three phase power to single phase water heater

[roger]

Rick, I never said it would apply to the OP's scenario, I was deliberate in saying it would work for the OP's voltage.

Roger

 

[LarryFine]

You can't make a delta configuration with two elements (or a Y config for that mater).

I pictured two elements connected to phase B and one element apiece to phases A and C.

In other words, connect it in open Delta, the way you'd connect two 208v 1-ph loads to a 3-ph supply.

This can be done as long as there is a way to supply the controlling components with separate supplies.

 

[iwire]

This can be done as long as there is a way to supply the controlling components with separate supplies.

Why would the controls need separate supplies?

 

[LarryFine]

Why would the controls need separate supplies?

I mean they would need to be capable of that, and I said 'controls' and not 'elements' because I pictured the typical electro-mechanical thermostats, and not electronics. Follow me:

A typical water heater upper t'stat control is an SPDT device which prevents both elements being energized simultaneously, but one could split the common side to provide separate feeds.

However, there would be no way to completely supply one with two separate supplies; the SPDT t'stat would require one line in common. This would still work with a 3-phase system, though.

Of course, since the elements would never be energized simultaneously, there would be no advantage to splitting the supply as the OP asked about. But, the OP says the elements in his heater can run simultaneously.

With that in mind, to do what he asked, there would need to be a way to separate the elements and their controlling components, or at least one line side of them, which is how I ended up wording my post the way I did.

 

[iwire]

With that in mind, to do what he asked, there would need to be a way to separate the elements and their controlling components, or at least one line side of them, which is how I ended up wording my post the way I did.

I think we all have different ideas of what the OP has.

The only electric water heaters I have hooked up that 'alternate' elements are home units.

As this is three phase I take it to be a commercial unit which in my experience will run all the elements at the same time when needed.

 

[rattus]

Nameplate info

Nameplate info

We have an installation to connect a three phase water heater. the unit has two 4500 watt elements inside. We are to connect three legs of the incoming three phase with the center leg connected as a "common" between the two elements. What is the calculated amperage load for each leg if operated at 208 volts?
If this were single phase, then the center leg would be the sum of the other two legs. But with three phase power, shouldn't the "three phase factor" (1.73) be involved in the calculations for the "common" conductor?

John

Yes, the common current would be 1.73 times the current in the other legs. That is, Ic = 1.73(Ia + Ib), where "C" is the common leg.

Can you supply us with the nameplate info on the water heater so we can come up with exact numbers?

 

[Smart $]

I think we all have different ideas of what the OP has.

The only electric water heaters I have hooked up that 'alternate' elements are home units.

As this is three phase I take it to be a commercial unit which in my experience will run all the elements at the same time when needed.

I concur with sceepe...

If it were a three phase water heater it should have three elements.

If it is to be wired 3? in "open delta" configuration, what would be the advantage over 1?? It would certainly be a costlier installation, as 'stiff mentioned. Perhaps the manufacturer made wiring optional so one can balance panel loading

From this point, I'm with rattus...

Can you supply us with the nameplate info on the water heater so we can come up with exact numbers?

 

[iwire]

I concur with sceepe...

The only person posting to this thread that has actually seen the unit said it's three phase.

As I don't have the power to see through the Internet yet I figured I would take their word for it.

But as long as you say it's not three phase it must be the fact. :grin:

 

[Smart $]

The only person posting to this thread that has actually seen the unit said it's three phase.

As I don't have the power to see through the Internet yet I figured I would take their word for it.

But as long as you say it's not three phase it must be the fact. :grin:

Ummm... a good indication was the OP/thread title?three phase power to single phase water heater :wink:

 

[kbsparky]

More information needed here ...

More information needed here ...

We have an installation to connect a three phase water heater. the unit has two 4500 watt elements inside. We are to connect three legs of the incoming three phase with the center leg connected as a "common" between the two elements. What is the calculated amperage load for each leg if operated at 208 volts?....John

The first question I would ask here is are the elements rated for full output at 208 Volts or are they 240 Volt rated elements that are intended to be connected to a 208 Volt supply?

Most 4500 watt water heater elements are 240 Volt rated, and when connected to a 208 Volt source will operate with approx 25% less output, producing about 3375 watts.

 

[iwire]

Ummm... a good indication was the OP/thread title?three phase power to single phase water heater :wink:

Maybe some smoke was in your eyes...:grin:

First line of the OP.

We have an installation to connect a three phase water heater.

So unless the OP provides some more info we are left guessing.

 

[hardworkingstiff]

So unless the OP provides some more info we are left guessing.

True, but since it has only 2 elements, it sure doesn't sound like a 3-phase unit.

The OP and title give conflicting opinions on whether it's single-phase or 3-phase. IMO, the 2 elements indicate it is single-phase. Loading the common conductor (to the 2 elements) does not seem to be an effective method of using 3-phase.

 

[diopmarilyn@bellsouth.net]

Water Calculation

Water Calculation

You Take 4500*3= 13500w
And You Dvide By 360v.=37.5a Since These Water Heater Came With 3sets 37.5*3=112.5a At125%=140.625a Required 150a Cb.

Corect Me If I Am Wrong

 

[LarryFine]

360 volts?

 

[hardworkingstiff]

You Take 4500*3= 13500w
And You Dvide By 360v.=37.5a Since These Water Heater Came With 3sets 37.5*3=112.5a At125%=140.625a Required 150a Cb.

Corect Me If I Am Wrong

From the OP:

....the unit has two 4500 watt elements inside

So I would say you take 4500*2 = 9,000 VA, not 4500*3.

IF the water heater came with 3 elements, then you could take the 4500*3 to come up with a total connected 3-phase load of 13,500 VA. IF the unit was rated 208-volts (not having 240-volt elements) then you could take 13,500 VA and divide by (208*1.732, aka 360) to get the 37.5-amps. This would be the total connected load for the water heater. You do not multiply by 3 because you already did it at the beginning of the calculation.

37.5*125% = 46.9-amps. 50-amp CB.

 

[frenchelectrican]

May i step in i think i got some info what the OP been asking for and i will provide the link here http://www.hotwater.com/lit/spec/com_elec/A2130.pdf

this link it is in PDF format so when you get to the info on second page it will be on lower right corner on this sheet it will tell you the two verison of it

Merci , Marc