I bought a house about 7 months ago with a 2 ton geothermal "waterfurnace e-series" system.  It's the kind that takes water out of one well, and dumps it in another well after it's done with it (whatever that is called..I have 2 wells for this).  System works fine for both heating and cooling my ICF 2,400sqf bungalow (including basement).  - But everytime the system turns on (about 4-5 times an hour), the lights in the house dim a little bit for less than a second.  - I'm on a 200amp standard service.... what gives??

I'm trying to size a generator for backup purposes (I live in a rural area and would like to have backup in case power ever goes out, which seems to happen frequently here).  I've done the math for all my other electrical needs, but I can't seem to find anywhere or anyone that knows what the SURGE (startup) power needs of this system are! 
My total monthly electricity usage is about 700kw ... averaging roughly 20kw per day.

The waterfurnace folks said they did not know!!! LAUGH! ... The service guy said "maybe up to 20amps, but not sure".

I just need to know peak power usage in watts so I can get the proper sized generator.  I was looking at a stand-by 15kw one, but I'm not sure if that will be enough to start it up.  - I've read on a green-power web site that these things can take up to 30kw to starup... but I find that a bit much!

If anyone here in this field has the competency to answer this, you will be saving me a lot of headaches!!


Thanks,
Patrick

Look at the nameplate on the heat pump. How many amps is the LRA? That should suffice for what you need to know.

There's a whole bunch of data on a pink sticker on the unit;

Compressor VAC 208/230
PH: 1
RLA: 12.2
LRA: 66.0

Blower: 208/230 Min Amp 60
Loop Pump: 208/230 Min Amp 60
DSH Pump: 208/230 Min Amp 60

Unit Voltage: 208/230
HZ: 60
PH: 1
FLA: 22
MCA: 25

I'm not an electrician... what does this mean in terms of KW ? .. And is this operating or startup load?

I don't think the reason for the dimming lights is what the furnace draws but rather how the lights and furnace are wired or not wired.  I'm not a electrician but I've seen some really stupid wiring jobs because that switch or box was easy to get to and every electrical wiring change went to that box, and caused the same problem you described. 

PatrickG26,

Ask your electrical power company to check the transformer feeding the wires to your home. On one of my homes I had a dimming problem that was partially cleared up by increasing the transformer size.

Well I am not so concerned with the lights dimming.  I only refered to this to illustrate why I thought my geothermal furnace used quite a bit of startup "power".

Again, I don't seem to be able to get an answer... All I want to know is how big a generator I should buy.  My peak "startup" usage for everything else in the house is less than 5kw.  I just need to be able to add the geothermal waterfurnace system to the list to get a total count.  So far, I've heard from various sources, anywhere from 3kw to 40kw and everywhere in between.  Why is it so hard to find this out lol!

I just don't want to go out and buy a 10kw generator simply to find out it won't start my furnace.

Shouldn't all 2 ton waterfurnace e-series systems use the same amount of power?

I have a gaurdian 15kw natural gas backup generator. It runs my 3 ton geothermal heat pump and water pump, as well as a good portion of my home needs. For $2,500.00 on ebay, its worth every penny and works fine. However it does not run my electric backup, I have fireplaces for that, however there is room for a 5 kw electric strip heater.

Email me if you would like more info, I will do what I can to provide.

Mark Ross

From the Guardian: Make sure the surge capability (Amps) of the generator is greater than the LRA listed on the data plate of the A/C before purchasing.

You can replace 'A/C' with any product that uses a motor. A Guardian 13kW has a Surge Amps of: 95.

LRA = locked rotor amps, the highest possible current draw condition for a motor. 66.0 x 230 = 15,180 watts, or 15.18 Kw. But that current only lasts for a very short time. Most generators can handle a surge well in excess of their running load capacity. Look for a generator that is rated for continuous duty at the highest expected full load you will have on it, plus a reserve. Then make sure it has the surge capacity to handle all of the running load except the heat pump, plus the startup load of the heat pump.

Running load for the heat pump will be on the order of 12.2 x 230 = 2.8 Kw plus the fan load.

HTH,

EXACLY what I needed guys.  Thanks a billion!  So I will buy a generator with peak 20kw and I should be laughing

Pat