Markings on Panel Boards, are they right?

[iwire]

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.

My daily use meter is a Fluke T5-1000. It is digital but it is not true RMS meter so I take the readings with a grain of salt.

 

[mbrooke]

My daily use meter is a Fluke T5-1000. It is digital but it is not true RMS meter so I take the readings with a grain of salt.

Even if its RMS, voltage varies in real time. But I do agree, I never take meter readings too seriously.

 

[JFletcher]

: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.

That is the movie "Mr. Mom". Why? It isnt 230V to N/G, it's 128V (or thereabouts).

Ill agree that lowering the primary taps to overdrive the secondary side isnt the best solution in the world, but until the OP chimes back in, we dont know why the taps are on the 444V lugs. They dont come that way from the factory.

Ive seen at least one warehouse that I would have done the exact same thing to on the primary side of the xfmr.

 

[mbrooke]

That is the movie "Mr. Mom". Why? It isnt 230V to N/G, it's 128V (or thereabouts).

Ill agree that lowering the primary taps to overdrive the secondary side isnt the best solution in the world, but until the OP chimes back in, we dont know why the taps are on the 444V lugs. They dont come that way from the factory.

Ive seen at least one warehouse that I would have done the exact same thing to on the primary side of the xfmr.

128 at the time of the reading, nothing stops that value from going up (it will be totally legal), and chances are no one would notice either unit that breaker tried to interrupt heavy fault current.

 

[kwired]

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.

Just trying to make sure he actually measured 480 and didn't just assume that 480 nominal will actually be 480. 495-502 is pretty common actual measurement around these parts on a 480 nominal system, at least with minimal loading.

Had he said 479 or 485 or something other then 480 this may be more of an indication that he did actually measure it.

 

[JFletcher]

Just trying to make sure he actually measured 480 and didn't just assume that 480 nominal will actually be 480. 495-502 is pretty common actual measurement around these parts on a 480 nominal system, at least with minimal loading.

Had he said 479 or 485 or something other then 480 this may be more of an indication that he did actually measure it.

and 500V connected to the 444V tap would give 234V L-L, right in line with what a 230V 3ph load needs.

to mbrooke's post: 128V or 131V, the line voltage to neutral isnt going much higher than that, barring him using tap #7 (432V). Should 230/240V equipment be run from a buck/boost, or dedicated xfmr? yes. If the only (or major) loads in the place are 230/240V, changing primary tap position to overdrive the secondary at the risk of occasionally frying 120V loads may be acceptable to the customer. I've seen 127V L-N here, and none of my computers or appliances have gone to the big scrapyard in the sky over it.

I will lose no sleep over a slash rated breaker seeing less than 10% over voltage, even permanently.

A classic question of what's "right" vs what works.

I work under the assumption the original or last EC knew what they were doing. That isnt always the case, but summarily switching taps from 444V back to the original 480V (or higher) just to get panel voltages back in line with expected/nominal may have some serious consequences w/o further investigation.

imho, the first question one should ask upon seeing the 444V taps used is "why did the previous electrician use these taps?"

 

[mbrooke]

and 500V connected to the 444V tap would give 234V L-L, right in line with what a 230V 3ph load needs.

to mbrooke's post: 128V or 131V, the line voltage to neutral isnt going much higher than that, barring him using tap #7 (432V). Should 230/240V equipment be run from a buck/boost, or dedicated xfmr? yes. If the only (or major) loads in the place are 230/240V, changing primary tap position to overdrive the secondary at the risk of occasionally frying 120V loads may be acceptable to the customer. I've seen 127V L-N here, and none of my computers or appliances have gone to the big scrapyard in the sky over it.

I will lose no sleep over a slash rated breaker seeing less than 10% over voltage, even permanently.

A classic question of what's "right" vs what works.

I work under the assumption the original or last EC knew what they were doing. That isnt always the case, but summarily switching taps from 444V back to the original 480V (or higher) just to get panel voltages back in line with expected/nominal may have some serious consequences w/o further investigation.

imho, the first question one should ask upon seeing the 444V taps used is "why did the previous electrician use these taps?"

