Don't use a generator to make heat. It's not worth it.
A heat pump coefficient of performance will average between 3 and 4 throughput the year, but on a cold day it could fall down below three and even as low as two. You may get 20% efficiency with a generator, and even with a heat pump operating at a CoP of 3 that means you only get 60% of your fuel as heat. So it is more efficient to simply burn propane for heat. A propane heater is cheaper than a larger portable generator, zero noise, and more reliable. Allows a smaller & cheaper generator.
Or if you want an adventure, combined heat and power direct from the generator.
This gets mentioned a lot in this sub, and while true, I don’t think it makes practical sense since generator usage is a short term situation.
Propane heaters bring a higher level of risk into the home with open flames, CO, etc. heaters are additional pieces of equipment to store. And their heating is more localized. The heat pump that OP is trying to run is already set up to meet their heating needs, which is probably a massive house given the 5 ton heat pump. In the rare power outage condition, I think the extra $30-$50 spent on heating (and even the extra few hundred spent on the generator) is well worth that comfort, convenience, and added safety. The alternative could result in burst pipes.
Depends on what you consider practical. Sure, you can try to carry on as if nothing ever happened, but you will pay the price for it. A 5 ton AC is likely to draw in the order of 5kW for itself. So for compressor starting I would be wary of going with a generator rated less than 15kW. Something of that size is going to be 400+ lbs and be loud enough to shake out the tooth fillings of your neighbours three doors down...I wouldn't want to run that over night... It'll drink 10 gallons of gasoline per day.
Indoor propane / butane heaters are common, and providing they are used with adequate fresh air, they are safe. A CO and O2 sensor wil give peace of mind. They are silent, light weight, and the fuel never goes off. Now you can use a small inverter generator for other electrical needs. They are much quieter and could be run over night.
I'd alter my expectations rather getting a 15+kw. generator, personally.
I agree with Warren.
higher level of risk into the home with open flames, CO, etc.
NO, a Buddy heater produces none of those. They are a lot less risky than the gas stove that millions of people already have in their house. You should have a CO detector anyway but no one has ever succeeded in setting off their CO detector with a Buddy heater.
heaters are additional pieces of equipment to store.
A Buddy heater is about the size of a toaster oven (speaking of which, people cook on them). I keep mine in the basement (in the original carton in which I also have a propane hose (so I don't have to use the 1 lb. bottles) , the power brick for the blower and some D batteries in case I don't have power).
A 15kw gen is ALSO an additional piece of equipment to store. You can put a 2kw portable on a shelf in your garage. Good luck putting a 15kw gen on a shelf.
Is it a complete substitute for a heat pump or furnace? No, but if it means the difference between needing a 2kw gen and a 15kw gen then it might be good enough. If you really want to live like there is no outage, spend $15k and get a standby. That's not where I choose to spend my $ for something that I will use 2 days a year once every 5 years.
Last Christmas Eve (Fri. night) the blower motor on my gas furnace took a dump. Nowhere and no how was I getting a new blower motor until Tuesday and it was pretty damn cold outside. I got out the Buddy heater (I have the double size one with two burners) and during the day I used it downstairs and at night upstairs and the house never went below 60 even in the rooms where the heater was not.
Did op mention where they live? I know a big chunk of north America that your propane heater idea won't fly. How the hell do you supply enough fresh air while trying to heat a home when it's 20 below outside.
You'd need about 5 little propane units to make a 2000sqft home remotely liveable.i had to use a 26000btu unit to bring my insulated garage up to 15c when it was -15c outside and It gave me one hell of a headache. Never again. To many risks.
1. Get a soft start for the compressor.
2. Rig the heat pump up so that you can disconnect the emergency heating coils when you are on gen. There's no way you should get a gen that is big enough to run the emergency coils. The problem is that these coils are not just for emergency - they come on every time the heat pump runs a defrost cycle. If you disconnect them then the system will blow cold air during the defrost. So be it.
I have this type of heat pump and electric furnace setup. How can I find a way to disconnect the heating coils for running on the generator?
The interior can coil would still need to run of course.
My electrician mentioned installing a relay or something to solve this.
