Transfer Switch Failure

[evolvingpowercat]

For sure I would de-power, open the transfer switch box, and in a couple of days and re-tighten all the connections. And for sure use some needle nose and wiggle those wires and tighten again if you have not done so already ! I have seen that kind of damage on a wire leading to a 30 amp electric dryer breaker that had a loose connection. Eventually the heat destroys something in my case the breaker finally failed due to the heat.

It appears that there is no vents of any kind on that box, so it looks like it worked like an oven and trapped all the heat inside cooking more than just the wire connection that was generating all the heat. Chances are that it was all caused by one loose neutral or hot on the shore cable lugs or on the lugs on the wiring going to the breaker panel. Assume you are like most and use your generator infrequently so not likely was one of those.

One thought - you could take one of the little indoor/outdoor LCD thermometers that sell for $10 and tape the outside sensor on the top of the metal transfer case box and then you could view its temp and compare it to the air temp in the basement where its located and it would give you a heads up that something is getting warm in there.


Personally I check all the AC and DC connections I can readily get to in my Edge every season. The first time I did it after I bought the Edge used there were some that could be tightened some, but they have all stayed tight since.

 

[danemayer]

I'll be home in 2 weeks and have a couple of maintenance items saved up. Re-tightening the connections is on the list.

 

[wdk450]

Regarding the possible build-up of heat in the transfer switch box:
I had a similar problem with a totally enclosed box enclosing the power control electronics (including a large power SCR) when I first started maintaining an older brand of 1000 watt radiant neonatal warmers. These were cooking the internal capacitors and SCR's at an alarming rate. I came up with the idea of venting this box while maintaining it's resistance to spilled fluids (important in a hospital setting) by using vented hole plugs. I cut a 1 inch hole at the bottom of the metal box and one at the top (with a hole punch) to allow for thermal convection cooling. I inserted the vent plugs into the holes. The failure rate went down to near zero. The top vent plugs I used had a thin metal screen mesh. These are somewhat resistant to fluid entry.

Here is and image of a vented hole plug. You can even buy regular hole plugs at a hardware store and drill your own holes in them. These could be mounted on the sides and top of the transfer switch box, since the bottom is screwed to solid wood.

Image of a screened metal vent plug:

 

[SeattleLion]

I know it's hard to do, but switching with a load on invites arcing in the contactor. The higher the load, the more likely there will be arcing. When the current draw is low or off, the stress on the contactor is much lower. When the power fails, by definition there is no load when the contactor breaks shore connection. However, when the shore power returns, any load in the coach will have to be transferred. This is the same issue as connecting to shore power with the pedestal breaker on. High power switching (as in power companies) is always done at the point in the AC sine wave when there is zero voltage. In the case of smaller stuff like transfer switches, this isn't possible. I always had manual transfer switches in my house for emergency power. That way I could minimize the transfer load.

It might make some sense to consider a more manual system to transfer from shore to gen and back to shore power, especially when you have heavy resistive loads like the fireplace, microwave, and other heating devices.

 

[wdk450]

I know it's hard to do, but switching with a load on invites arcing in the contactor. The higher the load, the more likely there will be arcing. When the current draw is low or off, the stress on the contactor is much lower. When the power fails, by definition there is no load when the contactor breaks shore connection. However, when the shore power returns, any load in the coach will have to be transferred. This is the same issue as connecting to shore power with the pedestal breaker on. High power switching (as in power companies) is always done at the point in the AC sine wave when there is zero voltage. In the case of smaller stuff like transfer switches, this isn't possible. I always had manual transfer switches in my house for emergency power. That way I could minimize the transfer load.



It might make some sense to consider a more manual system to transfer from shore to gen and back to shore power, especially when you have heavy resistive loads like the fireplace, microwave, and other heating devices.

Your post agrees with my previous one advocating turning off the main power breakers before disconencting or connecting shore (or other ) power. Although this now transfers the arcing wear to the circuit breaker contacts, circuit breakers are easier to get at for repair, and more readily available, than transfer switch or EMS relays.

 

[porthole]

Although it may be ideal to have all the breakers off when transferring power, I don't do it. The whole purpose of the TS is convenience. Do the same thing in the house when the standby Genny.

Everything is automatic, and I like it that way.
If you think the transfer switch in your coach makes a big thump, you should hear the one used in a whole house system.

 

[wdk450]

Although it may be ideal to have all the breakers off when transferring power, I don't do it. The whole purpose of the TS is convenience. Do the same thing in the house when the standby Genny.

Everything is automatic, and I like it that way.
If you think the transfer switch in your coach makes a big thump, you should hear the one used in a whole house system.

