Pool heater overload?

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Stevenfyeager

Senior Member
Location
United States, Indiana
Occupation
electrical contractor
A 3800 sq ft all electric house Including 800 sq ft finished basement. They want to add a 50 amp pool heater. Built in the 70 s. I’m concerned about overload. With In ground pool pump already there, should I be concerned? Heater is seasonal I understand, but … ? Thanks
 

tom baker

First Chief Moderator
Staff member
Seems close to me...can always determine existing load see 220.87
Load calcs are very conservative and finding the existing load will be much more accurate
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
A down-n-dirty quick way to check existing loads would be to turn on every load in the house, for sure the stove, if electric, and HVAC. Microwave, irons, bath fans, all lights, etc. Then put your amp clamp on the service wires and take a reading. You can tell pretty quick if you can add a 50A load. Most likely, if the pool heater is a heat pump type, you will seldom reach close to 50A.
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
What are the size of the service conductors and main?
Overhead or underground service?
Whats the nameplate kVA of the pool heater 12kW?
Happy Friday
 

Stevenfyeager

Senior Member
Location
United States, Indiana
Occupation
electrical contractor
my textbook has an all electric house load calculation of a 3200 sq ft all elec house (600 ft smaller) of 249 amps. I'm going to tell the customer to check out a propane tank, gas heater. No natural gas is available there.
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
Seems like a house that size is going to perhaps need a class 320 amp service sooner or later.
 

SSDriver

Senior Member
Location
California
Occupation
Electrician
A 3800 sq ft all electric house Including 800 sq ft finished basement. They want to add a 50 amp pool heater. Built in the 70 s. I’m concerned about overload. With In ground pool pump already there, should I be concerned? Heater is seasonal I understand, but … ? Thanks

This might come into play. Is the heater rated 50 amps or does it need a 50 amp OCPD?

680.10 Electric Pool Water Heaters. All electric pool water
heaters shall have the heating elements subdivided into loads
not exceeding 48 amperes and protected at not over 60 amperes.

The ampacity of the branch-circuit conductors and the rating or
setting of overcurrent protective devices shall not be less than
125 percent of the total nameplate-rated load.
 

suemarkp

Senior Member
Location
Kent, WA
Occupation
Retired Engineer
I would hope this pool heater is a heat pump type. That's expensive enough, resistance heaters for a pool would cost a fortune to run. If a heat pump, its basically a 5 ton air conditioner. Would you hesitate to put a 5 ton AC in a house this size with a 200A service? Pool heaters usually run when the house needs the least HVAC -- if its over 80 outside, the pool heater probably doesn't need to run. If its between 60 and 80, the pool heater runs but the house doesn't need much. Below 60, and it is getting expensive to run the heater and the house needs more heat. All of this doesn't help the load calc since house HVAC usually isn't locked out to the pool heater. But we don't know if the house has an AC unit nor how big it is. Square footage isn't much of a power driver in the load calc unless you're talking a castle.
 

retirede

Senior Member
Location
Illinois
I would hope this pool heater is a heat pump type. That's expensive enough, resistance heaters for a pool would cost a fortune to run. If a heat pump, its basically a 5 ton air conditioner. Would you hesitate to put a 5 ton AC in a house this size with a 200A service? Pool heaters usually run when the house needs the least HVAC -- if its over 80 outside, the pool heater probably doesn't need to run. If its between 60 and 80, the pool heater runs but the house doesn't need much. Below 60, and it is getting expensive to run the heater and the house needs more heat. All of this doesn't help the load calc since house HVAC usually isn't locked out to the pool heater. But we don't know if the house has an AC unit nor how big it is. Square footage isn't much of a power driver in the load calc unless you're talking a castle.

Heat pumps on pool systems are also used to cool the water. I use mine when the pool water exceeds 90F. This usually happens to coincide with the max use of my central air! I have a 200A service and have never had an issue.
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
I have a 1800 SQFT all electric house with a 200A service, if I had a 3200 sq ft all electric house I'd want a 320A service.
 

kwired

Electron manager
Location
NE Nebraska
I have a 1800 SQFT all electric house with a 200A service, if I had a 3200 sq ft all electric house I'd want a 320A service.
Still depends on your load. My house not quite that big but probably not a lot smaller. All electric, 200 amp service. Only 15 kW of backup heat. willing to bet that the demand seldom if ever has gone over 100 amps. Half that area is finished basement with ICF exterior walls and is easy to keep heated/cooled.
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
Good points however I said I'd want it not that I'd need it. :)
A 320Amp meter with two 200A panels gives a nice opportunity to generator back up one of them.
There is really neat house we have serviced for many years, spanning two different owners, that has three 200A panels and a CT meter.
Built in the late 60's, over 5000Sqft for sure, formerly all electric, I am sure the load now is less than ever with LED and more efficient stuff.
But it sure nice to not have to worry about it every time they need to add something like a hot tub, solar or EV car chargers for him and her....
 

kwired

Electron manager
Location
NE Nebraska
Good points however I said I'd want it not that I'd need it. :)
A 320Amp meter with two 200A panels gives a nice opportunity to generator back up one of them.
There is really neat house we have serviced for many years, spanning two different owners, that has three 200A panels and a CT meter.
Built in the late 60's, over 5000Sqft for sure, formerly all electric, I am sure the load now is less than ever with LED and more efficient stuff.
But it sure nice to not have to worry about it every time they need to add something like a hot tub, solar or EV car chargers for him and her....
I did one about 12-15 years ago that was maybe close to 10k SF all electric. has 4-200A mains, 4 200 amp conductor runs to a padmount with CT metering at the padmount. Probably could have gotten away with 600 amp main 400 maybe just a little too small though it probably would be fine most the time until it is extremely cold outside. But it cost less to just do the 4 - 200 amp mains then to mess around with a single larger main then needing wireways, tap boxes, etc. then connect to same four 200 amp panels with mains in them anyway. And kind of have extra capacity from the start, where a 600 amp main maybe would be more limiting should they need to add more load someday.

add: of course things would have to be different under 2020 code as an exterior emergency disconnect would be required. I went straight into the basement with the four lines from the transformer pad.
 
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