480 208 120 commercial service

[CLEMDVA]

My electrician is out of town till next week and my curiosity is getting the best of me. Perhaps someone can take a minute to clarify this to me, a dumb facility manager. We will be ordering a three-phase HWH next week and if I mis-identify the voltage I will be eating it.

The electrical service (Virginia) is 480 4wy service per the utility (and the meter). This feeds an unlabelled cabinet which I assume houses a transformer which steps it down to three phase 208/120. From there to a sweet Square D panel (QMB type) labelled 3 phase 208/120. If I measure voltage in a three-pole disconnect I get 120 from any single pole to ground, but I don't get 208 between any two of the three, I get 212-215. I got this on all the three-pole disconnects (and with a second meter). Is this voltage within the range of tolerance?

This matters as the HWH we are looking at are specific for these voltages. Don't want to spec 208 and fry the unit.

Lastly, why does the meter say "4wy 120 480" -- if 480 why doesn't it say 277 somewhere? Just wonderin'.

 

[augie47]

212-215 is in tolerance for a 208 system which, from all indications, is what you have.
Depending on the power available and the proximity of the panels you can use a 208 or 480 WH. (It is usually more economical to put as much load as possible on the 480 system since you are not loading your transformer as you will on the 208)

 

[Open Neutral]

Depending on the power available and the proximity of the panels you can use a 208 or 480 WH. (It is usually more economical to put as much load as possible on the 480 system since you are not loading your transformer as you will on the 208)

Not clear he has any 480 dist. panel installed. Agree that's less loss but suspect his choice is really "208" vs "240".....

 

[kwired]

I suggest you talk to your electrician or you may eat some unnecessary cost anyway.

Without seeing what you have we can't possibly know what is the easiest or least costly to install. Sounds like a 208 or 480 can be made to work but there is too much unknown information to make a wise decision on which is best to use.

 

[Chamuit]

What does the panel that the WH is going to be fed from say. Are you looking at the main section or further down the distribution? There could be xfrmrs along the way.

When we have done surveys of jobs (for A/C equipment) we access either a panel or disconnect and put a DMM on.

Sometimes things are not what they say.

 

[BJ Conner]

Wait until next week

Wait until next week

My electrician is out of town till next week and my curiosity is getting the best of me. Perhaps someone can take a minute to clarify this to me, a dumb facility manager. We will be ordering a three-phase HWH next week and if I mis-identify the voltage I will be eating it.

The electrical service (Virginia) is 480 4wy service per the utility (and the meter). This feeds an unlabelled cabinet which I assume houses a transformer which steps it down to three phase 208/120. From there to a sweet Square D panel (QMB type) labelled 3 phase 208/120. If I measure voltage in a three-pole disconnect I get 120 from any single pole to ground, but I don't get 208 between any two of the three, I get 212-215. I got this on all the three-pole disconnects (and with a second meter). Is this voltage within the range of tolerance?

This matters as the HWH we are looking at are specific for these voltages. Don't want to spec 208 and fry the unit.


Lastly, why does the meter say "4wy 120 480" -- if 480 why doesn't it say 277 somewhere? Just wonderin'.

Curiosity has killed lots of cats and probably a few facillity managers. IF you don't know what your doing STAY OUT. IF you have ot hire another electrican for a day do it. It's cheaper than a stay in the burn unit or a funeral.
I have been in the business 40 years as an engineer (field,design, testing, startup, construction management ) but I never open panels or get into live stuff. I got my rice bowl , electricans got theirs. Together we do great work.
Ignorance is one of the most dangerous things on a jobsite.

 

[cadpoint]

Where's your Single Line Diagram or Riser diagram that were used to build the building? These plans should exist somewhere!?

The record drawings will show (hopefully) the correct sequence of the power distrubition, these same plans should have been or be altered to reflect any changes that have happened over time. You could check the verbage of the drawings to be used for new labels on all your equipment. You can load up the electricain after he gets back.

Depending on where your are in the commonwealth the Power Company might be running their voltage a little higher. I know Duke Power seems to always be a little higher.

From my experience it's not unusall to see higher voltage on lightly loaded service points and in "newer commissioned (the whole system)" service/equipment. It always measures a few volts higher, I usually work in new construction so it's always new POCO feeds, and new equipment over-all!