contactor confusion

[Giwatcher]

20 yo heil package unit, NOT a heat pump, contactor is humming, not loud, but I thought the contactor was on it's last legs. It still works, but in checking I noticed it is a 2 pole 40a/24v. The oe replacement parts list shows a part number for a single pole, 35a, 24v. If I simply go by the originally installed part, I would use a 40a 2 pole part. Would there be harm in using a single pole 40a/24v part, because the parts list says ssingle pole? If using a single pole, does it matter what wires are hooked to the shunt vs the pole, since nothing works till both legs are energized?
Also, for an uncomplicated hvac with no accessories hooked into the system, why have a 2 pole contactor in the first place? are single pole/2 poles contactors sometimes interchangeable?

 

[Fitter30]

Sometimes manufacturers use a single pole contactor because they saved a nickel. Somethings they wire a crankcase heater across the working contact so when contact is open there's power across heater. If it doesn't show a heater doesn't matter if you wire it one or two.pole. Take a pic of the diagram if you have any questions. Contactors humm from rust building up on the laminate core where the two matting surfaces touch. Just replace the contactor and fix would be short lived. Take a pic of contactor for where the wires go.

 

[Sponsor]

 

[Giwatcher]

20 yo heil package unit, NOT a heat pump, contactor is humming, not loud, but I thought the contactor was on it's last legs. It still works, but in checking I noticed it is a 2 pole 40a/24v. The oe replacement parts list shows a part number for a single pole, 35a, 24v. If I simply go by the originally installed part, I would use a 40a 2 pole part. Would there be harm in using a single pole 40a/24v part, because the parts list says ssingle pole? If using a single pole, does it matter what wires are hooked to the shunt vs the pole, since nothing works till both legs are energized?
Also, for an uncomplicated hvac with no accessories hooked into the system, why have a 2 pole contactor in the first place? are single pole/2 poles contactors sometimes interchangeable?

 

[Giwatcher]

Helpful, thanks. What do you mean replacing the contactor is short lived? Do you think something is causing the oe contactor to fail?

 

[Fitter30]

Helpful, thanks. What do you mean replacing the contactor is short lived? Do you think something is causing the oe contactor to fail?

Meant trying to repair old contactor is a waste of time.

 

[Giwatcher]

understood. Thanks.

 

[shieldcracker]

About 30yrs ago mfg began to phase out 2 pole contactors in residential units with 1-1/2 pole contactos; ask the bean counters why. The 2 pole contactor is superior and since you all ready have a working unit with one installed I would replace it with the same type.

 

[Giwatcher]

agree, thank you.