2 blown starter caps Grundfos MS 402

[gmanj]

Hello.
Looking for some help.
Recently installed MS 402 single phase 1/2 hp submersible pump 3 wire.
It is controlled by pressure switch and motor control box with Starter cap and relay.

When pump was first started the vent on the water tank was not opened. Oops

the water pumped for a short time then tripped the breaker (15Amp 120V)

After this the starter cap was very hot and lost many micro farads. Cap was rated at 250 mfd and was reading 129.

Replaced cap and pump again started but the cap smoked out within seconds.

Tested resistance between leads and had results on all but lower than expected.

Any thoughts?

Thanks in advance

 

[Valveman]

Starting caps and relays go bad because the pump is cycling on/off too much. "Vent on the water tank was not open?" That doesn't make sense, but the tank waterlogging is usually the reason the pump is cycling enough to burn a start cap.

A new start cap getting hot and going bad in a few seconds usually means the start relay is bad and doesn't turn off the start cap after the pump is started.

 

[Sponsor]

 

[gmanj]

Starting caps and relays go bad because the pump is cycling on/off too much. "Vent on the water tank was not open?" That doesn't make sense, but the tank waterlogging is usually the reason the pump is cycling enough to burn a start cap.

A new start cap getting how and going bad in a few seconds usually means the start relay is bad and doesn't turn off the start cap after the pump is started.

Thanks for the reply.
I replaced the motor control box and all seems good now.
Cheers