240 3 phase to 120 not possible? What to do?

[MARKFLYNN]

We have a commercial building, and recently purchased a water heater which requires 240v.

We have two older 240 3 phase power panels (one not being used) (I think called "B" phase) which we cannot obtain 120v from.

We also have 120v coming in on a separate panel which is only 100 amp service.

The water heater requires 112 amps at full load, and gets it sequentially from 3 - 40 amp GFI breakers. Hooking up to two of these 240 3 phase wires as the licensed electrician advised gives us 239v at the heater, but apparently we also need 120, as we are not getting sufficient heat from the unit. Are we better off upgrading the 120v 100 amp service to 200 amp (or more), or is there a way to get 240v and 120v from the old B phase which would be more cost effective than using the 120v service?

 

[readydave8]

Is licensed electrician doing work or just advising? I'm not sure if your question makes sense, I wonder if you need all 3 phases at water heater, can't think why 120v would make it heat better . Try checking amps to see if all 3 sets of elements are heating, if not get that electrician to check voltages, if wired correctly call manufacturer?

 

[FJSFRED]

Fred Smith owner of FJS Electrical Services

Fred Smith owner of FJS Electrical Services

The reason the water heater is not performing properly is that it is fed with only 80 amps of power (2- 40 amp circuit breakers) Your water heater needs 110 amps as you stated not 80 amps. The 120 volt should not have any thing to do with the performance of the water heater. It is performing at about 70%. What is the full rating of the 240 volt 3-phase electrical panel in amps? If is 100 amps that is all you are going to get without upgrading it to a 200 amp panel. The water heater needs to be fed with (1) 3-pole 110 amp circuit breaker or more (at lease 20% more) depending on what the manufacturers rated plackard states. Hope this helped.

 

[George Stolz]

I am closing this thread, in accordance with the Forum rules. This Forum is intended to assist professional electricians, inspectors, engineers, and other members of the electrical industry in the performance of their job-related tasks. However, if you are not an electrician or an electrical contractor, then we are not permitted to help you perform your own electrical installation work.