TDOB causing coil failure

[coyote]

I am working on a walk in cooler condenser and the contactor coil keeps failing. It was short cycling so I put a TDOB relay wired between low pressure switch and contactor coil. But now the coil on the contactor keeps failing on contactor not sure what is causing this I removed the TDOB for now . I guess I need to replace the solenoid valve so it will pump down and stay there it must be leaking .

[pecmsg]

Why was it short cycling?

[coyote]

solenoid valve is leaking during shut down

[ammoniadog]

Does it have an adjustable low pressure switch? If so, can you widen the differential? Since Ohio is a relatively warm state, you should be able to get by with a higher cut-in than what I would be able to get away with here in Minnesota.

Try adjusting it so it cuts out at about 5psi, and cuts in around a saturated suction pressure/temperature of about whatever the lowest outdoor temperature is that the thing will see. If this happens to be an indoor condensing unit then you can set the differential even wider to cut in at a saturated pressure/temperature of about 40°F.

As pecmsg said, what's making it short cycle? I kind of doubt it's you solenoid, although it is a possibility. Another possibility would be weak suction valves if it has a reciprocating compressor, or a leaking internal compressor check valve if it's a scroll. If it's a scroll, it's also somewhat common for the thing to "burp" after it pumps down, which can cause a viscous cycle of short cycling too, which can sometimes be helped by widening the low pressure switch differential, or adding the time delay relay.

[coyote]

It is possible the valves in compressor is leaking I haven't tried closing the valve on liquid line to see for sure which is leaking. The pressure switch is fixed. I'm going to order one with a wider range. But I still don't understand why TDOB relay is doing what it is.