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Old 01-05-2011, 09:56 PM   #1
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Suburban Propane Heaters / Condensation

My family of 4 recently spent a week in our Sprinter Sportsmobile over Christmas and New Years - what an awesome vehicle and a great way to travel.

I had one major issue on the trip - my Suburban Propane furnace would fail to light most of the time, which is a bit of a bummer in the middle of winter. The blower turns on, the electric sparker lights, but it fails to ignite the propane. After 10-20 tries I could finally get it to light, and once lit it would stay lit and put out heat just fine. One more interesting irony - the colder is was, the harder it was to light.

I took it apart and looked for something obvious, but couldn't find anything. I made sure I was getting a spark, and could smell propane when it wouldn't light. My current theory is that it's partially clogged and not enough propane is making it into the ignition chamber. With enough tries, there's enough residual propane to finally light - any recommendations on what to check?

Also, when I did finally heat up the van, I was getting a ton of condensation on the insides of the windows and on any exposed metal, due to the temperature difference. Does anybody have recommendations on 12V de-humidifiers or other ways to prevent condensation in the winter?

Thanks, Vic
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Old 01-05-2011, 10:18 PM   #2
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Suburban Propane Heaters / Condensation

I have no idea about the heater specifically, but the combustion of propane has the byproduct of H2O, in the form of water vapor.

This is why you see an excess of condensation in the interior. I would think that a dehumidifier would really have to work hard to keep up with a propane heater, especially since the water vapor is being produced with a heat source and therefor should be higher near the roof and lower on the floor where the dehumidifier would be.

Just a thought.
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Old 01-05-2011, 10:36 PM   #3
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Re: Suburban Propane Heaters / Condensation

I am going to have to disagree with Rockman on this. The Suburban furnace sources air from and exhausts air to the exterior. H2O as a byproduct of combustion should not be part of your condensation problem.

We have the same furnace fire up issues you describe. I checked everything on the furnace and looked to this forum for ideas and came up empty on both. Still, it does light up eventually and once it does, it seems to work fine. I don't keep cycling the thermostat - I just let it do its thing.

One question - you said you can smell propane. Is that inside or outside the van? You shouldn't smell propane inside. That could mean you have a leak.

As for condensation, I can tell you what we do - extra towels and a long warm up with the defrost on high.
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Old 01-05-2011, 11:39 PM   #4
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Re: Suburban Propane Heaters / Condensation

I only smell propane when I put my nose right up to the heater vent while it's trying to light - I would think this is normal as some propane must be released into the vent tube in order for the spark to light the gas.

The heater attempts to light 3 times and then after that it must be turned off/on to attempt another light. There is no propane smell after the 3rd attempt so I think that's working fine. One thing that's frustrating is that the blower stays on even if it doesn't light, so if you set the thermostat, and the heater doesn't light, the blower will run until you wake up and shut it off, or it kills the battery.
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Old 01-06-2011, 05:47 AM   #5
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Suburban Propane Heaters / Condensation

I digress,
I didnt know it exhausts to the exterior. Aldercrest is correct.

Sorry, I'll take my two cents back
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Old 01-06-2011, 07:03 AM   #6
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Re: Suburban Propane Heaters / Condensation

Vealessi,

One thing to look at when the suburban does not start correctly is your battery voltage. Lower voltage and altitude can cause issues with the exhaust vane safety switch. Since the DC blower RPM would be a direct correlation to the voltage, and as you go up in altitude less air for blower to push. If the switch doesn't close it won't light.

A second thing to check is that your tank valve is open completely, a partially open valve may work to run the stove, but not enough fuel to run the furnace.

Also I did have an issue early on, that apparently went away when the control board connections were cleaned (this was from the right up from camping world tech).

There is also a possibility of having air in the line, somewhere on this forum there was a link to purge. see below or this link viewtopic.php?f=40&t=1858&hilit=suburban
Quote:
Hello,

The usual culprit for the furnace not operating at high elevations is air in the system. If the furnace performs well at lower elevations, then you can almost bet you have air in the tank that needs to be purged.

