Transfer Switch Questions

MEXICOWANDERER wrote:
Decades ago when solar was an infant I (plus a crew) installed 46 51 watt panels on eight trackers. A 24 volt system with a 500-ampere mercury filled relay. When a disconnect voltage threshold was breached, the relay would open. It would open roughly twice per second and kept it up for the 12 or so years I kept track of the job via phone and surface mail.

The radiator fan relay in my toad is so critical, I added an 80 ampere relay to support the 16-amp burden. The relay to fan circuit now has TVR's, One MR2535 avalanche diode, and some 18 volt MOVs. The replaced relay was a Tyco 30/20

I dissected it and was not pleased at the condition of the contacts after 5 years of us

MoPar really screwed-up when they designed the cooling system for the car. A ONE row radiator. The temp creeps up toward 230 F on an 80F day without A/C at 60+ mph without the fan. The radiator is/was new, new water pump, gauge accuracy verified, yadda. Back off to 50 mph the coolant drops to 195F. Drop below 30 mph without the fan and it's a boil over within 4 miles.

With the fan operational the car acts like it's not insane. Keep in mind, this is Mexico, and what I drive is immune to robbery or carjacking. A robber would commit suicide before he would allow himself to be seen behind the wheel.

REGARDLESS. Relays and contactors are not plug n play. I have seen many newer units that have had the power contacts blown off their arms because of high loading disconnect.

It would take a 400 amp rated contactor to assure several years of fail-safe full-load (30 ampere) disconnects. Smaller contactors or relays need too high of coil va to pull against a strong disconnect spring. Magnetic coil overheating.

All of this nonsense could be avoided with load shutdown before disconnect.

Good luck with that.