So what happens when the POCO (to compensate for load growth) raises the incoming voltage to 508 volts?

 

[iwire]

A classic question of what's "right" vs what works.

Yet the OP is there and seems interested in making it "right".

Why do you seem opposed to it? :huh:

 

[kwired]

and 500V connected to the 444V tap would give 234V L-L, right in line with what a 230V 3ph load needs.

to mbrooke's post: 128V or 131V, the line voltage to neutral isnt going much higher than that, barring him using tap #7 (432V). Should 230/240V equipment be run from a buck/boost, or dedicated xfmr? yes. If the only (or major) loads in the place are 230/240V, changing primary tap position to overdrive the secondary at the risk of occasionally frying 120V loads may be acceptable to the customer. I've seen 127V L-N here, and none of my computers or appliances have gone to the big scrapyard in the sky over it.

I will lose no sleep over a slash rated breaker seeing less than 10% over voltage, even permanently.

A classic question of what's "right" vs what works.

I work under the assumption the original or last EC knew what they were doing. That isnt always the case, but summarily switching taps from 444V back to the original 480V (or higher) just to get panel voltages back in line with expected/nominal may have some serious consequences w/o further investigation.

imho, the first question one should ask upon seeing the 444V taps used is "why did the previous electrician use these taps?"

I've seen over 125 volts quite often myself, until it gets over 130 I usually don't get too concerned. I don't think it is all that hard on electronic lighting power supplies, but when there was much more incandescent lighting it would shorten life of lamps.

 

[JFletcher]

Yet the OP is there and seems interested in making it "right".

Why do you seem opposed to it? :huh:

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

short answer:

Im not opposed to the panel voltages being closer to nominal, Im opposed to changing the taps from 444 to 480 without investigating WHY the 444V taps were used in the first place.


long answer:

... and my original and subsequent posts detailed several reasons why the 444V taps may have been used. Until the OP chimes in with more information, we will never know.

