What could be causing my HVAC secondary circuit to keep blowing a fuse after the AC Compressor ran for 10 hours?
Yes its a short. I've seen a weakening component cause that but 99% of the time its a short. Look where your control enter your o.d. unit. The wires can rub on the metal where the small hole is for the wires to go through. If your o.d. unit has any low voltage wires inside where the piping to the compressor are, look there. A low or high pressure switch may be installed and the low voltage wires inside can rub on a copper line causing an intermittent short. Look anywhere a low voltage wire can touch anything , other than intended points. If its a component then you may end up with new parts all over and still have a short. The control wires can get damaged by varmits in the attic, crawl space, and where the wires go through the wall or sophet. To isolate it may take a pile of fuses or a transformer with a micro-breaker can be installed. Basically has a 3-5amp micro breaker that trips and can be reset. If you were to remove all control wires leading to the o.d. unit, start the cooling, and it shorts then your short is not at o.d. unit. With o.d. control wires wired in at the ahu, disconnect the low voltage wires from the o.d unit. Cycle cool and if it shorts, the wire between is the cause. If it don't short, then you know its at the o.d. unit. At the o.d. unit, if it has any low voltage safeties(low pressure, high pressure, delay timer, ect...) you can maybe bypass all to allow the contactor to be the only component wired in the low voltage circuit at the o.d. unit. And if it shorts keep chasing it. Bugs and geckos can get behind circuit boards causing a short. Ants in any components can cause a short. Hard to help more from here. Above all, work safe!
Jun 22, 2015 |