Furnace stuff...

[Chuck]

tried out the furnace last night for the first time. PO told me that it was all "checked out" by their repair guy before I picked it up in June. (they never used it themselves...seldom camped in cold weather, and when they did, they just used the catalytic heater). Haven't had opportunity to use it yet, and as there was a frost warning last night, and I'm not ready to put it away for the winter yet, I figured it would be a good time to try it out. (going to need it this weekend...)

took a while to get the pilot to light, but once it did, everything seemed to work...blows hot air, and all, but I noticed a couple of things that may need some "tweeking".

once I turned the t-stat up, and the furnace started actually running, I took the cap off to check the flame, and a big 8-inch flame shot out of the cap at me. from browsing through a manual that was just posted in another thread, this doesn't sound normal to me. Anyway, I turned down the t-stat, put the cap back on, and then turned it back on again...like I said, it blows hot air.

Not very much air comes out the vent under the street-side bunk. Lots of air blows out the vent on the side of the sink-cabinet, which is about 6 inches from the furnace...so this might be normal.

So I left the tstat at 60, let it run all night, and checked it thismorning. everything seemed fine..trailer was warm. I did notice some black sooty stuff outside the exhaust port. Does this mean something needs adjusting? any tips?

[3Ms75Argosy]

I'm glad someone else is "firing up" for the first time. We too tried our furnace last week, when we had the dealer check out the unit, the furnice pilot let up right away - I had considerably more trouble. I found success by lighting the oven burner (only one), letting it run awhile, turning it off, cursing the heater (silently!), leaving it alone for five minutes, and then attempted again. Lit right up! Anyway, we left our door open - I wanted to watch the kids play outside, and was a bit afraid of CO (going to Home Depot this weekend to get the combo smoke/CO detector). When I went to close the door, I noticed the door was stained with soot! Good thing I'm planning on stripping the paint. The front did seem a bit warmer then the back, but I too chalked that up to the vent run length. No shooting flames however. What does concern me is that I THINK I smelled propane in the trailer during the furnace run, but could it be just the smell of the flames burning? Anyone else with a faint smell?
Marc

[davidz71]

3ms75Argosy,
It seems we share the same method of purging the LP line of air. After turning the LP tank valve on, I go into the trailer and smell for propane. If no smell, I turn on a stove eye and light it. I sometimes light all 4 and let them run for a minute or so. I then shut them off and try to light the refrigerator which always takes a few tries but not as many if I haven't followed the above procedure. I can then light the furnace and it fires up the first if not the second attempt.

[thenewkid64]

If you look under the gaucho or bed that the heater vent travels under you will see why the output from the rear heat duct is minor. If you are afraid to look, here is the answer. The ductwork here branches and goes into the belly to heat the holding tanks.

As to the soot issue, I have no clue. I am sure someone with more experience here can help. Be sure to check where your furnace exaust is. The ones that are behind the door can and will blister the clearcoat or paint if the door is left open while the furnace runs.

[Silver Bullet]

I'm assuming you have a Suburban (I don't). I have an old International furnace. My problem was similar to yours, upon further investigation the heat-exchangers had rusted holes through them. When fan was running it would shoot the flames all over the place (inside the burner compartment) and when the flames were out, the pilot light would get blown out by the fan force. I'm not HVAC but flames and fan are and should be separated from each other, to avoid CO poisoning. I pulled ours out and refurbished the heat exchangers, used it last weekend and was toasty warm and no CO alarms sounded. Flames and pilot were constant throughout cycle. Oscar

[Chuck]

Ok, well we're back from our camping weekend, and we're still alive! I figured out where the adjusting screw was hiding on the furnace, and adjusted it as much as I could to add more primary air to the burner...turned the screw to what I think is the limit, and not much changed. There was still a little bit of sooting on the exhaust port. Furnace never made any noise, as the manual said it would if it got "too much" primary air. So I don't know what's up w/ that. can't seem to give it any more than its getting....CO detector read "0" at all times, and like I said, we're still alive. Furnace seems to "work" just fine.

