Generator size for geothermal

[6fthook]

We're getting an interlock kit setup for our panel and we're figuring out what generator size that we need to run our geothermal. We also have a well pump, 80gal electric hot water, refrigerator, chest freezer, and LED bulbs throughout; but they can be turned on independently if the generator is not big enough.

The specs of the geothermal are (I can take a pic of the sticker if needed):
- 5 ton unit
- RLA 27.1
- LRA *152.9
- 208/230 V
- Minimum circuit amps 46.6
- Max fuse 70a

It has the GeoStar Intellistart so according to them it cuts down the surge LRA to 30%.

My calculations are:

152.9 x 230 = 35,167 watts to start
35,167 x .30 = 10,550 watts to start with intellistart

27.1 x 230 = 6,233 watts running

Am I correct with these numbers? We were planning on a Champion generator 9,200 run/11,500 surge and hopefully thats enough to run the geothermal along with the other stuff also. If it's not then maybe in the future a Generac 15,000run/22,500 surge but it's double what we can spend on a generator.

Thanks for any advice you can provide!

 

[theoldwizard1]

I would go with the 15K unit, maybe even the Generac 17,500 kW. Even then, you should make sure that the water heater and freezer are not starting at the same time.

LRA = Locked Rotor Amperage is the "worst case" starting. It can happen when a compressor tries to start and fails and does not have enough time to relieve the head pressure before trying to start again.

For an "all electric" house you want to make certain that your backup is big enough

 

[kwschumm]

We had a six ton geothermal heat pump and IIRC it would have taken a 25kw unit to meet FLA startup requirements. Instead we bought a 14kw unit and bought a bunch of space heaters.

 

[LS6 Tommy]

You don't use LRA to figure generator sizing. You need to calculate your inrush current.

Tommy

 

[Bardini]

So what size of the generator did you buy for your geothermal

 

[mike93lx]

Edit... Just saw this is from 2016....

Do you often lose power or is this for infrequent use? For infrequent use, sacrifices can be made like only running the water heater when absolutely necessary. That alone will eat up a massive amount of power.

How do you intend to fuel this? If gasoline, it is going to burn a lot (could be a gallon an hour) so you'll need to consider storage as well

 

[Tduby]

Edit... Just saw this is from 2016....

Do you often lose power or is this for infrequent use? For infrequent use, sacrifices can be made like only running the water heater when absolutely necessary. That alone will eat up a massive amount of power.

How do you intend to fuel this? If gasoline, it is going to burn a lot (could be a gallon an hour) so you'll need to consider storage as well

There should be a tag put under your name for people who ask questions then never follow up with what they did.

 

[AP514]

There should be a tag put under your name for people who ask questions then never follow up with what they did.

I totally agree a Half Assed tag.
(A Donkey with the Body cut into two halves and a red X over the front half)

 

[jeepxj]

There should be a tag put under your name for people who ask questions then never follow up with what they did.