# New standby generator shut down briefly when well pump came on



## JEG in Raleigh (Feb 9, 2020)

Newbie here....first post. I have a Generac Centurion 16kw whole house backup generator that was installed last year. I also have a 1 hp Grundfos submersible pump supplying my house. 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. I have a pump-saving device on my well-water system called a Cycle Sensor, and it has a window that displays the number of amps being drawn when the pump is running. 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: Does anyone have any idea what happened? I'm concerned about that happening each time the pump comes on under generator power. I have checked with the Cycle Sensor manufacturer, and they say the Cycle Sensor would not have affected anything. I have not yet talked to Generac. Thanks for any insights anyone can provide on this.


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## drmerdp (Apr 10, 2018)

I appreciate all the background info. The devil is in the details. 

So the 48 LRA of the well pump isn’t very high at all, I would absolutely expect your standby unit to handle that starting load no problem even with the hot water heater running. 

Your cycle sensor is a nice piece of monitoring equipment but I wouldn’t expect it to display inrush amps properly. It happens for a fraction of a second. The only way to properly measure inrush is using a clamp multimeter with an inrush function. Max min memory is also useful. Klein has a inexpensive hvac clamp meter that would be perfect for you. This would require working around hot wires, so use caution or have a pro come in to check it. 

Standby generators use a fixed orifice jet for fuel metering. They come ready to run with a 2 position adjustment. One position for NG and one for LPG. I’m not sure what your elevation is but you may want to read up or contact generac about the possibility of air density causing improper fueling. To lean of an air fuel ratio and the engine will struggle with sudden loads.


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## Melson (Dec 8, 2019)

I agree with drmerdp (need clamp-on with inrush function; locked rotor shouldn't be a factor), including the nice job of detailed background info - something that definitely helps put things into proper context. 

I would like to further consider drmerdp's interesting thoughts about the fueling: This is an NG fed unit? If so, is it possible the regulator isn't reacting or maintaining proper pressure?
Another thought: Is it possible the set was shutdown via GFI protection? I was involved in a similar situation that randomly tripped a 600 amp bkr. So I'm just throwing it out there. Or maybe a quick (meaning one or two cycles) over voltage spike?

As a starting point, I'd want to recreate the scenario as faithfully as possible. I'd want to positively verify our locked rotor assumptions, for one thing. I'm definitely with drmerdp that this is no factor - but... I'm a skeptic by nature, want to rule out assumptions. 

By manually recreating the scenario you can control situation, add loads in a controlled fashion, while monitoring all the good stuff (engine mechanical and electrical performance).

so I'll add that my friends 22kw NG generac has worked flawlessly for three years. While generac wouldn't be my first choice, I've been impressed with this air cooled twin's performance; his house can nearly fully load the unit, and it doesn't seem bothered by how hard we hit it with loads.


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## JEG in Raleigh (Feb 9, 2020)

Thank you both for your replies. 

We are only 300' above sea level, so altitude is not an issue. the generator is fueled by natural gas. 

Some additional info.....my nephew worked for Generac in Wisconsin, and I got an employee-discount deal on my generator and transfer switch. When I received the generator, I contacted a few Generac dealers in our area to do the installation, and none of them would give me the time of day since I did not buy the generator from them (subsequently, I have found a great Generac-authorized service guy, who has been very helpful with a different problem of my own making that I had, unrelated to this current issue). Anyway, a neighbor of mine had bought a second-hand Generac whole-house generator and had a local electrician and a local plumber do the installation. I used those same two subcontractors to install my generator. When we tried to start the generator for the very first time, the starter cranked, but the generator would not start. The plumber checked the gas pressure coming off the regulator and it was correct. At that point, since I had not used a Generac dealer to do my install and the gas guy had done everything he should have, I figured it was my problem, and I would have to try to get a Generac dealer to come out and troubleshoot the starting problem. Naturally, the same dealers who did not want to help with the install did not want to help with the troubleshooting. But, it was through this episode that I did finally find the Generac-authorized service guy who has been very helpful. He talked me through troubleshooting over the phone. At first, we tried several things to no avail. Then he said, "under the control panel is a connector and cable that runs the stepper motor that controls the throttle and sometimes that is not fully seated when it comes from the factory" and sure enough, when I reached under there and pushed on that plug, it snapped and seated into place and the generator then started right up, and everything worked properly. Once the generator was able to run, the electrician came back out and went through the start-up checklist in the installation manual, and everything worked properly and the voltage outputs were correct. But, I never had the plumber come back out to do any further checks on the gas. The service guy I now have is able to do complete tear-downs and rebuilds of the equipment, and knows everything about these machines. He can definitely troubleshoot any fuel metering issues. 

