Most A/C thermostats allow enough off-time in their cycling to get rid of actual "Head Pressure." Violate that, by turning Off/On while it's cooling, switching power sources, setting it to Colder right after it's stopped, AND it's unlikely it'll restart with ANY power source. Might even trip the internal temp cutoff in the compressor and not restart till the whole massive part cools down for 15-20-mins or so
This is a case where it'd pay to be sure the 15K A/C has a "hard start" or "start assist" kit on it. Our Coleman 15K has the OEM kit with capacitor and a relay. That's about the best kit. There's a kit called "5-2-1" that claims to approximate a relay but electronically. Many of us use and recommend SUPCO's SPP6e, another electronic start assist. A BTN (not a brand name, but Better Than Nothing) start assist uses a capacitor and a PTCR (Positive Temperature Coefficient Resistor) to get the capacitor out of circuit. It can be done with separate Capacitor and PTCR, where PTCR looks like a ceramic spool, or combined like SUPCO SPP6 (without "e"). They won't help in a short cycle high-head condition. That's because the PTCR has to cool down before the next start attempt or it keeps the assist capacitor out of circuit.
The only way to see if and what an A/C has for stert assist is to look. It might show on wiring diagram/parts list but not have been installed. Could be listed as installed but somebody removed it. Or, not listed and somebody added it. And if it IS there, is it Electronic like 5-2-1 and SPP6e, or simply a PTCR device?
