transfer switch

[Turbo Thom]

Question for all the electric minded guru's out there.



. . Does the transfer switch, in todays RV's, have to have DC current to operate?. .



I've been told no and yes. Where does the put the truth? Is it so or ain't it?



. . PT. .

 

[jelag]

Please tell us which transfer switch your talking about... .

 

[bulabula]

If the transfer switch is on a 12V circuit it would be DC; if its a 110V circuit it would be AC.

 

[Rman]

The transfer switches in RV's are almost always AC. I've never heard of a DC switch, in an RV, unless I'm just thinking of the wrong thing here. The do not require any power, other than the input power for which it switches. So the inverter must be hooked up, and the wall or the generator. You can hook up two switches to switch between all three. The coil inside is what senses (inductively) the input and changes the relay, since there's no real components it needs no power and rarely fails. If it does fail, its normally from switch chatter from low voltage situations at camp grounds where everyone is cranking AC on a weak circuit.

 

[Turbo Thom]

Then how does the tansfer switch know if shore power from generator power. Both are 115Vs.



And the switch has LYGHT automatic transfer switch, LPT50CA on it. That's all I see on it. It's on my 03 Teton.



. . Preston. .

 

[TowPro]

Mine (and most new) RV's don't even have a transfer switch



Mine has a 12V system that goes around to all the lights. Also hooked to this system is the output from the progressive Dynamics charger. It is designed to work up to its max output. I have a 60 amp charger. If your lights are drawing 10 amps, and your battery is charging, my convertor can supply 50 amps to the battery.



The old style had a relay inside the power supply. When you applied AC to the power supply it switched a relay that isolated the 12v system (lights) from the battery. This type system also had a trickle charger (a couple amps) to charge the battery. This charging system was not very well regulated, thus the problems of boiling the water out of the battery when leaving it plugged in. I can't recall if that relay was 12v or 120v, but I think it was 120. Keep in mind these old ones are 1/2 wave AC supplies and are real dirty (RF noise on wires)



Your best bet is to gut the orignial and put a a progressive dynamics charger inside like this There is a guy selling them on Ebay for a good price. Its worth the extra money to get the charge wizard that plugs into the box.

 

[Turbo Thom]

OK... ... let me tell you the whole story.



I've had trouble with the transfer switch for some time now and have had the fiver into the dealers about 6 times for trouble. One of the main problems is the transfer switch would not transfer like it should. Sometimes I would have to start the genset 8 times for it to transfer. It just got worse and worse. Then I just got to where it would not work at all. Different thing were changed, to no avail. Then a new transfer switch was installed, same thing. Yesterday I brought my fiver to my shop for maintainance and found one of the batteries was shot. I bought a new one, installed it and now every time I start the gen, the trasfer switch works and even has a different sound to it. More of a soft thud, instead of a sharp crack.



Therein is the basis of my question. Why did this change with the installation of a new battery? If what you say is true, there should be no change. But there has been, so why. I'm lost and am just looking for answers.



. . Preston. .

 

[Rman]

Are you running your inverter while starting the genset? The transfer switch (as I'm sure you know is a AC switch, DC has nothing to do with it) It can sense the power from the genset (it does this inductively with a coil) then will switch to use the Generator power. Since this is not constant power, the switch will default back to the inverter when power is removed (the normally closed position on the switch).



Dead batteries are very difficult to troubleshoot (when used with another good battery, like in an RV). The reason for this is the good one is constantly working it's guts out to make up for the bad cell in the bad battery. Circuits will act differently because of this increase in load. If you were using your inverter while starting the genset, this may explain the problem you were seeing. The inverter may have been outputting low voltage, which could have lead to switch chatter, which may have lead to the x-fer switch failing.



It's an all encompassing system, and unfortunately thats what can happen. If this isn't the case, well guess what it's electrons so the FM theory comes to mind (friggin magic for those ho aren't familiar).



IMHO, you should always replace BOTH batteries when one fails. The "good" battery is damaged from the bad one. Replacing just one will result in premature failure of BOTH. Keep the "good" battery as a spare.



I've gotten very intimate with my RV system, and ran into a rather simple but easy to over look failure with my converter last year. High resistance short across a couple fuses caused it not to work. www.klenger.net is a great resource. Ken has a great write up on RV electric systems. I used that to help me draw my own schematic from tracing all that wires.



Also, from experience, RV's are assembled by morons. I repaired more "cheesy" electrical connections while troubleshooting my inverter problem last year then I ever have before. I have a Lance, supposed to be the best in the business. Yeah, well tell that to the guy making 2 bucks an hour puttin it together. It was pretty cheesy to me. Take the time and make sure all your fittings are snug, escpecially the DC connections. People have little knowledge or respect for DC, it's DANGEROUS stuff in an RV.

 

[TowPro]

sorry, I thought you were talking about the transfer switch inside the old Magtronics power converters you hear "click" when you plug the RV in. Never had a generator in an RV