6KW water heater

Status
Not open for further replies.

gaelectric

Senior Member
I have a storage tank/heater for geo thermal system that has a 6KW element for backup on the heating system in case it gets really cold. Or so it was explained to me by the geo thermal installer.

My question is if this unit can be connected with a 30 amp 240 volt circuit. There is no actual nameplate on the unit just an element with the 6KW rating.

This also is on a backup generator so the element would probably run any time the power was out as the compressors don't.
 

iwire

Moderator
Staff member
Location
Massachusetts
6,000/240=25 amps

I would likely go with #8 and a 35 amp circuit breaker but that assumes I would hook it up at all without a label.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Wouldn't he need to take the 25 amps and multiply by 125%? I assume you did it but did not show it. Now it is 31.25 amps so a #10 will not be sufficient. You can use a 35 or 40 amp breaker
 

iwire

Moderator
Staff member
Location
Massachusetts
Wouldn't he need to take the 25 amps and multiply by 125%? I assume you did it but did not show it. Now it is 31.25 amps so a #10 will not be sufficient. You can use a 35 or 40 amp breaker

Not enough info for me to say for certain that this unit is covered by 422.13. I think it may be and that is why I moved up. I know that 24 amps is 80% of a 30 amp circuit so I moved up to a 35 amp breaker which necessitates bumping up the wire size as well due to 240.4(D). :)
 

gaelectric

Senior Member
I guess the thing does not have a nameplate because it typically does not have an element installed. It's a storage tank. So it could have any size element put in according to the installers discretion.

There is a sticker that says to refer to the rating on the element for determining.

I see now that no matter if you go with the 80% of 30 amps or you go with the 125% from 420.13 it still needs a #8CU and a 35 or 40amp breaker.

Just wasn't thinking clearly and hoping for a little easier and less expensive install.

Thanks for the input.
 

under8ed

Senior Member
I would suspect the installer is missing some paperwork or equipment. How can the control components be properly sized for "any" chosen size element? A closer look into the systems controller may reveal a relay dedicated for this.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
I would suspect the installer is missing some paperwork or equipment. How can the control components be properly sized for "any" chosen size element? A closer look into the systems controller may reveal a relay dedicated for this.


It sounds odd but maybe this element is a separate piece of equipment
 

iwire

Moderator
Staff member
Location
Massachusetts
There are very important safety issues to consider when heating water in a sealed vessel. I would not connect it without firm direction from the vessel manufacturer. Things like high limit and a T&P valve are critical.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
There are very important safety issues to consider when heating water in a sealed vessel. I would not connect it without firm direction from the vessel manufacturer. Things like high limit and a T&P valve are critical.


I would only think this would be a non-sealed vessel as I agree with you. You cannot just install any element size unless they have some proprietary setup thaty can limit the element size. Odd that there is no nameplate-- that is why I was thinking a separate element in an open container but that should odd also
 

kwired

Electron manager
Location
NE Nebraska
They are already heating the water with the heat pump - likely already have a T&P relief valve. HI limit for heat pump source is probably taken care of with the heat pump unit and a sensor on the line, but hi limit for electric heat elements I do understand can be just as questionable as the heating elements or control thermostats themselves.

I have never seen a setup like this that didn't just use a typical 4500 watt water heater or a tank only that is preheated by the heat pump and then is in series with another water heater (usually 4500 watt electric unit). This way if the heat pump doesn't run for some time because of nice weather you still have hot water, but the supply is preheated by waste heat from heat pump so you at least only need to raise temp a few degrees instead of 50-70 degrees depending on your incoming water temp.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
I think we have this all wrong. My guess is the 6kw are the elements for the blower in the furnace as a backup for when the water source heat pump cannot keep up. I don't understand the storage tank part.

There is a label on the unit but it has to be scratch off for the correct size elements that are installed. This is the best I can do with this scenario
 

kwired

Electron manager
Location
NE Nebraska
I think we have this all wrong. My guess is the 6kw are the elements for the blower in the furnace as a backup for when the water source heat pump cannot keep up. I don't understand the storage tank part.

There is a label on the unit but it has to be scratch off for the correct size elements that are installed. This is the best I can do with this scenario
You could be right, but it is common to heat domestic water with geothermal heat pumps. If not using any customized tank for the purpose - they just use a standard water heater, take the drain cock out and replace with a tee so you can still drain it but the other outlet from the tee circulates through a refrigerant coil in the heat pump that is in the hot gas section of the refrigerant circuit and is then circulated back to the usual cold water inlet - which also has a tee with cold water inlet/ heat pump return coming into it. They do put a thermostat on the circulating line so if the water temp is already above a certain level it shuts off the circulating pump so it doesn't continue to dump heat into the tank. Any heat not absorbed by this hot water circuit is dumped into the usual condenser and either put into the home when heating or transferred to discharge water or to the ground loop depending on what kind of geothermal system is being used. During cooling season you essentially get free hot water if you don't use it faster then the heat pump can heat it - which makes it even more cost effective to use a two tank system and dump heat pump heat into the preheat tank and let the second one be the typical electric or even gas heated tank - with pre heated water that only needs just a little rise in temp instead of full rise from incoming water temp.
 
Status
Not open for further replies.
Top