Neutral Required?

[charlie b]

Building with 120/208V service has one load that needs 480V and that does not need a neutral. Plan is to use step-up 208-480 transformer, with an enclosed circuit breaker (ECB) feeding directly to the load. I am thinking that I need to connect a GEC to the secondary center point. I would call for the N-G bond at the transformer. I believe that I need not bring a neutral to the ECB or to the load itself.

Comments?

 

[david luchini]

I believe that I need not bring a neutral to the ECB or to the load itself.

I would agree with you.

 

[jumper]

Only problem I see is that I cannot find a 208V to 480V single phase transformer.

 

[Buck Parrish]

I've always thought it was required to go with hots to the panel. Then from there not required.

 

[jumper]

I've always thought it was required to go with hots to the panel. Then from there not required.

Yes, 250.24(C)

 

[Dennis Alwon]

Only problem I see is that I cannot find a 208V to 480V single phase transformer.

Why would it need to be single phase? We don't know the load

 

[jumper]

Why would it need to be single phase? We don't know the load

I was going by the OP’s voltage designations. He wrote 120/208V, not 208Y/120V.

 

[Adamjamma]

but Jumber, the /acme step up transformers have one similar to that I believe... Used to have their catalogue numbers sitting around... Just not on PDFs so it would be like everything else, in a box in Jamaica...lol
Or, I could tell you the numbers on it... although 240/480 is more common...

 

[Dennis Alwon]

I was going by the OP’s voltage designations. He wrote 120/208V, not 208Y/120V.

I have seen that denotation both ways. I would assume if it is a service it is 3 phase. I have never seen a 208 single phase service

 

[charlie b]

I was going by the OP’s voltage designations. He wrote 120/208V, not 208Y/120V.

I steadfastly refuse to succumb to the notion that it makes a difference. :happyno: And I don't care what any IEEE standard has to say on the subject, despite being an IEEE "Senior Member" for over 30 years.

The load is an on-demand water heater, three phase, about 108KW. It serves an eye wash station in a new building where aircraft engines will be tested. The Mechanical Engineer selected this water heater because his requirements included a water temperature range that has to be held steady for at least 15 minutes.

 

[charlie b]

I've always thought it was required to go with hots to the panel. Then from there not required.

Yes, 250.24(C)

That only applies to a service. This will be a separately derived system.

 

[Jraef]

Building with 120/208V service has one load that needs 480V and that does not need a neutral. Plan is to use step-up 208-480 transformer, with an enclosed circuit breaker (ECB) feeding directly to the load. I am thinking that I need to connect a GEC to the secondary center point. I would call for the N-G bond at the transformer. I believe that I need not bring a neutral to the ECB or to the load itself.

Comments?

That's fine, done all the time really if you think about an MCC that has no loads requiring neutral, but is fed from a 480Y277 service. The service gets bonded, but no need to put the N bus in the MCC, so no need to run the N conductor out to it.

My only suggestion (based on experience) is to not assume the installer understands that the "secondary" in this case is the 480V side, so refer to it as the HV and LV sides of the transformer. Also make sure that they know that they need to use a transformer with a wye on the 480 side and not to bond the X) on the 208V side (if there is one). Common off-the-shelf distribution transformers are mostly 480 delta, 208 wye. It's not hard to find a 480V wye version, it's just not something they will pick up out of a distributor's stock.

Edit:
Or use a delta on the 480 side and corner ground it. Not a good plan if there are power electronics, but it sounds as if that's not the case here.

 

[jumper]

I steadfastly refuse to succumb to the notion that it makes a difference. :happyno: And I don't care what any IEEE standard has to say on the subject, despite being an IEEE "Senior Member" for over 30 years.

I’m gonna tell Jim D on you!

 

[jim dungar]

I’m gonna tell Jim D on you!

I am a believer in adding the number of phase and the number of wires to any voltage description (e.g. 1PH 3W or 3PH 4W).
Even though there is a specific standard, that I often promote (which came from ANSI, and one which most utilities do not follow), trusting that a single description is being used correctly often results in miscommunications.

 

[jumper]

I am a believer in adding the number of phase and the number of wires to any voltage description (e.g. 1PH 3W or 3PH 4W).
Even though there is a specific standard, that I often promote (which came from ANSI, and one which most utilities do not follow), trusting that a single description is being used correctly often results in miscommunications.

Agree. You done convinced me long ago.

 

[Adamjamma]

I am a believer in adding the number of phase and the number of wires to any voltage description (e.g. 1PH 3W or 3PH 4W).
Even though there is a specific standard, that I often promote (which came from ANSI, and one which most utilities do not follow), trusting that a single description is being used correctly often results in miscommunications.

I think I may have to start doing that as well..need to make a note of that.

 

[victor.cherkashi]

what did you do for 230(A)(3) or 230(A)(4) requirement?

Sent from my Nexus 5X using Tapatalk

 

[electrofelon]

Building with 120/208V service has one load that needs 480V and that does not need a neutral. Plan is to use step-up 208-480 transformer, with an enclosed circuit breaker (ECB) feeding directly to the load. I am thinking that I need to connect a GEC to the secondary center point. I would call for the N-G bond at the transformer. I believe that I need not bring a neutral to the ECB or to the load itself.

Comments?

I disagree. Change "need" to "should" . You have the option to run it ungrounded.