Transfer Switch Questions

Just a little update. When I went out and switched the wiring back over to shore power I figured out how to get the box off the back of the panel. I had to take out all the ac circuit breakers and also the board that holds the dc fuses. Behind there are two screws that hold the switch box on the back.

I took the screws out and was able to tip the box enough to see inside just a little. Getting it out is going to require removing some wiring. I didn't take it all the way apart because I'm getting ready to go on vacation and don't want to be waiting on parts.

I can barely see the contactor. I can also see what what looks like the connector side of a standard automotive/generic type relay.

I used a screwdriver and checked to see if the contact is welded. It is not, moves freely. I thought it might work after messing with it but no such luck.

When I get back from vacation near the end of October I will take it all the way apart and post what I find.

Thanks

Hi time2roll,

I believe that was the item that started the failure inside my Magnum where the unit caught on fire. That and their design decision to use 120 volt fans--so if you shut down the inverter all cooling stops. If they had chosen a 12 volt fan......

I know the OEM charging path from the alternator to the house batteries was fused at 60 amps. The OEM relay did not last a year, and I had 3 fuses blow. The relay worked just fine but the contacts were burned so no power got through. I upgraded by adding a 2nd #8 path and two 200 amp relays that are protected by 50 amp automatic circuit breakers. Not a hint of a problem since then.

RV makers use the bottom of the barrel approach to parts using the bare minimum. By all means use a transfer switch--but get one that is 4 to 6 times the rated capacity of the circuit.

I should have said "welded contacts" rather than "burned contacts" in my original post.

time2roll wrote:

pianotuna wrote:
I prefer to do manual switching. After all, you are supposed to turn off everything before you cause the transfer switch to cycle. Not doing so, sooner or later leads to burn contacts and failure.

I seem to read more posts of a loose connection or failed control module. Not so much actual burned contacts.

But then I do read about burned out plugs and connectors.

Even if switched 3x a day it is only 1,000 cycles a year. Are the relay contacts really rated that low?

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.

Have any experience with SSR's Mex?

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 use.

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.

MEXICOWANDERER wrote:
LIFESPAN at full rated power disconnect 300 (which is 3x times higher than recommended)

LIFESPAN at recommended amperage limit 10,000 cycles

Hopefully the OP will post what actually failed.

I did not find make and model that OP posted.
Did anyone try to search for it?

German TEMP THERM power disconnect (which is a safety shutdown)

LIFESPAN at full rated power disconnect 300 (which is 3x times higher than recommended)

LIFESPAN at recommended amperage limit 10,000 cycles

Get the drift?

Contact deterioration does not occur upon contact, it occurs upon disconnect.

If contacts were submerged in MERCURY lifespan would increase to the point of the life of the magnetic coil.

But of course the use of mercury is absurd

About as likely has having an RV owner shut down all loads before transferring.

And *That* is the key.

"Burn Baby, Burn"

pianotuna wrote:
I prefer to do manual switching. After all, you are supposed to turn off everything before you cause the transfer switch to cycle. Not doing so, sooner or later leads to burn contacts and failure.

I seem to read more posts of a loose connection or failed control module. Not so much actual burned contacts.

But then I do read about burned out plugs and connectors.

Even if switched 3x a day it is only 1,000 cycles a year. Are the relay contacts really rated that low?

Not sure about which one is higher quality but when I replaced ours, it originally had a 30 amp Lyghtpower. Searching on the internet I found a WFCO transfer switch with the exact same model number relay. So no difference in quality. Per many here on the forum "WFCO" isn't too appreciated, at least for their converters.

Since they were identical, I planned on swapping out the relay, but when I got it the WFCO case was a smaller foot print and a bit better design so I swapped the whole box. In March they were running in the average neighborhood of $60. I lucked up and found one that said "not in original packaging" for $27.

Per darsben1, you can just mount it on any surface and wire it up. If wired properly it should not get hot. But since I've had one melt the wiring, I prefer having it wired in some type of metal enclosure.

pianotuna wrote:
It is quite possible to have access for a manual switch from inside the RV and also for a plug.

I've noticed that boats use a special switch to switch form shore tie to generator. Beyond being very heavy duty, it has a "keeper" that has to be moved to operate the switch. Either way, it takes two hands to make the change, so it isn't going to be getting bumped inadvertently.