What is a "start motor"

[dznf0g]

That is the motor starter that is inline with the start capacitor?

What does it do, and is it normal for it to be pretty warm during A/C operation?

[daveswenson]

My guess is that it's a PTCR. The doohickey that disconnects the start capacitor once the motor gets started.


Stolen from modmyrv.com in a blog about hard start capacitors.

This capacitor has an electronic disconnect and provides about twice the current boosting power as the factory start capacitor. If your A/C doesn’t have a seperate boost capacitor as shown in the pictures above, it’s likely that the run capacitor doubles as the boost capacitor, and also has a Positive Temperature Coefficient Relay (PTCR), a fancy term for the way the capacitor is removed from the circuit once the motor starts. The PTCR is prone to failure which can cause the capacitor to fail, and thus make the compresor motor startup current demands very high or not able start at all. This is the reason Supco makes an electronic version of the PTCR. It is much more reliable and is integrated in to the capacitor packaging.

[dznf0g]

Since the Penguin 13.5 heat pump A/C has a run capacitor and a start capacitor, it wouldn't have a PTCR, would it? See schematic.

[daveswenson]

Originally Posted by dznf0g

Since the Penguin 13.5 heat pump A/C has a run capacitor and a start capacitor, it wouldn't have a PTCR, would it? See schematic.

Maybe PTCR is not the correct terminology, but the hard start replacement cap has an electronic disconnect that corresponds to the schematic. Here's the link to the source of my limited knowledge.

RV Air Conditioner Hard Start Capacitor | ModMyRV

[dznf0g]

Thanks, Dave...my knowledge is limited on this subject as well. So, based on another post on RV.net, if I replace the start capacitor with a Supco SPP6E, with the electronic version of the PTCR, the "start motor" (PTCR) should be removed from the circuit along with the old failing start capacitor?

[daveswenson]

Originally Posted by dznf0g

Thanks, Dave...my knowledge is limited on this subject as well. So, based on another post on RV.net, if I replace the start capacitor with a Supco SPP6E, with the electronic version of the PTCR, the "start motor" (PTCR) should be removed from the circuit along with the old failing start capacitor?

That's my understanding. But I'd make sure that the Supco was the correct size for your unit.