Furnace fuse blows on 50 amp power

[KLRTN]

Our furnace fuse has been blowing when hooked up to 50 amp shore power. This does not happen when hooked up to 30 amp. I have not tested on battery power only.

Before we discovered it only happened on 50 amp, I took out the electrical panel and tightened all grounds (some were very loose) and reconnected a duct that was unhooked from the furnace. I then hooked up to 30 amp at my house and everything worked great. Next camping trip with a 50 amp site, the furnace blew 2 fuses within 5 minutes.

Anyone have any ideas? We have a 2022 Cougar BHS with Dometic DFMD35121 furnace.

[jxnbbl]

I thought the furnace was all 12V?

[NH_Bulldog]

As far as I know, the furnace is 12v DC-only with no AC power components, so what you are experiencing is a likely coincidental symptom of an issue with your shore power connection or converter?

1) Are you connecting to a known, trusted and properly wired 50A connection? Have you used this connection before without issue?

2) Are you connected through an EMS which could alert you to an issue in the power feed? If not, it is highly recommended, especially if connecting to an unknown, untested and “public” power connection.

I tend to see and hear more 50A pedestal issues than 30A issues, in part because of how they are wired.

[chuckster57]

Furnace is 12VDC. Check converter output on both 30A and 50A.

[KLRTN]

Originally Posted by NH_Bulldog

As far as I know, the furnace is 12v DC-only with no AC power components, so what you are experiencing is a likely coincidental symptom of an issue with your shore power connection or converter?

1) Are you connecting to a known, trusted and properly wired 50A connection? Have you used this connection before without issue?

2) Are you connected through an EMS which could alert you to an issue in the power feed? If not, it is highly recommended, especially if connecting to an unknown, untested and “public” power connection.

I tend to see and hear more 50A pedestal issues than 30A issues, in part because of how they are wired.

We have camped at 3 different places with 50 amp service and it has happened at all 3. We have a 50 amp surge protector/circuit analyzer and it has shown no problems at any site. We have a 30 amp hookup at home and it has never had a problem hooked up there.

We have not had any issues with anything else electrical. We took it in to have it looked out and service center didn't find an issue. However, this was before we determined it only happened on 50 amp hookup.

[wiredgeorge]

Originally Posted by KLRTN

We have camped at 3 different places with 50 amp service and it has happened at all 3. We have a 50 amp surge protector/circuit analyzer and it has shown no problems at any site. We have a 30 amp hookup at home and it has never had a problem hooked up there.

We have not had any issues with anything else electrical. We took it in to have it looked out and service center didn't find an issue. However, this was before we determined it only happened on 50 amp hookup.

Which "surge protector" are you using?

[KLRTN]

We are using a CARMTEK surge protector.

CARMTEK RV Surge Protector 50 Amp - RV Circuit Analyzer with Integrated Surge Protection - Smart 50 Amp Surge Voltage Defender with Grip Handles

[NH_Bulldog]

A surge protector is just that, and only marginally so. It has lights that show a circuit is wired correctly. It is very limited in function and at $45+/- is very inexpensive (cheap).

An EMS is typically $300-$400+ and can analyze circuits, voltage, stray voltage, etc. and shut power down to the camper before it burns something up or blows 12v fuses.

Based on what you have shared so far, I am leaning towards an issue with the shore power cord or converter. The 30A circuit is 3 wire and the 50A is 4 wire and that is leading me to believe the 4th wire is the issue in some way.

[chuckster57]

Originally Posted by NH_Bulldog

A surge protector is just that, and only marginally so. It has lights that show a circuit is wired correctly. It is very limited in function and at $45+/- is very inexpensive (cheap).

An EMS is typically $300-$400+ and can analyze circuits, voltage, stray voltage, etc. and shut power down to the camper before it burns something up or blows 12v fuses.

Based on what you have shared so far, I am leaning towards an issue with the shore power cord or converter. The 30A circuit is 3 wire and the 50A is 4 wire and that is leading me to believe the 4th wire is the issue in some way.

That’s why I said to check converter output on both 30A and 50A.

[KLRTN]

Thanks for the tips. I will check these on our next camping trip. Unfortunately, I don't have access to 50 amp power until our next trip. I will follow up if I get it figured out.