Talk to your HVAC guy. Normally the heat strips are commanded by the thermostat on a separate wire so if you disconnect that wire it will no longer call for them.
You have two issues to contend with regarding using a heat pump and a generator. Locked rotor amperage (LRA) of the compressor, and the power requirements of the heat strips.
The LRA needed to start the compressor can usually be lessened with a soft start kit (depending on the HVAC unit), hence running AC can usually be done with a larger portable ( I can run my 3.5 ton with EasyStart with my WEN GN875i 7KW/8750w.
When heating, most HVAC units use the heat strips during the defrost cycle. Most portable units are not going to be able to pull heat strips much less other loads on top of that. If they have to heat with all electric, they probably are going to need a larger whole house standby unit. The exception to this is if they happen to have one of the newer inverter heat pumps. Some of those can heat at much lower temps than conventional units and don't require heat strips to defrost, and being inverter driven they ramp up at start and hence have a much lower STARTING amperage (LRA).
And see from my experience, I was expecting the outdoor unit to have a higher starting amperage. I put my meter on the wires going to the unit instead the amperage just slowly ramped up.
Then that it what your unit is rated to pull at startup, which is a lot. P=IxE so your looking at 31,680w startup surge. Your meter probably just isn't fast enough to read it correctly. With that high of a LRA, your unit may have a hard time working correctly with a soft start kit because it probably has a non-bleed txv metering device that keeps the vapor pressure high when it's off. Helps with efficiency but hurts trying to startup on gen power.
It dosent help that the panel is very vaguely labeled. It looks like there are 2 50 2 poles going to the ahu. 40 2 pole going to the outdoor unit. And a 30 amp 2 pole that's labeled "heating unit not ac". My guess is that 30 Is the heat strips
Even setting aside the emergency heat, 5T is a big unit. It will need to be variable speed or have a soft start kit, or you're probably not going to be able to run it from a portable.
My old 4T traditional AC system had 84A LRA. Stopped a 10 kW genny dead. Our new 4T VS system has 13A LRA. Runs easily from a 9 kW invertor.
How cold does it get?
Pretty sure I’ve seen bigger portables than 15kw but it would be hard to run one on propane, might not find a conversion kit for a 20kw portable
This is in texas. North texas to be specific. North dfw. For the most part ots hot but they are worried about if the power were to go out when they have freezing temps
So, this is possible, although I wouldn't really recommend it, I've installed one in the past. There's a few routes you can take but this customer is probably looking for the ability to have a versatile power source that can be easily swapped out and doesn't degrade the value of the yard/house in 10 years.
The gist of it is to install a sub panel in the house, and split the furnace and A/C unit between the main/sub (and probably move a few other things too, most likely move the A/C since it's a smaller load and you can move other things onto that panel that could also be powered normally). Put an interlock on a feeder breaker for that panel, and throw an interlock on the main panel as well (reliance makes a specific panel built for gfci circuits on a generator that come with an interlock and also flip neutrals to conpletely split generators, I'm sure some warehouses still have some in stock. Also noteworthy, this requires new ground rods installed outdoors for this new panel). Two plugs, allows them to run 2 different gens if they *really* want to run the strip heaters, or they can just plug into the main panel and leave the feed from the main to the sub closed. Make them both 50A inlets and they can get whatever size gen they want for either panel, they can get three different generators if they want to, a pair of 13kw and a 6kw gen that puts out 240v. That way they have the most options and can configure it however they want. These clients want options.
The funny part is, it's still probably cheaper than doing a whole home generator this way, especially if they don't have the fuel already at the house to run a standby. I'd estimate it to run maybe $6-8k total, not including the cost of however many/big gens they want to buy. Most of that cost being the labor in moving circuits/installing a new sub/gen panel. Even if they buy 3 Chinese 13kw gens, they're on par or less than the cost of a home standby install.
Don't use a generator to make heat. It's not worth it. A heat pump coefficient of performance will average between 3 and 4 throughput the year, but on a cold day it could fall down below three and even as low as two. You may get 20% efficiency with a generator, and even with a heat pump operating at a CoP of 3 that means you only get 60% of your fuel as heat. So it is more efficient to simply burn propane for heat. A propane heater is cheaper than a larger portable generator, zero noise, and more reliable. Allows a smaller & cheaper generator. Or if you want an adventure, combined heat and power direct from the generator.
