Power Transfer Switch

[GaryS2]

I have an old Monaco Signature series, the power transfer switch is a 50 A, shore on one side and Generator on the other it has started to chatter on the shore side. I would like to replace it but the coach is 22 years old can I just use any 50A transfer switch that I might find at a motorhome dealer? Any one recomend a best brand?

GS

[wolfe10]

Gary,

Yes, a 50 amp ATS is a 50 amp ATS. Having only had one fail 5 years ago in the many years we have been RV'ing, I am not up on the "best" presently on the market. Hopefully others with more recent experience will chime in.

Brett

[hermanmullins]

Gary,

If the switch has lasted for 22 years I would try to replace it with the same mfg. if you can find one. Many really good thing don't last 22 years.

Have a Safe & Happy New Year.

Herman

[GaryS2]

Thanks Brett

Is the chattering typical of how they fail?

[desertdeals69]

You might check to see if the connections are tight.

[vtbigdog]

I would tighten all connections before replacing. BE CAREFUL.

[wolfe10]

By "be careful" he means shore power disconnected, generator OFF and inverter (if equipped) OFF. 120 VAC is nothing to play with!

[dickandlois]

Gary,

Along with the connections at the transfer relay you might want to check all the shore power wiring connections from the shore power cable to the relay connections. There could be a loose or corroded connection anywhere in the wiring. Hot sides, neutral or ground.

The fact that the relay locks and does not chatter when the generator is running leads me to think its worth checking.

Rich.

[desertdeals69]

Gary,

Along with the connections at the transfer relay you might want to check all the shore power wiring connections from the shore power cable to the relay connections. There could be a loose or corroded connection anywhere in the wiring. Hot sides, neutral or ground.

The fact that the relay locks and does not chatter when the generator is running leads me to think its worth checking.

Rich.

When the gen is running the ATS relays are not energized.

[dickandlois]

You are correct, no coil power at the ATS, but the way a post is worded also tells me about the contacts on the ATS---- generator side are in good or bad condition.

When I have the generator running on our coach and connect to shore power the transfer relay transfers the load to shore power that is how, I think all ATS relays work. So the load contacts on the relay should be OK. (Generator Side) That leaves the control coil and the other side of the relay contacts in question along with all the wiring between the Power Riser to the ATS and power panel in question.

I have watched owners start there generators with the AC units power on and the load causes a real arc on the Generator Main breakers. The same for the shore power side at the ATS.

When I read a post that the generator circuit works, I do make an assumption that the owner is one that does not leave heavy loads on when connecting to a power source. (That may not always be a good thing though)

Rich.

[RVerOnTheMove]

The generator should be wired such that it has priority over all other power sources. If you have the generator running and plug into shore power, nothing should happen. However, if you are plugged into shore and you fire up the generator the ATS should switch you to the generator. Of course, once you then power off the generator your shore power connection would be automatically restored. If neither source is available you should be running off 12V power or power from your 12V to 120V inverter.

[desertdeals69]

The shore cord has priority when live. If the gen is running and the shore cord is live the shore cord will power the coach. The transfer relays are dpdt and it is not possible for the shore cord to feed 120v to the gen.

[wolfe10]

The choice of whether generator or shore power is "favored" is up to the coach maker. I have occasionally seen shore power the favored source-- whether "marching to the beat of a different drummer" or just mis-wired at the factory I have no idea.

But, yes, generator is much more common as the "favored" source.

[RVerOnTheMove]

Thanks, didn't know it was an option. My 2 coaches were both setup for generator priority and all of our friends coaches I have been setup that way.

I simply made a bad assumption based upon my experiences just as desertdeals69 did.

[desertdeals69]

Thanks, didn't know it was an option. My 2 coaches were both setup for generator priority and all of our friends coaches I have been setup that way.

I simply made a bad assumption based upon my experiences just as desertdeals69 did.

No bad assumption, I have been wiring with gen priority for 37 years in our business. We made our own ats before they were readily available in the market place and anyone knew what one was.

[GaryS2]

Thanks for all the replies. On my coach the book says the shore power is priority side. I have never started the gen set while plugged into shore power as there is no point. My book says that when you connect shore power you hear the ATS snap and that to charge the batteries the inverter needs to be turned on. With shore power connected the only circuit that works in the inverter is the charging system and the inverter 12V to 120 only works on battery power alone.

My symptoms are when I turn on the inverter to charge the batteries there is a about a 30 second pause and then the shore side of the ATS starts to chatter. it quits then starts again etc. One other thing is that most of the time I am plugged in it is to a 30 A circuit not a 50 A so as I understand it there is only one 120V hot line to the ATS while on 50 A there would be two hot leads could this over the years have wore out one side of the shore power side in the ATS?

Is chatter typical of how they fail?

[dickandlois]

Gary ,

The 30 second delay is normal. That gives the generator time to settle down to a good steady line voltage.

I get a chatter from the ATS when I have the Inverter running and start the Generator. No problem with it off and switching from shore power to generator or generator back to shore power.

I have a BCC (Battery Control Unit) and the circuits that power the ATS relay both shore power and generator power go through that unit. IF I have AC from both, the delay relays will cause the ATS to chatter. but only if ac is present from both.

Now, I have to look at the wiring in my coach to see if I might have an issue. All these years its been, remember to power down the Inverter before connecting to shore power.

When dad was alive he (we) would install backup power to homes and business. The back up power would come on with loss of line voltage and power down when power was restored. Transfer relays in the power panels disconnected the structures from the power supplier so no back feed was present on the line from the backup source.

Rich.

[GaryS2]

My inverter has to be on to charge the batteries, and then the only circuit alive is the charging circuit. With shore power connected only and only while trying to charge the batteries is when I get the chatter.

[desertdeals69]

Thanks for all the replies. On my coach the book says the shore power is priorithy side. I have never started the gen set while pluged into shore power as there is no point. My book says that when you connect shore power you hear the ATS snap and that to charge the batteries the inverter needs to be turned on. Whith shore power connected the only circut that works in the inverter is the charging system and the inverter 12V to 120 only works on battery power alone. My symptoms are when I turn on the inverter to charge the batteries there is a about a 30 second pause and then the shore side of the ATS starts to chatter. it quits then starts again etc. One other thing is that most of the time I am plugged in it is to a 30 A circut not a 50 A so as I understand it there is only one 120V hot line to the ATS while on 50 A there would be two hot leads could this over the years have wore out one side of the shore power side in the ATS? Is chatter typical of how they fail?

If your book says that the ats snaps when you plug into shore power that means the gen is connected when the relays are relaxed.

[GaryS2]

The coach gets 120v two ways one is shore power, the other is the generator. The circuit snaps when the gen comes on also but the shore power is the one chattering. The chatter is only when the inverter is on to charge the batteries. Without the gen set or the shore power then the inverter cant sense 120v that is when if turned on it will make the 120v out of the batteries.

[wolfe10]

I believe (been awhile since I replaced an ATS) that some use 120 VAC to close the relay and some use 12 VDC. Again, if you tell us the make and model, perhaps someone with specific knowledge of your ATS may be able to help.