Power fluctuations when discharging Powerwall?

Power fluctuations when discharging Powerwall?

We recently had two Tesla Powerwall2 batteries installed under a program with Green Mountain Power (GMP) in Vermont. GMP (heavily) subsidizes the batteries, but retains the right to discharge the batteries to generate power for the grid (e.g., at peak times).

Last Tuesday and Wednesday, our batteries were discharged by GMP for the first time. On Tuesday, our gas furnace went out – the flame sensor (wrongly) indicated there was a flame when there was no flame, which leads to the furnace to shut down (the furnace provides heat and hot water for us).

I think this sensor glitch in the furnace may have been caused by fluctuation in power in the home when the discharge started. I cannot be sure that this was the cause, because I don’t know exactly when the furnace went out. (The clocks and other appliances in the house were apparently unaffected.) We had a technician check the furnace and he found no problems that would explain the sensor glitch.

Are power fluctuations normal when discharging the battery like this? Or is this perhaps a symptom of a problem in the installation?

Is there anything we should do to monitor this issue? Or do I need to buy a power conditioner for the furnace?

cwied | 16 ottobre 2018

I have never noticed any issues with the power when the Powerwalls discharge. It would seem unlikely that the Powerwalls would cause the problem since you're still connected to the grid and the Powerwalls should sync with the grid power. I wonder if it was a grid issue.

markbraukman | 20 ottobre 2018

My TV is connected to a power conditioner (to regulate voltage and supress surges to the TV) which displays the current voltage. When I'm on utility power or when the PW2s are providing power to the house and the utility power is up but not providing any power to the house, the conditioner shows 120-122 volts. BUT, when the utility power went out (all neighbors houses were dark), and I was running solely on the PWs, the voltage showed 115. That drop in voltage didn't affect lights or clocks, but the power conditioner shut down and a UPS I have for my computer started beeping. I reported this to Tesla service and they asked me to take a picture of the conditioner when up and when there is no power. So far, the utility has stayed on, so I can't finish the task.

cwied | 21 ottobre 2018

@markbraukman - you could just flip the main breaker to your house to see the same thing, couldn't you?

markbraukman | 26 ottobre 2018

@cwied: I could be wrong, but as I watched the electricians install the system, the gateway is between the utility source and the main house breaker. It determines where the house gets its electricity (Solar, battery, utility or any combination). If I cut the house breaker, the house gets no power from any source. If I cut power to the gateway...I'm not sure what would happen. I don't want to have to reset clocks to see. I'm guessing that the gateway needs some juice from the utility to properly regulate volts to the house.

Patrick | 27 ottobre 2018

@green - congrats on being part of this interesting project in Vermont! Have read about it - seems like a great approach to accelerate the adoption of both residential solar and storage.

We don’t have PW2s yet so I can’t offer suggestions or comparisons, but would love to hear more about how things are going with the overall program. When time permits can you share any other observations good or bad so far?