HELP! Run Capacitor size for Duo Therm 13.5k p/n57915.331

First, Thanks for posting the detail information on what you're working on.

Page 14 HERE should be your wiring diagram or close to it.

If a plastic capacitor is what exploded, those are usually START capacitors for the Compressor, not the RUN capacitor as you first asked.

According to the Diagram, your unit has a Dual FAN/HERM (Hermetically Sealed, meaning Compressor) RUN Capacitor. Its values should be marked on it and they'll be close to what Fred said. Case should be metal, little SPAM can with three sets of terminals on it: FAN, HERM, COM (Common)

Diagram says a Start Assist may or may not be present. If it doesn't have one, it should, and it should be a smart kit such as SUPCO SPP6e. The setup the diagram shows (if it's there) is a cheapo using a PTCR (Positive Temperature Coefficient Resistor). The PTCR is supposed to get the Start Cap (usually plastic cased). The better kits use electronics to drop the Start Cap out, and will work better with your generator.

Start Assist Capacitor runs more like 100-mfd. Think of the compressor like the engine in a car and Run Capacitor as it's ignition. Start Cap like the starter motor and PTCR like the Start position of the Ignition Switch. Once the engine (compressor) starts, the starter (100-mfd plastic start cap) has to get out of play, and the PTCR (per your diagram) lets go of the "Key." Like a car starter, bad things happen if the Start Cap doesn't get out of circuit.

Can you get pix of the Capacitor(s) and the Wiring Diagram?

The fan motor normally takes a 5 mfd capacitor. Even if you had a 3 or 4 or 7.5 MFD the 5 can replace it, and it will work.

The compressor can be anything from 35 to 50 Mfd. You what one of those to be 'close' to the right size, not off by more than about 5 mfd.

I have seen home capacitors in the 70 mfd range, but this one should be 35-50.

For a 120 volt compressor, a 370 volt rated capacitor is used.

Good luck,

Fred.