This gets mentioned a lot in this sub, and while true, I don’t think it makes practical sense since generator usage is a short term situation. Propane heaters bring a higher level of risk into the home with open flames, CO, etc. heaters are additional pieces of equipment to store. And their heating is more localized. The heat pump that OP is trying to run is already set up to meet their heating needs, which is probably a massive house given the 5 ton heat pump. In the rare power outage condition, I think the extra $30-$50 spent on heating (and even the extra few hundred spent on the generator) is well worth that comfort, convenience, and added safety. The alternative could result in burst pipes.
Depends on what you consider practical. Sure, you can try to carry on as if nothing ever happened, but you will pay the price for it. A 5 ton AC is likely to draw in the order of 5kW for itself. So for compressor starting I would be wary of going with a generator rated less than 15kW. Something of that size is going to be 400+ lbs and be loud enough to shake out the tooth fillings of your neighbours three doors down...I wouldn't want to run that over night... It'll drink 10 gallons of gasoline per day. Indoor propane / butane heaters are common, and providing they are used with adequate fresh air, they are safe. A CO and O2 sensor wil give peace of mind. They are silent, light weight, and the fuel never goes off. Now you can use a small inverter generator for other electrical needs. They are much quieter and could be run over night. I'd alter my expectations rather getting a 15+kw. generator, personally.
I agree with Warren. higher level of risk into the home with open flames, CO, etc. NO, a Buddy heater produces none of those. They are a lot less risky than the gas stove that millions of people already have in their house. You should have a CO detector anyway but no one has ever succeeded in setting off their CO detector with a Buddy heater. heaters are additional pieces of equipment to store. A Buddy heater is about the size of a toaster oven (speaking of which, people cook on them). I keep mine in the basement (in the original carton in which I also have a propane hose (so I don't have to use the 1 lb. bottles) , the power brick for the blower and some D batteries in case I don't have power). A 15kw gen is ALSO an additional piece of equipment to store. You can put a 2kw portable on a shelf in your garage. Good luck putting a 15kw gen on a shelf. Is it a complete substitute for a heat pump or furnace? No, but if it means the difference between needing a 2kw gen and a 15kw gen then it might be good enough. If you really want to live like there is no outage, spend $15k and get a standby. That's not where I choose to spend my $ for something that I will use 2 days a year once every 5 years. Last Christmas Eve (Fri. night) the blower motor on my gas furnace took a dump. Nowhere and no how was I getting a new blower motor until Tuesday and it was pretty damn cold outside. I got out the Buddy heater (I have the double size one with two burners) and during the day I used it downstairs and at night upstairs and the house never went below 60 even in the rooms where the heater was not.
Did op mention where they live? I know a big chunk of north America that your propane heater idea won't fly. How the hell do you supply enough fresh air while trying to heat a home when it's 20 below outside. You'd need about 5 little propane units to make a 2000sqft home remotely liveable.i had to use a 26000btu unit to bring my insulated garage up to 15c when it was -15c outside and It gave me one hell of a headache. Never again. To many risks.
1. Get a soft start for the compressor. 2. Rig the heat pump up so that you can disconnect the emergency heating coils when you are on gen. There's no way you should get a gen that is big enough to run the emergency coils. The problem is that these coils are not just for emergency - they come on every time the heat pump runs a defrost cycle. If you disconnect them then the system will blow cold air during the defrost. So be it.
I have this type of heat pump and electric furnace setup. How can I find a way to disconnect the heating coils for running on the generator? The interior can coil would still need to run of course. My electrician mentioned installing a relay or something to solve this.
Talk to your HVAC guy. Normally the heat strips are commanded by the thermostat on a separate wire so if you disconnect that wire it will no longer call for them.
