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Transformers

4K views 41 replies 11 participants last post by  micromind 
#1 ·
I have an existing 45KVA 480/ 240 Wye transformer supplying a 45kW water heater. Is the transformer undersized for this load? Been forever since I did any transformer/ commercial 3-phase wiring and I'm just not certain. The wiring looks a little hack-ish (conductors aren't identified, lack of insulated bushings, etc).
 
#10 ·
I got a call today and was told they smelled something funny coming from the transformer so they turned the disconnect off. None of the conductors were properly identified and were missing some plastic bushings. I suspect things weren't right here. This area is not area of specialty. Maybe Peter D can help me I thought so I posted here.
 

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#11 · (Edited)
Yeah....that transformer will JUST handle that as long as there is no other connected load. That tank draws 108 amps when wired up as 3 phase unit and the transformer will do 108 amps.

Connect a few 100 watt bulbs and you're overloading the transformer.


FWIW......I would prefer to see a 75KvA transformer in that situation
 
#13 ·
Wow.....a helpful question.:laughing:

If its connected single phase it will WAY overload that transformer. Are you guys required by the NEC to fuse the secondaries of transformers?
 
#22 ·
It's less than a year old.

I asked the maintenance guy which electrician installed it and he said he couldn't find the invoice. I thought that was a bit strange. The building itself is a church/ learning center in Rahway here and is less than 12 years old.
 
#29 ·
A 45 KVA transformer will operate a 45 KW water heater all day long without issue provided that......

1) The ambient temperature where the transformer is located is less that 104ºF and there's no airflow restriction around it. Including it being mounted too close to walls.

2) The low side voltage does not exceed 240 under load. If it does, then the current will be above the rating of the transformer.

If I were installing this system, I would change the taps on the high side a step or two above 480. This way the low side voltage will be below 240 and the current will be well within the rating.

Of course, this will result in the 45 KW heater being actually 44 or 43, but I seriously doubt it'd matter.
 
#36 ·
A 45 KVA transformer will operate a 45 KW water heater all day long without issue.
The available power is there as long as nothing else is connected to that tranny.
I notice there are 9 heater elements in the water heater....I wonder if they all come on at once or just as they are required. Maybe they only noticed the smell from the transformer because all the elements were actually working.
Just thinking out loud here:)
 
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