RV AC 521 compressor saver

Chris Bryant wrote:
Here's the Dometic kit that uses the potential relay for a decent price. This kit should act identically to the 5-2-1 device.

That does look like a 521 kit. I downloaded the installation manuals for Dometic and all wiring diagrams show PTC kits as installed or optional. The 'RV Parts' part number listed is a PTC type with an optional relay. The installation docs say that this circuit may not work in high ambient temperatures. That's what I expected from a PTC circuit and means a small inv-gen will not be able to start the AC when it's hot outside. So, I don't think it's a true 521 circuit. Supco makes an adjustable potential relay that works with all single phase AC's. They also make one that adjusts automatically for 120 or 240 vac operation. Amamzon has this same kit for $107 so, $48.20 is a very good price if it will work. The EasyStart 'smart' unit is looking more attractive the deeper I get into this.