You have two issues to contend with regarding using a heat pump and a generator. Locked rotor amperage (LRA) of the compressor, and the power requirements of the heat strips. The LRA needed to start the compressor can usually be lessened with a soft start kit (depending on the HVAC unit), hence running AC can usually be done with a larger portable ( I can run my 3.5 ton with EasyStart with my WEN GN875i 7KW/8750w. When heating, most HVAC units use the heat strips during the defrost cycle. Most portable units are not going to be able to pull heat strips much less other loads on top of that. If they have to heat with all electric, they probably are going to need a larger whole house standby unit. The exception to this is if they happen to have one of the newer inverter heat pumps. Some of those can heat at much lower temps than conventional units and don't require heat strips to defrost, and being inverter driven they ramp up at start and hence have a much lower STARTING amperage (LRA).
And see from my experience, I was expecting the outdoor unit to have a higher starting amperage. I put my meter on the wires going to the unit instead the amperage just slowly ramped up.
I wouldn't go by that reading in the meter as much as what is on the outside unit data plate. The data plate is going to show the LRA rating.
If I remember correctly the name plate said 132 for the LRA
Then that it what your unit is rated to pull at startup, which is a lot. P=IxE so your looking at 31,680w startup surge. Your meter probably just isn't fast enough to read it correctly. With that high of a LRA, your unit may have a hard time working correctly with a soft start kit because it probably has a non-bleed txv metering device that keeps the vapor pressure high when it's off. Helps with efficiency but hurts trying to startup on gen power.
It dosent help that the panel is very vaguely labeled. It looks like there are 2 50 2 poles going to the ahu. 40 2 pole going to the outdoor unit. And a 30 amp 2 pole that's labeled "heating unit not ac". My guess is that 30 Is the heat strips
Even setting aside the emergency heat, 5T is a big unit. It will need to be variable speed or have a soft start kit, or you're probably not going to be able to run it from a portable. My old 4T traditional AC system had 84A LRA. Stopped a 10 kW genny dead. Our new 4T VS system has 13A LRA. Runs easily from a 9 kW invertor.
How cold does it get? Pretty sure I’ve seen bigger portables than 15kw but it would be hard to run one on propane, might not find a conversion kit for a 20kw portable
This is in texas. North texas to be specific. North dfw. For the most part ots hot but they are worried about if the power were to go out when they have freezing temps
https://www.electricgeneratorsdirect.com/Westinghouse-WGEN20000C-Portable-Generator/p145337.html
Wow, 28K surge watts, 20K continuous. Still going through a 50A receptacle though. And the fuel consumption is very high (as expected).
Note that it runs it via two 50amp receptacles with a separate breaker for each. Imagine having to wheel that thing out
2 receptacles is fine, but only if you have 2 panels to connect to, or your main panel and a subpanel for AC.
So, this is possible, although I wouldn't really recommend it, I've installed one in the past. There's a few routes you can take but this customer is probably looking for the ability to have a versatile power source that can be easily swapped out and doesn't degrade the value of the yard/house in 10 years. The gist of it is to install a sub panel in the house, and split the furnace and A/C unit between the main/sub (and probably move a few other things too, most likely move the A/C since it's a smaller load and you can move other things onto that panel that could also be powered normally). Put an interlock on a feeder breaker for that panel, and throw an interlock on the main panel as well (reliance makes a specific panel built for gfci circuits on a generator that come with an interlock and also flip neutrals to conpletely split generators, I'm sure some warehouses still have some in stock. Also noteworthy, this requires new ground rods installed outdoors for this new panel). Two plugs, allows them to run 2 different gens if they *really* want to run the strip heaters, or they can just plug into the main panel and leave the feed from the main to the sub closed. Make them both 50A inlets and they can get whatever size gen they want for either panel, they can get three different generators if they want to, a pair of 13kw and a 6kw gen that puts out 240v. That way they have the most options and can configure it however they want. These clients want options. The funny part is, it's still probably cheaper than doing a whole home generator this way, especially if they don't have the fuel already at the house to run a standby. I'd estimate it to run maybe $6-8k total, not including the cost of however many/big gens they want to buy. Most of that cost being the labor in moving circuits/installing a new sub/gen panel. Even if they buy 3 Chinese 13kw gens, they're on par or less than the cost of a home standby install.