Well guys, what do you all think?

Been working around getting things ready for the first run to Seattle next month and looks like I may have a major furnace issue. When the furnace starts, everything seems to be in order, fan starts, combustion starts, heat builds and when the thermostat is satisfied, combustion stops and the fan runs for a short period of time. Now the bad news, I get an eye irritation after a few cycles of operation, fairly strong at times. I have a good and functioning CO detector and it is NOT going off but it sure seems as if I am getting combustion gases into the coach from either a cracked combustion chamber or leak.

I have checked the outside door and it does seal tightly. Also checked the plastic inner door that separates the combustion area from the fresh/heated air area and that seems good also. Plenty of air movement thru the hoses/outlets and the furnace does not shut down do to an over temp or low air flow. I tested the limit switches and they all work.

All this is leading me to suspect that I have a cracked combustion chamber. I would not look forward to changing this out but if I can't find anything else, I will replace the furnace.

Any and all comments are appreciated.

Could the irritation be coming from dust or mold in the ductwork or the furnace air box?

If there were combustion gases in quantity enough to irritate you, the CO detector should have gone off long before. CO, of course, wouldn't cause the irritation.

Propane exhaust also has a distinctive odor, which you would be able to smell.

In any event, you might try placing the CO detector bext to the register closest to the furnace.

My unknowledgeable, unreliable, guess is that it's something else besides a cracked combustion chamber.

Thanks Rusty:

I have placed the CO detector next to the output of the hot air and nothing. I have talked to "RV furnace experts" and they all say that the CO detector will not go off if it is a crack in the combustion chamber. It will not set off the LPG detector either. The only way they say, is with a sniffer designed for these tests and usually a furnace guy has one.

I also took off the blower moter and blew out the chamber with compressed air, no change.

Will keep all posted.

Good luck...

I don't especially buy the "CO detector won't go off". My ex-wife was at her brother's and she and his family nearly died from CO poisoning - but the CO detector went off finally. It was a crack in the furnace's combustion chamber...

But a sniffer seems like the best way to be sure.

I would try your local Fire Department, My neighbor loves to find furnace problems with our local fire depts equipment, he says it better than pulling kids out of a house that has a bad furnace and its good training on the equipment. The equipment they have is far better than any home CO detector . JKB

Great suggestion for using the local fire department.

One quick check you can make (and may have already) is to ensure that critters haven't blocked the exhaust. Doesn't take much.

Mike

quote:

Originally posted by MWrench:
I have a good and functioning CO detector and it is NOT going off but it sure seems as if I am getting combustion gases into the coach from either a cracked combustion chamber or leak.

What did you test it with. The first rule I always follow is "test the test equipment" That little button isn't the answer. Start up your generator and place the CO detector by the exhaust pipe for a few seconds. Not to long!

I'm going to go with Relatives assumption about the critter factor first.

I'd go with your assumption about the cracked combustion chamber next.

Low on the list but, is the refrigerator running? It could be leaking, try turning that off as well. I'm not there with you and don't know if your throwing your main and then running your furnace and then throwing it back off again when you start to notice the irritation. Is there an ammonia type of smell?

Can you take the CO detector from your house and try it next?

If you don't have the proper test equipment then check with the volunteer fire department. They love to play with there toys as SLOOP JOHN B pointed out.

Well, the combustion chamber has a crack, was confirmed by a heating specialist by a gas analysis. I later looked at the combustion chamber thru a boroscope placed into one of the heat ducts openings, during ignition I could see a small crack, after a short time the crack would close but obviously it could not be a gas tight seal.

I have a new furnace on order and NOT looking forward to doing the changeover, may have to remove some of the bathroom area stuff to get at it, very tight in there! I will be changing all the heat runs as well.

Thanks for all your comments.

quote:

Originally posted by MWrench:
I have a good and functioning CO detector and it is NOT going off but it sure seems as if I am getting combustion gases into the coach from either a cracked combustion chamber or leak.

quote:

Originally posted by MWrench:
Well, the combustion chamber has a crack, was confirmed by a heating specialist by a gas analysis.

Imagine what could have happened. Get a new CO detector fast!

Ed, before you tear out the bathroom, do a careful survey. I R & R'd my furnaces from outside.

I drilled out the rivets to remove the outer door, & disconnected the gas inlet at the furnace. Inside, I accessed the hold-down screws on the back of the furnace, the wiring & ductwork, disconnected all that stuff, & slid the furnace out from the outside. On the wiring, I found it easier to clip the wires, leaving enough on each end to easily reconnect them with butt connectors, rather than messing with the nearly inaccessible plug connectors inside the furnace. Check it out, yours might be different.

When you get your new furnace you'll be able to see better how to proceed.

My rear furnace is under the street side twin bed, and the front one under the front couch. I replaced the rear one, & had a new motor installed in the front. Had to R. & R. the front one to have the motor replaced in a shop.