Furnace made multiple "Bang!"

[AKA]

I'm new.
My 1975 31 foot Sovereign just came to me with no LP tanks and I have never owned an RV. I have all the manuals and I read them. I used the forum to familiarize myself with the heating system and I inspected everything prior to testing the LP system.
When I tested the suburban furnace, it lit up and started pumping heat out of the front vent at the sink. It Seemed ok. I left the door to the trailer open in case I actually needed an exit. (HMMM may need to come back to that) All seemed well and then there was a loud "WHOOMP" followed a few seconds later by another one. I exited the trailer through the open door and shut off the gas. I wasn't staying in it long enough to get to the rear controls and then the forward exit. (learned that trick in the Marines.) I inspected the system again and noticed that the open door actually blocks the exhaust vents for the furnace. HMMM... Is that the cause of the loud "flare"? there is a nice little hot spot on the door there, I wiped it off with a towel. Did I actually cause back pressure in the system by leaving the door open?
AKA

[nrgtrakr]

Try it again and see ...
(most likely)

[tjdonahoe]

You were also blocking the fresh air intake and the exhaust....

[mandolindave]

MAKE SURE THAT YOU HAVE A REGULATOR ON THE GAS TANKS.

The pressure from unregulated gas tanks can blow seals, and cause a gas leak

[mandolindave]

Consider why the trailer had no propane tanks. Might the seller have had a problem with the regulator or the furnace.

Sorry if I am being an alarmist. But in my opinion, it might be a job for an expert, and not a try again see what happens situation

[mandolindave]

The tanks might have been missing for a long time. Leaving open hoses, available for a variety of insects to set up shop.

Spiders seem to like the smell of the perfume in propane. Mud Daubers can clog up orifices as well. It could be that the pressure from the tanks blew out the homes that the insects made, causing a sudden blast of propane.

It would be hard to make a determination without close inspection. And I wouldn't want to be responsible for damage or injury.

[mandolindave]

A door that opens in front of the furnace vents seems to be a really bad design.

But I am doubtful that the door could seal up the vents. I am thinking that there would still be airflow.

[idroba]

It is a 40 year old furnace. It is time to replace it no matter what the exact issue with it is now. There were many recalls of those Suburban furnaces from those years. Parts are no longer available from Suburban for the recalls (or much else). The burners (cast iron) can clog up, the combustion chambers very commonly rust out, insects build nests inside them restricting combustion and exhaust air flow. Those are hard to find and clean out. If inside the combustion chamber, virtually impossible.

If you are not familiar with Propane, how it is plumbed and how it works, please have a professional do the work on any regulators, or lines. You can most likely replace the furnace itself, by yourself.

There are lots of safety issues here, I mean your life safety.

[mandolindave]

I was lucky…My furnace just stopped working ( on a 28 degree night ON THE FOURTH OF JULY !!!!!!!!!!!!!!!!!!!!!)

[nrgtrakr]

Furnace recall info here:
http://www.airforums.com/forums/f427...call-2889.html

[JCWDCW]

Our door blew open in the night with furnace running. There is enough clearance (on my '89 at least) that it continued to run without problems. My biggest fear was the door might be damaged, but there was no stain or blistering....good thing as the clearcoat was only 2 months old.

Try it again..with the door propped to give enough clearance. Could be a furnace sensor is failing. The gas should shut off if there is no flame or an interruption in flame. Could be the furnace burner is not getting enough air, and some un-burned gas build up is getting ignited closer to the vent rather than in the heat chamber. That could be caused by blocked intake...possibly bee nests. If the problem persists get it replaced as noted above. An old furnace is just not worth fighting.
JCW

[airdreamers]

I tend to agree with lack of fresh air to the furnace. Having said that I also agree that gas is not to be treated lightly as it pertains to appliances. Just the "Bang" would give me concern enough to have an expert check it out. Better be safe then sorry, there is no price on safety. Good luck!

[andreasduess]

Change the furnace. Furnaces that old aren't the safest bet to start with, and with rust and rot added to that, I would not run the risk.

[Sodbust1]

I understand all the good advice above,,, as throwing out $$$ for a new,, installed unit is a sure bet to fix it...

I can picture the open door sealing off enough fresh air to trigger your as it recycled its own air enough times it ended up with the event you talked about. Throwing the door open on our trailer gives about 3/4" of clearance and I can picture it might choke things off to trigger your event.

I ran into about the same issues when I fired up our 72 Overlanders heater the first time.. Turned out to be a combination of mud dobbers nests,, old spider webs and some outer space looking fossils plugging up the intake and exhaust side of the heater. Even the blower fan had wads of mud,, leaves and such throwing it out of balance.

Did a full take down and clean up and inspection of the old girl and added a few drops of high grade sync. oil to the motor shaft bearings. Has ran like a champ every since. I did study the condition of the main burner and fire box and looked to me it had only been ran a few times before as it still had 1/2 of its paint still on the outside. Might have been just the testing when the trailer was built?

Anyway,, I like the old tech items and it seems the older they get the more trouble free they are once you understand the basics and safety related side of it all.
Sodbust

[nrgtrakr]

When I inspected the furnace on our 75 it was like new inside so it stays for now. I've seen older forced air units. I've also seen 50 year old gas water heaters that still looked like new. Maintenance, amount of use, and the environmental conditions where used is more critical than age alone.

[guskmg]

One morning in 1974 at 5:00 a.m., I watched as three people including an infant were carried out of an Airstream. All were overcome by cabin monoxide from a leaky Suburban heater combustion chamber. I would not mess around with your old furnace. Even if you could find the parts it just isn't worth the risk using a potentially hazardous heater with that reputation. I have not heard of any recent model problems, but I would sure check them out before purchase.
guskmg

[xrvr]

Carbon monoxide detector? What a tragedy.

[andreasduess]

I've got two CO2 detectors on board, a hangover from my days living on a boat heated by a solid fuel stove, but I still removed the furnace of our Airstream because there was too much rust for my liking.

Carbon monoxide is a silent killer and old furnaces are notorious for leaks. This isn't the place to start looking for savings.