I think the big difference between a home house power transfer switch and an RV transfer switch (or EMS relay) is how often it is used. The house switch is going to transfer a load through its contacts whenever you have a power outage (maybe once a year??), where the RV transfer relays are going to be switching either every time you use the generator, or the EMS relay switching EVERY TIME YOU CONNECT YOUR RV TO SHORE POWER. Your EMS starts out with the power relay deenergized every time you connect to shore power, the EMS circuitry checks the power is OK, and 30 seconds later the relay is energized switching the entire RV load across its contacts.

 

[danemayer]

Follow up: now that we're home (1000 mile drive) I checked the transfer switch wire connections this morning. Everything was still tight.

 

[scottyb]

Although it may be ideal to have all the breakers off when transferring power, I don't do it. The whole purpose of the TS is convenience. Do the same thing in the house when the standby Genny.

Everything is automatic, and I like it that way.
If you think the transfer switch in your coach makes a big thump, you should hear the one used in a whole house system.

I have had to replace my transfer switch two times in the 1st year, but it was not due to the contacts. The 1st, 2 days after taking it home and the 2nd due to loose wiring in a j-box. However, I have to agree with porthole on this one. I do remove most of the load except fridge, converter, etc.

 

[danemayer]

Update:

Went over to storage today to fix the vacuum cleaner. Found the loose wire, fired up the generator, but it still wouldn't run.

Turned out the contactor on the generator side of the new transfer switch is failing. Checked an outlet and found 120V between hot and ground, 90V between hot and neutral, and 30V between neutral and ground. Checked a bunch of stuff. Got on the phone with Progressive Dynamics support and with power off, checked continuity on the neutral line coming into the switch with the line going out while manually depressing the relay. Open. Checked L1 and L2 and had continuity. Checked the shore power lines and all had continuity.

Progressive Dynamics is sending a replacement transfer switch.

 

[danemayer]

A new transfer switch arrived yesterday afternoon and I installed it this morning. Unfortunately, the contactor just chatters and then fails to hold. It's got 120V coming in from the genny on L1, so it looks like it's another bad transfer switch. Very disappointing. Left messages and am waiting to hear back from Progressive Dynamics.

 

[scottyb]

Dan, I know you probably have already done this, but just in case, have you checked the J-box outside the generator? It was the culprit behind my transfer switch woes (2 in under a year).

 

[danemayer]

Scotty,

What was wrong in your j-box and what were the switch failures?

 

[jbeletti]

I should probably check my j-box too. Disconnect shore power first in case any voltage is leaking back.

 

[scottyb]

The wiring was loose with just a few strands making contact. The neutral was actually charred.

 

[jbeletti]

I haven't posted it on the forum yet but I too replaced my transfer switch, though a different brand than Dan's. TRC told me that low voltage can cause the contactors to chatter. So poor connections can lead to hyper-current draw and big voltage drop. They also told me that a lot of chatter can weaken the contactors and I should replace the transfer switch - so I did. None of my connections were poor or loose in the transfer switch box. So I'm not sure that I found my real problem. I'll check the j-box on the next trip out.


Sorry Dan for the semi-hijack

 

[jimtoo]

Dan,, maybe you just need to get one like this...



You just have to remember up for power lines,,, down for genny.

Jim M

Well,,, maybe both of you should get this type...

 

[wdk450]

Dan,, maybe you just need to get one like this...

View attachment 29378

You just have to remember up for power lines,,, down for genny.

Jim M

Well,,, maybe both of you should get this type...

That looks like the "energize" switch for an electric chair . . .or Frankenstien!!!

 

[jimtoo]

That looks like the "energize" switch for an electric chair . . .or Frankenstien!!!

I think it's actually listed for multipurpose use. 12v or 120v or even more.

Jim M

 

[danemayer]

Dan, I know you probably have already done this, but just in case, have you checked the J-box outside the generator? It was the culprit behind my transfer switch woes (2 in under a year).

I can't see where they put the J-box. Even looked above the coroplast. Jim, I know where your J-box is located. If you had the Onan generator, you'd have to remove the generator to get to it.

Scotty, where is your J-box located?

In the meantime, I re-checked and I do have 120V between L1 and neutral and between L2 and neutral, although I don't know how much current it'll conduct. I'd still like to check it, but I think a bad connection in the J-box is low odds. I've had 3 very different failures. The first was on shoreline side of the switch - don't see how a generator wiring problem would have caused that. The 2nd was an open neutral contact on the generator side of an almost new switch that was run on generator maybe 3 or 4 times, primarily to test things - it's not clear to me how a loose wire in the J-box would have caused the switch contact to fail after a few minutes of run time. The 3rd failure is the contactor relay failing to energize on a new switch - could be a loose wire, but it seems awfully coincidental that the switch is failing out of the box.

Progressive Dynamics is sending another new switch.