Blown Transfer Switch?

Short version of the problem - we plugged into a 50 amp pedestal at Escapees in Livingston, and instead of transferring power, the 50 amp breakers at the pedestal popped. In three and a half years in this coach, that has never happened. Tried it again, breakers tripped. Taking a chance, tried the dogbone for the 30 amp, no joy. Then find out from the neighbor, "oh, the guy last night had a problem there!". We moved to yet another site, same deal.

I am not an electrician in any lifetime, but had a transfer switch in my previous coach which had a bad relay that you could pop with a screwdriver handle and fire up. But that board was exposed, where this one is a Progressive Dynamics PD-52 in a box which looks like it has a removable cover.

Given that the generator side still works fine, i.e. the generator fires us and lights the coach, and charges the batteries, is there another breaker at the inverter (Magnum 2500 pure sine wave) that could be tripping? When I recently had all my batteries replaced and a battery monitor installed, something similar happened, but I did not see what the tech did, possibly at the converter to remedy this.

If there is a simple diagnostic procedure to determine where my issue is, I'd love to hear it. We are crossing the country, now in Louisiana with 80 degree temps and 90 percent humidity and momma ain't happy boondocking. We just left the cool of the warm desert with cold nights and there is no joy in Coachville.

Appreciate your thoughts.

Kim

I'd be very careful - it's quite likely you have one or more contacts welded together inside the relays.  You can pop a single relay with a screwdriver handle and get away with it, but dual relays mean one and only one can be energized at the same time.  Hit the wrong one and you'll have sparks.

If you have a welded contact in one of the relays, it can cross-connect between the generator and shore power plug.  When you run the generator you'll have voltage on the exposed pins of the shore power plug.    And when you plug into shore power voltage is applied to the generator windings, shorting out the shore power and tripping the breaker.

There's not much to the transfer switch except for the main relays and a small controlling circuit board, and this is probably a case where it would be easier and cheaper just to get another one instead of trying to repair or replace the relays.

In the meantime, I'd get some large wire nuts and remove the load and line connections from the transfer switch and wire-nut the connections together to bypass the switch so you can plug into shore power.

The load is connected to the side of the relays with jumper wires running from one to the other.  The generator and shore power come in on the other side of each relay, and only one relay at a time should be connected from source to load.

My favorite transfer switch is a 50 amp socket in the same compartment as the shore power cord, connected to the generator.  And the shore power cord connected directly to the power center.  When you disconnect from shore power and store the cord, plug the end into the generator outlet and you're set.

Lou,

Thanks for the reply. My intention is to replace everything, including a later model PD-52 with some circuit protection, but I need to see if I can get to a point where I can have shore power. When we land mid day today in Baton Rouge, I will be popping the cover, and see what I see. I will not be touching anything at this point, I assure you!

I don't want my learning experience to be a burning experience.  :'(

Kim

skyking4ar2 said:

I don't want my learning experience to be a burning experience.  :'(

Click to expand...

It could also be another 4th of July.  :

It is equally possible your shore cord is shorted internally. Maybe even more likely than the transfer switch, since the ATS has to fail in a fairly unique way to cause a short.  It's not unusual for the plug on the shore cord to have a broken wire that either is open or shorted.

Get a VOM and test the shore cord for continuity from either of the hots to ground or neutral.

Gary,

My shore cord is on a power reel, so it would not surprise me if it had an issue after all the pulls and tugs. I would not have looked there, so thanks. This will be a good education in troubleshooting for me.

Just landed, finally, and am heading out with my trusty volt meter and see what I see...

If your cordreel is like mine, the commutator rings inside can arc to the brushes and burn up. Mine failed by burning up one hot lead enough to not pass any power thru. I didn't have a breaker tripping problem, but I only had power to one half of the coach. The genset provided power to everything. I found the problem by taking the cover off the side of the reel and checking that I had no power coming out of the reel on the one hot lead. I confirmed that I did have power from the cord by reeling all the cord off, taking the cover off the center of the reel and confirming power at the cord ends.

And autopsy after replacing the reel revealed the burned commutator. No way to fix and no way to see without drilling out the rivets on the brushes panel.

$500 or so for the new reel and you can't buy it without the new cord. I guess that's one way to get a 50 amp extension cord, but it's expensive.

Ken

Ok, virtual electricians, here's what I know.

Opening the case to the transfer switch (and not being brave enough to poke stuff) I can see no evidence of heat or burning at any of the connections. They all look factory fresh.

Per Gary's suggestion and keeping Ken's in mind, I checked the power cable at the plug end.

I found no short between either hot leg to ground, but found a reading of 70 on one side and 107 on the other when I tested the legs to neutral.

I am going to assume I have to head down Ken's trail of popping the cover off the reel and see what I see.

Kim

p.s. it is important that you have a hot battery in your Fluke meter...another lesson learned..

You may be reading the resistance of the transfer switch relay coils when going from hot to neutral.

You can either pop the top off of the cord reel or disconnect the reel wires from the transfer switch, leave them hanging in mid-air and test the cord resistance again.  Whichever is easier.

Kim,

Do you have a Shoreline power cord reel?

Just in a chance I'll bescribe what happened to me.

If so on many installations there is no "stop" to protect the power cord head. It can look fine but be damaged internally. Naturally it happened to me when trying to power up after pulling in the Indio for an overnight on the way to Oregon. Naturally it was 105 degs and the engine compartment was still hot as I worked through the diagnosis.

