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Skidaver · 05-17-2018, 09:23 PM

Mud daubers plugged the exhaust tube on our furnace about 95%. They also had 1 or 2 nests inside the heat exchanger. Result was soot on the side of the motor home and fumes in the bedroom. I cleaned the nests out and am ready to reassemble. The problem is, the heat exchanger seems to have a lot of soot in it. I rattled around some nuts and bolts and got about 1/3 cup of soot out. But I am guessing there is a lot more in there, and that the heat exchanger will be inefficient at transferring heat if it is lined with soot. Does anyone have any ideas how to get the soot out?

Old-Biscuit · 05-17-2018, 11:25 PM

Blow the heat exchanger out using compressed air

OR
Completely disassemble furnace pulling heat exchanger completely out and then wash it out using water (will need a new element gasket for reassembly)

Quincy · 05-18-2018, 04:57 AM

Quote:

Originally Posted by Old-Biscuit

Blow the heat exchanger out using compressed air

OR
Completely disassemble furnace pulling heat exchanger completely out and then wash it out using water (will need a new element gasket for reassembly)

X2 But if you rattled some nuts around then you must have it out of the rig in which case you can flush it with water. The exchanger has two chambers, one where the burner lays and the other where the air from the coach is circulated.

If you have already put the unit back in the RV you can remove the burner and still flush it out with water from the outside. Dont worry about drying it out just fire it up when you get it back together, it will dry.

Good luck and keep us in the loop.

TripleEEE · 05-18-2018, 09:05 AM

https://www.etrailer.com/search/Furnace+Vent+Screen

Once you have everything clean, add a screen to keep them out....

Skidaver · 05-19-2018, 07:06 AM

I wasn't sure water would dissolve the soot, but I will try it. I know the wind blew some of the soot I already got out around the shop and it was hard to clean up. I also thought compressed air would not have much velocity once it rounded the first bend, but I will try that as well. My thoughts were along the lines of BB's or sand and a vibrating table. But I don't know where there is a vibrating table available to the public. I also thought there might be a silver bullet liquid that would dissolve it. MEK and mineral spirits didn't do it.

Old-Biscuit · 05-19-2018, 10:11 AM

Quote:

Originally Posted by Skidaver

I wasn't sure water would dissolve the soot, but I will try it. I know the wind blew some of the soot I already got out around the shop and it was hard to clean up. I also thought compressed air would not have much velocity once it rounded the first bend, but I will try that as well. My thoughts were along the lines of BB's or sand and a vibrating table. But I don't know where there is a vibrating table available to the public. I also thought there might be a silver bullet liquid that would dissolve it. MEK and mineral spirits didn't do it.

YOU are overthinking this.

Bob_C · 05-19-2018, 10:27 AM

You'd also be ahead if you screened off the roof A/C cover vents.....remove the cover and add to the inside.....they like to build nests on the fan...

Skidaver · 05-26-2018, 08:01 PM

To bring closure to this story, high water flow didn't seem to do much; compressed air did more than I thought it would; denatured alcohol seemed to dissolve the soot at least a little; and rattling nuts and bolts did the best job. I was surprised to get about 6 more mud dauber cells out of the heat exchanger. I had no idea they would go that far in to build their nests.

Thanks to those of you who offered constructive ideas on this. I feel better about the efficiency of the furnace without a coating of soot on the interior of the heat exchanger.