Question about the Furnace in my 2007 Roo 233

[LukeD]

this being my first larger camper im pretty new with some of this stuff.
So this past weekend the wife ad I headed down to the lake for a break. Grabbed the camper and got all set up Friday night. Was pretty cool here last weekend with lows in the 30s and I had never tried or messed with the furnace on this camper (got it used) so really didn't know much about it.
So sat morning had to run around a bit then back to the camper. So I messed around with the furnace for a bit and it worked fine which was good. only thing is that the camper has 2 heating vents. one in the front under the table and one in the back kinda in the hall way so to speak.
So the vent under the table really pumped a lot of air out. but the vent in the back had none at all coming out. thought it was kinda weird, so I went outside and the exhaust vent for the furnace has 2 outlets. one was hot and one was not.
I never really looked into it much as far as why it didn't put any heat out the back vent and if it meant anything that the exhaust vent only had one hot outlet and not the other.
Camper is a 2007 Rockwood Roo 233.
is there maybe a vent switch or something like that that cuts the air off to a vent im missing somewhere?
the rear vent is further away from the furnace but I felt the duct right next to where it comes out of the furnace and it wasn't even warm. so no air moving through it at all. Where the front vent you could barely hold your hand close to the vent it was so hot.

[bikendan]

No such thing as a "vent switch" in a Roo.
Most likely cause crushed or blocked ducting.

[rbq]

The exhaust vent does have two openings. One exhausts the fumes from the flame and the other part of the vent is the intake air to provide combustion air for the furnace.

[Bama Rambler]

The inside and outside vents are two separate air circuits.

As rbq said on the outside tubes, one is the intake for combustion air and the other (the one that gets hot) is for the burner exhaust.

On the inside you have a slotted grate that provides the heat exchanger supply air and them the ducted system that distributes the heat. Since you have one vent that blows air really well and the other does not, my guess is that the duct going to the vent that isn't flowing is blocked.

Pull the register off and shine a light in the duct toward the duct that's working and look in it and see if you see any light. You can also take your phone and hold it with the camera down in the duct pointing that way and take a picture. It'll be upside down but you should be able to see down the duct that way. You can also use a mirror to look down the duct.

[LukeD]

the duct that isn't blowing out air I can get to all of the duct pretty easily other than right where it attaches to the back side (towards outside wall) of the camper. it didn't look like it was blocked but ill have to check a little closer

[5picker]

Often times an inexpensive borescope/endoscope for a phone will help you look into those places hard to get to. Mice LOVE to chew through and build nests in heat ducts.

[Kimber45]

if you are camping in weather that cold on a regular basis and at a campground were you are not paying for electric go get yourself a $10 space heater and save yourself some propane

[TitanMike]

While not the same kind of trailer I had the same problem.

My rear heat vent didn't blow much air at all when compared to the vent closest to the furnace. I explored the duct's path and found that whoever installed it had no clue about air flow through a tube. Both ends had 90 degree bends that almost totally blocked the air flow as the bends were too tight. To make matters worse there were an additional number of 90 degree bends because the installer was too lazy to cut a hole in a partition to route the duct more directly to the rear vent. Went all the way from the rear of the furnace to the front of the furnace, did a complete U-turn (again too tight a bend), then around and behind the converter where he (or she) did the same thing to get past a partition under the refrigerator.


I'm going to wager that your rear duct tubing (3" accordion type ducting) is either crushed or was bent too tight and totally kinked off the flow.

I fixed mine by buying $16 worth of better quality duct material from Amazon and completely re-routed the rear duct on my TT, removing several 90 degree bends and shortened the overall length of the tube (by routing it more directly under the cabinets) to the rear vent.

FWIW, if you don't get air flowing through that second vent you run the risk of having the furnace shut down due to the high limit switch being triggered. The furnace needs plenty of air flow to keep the heat exchanger from overheating. May not happen during short runs to take the chill off but on a cold night, the low air flow could lead to overheating/shut down due to the longer runs.

[theengle]

Ditto on the space heater, why waste your propane when the electric is free

[njfishing]

Originally Posted by TitanMike

While not the same kind of trailer I had the same problem.

My rear heat vent didn't blow much air at all when compared to the vent closest to the furnace. I explored the duct's path and found that whoever installed it had no clue about air flow through a tube. Both ends had 90 degree bends that almost totally blocked the air flow as the bends were too tight. To make matters worse there were an additional number of 90 degree bends because the installer was too lazy to cut a hole in a partition to route the duct more directly to the rear vent. Went all the way from the rear of the furnace to the front of the furnace, did a complete U-turn (again too tight a bend), then around and behind the converter where he (or she) did the same thing to get past a partition under the refrigerator.


