240V, Three-phase water heater - convertible to single phase?

[JohnnyPElec]

General question for the forum. My team has received a 240V, 3-phase water heater spec for a large project where there will be several and we of course only have 240V, single phase services. The cut sheet states that

120, 277 single phase and 208, 240 and 480V unbalanced three‑phase delta; easily converted to single‑phase at terminal block with limited exceptions.
Single element heaters, single‑phase only.

So it seems the manufacturer designed the product such that the heating elements (assuming there are 3) aren't wired in a wye or delta config between the phases and they can be reconfigured at the terminal block so that all the elements run on a single phase. Is this typical for residential water heaters? I was initially going to push back and ask for a spec that doesn't require such modification post-factory but don't want to create a hub-bub if this is standard practice

 

[augie47]

Seemingly typical for the three phase units I have seen.
Many heating appliances have that feature

 

[roger]

Is this typical for residential water heaters?

No, three phase water heaters are not typical for residential.

 

[winnie]

I agree with @roger

A three phase heating device that can be converted to single phase is not surprising. I've seen this for things such as bakery ovens and the like.

What is uncommon is a three phase _residential_ water heater. I guess reasonable for a shared occupancy such as a dorm or hotel, but you won't see three phase water heaters for individual homes.

 

[Jraef]

Because 3 phase run to residential customers is itself rare…

 

[ggunn]

Seemingly typical for the three phase units I have seen.
Many heating appliances have that feature

Wouldn't the loading on the phase be 3X what it would be if it were wired 3 phase?

 

[augie47]

Wouldn't the loading on the phase be 3X what it would be if it were wired 3 phase?

Closer to twice (1.7) but it depends on how the elements lay out on 3 phase.

 

[kwired]

I have a local plumber that has been installing commercial water heater in dwellings at times where with similar demand situations in the past he may have used two typical 4500 watt single phase units. These units are only a 50 or 60 gallon tank both heating elements are connected individually and can run simultaneously. They also are 277 volt rated elements. Don't recall exact watt rating but when calculating draw @240 volts I recall needing to run 50 amp circuit.

There is terminal board in the wiring compartment, could run two circuits or single circuit and use jumpers to parallel connect the two elements. I suppose another possibility would be configure jumpers in an open delta you could go with the mentioned unbalanced delta configuration, or if you actually had 480/277 wye supply volts connect two phase conductors and neutral and get full nameplate rating out of it.