Help with this circuit.

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Twoskinsoneman

Twoskinsoneman

Senior Member
Location
West Virginia, USA NEC: 2020
Occupation
Facility Senior Electrician
Would someone explain to me what this part (that I circled) of the control circuit is for? Can't seem to figure out it's purpose.
vacuum%20pumps.jpg
 
petersonra said:
it just makes both pump stay on once PS2 is made until PS1 is not made. Otherwise as soon as PS2 turned off again the secondary p mp would shut off right away.
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I really appreciate the response.
I think it does make sense after pondering it. When vacuuming the system for the first time (or I guess anytime thereafter that the system was allowed to lose it's vacuum) there's really no good reason to shut off the second pump until PS1 threshold is reached.
Thanks
 
If one pump would fail, the second pump would still be started by P-S2 but stopped by P-S1. But if say M1 motor overload had tripped then you will be left with alternating cycles that start/stop with P-S1 one cycle and P-S2 the next cycle.

It could run that way indefinitely unnoticed unless you maybe connected an hour meter to each pump and monitored them to see that they are getting approximately the same run time.
 
kwired said:
If one pump would fail, the second pump would still be started by P-S2 but stopped by P-S1. But if say M1 motor overload had tripped then you will be left with alternating cycles that start/stop with P-S1 one cycle and P-S2 the next cycle.

It could run that way indefinitely unnoticed unless you maybe connected an hour meter to each pump and monitored them to see that they are getting approximately the same run time.
Click to expand...


A good point. They don't have meters and run infrequently in an unoccupied area. Little chance such a failure would be noticed.
 
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