Lightning strike, well pump box failed

[Valveman]

It's possible to measure voltages above line voltage in circuits containing VFD's or reactive elements (capacitors, inductors).

Yeah upping the 240V to 370V on the run leg is just what a run capacitor is supposed to do.

VFD's are a different story. You would need an RMS meter to read the voltage. But a 240V pump running on a VFD see's about 1000V spikes. It is a pulsing DC voltage trying to simulate an AC sign wave. Just can't chop the pulses off at 240V and they hit 1000V at the top of each sign wave. The longer the wire down the well the more voltage the motor sees, which is called a "reflective wave" or "ringing". These 1000+V spikes from a VFD greatly shorten the life of the motor and wire, which has insulation for 600V max.

 

[ponytug]

@WoodChuckDad In the FWIW category

If you are curious about capacitors, and the differences between "start capacitors" and "run capacitors", and why run capacitors tend to require at least 370V ratings for a 240V circuit.
There is a nice (I thought) summary here;

Start and Run Capacitors for Electric Motors - Alabama Cooperative Extension System

Before replacing any motor on the farm, check the motor capacitors. A producer can save up to 90 percent by replacing motor capacitors rather than “bad” motors.

www.aces.edu

(I got curious about how you came to have 370V on a pump lead while running. (240V*(2)^1/2)*1.1 ~=370 (voltage times the square root of 2 times a 10% safety factor))

All the best,

Peter

 

[WoodChuckDad]

@WoodChuckDad In the FWIW category

If you are curious about capacitors, and the differences between "start capacitors" and "run capacitors", and why run capacitors tend to require at least 370V ratings for a 240V circuit.
There is a nice (I thought) summary here;

Start and Run Capacitors for Electric Motors - Alabama Cooperative Extension System

Before replacing any motor on the farm, check the motor capacitors. A producer can save up to 90 percent by replacing motor capacitors rather than “bad” motors.

www.aces.edu

(I got curious about how you came to have 370V on a pump lead while running. (240V*(2)^1/2)*1.1 ~=370 (voltage times the square root of 2 times a 10% safety factor))

All the best,

Peter

Thank you. Gonna dig into this after I work on the fence for a bit.

 

[WoodChuckDad]

The 60 PSI Cycle Stop Valve will regulate on the high side of about 64 PSI. If the kitchen sink keeps the pump running continuously at 69 PSI, the pressure gauge could just be off by 5 PSI. I would just tighten the large screw in the pressure switch so the pump shuts off higher than 75 PSI according to that gauge. Maybe all it is.

My concern with that, is the 80 PSI safety relief valve. Setting for 70 was already getting kinda close.

 

[steve tym]

OP, you really should check the air charge in your tank.
My VFD driven well pump has been in for 18 years. It runs my domestic water, my geothermal heat pumps and irrigation.

 

[etpm]

For folks who may be worried about capacitor voltage ratings, because they can be confusing, the voltage rating of a capacitor can be higher than specified but never lower. Capacitors can be rated at a DC voltage or an AC voltage. The capacitor will usually have printed on it that it is rated at so many volts AC or DC. Sometimes starting capacitors, which are only for AC motors, will nevertheless have a DC rating. The capacitor will have printed on it, for example, 200 volts DC. This all gets confusing and I have seen capacitors blow up because they were installed according to their DC rating. It's stupid, I know. So, to avoid problems, if the cap just has a voltage rating and doesn't specify AC or DC just assume DC and multiply the AC voltage by 1.6 for the proper DC voltage rating. So if you have a 220 AC volt motor look for a cap with a voltage rating higher than 352. 370 volts is a common cap voltage. You would be safe with the 370 volt rating. Some AC motors will have starting caps that just go across the one leg of the 220 volt supply and so the caps will have a lower voltage rating. When shopping for a new cap don't worry if you can't find a cap rated for about 200 volts, just go with the 370 volt caps. The higher voltage rating just makes the cap more robust, it does not change the starting characteristics, the motor will start just the same with a higher voltage rated cap.
Eric

 

[Valveman]

My concern with that, is the 80 PSI safety relief valve. Setting for 70 was already getting kinda close.

Take the cap off the pressure relief valve and you can tighten the adjustment screw to make it work at higher pressure.

 

[Valveman]

OP, you really should check the air charge in your tank.
My VFD driven well pump has been in for 18 years. It runs my domestic water, my geothermal heat pumps and irrigation.

18 years is a good run for a VFD. I have seen some last 30 years. The ones that last that long help extend the average life to like 3-5 years, taking into account all the VFD's that didn't last a year or even a month. To get a VFD pump system to last a while the controller needs to be in a clean and cool environment, the control and power wires cannot be crossed, the drop wire needs to be as short as possible, all the parameters need to be set correctly, and many other things need to be correct. Even then they are temperamental to lightning, dust, and other things. Many VFD's do not even maintain constant pressure. I am currently helping a couple people with a Goulds Solo2 and a Pentair PID, and neither will hold a constant pressure. Many VFD's have a "bump feature" or just cycle on/off every minute or so because of the complexity of figuring the minimum frequency required for each different system. That is just one of the many ways VFD's do not function as you would think they should, on top of a high cost and high failure rate.

Then if you find a brand of VFD that has lasted a few years, that model will no longer be available. New model VFD's come on the market as fast a new cell phones. Each new model promising to have solved all the problems associated with the previous models. I have been waiting for more than 30 years for them to solve all the problems with variable speed pumps and controllers. I quit holding my breath long ago. In the meantime I continue to sell Cycle Stop Valves to solve the problems people have with VFD's and large pressure tanks.

But if I was still in the pump business I would sell a VFD to anyone who ask for it. Mad customers spend a lot of money keeping VFD systems working. Happy customers never call the pump man.

 

[steve tym]

18 years is a good run for a VFD. I have seen some last 30 years. The ones that last that long help extend the average life to like 3-5 years, taking into account all the VFD's that didn't last a year or even a month. To get a VFD pump system to last a while the controller needs to be in a clean and cool environment, the control and power wires cannot be crossed, the drop wire needs to be as short as possible, all the parameters need to be set correctly, and many other things need to be correct. Even then they are temperamental to lightning, dust, and other things. Many VFD's do not even maintain constant pressure. I am currently helping a couple people with a Goulds Solo2 and a Pentair PID, and neither will hold a constant pressure. Many VFD's have a "bump feature" or just cycle on/off every minute or so because of the complexity of figuring the minimum frequency required for each different system. That is just one of the many ways VFD's do not function as you would think they should, on top of a high cost and high failure rate.

Then if you find a brand of VFD that has lasted a few years, that model will no longer be available. New model VFD's come on the market as fast a new cell phones. Each new model promising to have solved all the problems associated with the previous models. I have been waiting for more than 30 years for them to solve all the problems with variable speed pumps and controllers. I quit holding my breath long ago. In the meantime I continue to sell Cycle Stop Valves to solve the problems people have with VFD's and large pressure tanks.

But if I was still in the pump business I would sell a VFD to anyone who ask for it. Mad customers spend a lot of money keeping VFD systems working. Happy customers never call the pump man.

Did you really just suggest he override or modify one of the safety systems?

 

[Valveman]

Did you really just suggest he override or modify one of the safety systems?

I don't think so. I believe you were talking about this quote instead.

Take the cap off the pressure relief valve and you can tighten the adjustment screw to make it work at higher pressure.

Adjusting the pressure relief valve higher as needed is normal operation. With a 55/75 pressure switch setting I would adjust the prv up to 90 PSI. But it is important to not adjust the prv to a higher pressure than the pump can build.