ScottO

whole house generator

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2500 sq feet, Minimally to only run the well and the furnace during the winter when we are gone.  Would appreciate the ability to have lights, no stove or dryer needed.  So what size do you think I could get away with?  12k?, 9k?  what have you used?  This will be propane with a dedicated tank as we have no gas at the house at this time.  Might consider a propane kitchen stove if we take the leap.  Scott

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Depends on the hp of the well pump, but 9K might be enough. The 12 would probably take you up to a 1 hp pump. 

 

Its not the running watts, but the starting on any inductive load. 

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May also depend on what kind of furnace you have.  Since it sounds like you are looking for a fully integrated system to work while you are away, you'll need switching gear integrated with your panel, and I think a separate/ sub panel that only has what is on the generator.  I would think anyone qualified to do such an install could run the numbers for you and size it appropriately. 

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I run a 3/4 hp pump on 8k with no problem.  I think when I looked at start draw it needed something over 5k.   You might get 1hp to start on 8k but would be with no other load.   Iirc rule of thumb for draw to start was 3x running.  

 

One thing I’m wondering about is whether new boiler with electronic controls are going to like generator current.  Some apparently don’t. 

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standalone with auto transfer switch. The transfer switch is bulk of expense. I would think Your looking at 12kw depending upon furnace and pump.

i run a 5kw with manual switch. It has my lights, outlets, fridge, pellet stove and fios on it. I filled tank before going to work and it was still running when i got home, 14 hours with wife and 2 kids.

Edited by Dave588

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Budget allowing, always get a little more than you think you need. As pointed out, transfer switch and installation labor are both a large part and effectively a fixed cost. 

 

For any electronics, including boiler controller, consider either a surge suppressor or even a small uninterruptible backup battery with integrated surge suppression. With the latter, the battery will supply continuous current to control circuit and internal surge suppressor will smooth out any spikes. You don’t need a big UPS nor really sophisticated controls.  

 

FWIW, in CT we had 22KW Generac which was used several dozen times over the years, that is cycled on and off to the house. During Sandy, given grid damage and the slowness of LP deliveries, I would manually shut it down at night and restart in the morning, for over a week. Never had any issues with furnace controller nor any other circuits, and I did not have UPS on those. 

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I considered solar with comm backup and generator 2nd backup. Split phase inverters stack on each other with load sharing, fallback to comm, generator start and lvdc all built in.

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On 3/19/2018 at 2:10 PM, big popper said:

volts divided watts = Amps  

I think you got it backwards; watts / volts = amps, comes from -----> P=IV (power = amps * volts). This is good for estimating roughly but really only works for resistive single phase loads. 

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On 3/31/2018 at 8:19 AM, ijuanaspearfish said:

9k if your utilities will allow it.

It's the initial startup of the items that gives you the biggest draw. 

This is the correct advise.  Start up amps with a house that has two fridge's and a separate freezer is much different that just running a hot water pump and one fridge

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