I don't see how it would work and have never heard of this. I always thought they used them because they were cheaper to make and still got the job done.
In over 90% of the cases where single pole contactors are used to operate the compressor there is no crankcase heater on the unit.
Originally posted by ricm
Been around a few years, I'm wracking the single brain cell left... maybe Bornriding can explain the exact science of that.... or mayby NormChris...
Support the claim, just don't repeat it.... I'm listening.
The primary use of a single pole contactor is to save money on the cost of the contactor.
Think the path of least resistance.....When the contactor pulls in the heater is in paralell with a higher resistance than the contactor so power will not flow through it.when the contactor opens the heater is the only complete circuit so power has to go through the heater and motor windings.The heater is not drawing power/heating when the compressor runs.
Originally posted by special ed
On older systems they wire the CCH to both sides of the buss bar on single-pole contactors thereby making a complete circuit.
I still don't understand how that's supposed to work....
Take your time & do it right!
I'll subscribe to the theory as I've mentioned earlier in this thread. Likely the best reconing of the reasoning or engineering of the single pole contactor is... the cost saving gig.
Simply put. One less screw to hold the cabinet togeather, on several thousands of units... will pay the engineer's mortgage.
I'm still trying to work out the suggested use of the run/or start windings as a surrogate crank case heater, as the windings don't have a complete ciruit or partial circuit to generate the heat.
I tried to sample the amperage on both legs of the contactor today, and if one was 'warming the start/leg or Run leg/ I would have gotten more than .01 amps....
Both report nearly nil in current draw. And if you pack of bastards were trying to pull a fast one...... Ok, ok... you GOT ME!
Teach the apprentices right... and learn from their questions and ideas.
Ok, maybe they now use one-poles for financial reasons instead of crankcase heat. But crankcase heat was its original purpose so I was taught.
But someone please explain why old Lennox units used to use
two compressor run capacitors in parallel rather than one run cap. I think some Trane units did this also, but not sure.
I was taught that this had to do with crankcase heat also, along with the one pole contactor.