I'm going to wager that your rear duct tubing (3" accordion type ducting) is either crushed or was bent too tight and totally kinked off the flow.

I fixed mine by buying $16 worth of better quality duct material from Amazon and completely re-routed the rear duct on my TT, removing several 90 degree bends and shortened the overall length of the tube (by routing it more directly under the cabinets) to the rear vent.

FWIW, if you don't get air flowing through that second vent you run the risk of having the furnace shut down due to the high limit switch being triggered. The furnace needs plenty of air flow to keep the heat exchanger from overheating. May not happen during short runs to take the chill off but on a cold night, the low air flow could lead to overheating/shut down due to the longer runs.

Some great advise above from Mike.... I found out first hand what a blocked or restricted duct or vent can do and it was on our last trip when it went down to the 30s at night... http://www.forestriverforums.com/for...ht-196241.html

[Larry-NC]

Originally Posted by TitanMike

FWIW, if you don't get air flowing through that second vent you run the risk of having the furnace shut down due to the high limit switch being triggered. The furnace needs plenty of air flow to keep the heat exchanger from overheating. May not happen during short runs to take the chill off but on a cold night, the low air flow could lead to overheating/shut down due to the longer runs.

And you may not even be aware this is happening. It would seem like the thermostat is cycling the furnace on and off as you expect--just not at the temperature you had set on the thermostat.

(I actually considered wiring an LED and resistor across the high-limit switch, so it would light when the switch opened.)

[Larry-NC]

Originally Posted by theengle

Ditto on the space heater, why waste your propane when the electric is free?

Where we are, the electricity at the permanent sites is metered. Propane is much less expensive. We've jumped our electric bill (usually around $15/mo with the dehumidifier on) to $45 and even $75 at times using electric heaters.

I have a bunch of 20 lb and 30 lb bottles and usually rotate them through Costco. But I also have a 100 lb tank. If I exhaust the others, I go to that. If it empties, the nice lady from the campground hefts it into her golf cart, takes it over to the filling area, fills it, and returns it. I can't remember how much it costs for that.

[TitanMike]

Originally Posted by Larry-NC

And you may not even be aware this is happening. It would seem like the thermostat is cycling the furnace on and off as you expect--just not at the temperature you had set on the thermostat.

(I actually considered wiring an LED and resistor across the high-limit switch, so it would light when the switch opened.)

Amen to not knowing.

I actually found it was happening when I changed the "analog" thermostat to a digital unit. On cold nights it was resetting itself to the default 72 degrees from where I had it set in the mid 60's for cooler sleeping temps.

In researching why these digital t-stats were doing this the general consensus was either an interruption in the T-stat power supply or electrical interference/noise on the 12 v line from other devices.

It was then that I started noticing the sound of the gas solenoid cycling on and off. Solenoid coils are known to create voltage spikes on their power lines when the power to the coil is suddenly cut and the solenoid produces a higher voltage spike.

Rather than put a filter or two on the T-Stat power line I first took a look at the furnace for wiring errors. THAT's when I noticed the kinked duct with all the 90's (even one 180) in it.

Fixed the duct and just spent three nights with the furnace running off and on all night. No more T-Stat resetting itself, no cycling of the gas solenoid valve, and quicker warm up in the AM when I run the set temp up.

[TitanMike]

Originally Posted by Larry-NC

Where we are, the electricity at the permanent sites is metered. Propane is much less expensive. We've jumped our electric bill (usually around $15/mo with the dehumidifier on) to $45 and even $75 at times using electric heaters.

I have a bunch of 20 lb and 30 lb bottles and usually rotate them through Costco. But I also have a 100 lb tank. If I exhaust the others, I go to that. If it empties, the nice lady from the campground hefts it into her golf cart, takes it over to the filling area, fills it, and returns it. I can't remember how much it costs for that.

True propane is less expensive but there is the "hassle factor". Electricity is delivered to your site 24/7/365 and propane has to be "hauled".

I hate using space heaters. Even the safest of them creates a risk. If not of fire, then risk of tripping over is there. Also a strain on the average TT's electrical system unless a 50 amp unit.

Then again, whatever keeps your nose and toes warm

[Larry-NC]

Originally Posted by TitanMike

Amen to not knowing.
I actually found it was happening when I changed the "analog" thermostat to a digital unit. On cold nights it was resetting itself to the default 72 degrees from where I had it set in the mid 60's for cooler sleeping temps.

Exactly why I wanted an indicator. With my preferred cheapie analog thermostat, I would never know. All it takes is an LED and 330 ohm series resistor across the high-limit cutout. The thermal cutout is readily accessible at the top front of the plenum. You don't even have to remove the plenum cover, just the grille. I will (someday) just bore a hole in the wooden frame just above the grille and stuff an LED through from the back. Might even spring a few cents for the plastic bezel.

