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Topic: Transfer switch issue (Read 329 times) previous topic - next topic

Transfer switch issue

Today I was working in the coach getting ready for our Thanksgiving trip next week.  I flipped the breaker for the fridge and heard the transfer switch clunk.  I went up front and sure enough, no AC power from the shore connection any longer.

I went out and unplugged the shore power from the receptacle, gave it about 30 seconds and plugged it back in again.  Nothing.  Fired the generator and got power to the coach, so that much of it is working.

After digging around in the transfer switch box for the next few hours, I have verified that the orange low/high voltage relay is working, and that there is power to the incoming side of the shore power transfer switch.  The lower switch is the shore power.

Leg 1 (Black) to Leg 2 (Red) reads 241V
Leg 1 (Black) to Ground reads 121V
Leg 1 (Black) to Neutral (White) reads 10.7V
Leg 2 (Red) to Ground reads 121V
Leg 2 (Red) to Neutral (White) reads 10.7V

I'm not sure why the neutral to either leg reads 10.7V.  I seem to remember that should be much lower, like near 0V, but it's not the case.  I also checked the trigger voltage to the transfer switch, which uses the neutral and power from Leg 1 to close the contacts.  At the plug-in piece to the side of the transfer switch, this read 6V.  I'm not sure why it wasn't the same 10.7V I saw at the input.

The transfer switch uses the neutral and power from leg 1 to engage the transfer switch.  Apparently this isn't enough to get it to engage.

Frankly, I'm stumped as to how this just happened while sitting, with no other changes.  One minute it's on shore power and the next it's inverting.

Any ideas?
Keith
2003 U320 38' #6197

Re: Transfer switch issue

Reply #1 –
There is something wrong with your neutral, the voltage reading should be the same
as red and black to ground. Red and black to neutral should be 120 volts. You have lost
your neutral somewhere from your transfer switch to you panel.
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport

Re: Transfer switch issue

Reply #2 –
You hit it on the head Peter.  Actually this initial problem may have created a second problem as I have two.

First, I had 20V from each leg to neutral at my outlet.  With the cooler temps, it looks like my connections loosened up a little.  Tightened the terminals on the 6ga wire and we're back to 122V from each leg to neutral.

Second, the transfer switch still didn't engage when providing correct power to the shore power cord.  I traced it to the priority relay.  Power comes from one leg of the shore power and go through a normally closed relay, then to the hi/low voltage relay and back to the transfer switch engagement.  I had 122V in to the relay but only 1V out.  Checking for continuity, it was getting an intermittent reading, so it looks like this little guy died too...maybe a result of the loose neutral.  I'll order 2 to have a spare on hand, since it will take your ability to connect to shore power away, and they are only $20.

http://www.mouser.com/ProductDetail/TE-Connectivity/T92P11A22-120?qs=PWRU6g5o8yJPKV%252BLXfTgbg%3D%3D

Keith
2003 U320 38' #6197

Re: Transfer switch issue

Reply #3 –
Contact only rated at 30 amps.  Need to get one at least 50 amps
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: Transfer switch issue

Reply #4 –
Everyone should periodically tighten every wire connection screw on 120v circuit. That is in the transfer switch, main breaker panel, and inverter breaker panel, etc. One loose screw could cause havoc ( and fire from overheating ). This is a good preventative measure. All connections need to be very tight (& clean). Simple operation, unplug pedestal, turn off generator master switch at generator, turn off inverter, use large size screw driver or other driver as required for screw head.

Re: Transfer switch issue

Reply #5 –
Quote from: turbojack –
Contact only rated at 30 amps.  Need to get one at least 50 amps
Are you talking about the rating of that relay?  This is just the relay that allows or doesn't allow the control of the transfer switch to engage.  I'm not sure how many amps it takes to cause the transfer switch to engage, but it can't be much or you'd be wasting your power on closing the contact.

The part above is the exact part that is installed currently as well.  Today I will also check to see if the other set of poles have the same issue as the set that the connectors were on, since this is a double pole relay.  Perhaps I can just switch to the other pole.
Keith
2003 U320 38' #6197