One thing I noticed, though, was that someone had installed a screen on the exhaust/intake port, and the manual says that is a "no-no". Wonder if that could be the source of my problem w/ the sooting? Its a heavy screen, with pretty big holes, like "hardware cloth". Doesn't seem like it should be putting a significant damper on airflow, but I suppose I can try to remove it and see what happens.

How do you keep critters out of there w/o some sort of screen? these things don't run much in the summertime....I would think this would be a prime location for bugs, etc....

[Inland RV Center, In]

Soot appears when the fuel/air mixture is incorrect. It is best to remove the furnace, disassemble it,clean out "ALL" the soot, reassemble it with new gaskets. Test it on a bench and adjust the burner air shutter. USE EXTREME CAUTION WHEN MAKING THIS ADJUSTMENT, AS THE BURNER INSPECTION CAP MUST BE REMOVED. A FLAME WILL SHOOT THROUGHT THAT OPENING, WHICH IS NORMAL. ADJUST THE AIR SO THAT THE TIP OF THE FLAME IS BLUE.
WHEN BENCH TESTING MAKE SURE THE LPG PRESSURE IS CORRECT (11-13 inches WCP), AND THAT THE FURNACE IS SUPPLIED WITH A MINIMUM BATTERY VOLTAGE OF 12 VOLTS DC.

Blowing the combustion chamber out with "AIR" will not properly remove the soot and probably a lot of rust with it. Some shops that are "LAZY" will use that method.

The big question is "HOW DID THE AIR ADJUSTMENT CHANGE?"
Back to the real basics. LACK OF PROPER WHEEL BALANCE!!!!
Unless there is some type of vibration, the air adjustment cannot change by itself.


Andy
inlandrv.com
airstreamparts.com

[Chuck]

Thanks, Andy. Glad to hear that the flame shooting out of the cap is normal.

How did the adjustment change? I don't know. I've only owned the unit for a few months, and this is the first time I've used the furnace. the PO's told me that they never used it, and they owned the trailer for 5 or 6 years. They only camped in warm weather, and when it got "a little chilly", they used the catalytic heater. The trailer was getting some water pipes repaired before I picked it up, and I was told by the PO that when they went in to check on it, the furnace was removed and was sitting on the living room floor...presumably the repair man had to get it out of the way to access the pipes. (?). Anyway, it was allegedly "all checked out" before I picked it up. LP system was checked, too.

Andy, I'll be your first wheel-balancing customer as soon as you open your Boston area branch office.
Until then, I'll do the best I can! Don't know if I can find anyone around here that'll do as thorough a job, but I'll try.

[davidz71]

Chuck,

The exhaust screen is indeed placed there to keep out little critters, especially mud daubbers which built mud nests inside the combustion chamber. It happened to mine so when the furnace was rebuilt, I bought a screen made for this purpose to fit over it. A friend had the same thing happen to his unit but it was not a Suburban furnace. They got in and made so many nests that his furnace wheels would not even turn when power was applied. He had to reach in and break the mud free. He then removed the furnace cleaned the wheels out and put it back in.

[NewStreamer]

Is it easy to remove the suburban furnace on a 72 AS
I never tried to light it as it is quite rusty and I don't trust it.

Ron

[Dbraw]

The burner inspection cap on the furnace in our 71 Safari has a small cracked area and it appears that there is a small smoldering area about 1/8 inch long on the face of it. Where can I buy a new cap?
Dan

[Guitars]

The inspection (and lighting I assume) cap on my 22 foot '67 Safari has rusted off. If the furnace is that rusty it is time for a replacement. (Life is short enough already). The question; the original furnace (Surburban NT-22) is rated at 16,800 btu if I recall. There is a NT-24 (24,000 btu) and a NT-34 (34,000) that should be fairly easy replacements. The boxes are the same size and either should heat the A/S well. The NT-22 draws 3.5 amps and the NT-34 draws 7.5. The prices are very close. So the question; other than the increased amps the NT-34 draws and the slightly higher price is there a downside to going with the larger furnace? Am I missing something here?