I guess the first thing I should do is try to recreate the situation I experienced the other day by manually operating the transfer switch. I just read through the manual's instructions on how to do this correctly and safely, so I'll give that a shot, and if I have the same problem again, I'll give Generac tech support a call.


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## tabora (Sep 6, 2018)

JEG in Raleigh said:


> I guess the first thing I should do is try to recreate the situation I experienced the other day by manually operating the transfer switch. I just read through the manual's instructions on how to do this correctly and safely, so I'll give that a shot, and if I have the same problem again, I'll give Generac tech support a call.


Just remember to wait the amounts of time specified in the manual for the timers to expire before moving on to each step in the process. Many people have been frustrated by trying to rush things!


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## iowagold (Jan 22, 2020)

send over the make and model numbers on the automatic whole-house transfer switch and the HVAC load-shed modules.

so how are they making the load shed?
the ats is at the 100 feet from the house right?

so what are they using for the load shed control?
is it rf or hard wire?

and are the load shed modules 2 piece?
one on the load center in the house and the other at the gen?

what size of wire is ran from the 100 foot pedestal to the house??
100 is a long run for sure... wow!

yea time for a fluke or Sperry clamp meter...

also check for a loose wire clamp.... some thing may not be tight!
kill everything and use a torque wrench...
and if it is aluminum wire make sure they used the protectant on the ends..

hey 100 foot buried cable... hum any chance of it getting nicked or water damage?
if in gray electrical pvc lots of seams!!

or did they use direct bury cable for the 100 foot feeder line from the meter?

and what is the main breaker for the panel?


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## drmerdp (Apr 10, 2018)

On the subject of fuel supply, have you loaded the generator up to atleast 75% load? If it’s a fuel starvation issue, it should be apparent under heavy load.

Be sure to check the vent ports on the demand regulator, if the ports, sometimes tubes attached, are obstructed them the regulator will under fuel.

The engines sucking of air is what pulls the diaphragm open, if the ports are blocked the diaphragm cannot react and you get stumbling, stalling, etc.


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## JEG in Raleigh (Feb 9, 2020)

The model number of the transfer switch is RXSW200A3

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 I have no other load-shed modules yet, One of the attached photos is of the interior of the transfer switch, where you can see the A/C load shed module. 

When the load shed module for the A/C is finally hooked up, I will be trenching 24" deep over to the outdoor heat pump unit, burying PVC conduit, and running a 20 gauge thermostat wire through the conduit from the transfer switch to the A/C unit. This is what my electrician told me to do. The outdoor heat pump unit is right behind the concrete wall in the photo showing the carport. There is a red arrow pointing to where the heat pump unit sits. 

The house is only 3 years old. I'm not sure of the wire gauge running from the pedestal to the panel, but it looks like the cable size running from the utility transformer to the meter base. This was all inspected by the building department and the utility. I'm sure the cable from the pedestal to the panel is the right size. It's in buried conduit. I also measured the distance and it is 80', not 100', FYI.

I can wire light and receptacle circuits.....hook up a water heater.....wire a pressure switch, etc., but I have a healthy respect for electricity and know my limitations. I won't mess with wiring a panel once I get the wires there. I have a Fluke 117 meter, but I don't have the clamp attachment, and I don't think the clamp attachment for the 117 has a peak inrush indicator. I do have an old Amprobe RS-3 analog clamp meter, but it does not have a peak reading indicator either, so I guess I need to get a Fluke 374? Is there anything cheaper out there that will do what I need it to do? I'm not trying to do diagnostics.....just see how high the inrush current is.

Thanks for the tip on a wire clamp......I can check that. The breakers on the disconnect and the house panel are 200 amps. I've attached photos so you can see the setup. When we wanted the remote pedestal, we had to put a service disconnect on the outside of the house, immediately behind the panel (see photo) so if the house had a fire, the fire dept. could easily find the disconnect. They maybe would not have been aware of the remote meter base. So now, there is a disconnect in the transfer switch, a disconnect on the meter base that was there before the generator was installed, a disconnect on the outside of the house behind the panel, and a main breaker on the panel inside the house. Needless to say, I can isolate the panel from any power source. 

I'll never be using a clamp meter that needs accuracy for the sake of diagnosing and repairing motors or electronics......way beyond my capabilities. But, if a cheaper clamp meter will give me enough accuracy to ballpark and inrush surge, please let me know what cheaper brand I should look at.

Thanks very much.


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## drmerdp (Apr 10, 2018)

I have another Klein that does inrush sorta, more of a max memory reading. But this one has inrush specifically. Not too expensive, certainly cheaper than a fluke.

https://www.homedepot.com/p/Klein-T...with-Differential-Temperature-CL450/305415014


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