Originally Posted by
zombie
Yes. You would use watts and amps readings to determine a dead return. High amps readings indicate a stalled pump. Low wattage readings indicate a broken impeller, loss of load (no water flow but not stalled), or failed winding. This is the code I use for my 25W, 0.3A return with a startup time of 6 seconds (I have tools to test that. Assume 10 seconds for yours).
A stalled motor will generate 2-6 times nominal current, but this will also occur during startup for the startup time. As a result, it's a good idea to lock out the return and send an alert if current exceeds 1.5-2 times nominal current for at least 1.5 times the motor start time (in my case I use 0.5A with a delay of 10 seconds). A significant failure in the impeller that loses load will typically reduce wattage to zero, but can be as high as 25% of nominal. This can also be confused during motor start, so the same delay is applicable to this as well.
PumpFail (virtual outlet)
Set OFF
If Outlet Return Watts < 13 Then ON
If Outlet Return Amps > 0.5 Then ON
Defer 000:10 Then ON
Defer 000:05 Then OFF
When On > 000:02 Then ON
Return
(Other code)
If Outlet PumpFail = ON Then OFF
The last defer and the when statement locks the PumpFail outlet to manual ON so that it stops the pump until I manually reset the VO before additional damage can be done to it.
You might be an engineer if...You have no life and can prove it mathematically.
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