 230 volts nominal the breakers need to be changed to either straight 240 volts rated or the paneboard must be upgraded to a 277/480Y version. Technically speaking those breaker can end up interrupting a voltage higher then they are rated for.
 
What is incoming voltage? Probably should check this at the most normal loading condition.

Tap should be set as close as possible to incoming voltage if you want as close as possible to 208/120. Most will prefer to round up instead of down when making a selection of which one to use.

Factory connections were likely set at 480 volts, so this was likely intentionally set for 444, or maybe was moved or conditions changed and supply voltage has increased since originally set for 444.
 
kwired said:
What is incoming voltage?
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480, it is right in the OP.




Many folks keep asking about the loading but unless the feeder is seriously undersized you should not be dropping 36 volts between loaded and unloaded conditions. Even the transformer itself will provide more consistent voltage from no load to full load.

I have done many power quality recordings and voltage generally stays pretty stable regardless of load. A few volts of change, not 36 volts.
 
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kwired said:
What is incoming voltage? Probably should check this at the most normal loading condition.

Tap should be set as close as possible to incoming voltage if you want as close as possible to 208/120. Most will prefer to round up instead of down when making a selection of which one to use.

Factory connections were likely set at 480 volts, so this was likely intentionally set for 444, or maybe was moved or conditions changed and supply voltage has increased since originally set for 444.
Click to expand...

This might be slightly off topic, but still relevant to the OP's transformer. Can setting that taps to 440 while applying an actual voltage of say 490 volts cause core saturation? I don't know how much safety factor is built into these small units, but Id imagine if the unit were strictly designed for 440 nominal (at those taps) 480 nominal might cause problems.
 
Interesting round off error. I did the calculation from the P-P number and wondered why you thought it was 1 1/2 volts off.

220 divided by 1.73 =127.16 or less than one volt error.

Youse guys are really nit picking!

Now if you use a calculator with a real square root of three function, you almost get a whole volt error...:p
 
Frank DuVal said:
Interesting round off error. I did the calculation from the P-P number and wondered why you thought it was 1 1/2 volts off.

220 divided by 1.73 =127.16 or less than one volt error.

Youse guys are really nit picking!

Now if you use a calculator with a real square root of three function, you almost get a whole volt error...:p
Click to expand...

I do math in my head, which sometimes is good enough :thumbsup: :p:)
 
iwire said:
I would not get too caught up in the calculations, we have no idea what meter was used. :)
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I agree. Voltages will vary for a number of reasons outside of a classic square root of 3 without being a problem or an indicator of something off.
 
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