I dont know about anyone else, but I dont go randomly measuring panel voltages. Why did the OP do that in the first place? His profile says industrial electrician, so maybe the reason was PMs, maybe some equipment was malfunctioning and in the course of investigating that, the higher than nominal voltages were discovered. Maybe he saw what apparently was a note on/in the panel/xfmr (the text I quoted back in red) and for his own edification grabbed a meter and too a look-see.

~~~~~~~~~~~~~~

As for the POCO boosting voltage from 480 to 508V, that's a 5.8% increase, and yes, coupled with the 8.1% increase (480/444) of the primary taps, would be 14.4% (508/444) over nominal for the panels that are fed from that xfmr. That puts L-N at 137V, and L-L at 238V. In this ever increasing "what if?" situation with many substantial pieces of information missing from the original post, I posit that 137V would probably cause problems for a lot of 120V loads; otoh, if those panels feed solely 230V 3ph and 240V 1ph equipment, they would operate better since they really needed a 480/240 xfmr in the first place, not the 480/208 one they are operating from.

 

[kwired]

I dont know about anyone else, but I dont go randomly measuring panel voltages. Why did the OP do that in the first place? His profile says industrial electrician, so maybe the reason was PMs, maybe some equipment was malfunctioning and in the course of investigating that, the higher than nominal voltages were discovered. Maybe he saw what apparently was a note on/in the panel/xfmr (the text I quoted back in red) and for his own edification grabbed a meter and too a look-see.

I don't randomly go checking panel voltage either. I found out my supply voltage at my home/shop was 135/270 one time only because I was troubleshooting a customer piece of equipment and discovered the voltage was high, and of course went to main panel and checked there as well. POCO was having issues with regulator equipment is why that happened.

 

[mbrooke]

As for the POCO boosting voltage from 480 to 508V, that's a 5.8% increase, and yes, coupled with the 8.1% increase (480/444) of the primary taps, would be 14.4% (508/444) over nominal for the panels that are fed from that xfmr. That puts L-N at 137V, and L-L at 238V. In this ever increasing "what if?" situation with many substantial pieces of information missing from the original post, I posit that 137V would probably cause problems for a lot of 120V loads; otoh, if those panels feed solely 230V 3ph and 240V 1ph equipment, they would operate better since they really needed a 480/240 xfmr in the first place, not the 480/208 one they are operating from.

And as such, this would demonstrate why slash rated breakers should not be used in that panel board.

 

[Fnewman]

There was another recent thread I recall where someone recommeded doing this very thing in order to get '220' volts on a 3 phase system. Maybe he wired this one!

 

[JFletcher]

And as such, this would demonstrate why slash rated breakers should not be used in that panel board.

Ok, the NEC limits using slash rated breakers to 120V to ground. A theoretical 137V to ground and 238V L-L (basically a 240/138V wye, if there was such an animal) still doesnt inspire me to use 240V only rated breakers. Certainly not 277V rated ones.

OP still hasnt chimed in on WHY the 444V taps were used in the first place. Short of conclusive evidence that a slash rated breaker would explode or otherwise cause harm under even 140V, I'm staying pat.

I want to know why the original EC used those taps. **** in one hand, wish in the other.....

There may be a method to the 'madness'.

 

[mbrooke]

Ok, the NEC limits using slash rated breakers to 120V to ground. A theoretical 137V to ground and 238V L-L (basically a 240/138V wye, if there was such an animal) still doesnt inspire me to use 240V only rated breakers. Certainly not 277V rated ones.

OP still hasnt chimed in on WHY the 444V taps were used in the first place. Short of conclusive evidence that a slash rated breaker would explode or otherwise cause harm under even 140V, I'm staying pat.

I want to know why the original EC used those taps. **** in one hand, wish in the other.....

There may be a method to the 'madness'.

Its still a code violation in theory. I'm sure that breaker won't be bothered interrupting 2ka current at 150 volts, but what guarantee do I have it will still do so at 10ka?


Remember, a POCO can legally bump that 480 volt service to an actual voltage of 504 volts (if not more) without the customer ever being contacted or even noticed.

 

[mbrooke]

By definition:

Voltage, Nominal.

A nominal value assigned to a circuit or
system for the purpose of conveniently designating its voltage
class (e.g., 120/240 volts, 480Y/277 volts, 600 volts).
Informational Note No. 1: The actual voltage at which a
circuit operates can vary from the nominal within a range
that permits satisfactory operation of equipment.
Informational Note No. 2: See ANSI C84.1-2006, Voltage
Ratings for Electric Power Systems and Equipment (60 Hz).

 

[JFletcher]

Its still a code violation in theory. I'm sure that breaker won't be bothered interrupting 2ka current at 150 volts, but what guarantee do I have it will still do so at 10ka?


Remember, a POCO can legally bump that 480 volt service to an actual voltage of 504 volts (if not more) without the customer ever being contacted or even noticed.

ive seen a CH breaker, 20A (22KAIC) 1p hold under a bolted fault. The 12ga wires melted/exploded before it tripped (which never happened). I dont rely on breakers to keep from killing me, nor sending molten copper plasma at mach whatever into my body, regardless the voltage. Do I stand to the side of any breaker or disconnect I throw? Damned right I do.

Is that a valid argument for allowing 500+V on a 480V breaker, which feeds a 480/208 xfmr? No. You're still going to have to convince me that 140V on a slash rated 120/240V breaker is a danger. Links. Studies. Case analysis. Something.

OP still hasnt chimed in on why the 444V taps were used. Without that, this whole discussion is academic.

 

[mbrooke]

ive seen a CH breaker, 20A (22KAIC) 1p hold under a bolted fault. The 12ga wires melted/exploded before it tripped (which never happened). I dont rely on breakers to keep from killing me, nor sending molten copper plasma at mach whatever into my body, regardless the voltage. Do I stand to the side of any breaker or disconnect I throw? Damned right I do.

Is that a valid argument for allowing 500+V on a 480V breaker, which feeds a 480/208 xfmr? No. You're still going to have to convince me that 140V on a slash rated 120/240V breaker is a danger. Links. Studies. Case analysis. Something.

OP still hasnt chimed in on why the 444V taps were used. Without that, this whole discussion is academic.

That breaker failed be it misapplication or defect which happens with everything.


You ask what can I give you? The code. The code specifically points to a document which defines nominal voltage.