Author Topic: Well pump with Cycle Sensor running off whole-house backup generator  (Read 111 times)

JEG in Raleigh

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I have a 1 hp Grundfos submersible pump supplying my house.  I have a CSV installed and just recently installed a Cycle Sensor.  Everything works great.  When my well pump kicks on, The Cycle Sensor shows it drawing approximately 9 amps and that gradually drops down to between 5.5 and 6 amps over then next 30 seconds.  I also have a Generac Centurion 16kw whole house backup generator that was installed last year.  Our house is very energy efficient....built to Passivhaus standards.  It's 1-story, 2400 square feet and has a 2-ton seer 17 two-stage heat pump.  It also has an electric water heater.  The stove is gas, but the dryer is electric.  So the big electric draws are the heat pump, water heater, well pump and periodically, the dryer. 

The generator has an automatic whole-house transfer switch that engages when utility power is lost.  This switch has HVAC load-shedding capabilities built into it, and you can add up to 8 more load-shed modules to it if you need to manage loads from other appliances/equipment.  Our generator installation is a little unusual in that our meter and service disconnect are remote and about 100' away from the house, and the generator is right next to that remote pedestal.  As a result, wiring the HVAC load-shed module requires trenching about 100' from the generator over to the outdoor unit of the HVAC, and I have not done that yet.  So at this point, the HVAC load-shed feature is not yet up and running.  I knew going in that this generator was not going to be able to handle starting the HVAC if the well pump or water heater were running, and likewise, I could not use the water heater or well pump if the HVAC was running.  I will be setting up the load-shed feature for the HVAC and will add a load-shed module for the water heater.  Until then, if we lose power, I need to switch off the HVAC breaker manually before running the well pump or the water heater, and if I need to run the heat pump, I need to flip the breakers for the pump and water heater.

So....we lost power for the first time since the generator install, for about 5 hours, last week.  I immediately turned off the water heater breaker and the HVAC breaker.  The only other electricity draws in the house at that point were the 2 refrigerators, 1 small chest freezer, and a half dozen LED lights.  Reminder, the generator is 16kw.  Also, the locked rotor amps of the HVAC system is 52, and the rated load of the combined HVAC outdoor unit, air handler, and ERV is 18 amps.  The locked rotor amps of the well pump is 48, and the rated load is 9.8 amps. With the HVAC system and water heater off, the only significant electrical draw on the system was the well pump, with a worst-case starting amperage of 48 amps.  The refrigerators, if running at the time, drew a maximum of 13 amps.  The lights, maybe 4 amps.  So the total draw on the generator before the pump kicked on was 17 amps at 120 volts = 2040 watts.  When the pump kicked on, if it drew all 48 LRA, that would be 48 amps x 240 volts = 11,520 watts.  So the total draw on the generator, in the worst case, would have been 13,560.  Sorry for the need for all the background info. 

I wanted to see what happened when the well pump kicked on.  I opened a tap and ran the water until the pressure switch turned the pump on.  At the instant the pump turned on, I watched the amperage indicator on the Cycle Sensor, and it was around 9.5.  To this day, I have never seen that spike above about 9.5....certainly never near 48, but maybe that spike happens so quickly that it doesn't register on the Cycle Sensor.  Anyway, as soon as the pressure switch engaged, all the power in the house, that now was being supplied by the generator, went out for about 10 seconds. The generator stopped running.   The pump did not kick on, and the Cycle Sensor LED's went out.  Then, after about 10 seconds, I heard the generator running again and the power came back on and the Cycle Sensor lit up at 9 amps, and the pump started running, and everything was working again. 

QUESTION:  Do you have any idea what happened?  I'm concerned about that happening each time the pump comes on under generator power.  Would the Cycle Sensor have anything to do with what I experienced?  I have not yet talked to Generac.  I wanted to rule out the Cycle Sensor having anything to do with it.  Thanks for any insights anyone can provide on this.
« Last Edit: February 08, 2020, 07:57:32 PM by JEG in Raleigh »

Cary Austin

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Re: Well pump with Cycle Sensor running off whole-house backup generator
« Reply #1 on: February 09, 2020, 06:59:39 AM »
Cycle Sensor has nothing to do with it.  The generator should not stop and then come back on?  When there is too much load the breaker on the generator should trip, but the gen set should keep running?  Probably has something to do with the automatic operating controls on the generator.

JEG in Raleigh

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Re: Well pump with Cycle Sensor running off whole-house backup generator
« Reply #2 on: February 09, 2020, 10:02:46 AM »
Thanks.