Will this work? (Two booster pumps for different purposes plumbed and wired in parallel)

[MarsGeo]

We bought a house 25 years ago that came with a well, 5000 gallon storage tank, and a 5hp pump to send water from the storage tank to a pressure tank and the house. (I believe the large pump is required to run the home's fire sprinklers and was required by code.) Everything worked fine until we bought a 14kw Champion Axis home standby generator for our frequent week-long power outages here in the Santa Cruz Mts. If the generator tries to start when the pressure tank is low, the startup-draw of the 5hp pump prevents the generator from starting.

I believe I found an electrical solution: Champion has a Load Management Module, that communicates via powerline and will disconnect the 5hp pump before the generator tries to start. But that will leave us without water when we're on generator power. The solution I'm asking about is:
Can I plumb a smaller pump in parallel with the big one, that will run on either generator power or PG&E. (Tentatively thinking of a 3/4hp pump for our 4-bathroom house that is ~200 ft away from the storage tank and pressure pump).

The new pump wouldn't be under load control, and would be the only pump running on generator power, and it would have its own check valve. Its pressure switch would be set to turn on at say 40 psi, whereas the big pump now turns on at 38 psi. Under normal operation (PG&E power), the big pump would only turn on if the small pump let the pressure drop lower down to 38 psi (which might never happen).

My questions are:
(1) Do you foresee any problems with this plan?
(2) If it turns out that the large pump never turns on, how often should I turn off the small pump to give the large pump a chance to work? It was 7 years old when we bought the house, so now it's 32. I'd like it to operate we ever did have a fire.

Thanks for any tips about this.

 

[Chucky_ott]

I can't answer your parallel pump question but did you contact Champion technical support for more information on the LMM?

Do the LMMs keep the power off permanently or will it periodically retry to see if the generator can handle the load? Maybe once the generator is running, it would be a non issue for the pump to start.

Maybe the solution is to have several LMMs with the priority on the pump LMM set to high and the priority on another device set to low.

Or maybe remove one or more house circuits from the generator load. I think running your water pump, especially if it is used for a sprinkler system, is priority one (along with heat and refrigeration).

Have you checked the current building code to see if the pump requirements are still the same?

Have you checked to see if newer pumps have lower startup draw?

 

[Sponsor]

 

[Reach4]

(2) If it turns out that the large pump never turns on, how often should I turn off the small pump to give the large pump a chance to work? It was 7 years old when we bought the house, so now it's 32. I'd like it to operate we ever did have a fire.

I expect each pump would have its own circuit breaker feeding the respective pressure switch.

Running the fire pump periodically makes sense to me. Maybe make that an annual test, and part of your annual procedure to check the air precharge, and whatever.

 

[Valveman]

Your plan is a good one. I would probably drop the on setting for the 5HP to 35 instead of 38, but it will work. I usually set an exercise clock to turn the pump on for a couple minutes every week.. If you just exercise the 5HP manually I would let it run a few minutes every couple weeks.

 

[MarsGeo]

I can't answer your parallel pump question but did you contact Champion technical support for more information on the LMM?

Do the LMMs keep the power off permanently or will it periodically retry to see if the generator can handle the load? Maybe once the generator is running, it would be a non issue for the pump to start.

Maybe the solution is to have several LMMs with the priority on the pump LMM set to high and the priority on another device set to low.

Or maybe remove one or more house circuits from the generator load. I think running your water pump, especially if it is used for a sprinkler system, is priority one (along with heat and refrigeration).

Have you checked the current building code to see if the pump requirements are still the same?

Have you checked to see if newer pumps have lower startup draw?

Thanks for these helpful suggestions. According to the manual, the load management module checks occasionally with the transfer switch and can re-connect a managed load. The problem is that a 5hp pump draws 15-25kw starting up, and my generator is only rated 14kw. Once I have the load management module wired, it would be easy to test if the generator can handle the startup power for a short time. I did read that some generators can handle short bursts of power that are higher than the generator rating, but the manual for mine doesn't specify this. The house won't be entirely without sprinkler protection when on generator power, because the parallel 3/4hp pump would be powered by the generator.

 

[MarsGeo]

I expect each pump would have its own circuit breaker feeding the respective pressure switch.

Running the fire pump periodically makes sense to me. Maybe make that an annual test, and part of your annual procedure to check the air precharge, and whatever.

Yes, a pressure switch and breaker for each pump.

 

[MarsGeo]

Your plan is a good one. I would probably drop the on setting for the 5HP to 35 instead of 38, but it will work. I usually set an exercise clock to turn the pump on for a couple minutes every week.. If you just exercise the 5HP manually I would let it run a few minutes every couple weeks.

Thanks for your suggestions.