Float Switch problems in powerpack

[DavidM]

We recently had a float switch go bad in one of our hydraulic power packs. I purchased a replacement from Sonny's and it failed quickly (a few weeks). Ordered another one and the same thing happened. I thought maybe they were a bad batch or bad design so I ordered a different one from Grainger's. Same problem again.
They fail by not shutting off the motor in the event of fluid loss. They work properly when installed but shortly after they no longer sense a low level condition. If I pull them out and slide the float by hand, there is no response, it doesn't shut down the powerpack like it should.
We are using a water based fluid. The original switch lasted many years.

Does anyone have any ideas?

David

 

[Washmee]

It sounds to me like you have a problem somewhere else. Have you done a simple continuity test on the float switch? Is there power flowing to the switch?

 

[DavidM]

I have done a continuity test on the float switch. There is power there. The float fails by not opening the circuit when the fluid level falls too low. The powerpack continues to run. If I didn't have power, the unit would shut off.

David

 

[Washmee]

I have done a continuity test on the float switch. There is power there. The float fails by not opening the circuit when the fluid level falls too low. The powerpack continues to run. If I didn't have power, the unit would shut off.

David

How is it wired? It sounds like yours is setup to interrupt the motor starter for that power pack. If so have you checked that connection?

Mine are wired in to the start/stop system for my DRB controller. If the level drops too low, the switch goes to open and acts the same as hitting a stop button. Adding more fluid resets the switch to a closed position and the wash runs again. Or I can override the switch through the software.

 

[MEP001]

There may be too much current draw through the switch and it's arcing the contacts closed.

 

[bigdadioofthepatio]

in my experance for float switchs to go bad that quick you are running to much current though them. Check to make sure the float switch is rated for the amp draw you have

 

[Washmee]

Float switches are designed to act as an interrupt for the control circut that turns on the motor starter for the hydraulic pack. Most of the time this is either a 24v or 110v system. If you are using 240v, that could be the problem. If you leave the switch unwired with the leads not touching, does the pump still run?

 

[DavidM]

I'll double check the voltage and amp draw. Maybe I made a mistake there.

With the float disconnected the pump does not run, if I connect the wires bypassing the float it runs, that is how I determined the problem to be with the float switch only.

 

[Nomoreusmc]

There may be too much current draw through the switch and it's arcing the contacts closed.

So your saying he welded the contacts of the switch closed? Ouch! Is the solution to get a big rely and have the float trigger a big amp rely?