The opening of the vapor tube is high in the tank. Since propane is heavier than air, the propane settles below any air remaining in the tank, and the air, which expands as you increase in elevation, is what the furnace is trying to ignite. To add confusion to this condition, you'll find that the propane stove and propane water heater usually operate okay at the higher elevations. They are not as temperamental as the furnace, which has many safety features preventing it from operating unless everything is as it should be.

To purge the air out of the LP Gas cylinder, make sure you are outdoors and away from any flame or spark producing item. Open the "Purge Valve" which is a small (about 5/8" diameter) brass valve above the main "on-off" valve. If there is air in the cylinder, the propane odor will not be as strong as if it were pure propane. I've seen it take up to 30 minutes to purge most of the air out of the tank (this was at 250' elevation, if you perform the purge at higher elevation it will purge quicker). You can also have a qualified LP Gas filling station purge your cylinder. You will have to run the furnace through several cycles before it will start after purging the air.

While this worked for almost every customer who reported this condition, there are a few other issues that occured. Confirm that there is nothing blocking the return air grill or path. The sail switch inside the furnace will not allow the gas solenoid valve to open if there is insufficient air flow. One way to determine if the gas solenoid valve is opening during start-up is to smell at the exterior vent after turning thermostat "on". If you don't have any LP Gas odor, you probably have an air flow issue. If you do have an LP Gas odor, you could have an ignitor problem (no manual overide), or it could still be an issue with air in the system (did I mention purging ALL the air out of the system!).

Let me know if you still have problems after purging the air out of the cylinder, I'll be glad to offer more detailed help.

John K.


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Old 01-06-2011, 04:49 PM   #7
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Re: Suburban Propane Heaters / Condensation

Quote:
Originally Posted by vealessi
I only smell propane when I put my nose right up to the heater vent while it's trying to light - I would think this is normal as some propane must be released into the vent tube in order for the spark to light the gas.
Okay, I did the same thing with the same results.

Greg - thank you for sharing the information from John Kalmbach. This sounds like maybe the source of my problem and I couldn't previously find this info on the forum. Very much appreciated.

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Old 01-06-2011, 06:24 PM   #8
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Re: Suburban Propane Heaters / Condensation

For what it's worth, you describe precisely how mine works (or doesn't). It appears to be primarily a function of what altitude I'm at. At low altitude, it fires up perfectly. At around 7000' I know it gives me problems. Higher than that is worse. Once you can get it to fire up once, it will work fine through the rest of the night.

If anyone ever figures out a resolution to this please post it up.

Phil
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Old 01-06-2011, 11:39 PM   #9
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Re: Suburban Propane Heaters / Condensation

We had this problem (furnace wouldn't light) and it usually seemed to be related to low battery voltage. If we really wanted to get the furnace to light, i would start up the van and it would fire right up. However once it cylced off it sometimes wouldn't fire up again when the thermostat called for it.

I think the Suburban type furnaces are pretty low-tech equipment. Fan speed is directly tied to voltage, propane pressure depends on single stage regulator at the tank (I think) which is affected by the temperature of the tank, and it has a mechanical air pressure/flow switch. The Espar heater advertises that it will work over a fairly large voltage range (probably has a variable speed fan controlled by air pressure). I wonder if the Propex unit works better over a wider temperature/voltage/ambient temperature range?

As far as condensation, we notice it mainly when we have wet clothes or melting snow inside the van. Towels and automotive defroster to clear up. Maybe crack the roof vent sometimes if it's not too cold out.
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Old 01-25-2011, 12:33 PM   #10
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Re: Suburban Propane Heaters / Condensation

Thanks for all of the suggestions.

With my particular issue, it's not altitude (I was at ~3000ft) and not low voltage (it fails with the van running or when plugged in to shore power)

I will check the return path, and have the air in my system purged when I refill my propane.

There's a place down the street that works on these furnaces, I am also going to have them look at it - If I get any sage advice I will post it.


I want to get the furnace working properly; it defeats the whole purpose of having a thermostat if you have to keep getting out of bed to manually mess with the furnace to get it lit.

Vic
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