Garage Heater in basement

Mark12198

Hello,
I recently removed my oil fired hot air furnace due to a cracked heat exchanged and installed a ducted heat pump system. It works great and I am very happy with it BUT I do have a concern about backup heating. I have a portable gasoline powered generator and a hookup to the main panel but the generator breaker is only 30 amps and the heat pump compressor uses a 50 amp breaker and a 15 amp for the air handler. Throw in a few lights and a fridge and I do not think the genrator is up to the task. I would like a heating source in case of power failure. Ideally propane because it stores well. I would also like it to be vented via the chimney that the old oil burner furnace use to use. I am concidering putting in one of those propane modine style vented heaters in my basement. They draw very
minimal power and blow a good amount of hot air. My house is 1100ft2 ranch with closed cell foam insulated basement walls. 6’6” ceiling. I spoke with the heaters technical support and they say the 8’ clearance underneith is so cars do not hit it. Located on cape cod. The basement ceiling is not insulated so I figure the heat would rise and keep the house somewhat warm.  Thoughts? Code problems? Foam catch fire? Other options?

Jamie Hall

You have just discovered one of the downsides of electric heat of any kind. It takes a really big generator to manage when the power goes off.

Check your clearances to combustibles -- like the floor and joist -- very very carefully. And check with your fire marshal and building inspector. And home insurance people.

Also check the chimney with them. It might need a stainless steel liner for the gas appliance.

It might be OK.

There are, however, a number of gas heating stoves of one kind or another which are a little more decorative and a little less industrial, also venter, which you might consider.

EdTheHeaterMan

Garage Heater in basement

Everyone knows that garage heaters only work in garages!

Next thing you will see is someone trying to heat the living room with a water heater.

WMno57

Mark12198 said:

I have a portable gasoline powered generator and a hookup to the main panel but the generator breaker is only 30 amps and the heat pump compressor uses a 50 amp breaker and a 15 amp for the air handler. Throw in a few lights and a fridge and I do not think the genrator is up to the task.

I agree most portable generators are probably not up to the task, but to more accurately figure this out, determine the starting and running watts the generator is rated to deliver. As a general rule of thumb, two horsepower per kilowatt. So a 10 horsepower generator can deliver 5000 running Watts. Or 2500 watts on each leg in the panel. Any 240 volt appliance would draw from both legs equally.
The 50 amp breaker sounds oversized for just a compressor. Does your heat pump have emergency heat from electric resistance heat strips?
Electric motors that start under a load require higher starting watts than running watts. Examples would be a well, fridge, and heat pump. Resistance loads like lights and electric resistance heat have no additional starting watts requirements. Starting and running watt requirements for these are the same.
A large portable generator can run a small heat pump or central AC. Yet another reason not to oversize an air conditioner.
No matter what you do, you should have several CO detectors throughout the house.

pecmsg

WMno57 said:

Mark12198 said:

I have a portable gasoline powered generator and a hookup to the main panel but the generator breaker is only 30 amps and the heat pump compressor uses a 50 amp breaker and a 15 amp for the air handler. Throw in a few lights and a fridge and I do not think the genrator is up to the task.

I agree most portable generators are probably not up to the task, but to more accurately figure this out, determine the starting and running watts the generator is rated to deliver. As a general rule of thumb, two horsepower per kilowatt. So a 10 horsepower generator can deliver 5000 running Watts. Or 2500 watts on each leg in the panel. Any 240 volt appliance would draw from both legs equally.
The 50 amp breaker sounds oversized for just a compressor. Does your heat pump have emergency heat from electric resistance heat strips?
Electric motors that start under a load require higher starting watts than running watts. Examples would be a well, fridge, and heat pump. Resistance loads like lights and electric resistance heat have no additional starting watts requirements. Starting and running watt requirements for these are the same.
A large portable generator can run a small heat pump or central AC. Yet another reason not to oversize an air conditioner.
No matter what you do, you should have several CO detectors throughout the house.

Depending on the heat pump system breakers are sized for minimum and maximum amperage.

That generator will only start a very small HVAC compressor or possibly 2-Ton inverter system.

WMno57

Hi Pecmsg. I was hoping you would weigh in on this. @Mark12198 has not told us the size of his generator. The 10 horse was my example. But my question for you is, what's up with that 50 amp breaker? Heat pumps are as uncommon as palm trees in my neck of the woods. 12F coming tonight. If a heat pump does have heat strips, could those be wired to a separate breaker? Should they?
I once started my old central AC (not inverter) on my 16KW Generic. Dimmed all the lights.
Thanks.

Jamie Hall

I believe the OP said that the generator breaker is 30 amps. If so, and the heat pump takes a 50 amp breaker, the generator simply isn't going to start the heat pump, although there is a chance that it might keep it running. Most circuit breakers (there are exception) are standard or fast trip, and must be sized to handle the starting, not running, current of rotating machinery. In his case, the generator breaker will likely trip. @WMno57 's comment on dimming lights starting a small AC is to be expected. Theoretically that 16 KW generator will keep it running (and I dare say it did!) but it simply isn't big enough to maintain voltage with a starting surge (and very likely not frequency either, but that's usually not a big deal).

As a sort of general rule, assuming all your breakers and fuses are sized to the loads or wiring properly, you simply don't want a smaller breaker between a larger one and the power source if you are planning to use the equipment protected by the larger breaker. That's not to say you can't have a generator with a 30 amp breaker plugged into a 200 amp service -- just that you shouldn't attempt to use equipment requiring the higher amperage when running the generator...

EdTheHeaterMan

WMno57 said:

Hi Pecmsg. I was hoping you would weigh in on this. @Mark12198 has not told us the size of his generator. The 10 horse was my example. But my question for you is, what's up with that 50 amp breaker? Heat pumps are as uncommon as palm trees in my neck of the woods. 12F coming tonight. If a heat pump does have heat strips, could those be wired to a separate breaker? Should they?
I once started my old central AC (not inverter) on my 16KW Generic. Dimmed all the lights.
Thanks.

Many of the larger residential heat pumps (3.5 to 5 ton) have a 60 to 100 amp service cable feeding the air handler. That service cable is then distributed to two or three 50 amp or smaller double pole breakers that connect to different stages of resistance heat. Only one of the sub breakers will have the control transformer (220 VAC to 24 VAC) connected while the other ones feed the resistance heater only, thru the sequencer(s).

It's all quite confusing to those not familiar with control circuitry.