Originally Posted by TitanMike

It was then that I started noticing the sound of the gas solenoid cycling on and off. Solenoid coils are known to create voltage spikes on their power lines when the power to the coil is suddenly cut and the solenoid produces a higher voltage spike.

Rather than put a filter or two on the T-Stat power line I first took a look at the furnace for wiring errors. THAT's when I noticed the kinked duct with all the 90's (even one 180) in it.

Not a filter. All you need is a flyback diode. The spike you get when the contacts open on a DC coil from the inductance (current wants to keep flowing) is a negative impulse. The resulting voltage drop is what resets your digital thermostat. To confine it to the solenoid, you put a diode across the solenoid, oriented so it does NOT conduct when the solenoid is powered. When the spike occurs, current flows only through the diode. A 1N4004 diode, for example, would be fine.

[Chuck_S]

My experience with electric space heaters is they rarely provide enough heat to make the camper comfortable. Maybe 20°F warmer than ambient temperature. No surprise, really, as they're all about 1500 watts or the same as the typical hair dryer and no one expects to heat their camper with one of those even if the electric is "free." All the outlets in our Roo are on one (1) 15 amp circuit so running two of these won't work for us.

The "heat strip" in the roof top AC units is the same wattage. Was darn near useless in our popup.

Camping at Fort Story VA last weekend wasn't THAT cold but the furnace was needed. Heater supplemented and maintained cabin temperature so the furnace didn't run that much.

Beware, the furnace burns about 1 pound of propane for every hour of flame time and pulls about 4 amps of 12vDC so you need lots of battery power when dry camping.

-- Chuck

[TitanMike]

Originally Posted by Chuck_S

My experience with electric space heaters is they rarely provide enough heat to make the camper comfortable.

It's simply a matter of numbers.

A 1500 watt space heater produces 5118 BTU's

Two heaters on high will provide 10,236 BTU's

Two of them will max out a 30 amp power supply (when other loads like converter, refrigerator, etc. are added).


Most camper furnaces range from 20,000 BTU's to 40,000 BTU's.


Unless the camper is super well insulated the best a space heater can do is ward off the chill from opening and closing the door when weather is cold.

BTW, when I say "cold" I'm not referring to a 60 degree day in the South

[Chuck_S]

Like I wrote, check your breakers. All my outlets are on one (1) 15a breaker so I can't run more than one (1) space heater.

I'm interested in knowing if any of these hybrids have more than one breaker for the outlets.

-- Chuck

[TitanMike]

Originally Posted by Chuck_S

Like I wrote, check your breakers. All my outlets are on one (1) 15a breaker so I can't run more than one (1) space heater.

I'm interested in knowing if any of these hybrids have more than one breaker for the outlets.

-- Chuck

Same with my TT, all outlets on one breaker but I can run two heaters. I just have to set them for Low (750 watt). I use my heaters for "freeze proofing" between winter trips when I don't winterize. Hooked to 30 amp power and leave tank heaters on too.

[Larry-NC]

Originally Posted by Chuck_S

My experience with electric space heaters is they rarely provide enough heat to make the camper comfortable. Maybe 20°F warmer than ambient temperature. No surprise, really, as they're all about 1500 watts or the same as the typical hair dryer and no one expects to heat their camper with one of those even if the electric is "free." All the outlets in our Roo are on one (1) 15 amp circuit so running two of these won't work for us.

The "heat strip" in the roof top AC units is the same wattage. Was darn near useless in our popup.

Camping at Fort Story VA last weekend wasn't THAT cold but the furnace was needed. Heater supplemented and maintained cabin temperature so the furnace didn't run that much.

Beware, the furnace burns about 1 pound of propane for every hour of flame time and pulls about 4 amps of 12vDC so you need lots of battery power when dry camping.

-- Chuck

Two experiences:

The furnace failed in our 22' SOB in 2012 while we were camped in southeastern Virginia on Thanksgiving. There was slushy snow, meaning the temperature was around 32F. We were okay with one 1500 watt resistance heater. The furnace is an SF-20 or SF-25, hence 20,000 or 25,000 BTU. The heater (per Titan Mike) was about 5,000 BTU. We had to wear warm clothes and use lots of quilts, but weren't uncomfortable.

The converter failed last year in our 38' Cherokee destination trailer, so the furnace wouldn't run. We used two oil-filled radiators, either both at 1500 watts or one at 1500 and one at 900, again in near-freezing weather. The bedroom got hot enough to be uncomfortable at 1500 watts with the door closed. (We ran one heater on the GFI circuit and one on the other circuit to split the load.) There were warm spots and cool spots, but again it was tolerable.