Since that day in the heat I couldn't figure out exactly what was wrong with the Shoreline I went to Home depot and bought a Range cord to bypass it. I wired that into the junction box next to the Shoreline and disconnected the Shoreline. I then connected the range cord to a 25 ft 50amp extension cord I carry.

I have attached what I see in the compartment with the transfer switch cover off and the power reel cover off.

If I am interpreting previous tips correctly, I now need to take the wires loose from the reel connections and test the reel connections to see if the issue is between the connections and the plug, i.e. there is a problem with the cord on the reel or ???? If I read Ken correctly, his problem was the actual reel itself.

The pictures are the compartment itself, the Progressive Dynamics PD-52 transfer switch, the schematic for that switch that is on the inside of the switch cover, and finally the connection the connects the power cord and reel assembly to the transfer switch.

While it is too dark to do much more, I have been trying to read and understand the testing required and if I find that the power cord section of the circuit is bad, then jumping the transfer switch and moving the wires is pointless and won't get me any power from the shore line.

Ken & Sheila said:

Kim,

Do you have a Shoreline power cord reel?

Click to expand...

Mine is not a Shoreline but this model....

To your point, I did pull the cord to the stop recently and that normally never happens. I suspect I damaged it as you describe. I will take the hint of carrying an extension, however.

I am still wrapping my head around your range cord solution... 

Kim

Kim,

No, my problem turn out to be the plug on the cord.

So noted.  8)

It looks like it would be easiest to disconnect the wires at the cord reel - they're on lugs and you don't have to work around tight spaces to get them on and off.

Once the lugs are clear you should read close to zero resistance (a few ohms is normal)  from each lug to it's corresponding pin on the power plug and infinite resistance from each pin on the plug to all the others.

The layout on the reel lugs follows the layout on the plug - green is the round bottom ground pin, white is the top center neutral pin.  Red and black are the two side hot pins.

Make sure you aren't touching the metal meter probes or any other part of the circuit when measuring an open circuit or the meter will measure your body resistance instead.  You won't get shocked but it will mess up the measurement.

If the cord and plug test good with the meter, leave the reel lugs open and plug into a shore power socket with it's breaker turned off.  Now turn it on and see if the breaker holds, if it does measure the voltage on the reel pins and verify there's 120 volts from each hot lead to neutral.

On the transfer switch, it looks like the wires on the top left relay board is the output to the house breaker panel.  The top right relay board is the shore power input and the lower right is the generator.

Looks like you have plenty of slack to remove the wires and use wire nuts to connect the house leads to either the generator or shore power if you need to bypass the switch.

Kim,

Do you have a multi-meter to test the cord?
Test for bleed over from one wire to another. Example. From the red wire terminal check the continuity to each blade on the plug. You should only have continuity on one blade. Then do the same on the Black, White and Green wire. While doing this flex the plug a little because the internal contact may only be in some positions.   Use Lou's directs to check the cord and the reel. To check just the cord you would have to probably take the reel out of the MH to disconnect the cord. I did this and it was a major PAIN.

Re-reading your original post, I'm not so sure this is your problem because if the short was bad enough to trip the breaker I would think you would see visible damage.

If you find you have a cord or power reel problem then try the range cord idea.

To use a range cord in your setup is easy. Cut off the lugs that come on the range cord. Disconnect the line from the Cord reel to the Transfer switch at the switch. Connect the range cord direct to the transfer switch.

Do you have a 30 amp extension? You could use it with a 50/30 amp adapter to get at least 30 amp power.

Alternative: you can buy 50amp 3 wire +ground cable at Home Depot. You'll also need to buy a plug to put on the cable. Its a lot stiffer than the power cord but it will work as a temporayy solution if there is a place to buy a 50 amp RV extension cord.

Make ALL power is off before touching the transfer switch.

Here's a copy of the Progressive PD-52 installation manual.

I'm not sure why, but on Page 1 under Warnings it specifically warns against mounting the switchbox the way it's mounted in your coach, saying it will shorten the life of the switch.  The recommended wall mounting has the relays side by side of each other, 90 degrees from your orientation.

Funny you should mention that, because I found the same thing when I was looking for background on the switch.

New power reel - $650 and change
New transfer switch - $150 and change
Finding the problem without replacing either - priceless!

Lou, your troubleshooting is always so well thought out - thanks, it's the only way I can work. I cannot jump back and forth like some, especially when I am not anywhere near my area of expertise.

First thing in the morning, I will head down your path and see if we can at least rule something out.

I appreciate all the background from everyone - the perspective is very helpful.

Kim

Sorry guys, I was out for pizza.

When mine was bad, the cord itself was good. All I had to do for a temporary fix was take the cord loose from the inside of the reel and then put it on the lugs on the side of the reel that go to the transfer switch. Bypassing the connections in the reel and using the lugs on the side, where the power goes to the transfer switch/coach as a terminal block.

Ken

Lou Schneider said:

It looks like it would be easiest to disconnect the wires at the cord reel - they're on lugs and you don't have to work around tight spaces to get them on and off.

Once the lugs are clear you should read close to zero resistance (a few ohms is normal)  from each lug to it's corresponding pin on the power plug and infinite resistance from each pin on the plug to all the others.

The layout on the reel lugs follows the layout on the plug - green is the round bottom ground pin, white is the top center neutral pin.  Red and black are the two side hot pins.

Click to expand...

When I perform this test, I get zero on the digital meter on each wire. However, if I switch the red and black lugs to the plug, they get a reading (maybe 44 or so) because I am guessing which hot side of the plug is which color wire. Is that expected? I may not have the terminology right, yet, just saying what I see.