Generator for all electric home

[JimPghPA]

One of the things to keep in mind is that if you run a 240 Volt water heater on 120 Volts the current draw will be 1/2 of the normal amount. Also because both the current draw and Voltage are 1/2 the Wattage draw will be 1/4, and it will take 4 times as long to heat the water. If you do this be sure to still include the original water-heater thermostat in the circuit so you do not risk overheating the water and having a steam explosion.

Better yet would be to get a propane water heater.

 

[SilverFusion2010]

Originally Posted By: Donald
Originally Posted By: Astro_Guy
What is the LRA (Locked Rotor Amperage) rating on the nameplate of the heat pump you want to run? This is the momentary inrush current needed to start the compressor. The RLA (Running Load Amperage) should also be listed on the nameplate, and it will be a small fraction of the LRA. Don't be surprised if the LRA exceeds the capacity of the breaker that protects the unit because we are talking about a momentary load.

When starting an inductive load, such as the compressor on a heat pump, the voltage will drop momentarily which results in more amperage at the same level of power output from your generator. I've read that covering 70% of your LRA load is considered acceptable for commercial applications, and that homeowners might be able to push that figure closer to 50%.

The bottom line here is that you are going to need to perform a load calculation, and that inductive loads like heat pumps cannot be treated the same way as resistive loads like a water heater or electric range. Installing a large, stationary generator is not normally a DIY project, so have some pros help you with this.


I understand the load concerns of starting an electric motor. But my real concern is when the electric booster coils kick in. It's all integrated and I am not sure there is any control of when it kicks in the booster coils.



Sure there is. The heater strips will be wired on their own breaker. Turn it off

 

[Astro_Guy]

Originally Posted By: Donald
Well riding out the storm will probably mean powering the first floor heat pump and it's electric booster coils if it's less than 30F.

The old 30F rule really doesn't apply to modern heat pumps. Modern units will happily run down into the teens and beyond without the need of the backup heat strips. The bigger problem with the modern heat pumps is that they may run the heat strips in defrost mode. It's going to be difficult for anyone to take this discussion much further without knowing the specifics of this heat pump, including model numbers of both the indoor and outdoor units. You might want to get that information and then take your question over to [URL='http://www.hvac-talk.com']www.hvac-talk.com[/URL] where you will find a lot of pros who install both HVAC systems and generators.

BTW - since you mentioned right up front that there are two gas fireplaces already installed, do you really need to worry about heat? It might be worth testing this before dropping 20k on a whole house generator.

 

[WyrTwister]

[/quote]

Sure there is. The heater strips will be wired on their own breaker. Turn it off [/quote]

If you have resistance heat strips , most likely the control transformer & fan in the furnace is 240 VAC . Be careful not to turn of the Circuit Breaker serving it .

Best I remember , at the unit , 60 amp fuses or CB will be the largest over current protection to an individual heat strip . For example , on single phase 240 VAC a 30 amp CB commonly feeds a 5000 watt strip & 60 amp feed a 10000 watt strip . This could be feed by a 90 or 100 amp CB & wire .

Defrost heat could be an issue . If it is , try to wire the controls to run only the smallest heat strip .

Our 2 ductless Mini Splits do not use defrost heat . Another consideration for MS's .

Best wishes ,

 

[meep]

You'd be better off first converting one of the heat pump to a gas furnace or gas auxiliary and ditching the heat strips. Then you also have the benefit to run whichever fuel is cheaper for the season. AND then you don't need a ridiculously large generator which will eat you alive if you ever have to run it in fuel use.

If you are riding out a storm, it doesn't have to be at 72F either. 55F is plenty to keep the pipes from freezing and doesn't require as much energy. Or run a space heater in the one room you're camping out in. It's all about how much fuel you need and can store...

-M

 

[WyrTwister]

Correct .

Best wishes ,

 

[jonnied1]

Originally Posted By: Donald
Originally Posted By: Astro_Guy
What is the LRA (Locked Rotor Amperage) rating on the nameplate of the heat pump you want to run? This is the momentary inrush current needed to start the compressor. The RLA (Running Load Amperage) should also be listed on the nameplate, and it will be a small fraction of the LRA. Don't be surprised if the LRA exceeds the capacity of the breaker that protects the unit because we are talking about a momentary load.

When starting an inductive load, such as the compressor on a heat pump, the voltage will drop momentarily which results in more amperage at the same level of power output from your generator. I've read that covering 70% of your LRA load is considered acceptable for commercial applications, and that homeowners might be able to push that figure closer to 50%.

The bottom line here is that you are going to need to perform a load calculation, and that inductive loads like heat pumps cannot be treated the same way as resistive loads like a water heater or electric range. Installing a large, stationary generator is not normally a DIY project, so have some pros help you with this.


I understand the load concerns of starting an electric motor. But my real concern is when the electric booster coils kick in. It's all integrated and I am not sure there is any control of when it kicks in the booster coils.


My electric backup coils are on a separate 50 amp breaker. The Heat Pump and fan motor are on another 50 amp breaker. I just turn the breaker off for the heat coils when I run on generator in the winter. My 15 KW Generac handles everything I throw at it but the backup coils.

 

[Donald]

Originally Posted By: JimPghPA
One of the things to keep in mind is that if you run a 240 Volt water heater on 120 Volts the current draw will be 1/2 of the normal amount. Also because both the current draw and Voltage are 1/2 the Wattage draw will be 1/4, and it will take 4 times as long to heat the water. If you do this be sure to still include the original water-heater thermostat in the circuit so you do not risk overheating the water and having a steam explosion.

Better yet would be to get a propane water heater.


Water heater is propane. So not 100% electric.

 

[Donald]

I asked and received from the power company a history of outages in my neighborhood.

Now to analyze.

Looks good. None in 2015/2016. Otherwise 2 per year.

Maybe I can ignore all the equipment related ones as they are short duration. Focus on the weather related ones. My concern is not an isolated wire or pole, but a 100 wires and poles down from a storm. As less populated areas get fixed latter than dense population.

Rethink the generator.

 

[jhellwig]

You have the propane fireplaces so that is a good base heat. You could get by with just running the heat pump part of the unit and not the electric heat part. You could probably make it on a 15kw unit and still have plenty to keep the fridge and freezer going.

 

[Al]

Originally Posted By: jhellwig
You have the propane fireplaces so that is a good base heat. You could get by with just running the heat pump part of the unit and not the electric heat part. You could probably make it on a 15kw unit and still have plenty to keep the fridge and freezer going.

And again..just remember 10KW sucks down 2 gal gasoline/hour.

 

[JimPghPA]

I had a uncle who lived in up state NY (Rochester). I think it was 1991 that they had an ice storm that knocked down the power lines to just about everyone. He was without power for 2 weeks. After 2 weeks his neighbor got power and he ran an extension cord from his neighbors house until his power was back on.

BTW, in order to get by during the electric power outage he connected garden hose to his hot water heater and ran it through all the rooms in his house. This kept the house hot enough to prevent the pipes from freezing.

After that ice storm he installed a coal burning stove including lightning protection (which done right cost quite a bit), and a automatic back up generator.