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View Full Version : Do you REALLY need to have a power transfer switch?


pchicky
03-15-2010, 01:41 PM
This message was also posted on the "C Owners" site. A little background,....my converter was not charging coach batteries with the genset running. I traced the problem to only one line in the breaker box operating, and have traced that to a potential issue in the power transfer box....so, here's the question:

OK, I messed with the RV this weekend. Found that with the genset running I only have one line being powered in the breaker box, and the converter was on the dead line. So, for a quick fix, I switched the breaker for the washer/dryer (which I don't have) with the converter and my house batteries are charging on genset. However, this doesn't fix the root cause.

The best I can figure, I've got a problem in the power transfer switch for the genset to shore power that is not supplying fully 50 amp service down both lines...put another way, I'm only getting half of the genset output in the rig. All is fine with the RV plugged into shore power, so that tells me it's in the genset side of the power transfer switch.

Here's the question. What value does this power transfer switch do, other than make it a convenience to switch between generator and shore power? My last C Class didn't have one, and you literally just plugged the shore power line into an RV recepticle hooked to the genset in the storage area where the shore power line was stored....it was simple and easy.

Seems to me that you could do the same with the 50 amp double pole line, couldn't you? I mean, if you're running the genset on a trip, you pull into a campround and want to plug it in, you have to get the cord out, so what's the harm in just unplugging it from the genset and plugging it into shore power. Yeah, your A/C units will be off for two seconds, but that seems like an extremely minor inconvenience and it bypasses the power transfer switch which, to me, is just another potential failure point.

With that said, if the power transfer box is performing another safety feature, somebody please tell me. I'd love to learn about it.

larrybell
03-15-2010, 05:37 PM
In my opinion, the saftey function provided by the transfer switch is the prevention of the paralleling of the genset and shore power. Large electrical upsets may occur with drastic results. I always connect to either the genset or shore power on de-enegized buses. I can't see relying on the transfer switch when, like you say, the power interruption is very short.

RJ82much
03-16-2010, 06:23 AM
I'm sure you've already checked, but it's worth mentioning anyway.

You have 2 breakers on the generator itself. It is common that one will trip, leaving you with the condition you've described. Exercise each off & on, then check to see if you have power to both lines.

Good Luck

pchicky
03-16-2010, 09:00 AM
I isolated the problem to the transfer switch. The generator output is fine, but the "output" side of the transfer switch from the generator has one side dead.

I agree with larrybell that the purpose of the transfer switch is to keep parallel feeding off of shore and genset lines, or worse a power feedback down the shore line to some helpless worker trying to fix the shore power.

However, a hard wire from genset to a 50 amp RV recepticle, then plugging the shore power directly into it when running the generator seems to me a more direct solution that is fool proof. That darn power transfer swith with all the connections, contacts, and circuit board, to me, is just a problem waiting to happen, and in my case, it happened (by the way, my rig is only 18 months old). And for the $650 it would cost to fix it, I can do the same thing for about $15 and have a more reliable power platform.

When I unplug from shore power, I'll simply plug the shore line into the genset plug when I'm storing the cord. Actually, this is probably good because it will keep the cord from moving around as much and protect the connectors on the plug end.

That's my story and I'm sticking to it!!! :D

tucson_sailors
03-31-2010, 04:34 PM
When I unplug from shore power, I'll simply plug the shore line into the genset plug when I'm storing the cord. Actually, this is probably good because it will keep the cord from moving around as much and protect the connectors on the plug end.

That's my story and I'm sticking to it!!! :D

Did this on my 91 Sun Voyager and it worked just fine. Bought a plastic mounting box and a 30 amp connector, and added about 8' orange colored romex (so that its easy to see) from the generator lines under the bed. When I want shore power, plug the shore cable into it, when I want genny power, connect to the internal 30 amp box. No overload, but does mean that have to go out and swap if I'm at a place that has outlets.

Glenn in Tucson
91 34' Sun Voyager

GStream40
03-31-2010, 04:36 PM
When my ATS went bad, I ordered a new one from this site: http://www.solarseller.com/iota_automatic_transfer_switches__iota_power_distr ibution_panels__inverter_load_.htm#its___50_r_

I believe it cost me $115.00 for a new transfer switch and I installed it myself. After I was done installing the new one, I then found out what was wrong with the old one and it only cost me $16.00 to fix that one. So now I have a spare.

Ron