Norcold Refrigerator Fire

[Jim_Arndt]

We have two N841R refrigerators on our houseboat at Lake Powell. Yesterday while running the generator with the refrigerators in AC mode, one of the refrigerator powerboards caught fire where the AC powercord attaches.

Fortunately several were on board and were able to quickly put out the fire.

We are having our dealer come out, but it is interesting to note that Thetford customer support provided no assistance, and refused to let us talk to a technician to determine root cause.

Surprising lack of support, we've bought 4 of these refrigerators in the past 5 years, you think they could at least take our phone call.

Link to pics:
https://photos.app.goo.gl/wqr5zK7TbjtHwf373

[WILDEBILL308]

When my cooling unit quit there was yellow powder. I would be looking at residential units to replace it. If you look at "counter depth" units they will fit better.
Bill

[Jim_Arndt]

Yep, the cooling unit is shot. Time for a new unit, have lots of spare parts... 😞

[SidecarFlip]

Ammonia fridges don't gurgle. They are silent.

[Jim_Arndt]

Oh no guys, I just put 350 in parts to repair the refir. I started it up in ac mode, 10 minutes later it is gurgling very loudly. I shut it down as we were heading into down for dinner, I will test again when I get back later.

Leaking cooling unit? Any wat to check, it was covered in yellow powder, I assumed from the fire extiguisher. Maybe the dark yellow ammonia mixed with the white powder exringuisher stuff. Anyways, sucks to diagnose this drom 1000 miles away. Had a good day at the lake today though...

Thoughts?

[Jim_Arndt]

mike-s wrote:

Jim_Arndt wrote:
Wow, ok, so the fuse would not blow? There is a 5 amp fuse on the powerboard, and a circuit breaker at the main ac panel.

The fridge won't draw more than 5 A normally, so that's the fuse size. It might try to pull, say, 4 A, but instead of powering the fridge, the power goes into the resistance of the bad connection, which heats up. 4 A @ 12 V is 48 watts, and confined to a small area that equals lots of heat. It's not quite that simple, but the concept is close enough.

Any time smoke comes from the area of a connection, suspect a bad connection. It may not have been the screw terminal, it could also be a crimped connection. Kinda hard to tell from the photo, not enough resolution.

I think if there was a direct short, it would of been enough current to pop the breaker.

I updated the link in the original post, with a before picture and a picture of a new powerboard. I'm not at the boat, but it looks like norcold has a special plug that goes over the spade connector on the powerboard, not sure? Also, yes the cable is clamped, you can see this clearly in the before picture.

A screw down type of clamping connector on the powerboard, similar to what you see on an AC circuit breaker, would of prevented this fire.

Link to pics:
https://photos.app.goo.gl/wqr5zK7TbjtHwf373

[SidecarFlip]

ScottG wrote:
First make sure the connection is sound and working.
Then, if you must, apply dielectric grease.
Just keep in mind that DG DOES NOT improve an existing connection.

correct but it slows corrosion. A good mechanical fit is always required first. I used DG anywhere there is a chance of moisture issues.

[mike-s]

Jim_Arndt wrote:
Wow, ok, so the fuse would not blow? There is a 5 amp fuse on the powerboard, and a circuit breaker at the main ac panel.

The fridge won't draw more than 5 A normally, so that's the fuse size. It might try to pull, say, 4 A, but instead of powering the fridge, the power goes into the resistance of the bad connection, which heats up. 4 A @ 12 V is 48 watts, and confined to a small area that equals lots of heat. It's not quite that simple, but the concept is close enough.

Any time smoke comes from the area of a connection, suspect a bad connection. It may not have been the screw terminal, it could also be a crimped connection. Kinda hard to tell from the photo, not enough resolution.

[shastagary]

look at way the other wires going to the circuit board are pinched against the metal back of the refrigerator by what is left of the black cover on the circuit board. if the ac power wires were pinched against that metal back and were getting hot enough to melt there insulation or pinched hard enough to cause there insulation to be thin in that spot they could easily short out. are they only protected by the breaker to the ac outlet 15?-20? amp through those smaller wires. now after blowing up the picture looks like the fire started below the black cover where the ac cord connects to the refrigerator was there some kind of a clamp there holding the power cord?

[ScottG]

First make sure the connection is sound and working.
Then, if you must, apply dielectric grease.
Just keep in mind that DG DOES NOT improve an existing connection.

[SidecarFlip]

I tend to check every connection myself and apply di-electric grease and or check the tension on wire clips. I do that with automotive Molex connectors too.

Far as sleeping, so long as your electric blanket don't catch fore, you are ok...lol

[Jim_Arndt]

Agreed with everything posted. I guess my concern is, this is not normally an end user maintenance item or servicable part. And this is a newer refir, with no visible corrosion.

At home, do you pull your appliances, open up the power cord electric box, and check the wire nuts for corrosion?

Even though it's a house boat, it's arizona and it's bone dry. There is little to no corrosion. There is more corrosion at my house 2 miles from the ocean. You would think the connection would be properly coated with dielectric grease or similar from the factory, especially since it will be mounted with the exterior exposed to the outside (in a vented compartment in the rv.)

Scary stuff, bad connections lurking everywhere, how am I going to sleep tonight... 🙂

[ScottG]

Jim_Arndt wrote:

Old-Biscuit wrote:
Well
Electrical fire at AC terminals on circuit board was probably due to loose/corroded connections.

Water environment requires higher degree of maintenance.

Wow, ok, so the fuse would not blow? There is a 5 amp fuse on the powerboard, and a circuit breaker at the main ac panel.

So, are you saying there was resistance at the powerboard AC connector, causing it to heat eventually igniting the wire insulation or other?

I guess I thought a fuse would blow, but I guess not in the above scenario as the current never exceeded the fuse rating.

Scary, as this would apply to a residential fridge or any appliance on board.

So how do you maintain this, after the applicance has been powered on for a while feel the wire for warmth? Learned something new today, thanks guys...

That's a common misconception about fuses blowing.
Think of it this way, with a given amount of current flowing through a connection, say three amps, if that same connection is severely weakened (corroded, loose) it wont be able to pass that same three amps without getting hot.
That three amps can cause so much heat through the bad connection that it can start a fire - all the while the 5 amp fuse is happily passing that three amps along.

[Old-Biscuit]

Jim_Arndt wrote:

Old-Biscuit wrote:
Well
Electrical fire at AC terminals on circuit board was probably due to loose/corroded connections.

Water environment requires higher degree of maintenance.

Wow, ok, so the fuse would not blow? There is a 5 amp fuse on the powerboard, and a circuit breaker at the main ac panel.

So, are you saying there was resistance at the powerboard AC connector, causing it to heat eventually igniting the wire insulation or other?

I guess I thought a fuse would blow, but I guess not in the above scenario as the current never exceeded the fuse rating.

Scary, as this would apply to a residential fridge or any appliance on board.

So how do you maintain this, after the applicance has been powered on for a while feel the wire for warmth? Learned something new today, thanks guys...

5A fuse on circuit board is for the AC circuit/electric heater element. Not for the AC power coming to board. That is what the AC circuit breaker for the OUTLET power cord plugs into is for.......15A CB

Need to check the tightness and keep terminals on circuit board clean.
As suggested..di-electric grease---water environment.
Also go thru your Main AC Panel and check/tighten ALL terminal lugs.

Best of luck!

[SidecarFlip]

I think I'd be making liberal use of di-electric grease in / on all electrical connections as well.