Transfer Switch Failure

[docj]

The other day, out of the blue, my MH tripped the 50A pedestal breaker. A quick analysis of the problem showed power as far down the circuit as my Progressive EMS but the pedestal breaker would trip unless the generator had been started.

Thinking the problem through, I reasoned that the fact that the breaker didn't trip when the generator was on and that the EMS showed power behind the transfer switch meant that the short wasn't in the power cable or the cable reel.

Eventually I convinced myself that the short was had to be in the transfer switch itself although this isn't a common failure mode for these switches. I opened the transfer switch case but didn't see any evidence of arcing.

Today, I bypassed the switch so that shore power was directly connected to
he coach while we wait for a new switch to be delivered. Sure enough, with the switch bypassed everything was fine.

My wife, who was in the coach when the power failed, says that she saw the 120V lights flickering just before power was lost. I had noticed a little flickering the last couple of evenings, but I attributed it to the power company.

My expectation is that when I tear apart the old switch I'll find a hairline crack in the contactor insulation structure. I'm posting this so people will know that this is a possible failure mode in a (20 year old) transfer switch.

Joel (AKA docj)

[twinboat]

Not sure why a hairline crack would create a 50 amp short, unless the contacts are hanging free and contacting each other in the enclosure.

Following.

[Piros1]

Originally Posted by docj

The other day, out of the blue, my MH tripped the 50A pedestal breaker. A quick analysis of the problem showed power as far down the circuit as my Progressive EMS but the pedestal breaker would trip unless the generator had been started.



Thinking the problem through, I reasoned that the fact that the breaker didn't trip when the generator was on and that the EMS showed power behind the transfer switch meant that the short wasn't in the power cable or the cable reel.



Eventually I convinced myself that the short was had to be in the transfer switch itself although this isn't a common failure mode for these switches. I opened the transfer switch case but didn't see any evidence of arcing.



Today, I bypassed the switch so that shore power was directly connected to

he coach while we wait for a new switch to be delivered. Sure enough, with the switch bypassed everything was fine.



My wife, who was in the coach when the power failed, says that she saw the 120V lights flickering just before power was lost. I had noticed a little flickering the last couple of evenings, but I attributed it to the power company.



My expectation is that when I tear apart the old switch I'll find a hairline crack in the contactor insulation structure. I'm posting this so people will know that this is a possible failure mode in a (20 year old) transfer switch.



Joel (AKA docj)

Not sure if the crack is causing the short but could be causing magnetic coil to not move the switch and properly transfer power through the switch. Not sure what is causing the short unless the coil has a dead short. Strange things do happen at times. I encourage you to post your findings.

[twinboat]

One other thought, was the 50 amp outlet a GFCI protected type ?

I know they are not common, but are out there, and can trip with the slightest ground fault or current imbalance.

[cavie]

Originally Posted by twinboat

One other thought, was the 50 amp outlet a GFCI protected type ?

I know they are not common, but are out there, and can trip with the slightest ground fault or current imbalance.

Yes they can and already do at new Marinas with older boats. Not long before we see them in campgrounds. I have seen Marinas put them in for inspection then remove them after they get a CO.

[Domo]

Sounds as if a contact blew off (due to cracked plastic as OP suggests) and is now shorted on the shore side of the contacts. Would be easy to verify with a meter once it's on a table... I'd guess.

It will be good hear what Joel actually finds as the failure point in his 20 year old transfer switch

[docj]

Originally Posted by twinboat

One other thought, was the 50 amp outlet a GFCI protected type ?

No, it isn't

[veraken]

What is he brand/model number of your old unit, and what are you replacing it with?

[docj]

Originally Posted by veraken

What is he brand/model number of your old unit, and what are you replacing it with?

It's an ESCO ES50M-65N and I'm replacing it with the same exact model

[ualdriver]

Originally Posted by docj

It's an ESCO ES50M-65N and I'm replacing it with the same exact model

Would love to see pictures, before, after, during. I know what a transfer is but don’t know exactly where it is, what it looks like, and what it takes to replace one.

[dendiet]

I had a five year old transfer switch fail for a different reason. One of the stranded power wires wasn’t caped and the lug screw separated the wires causing arcing. This burned out the switch.

[docj]

Originally Posted by ualdriver

Would love to see pictures, before, after, during. I know what a transfer is but don’t know exactly where it is, what it looks like, and what it takes to replace one.

This is what the transfer switch looked like prior to my opening it up and disconnecting it. On the left is the Progressive EMS system.

[ualdriver]

Originally Posted by docj

This is what the transfer switch looked like prior to my opening it up and disconnecting it. On the left is the Progressive EMS system.

OK that is helpful. I thought the transfer switch was some sort of solenoid inside one of the boxes in my electrical compartment. So if my transfer switch ever fails, you replace the whole box?

[vito.a]

Ours is also an Esco ES50-65N. It can get noisy at times.
Esco technician recommended a new LPT50BRD replacement. It's a new design and supposed to be very quiet.