Community Forums

ScottyBye · 11-03-2016, 03:40 PM

When I purchased my MH last summer I did all the normal checks...
But I did not check all the heat registers in the floor when running the LP furnace. (Lesson Learned)

So if found that I have little to no heat/air flow in the bathroom, and absolutly No Heat/Air flow in the bedroom.

Here is what I have done so far.

- found that the furnace runs fine for a few minuted till the internal furnace reaches the 190 degrees which then opens the circuit for the High Temp Limit Safety Switch. (located on a small bracket in the center of the heat exchanger.) So the switch is doing its job fine.

- removed the supply air metal duct from the furnace which directs the most of the air from the blower into the floor duct system. Located in the Return Air space under the fridge / behind the RA Vent Cover

- noticed that the hole that the manufacturer cut in the floor wasn't large enough to supply the correct air volume supplied by my model furnace. So I used a rotozip saw and fixed that problem.

- this did not make any difference to the air flow in bathroom or bedroom floor registers. (And is why the High Temp Switch is opening...is suspect)

- removed both registers and inspected with a mirror and flashlight but did not find any obstructions.

- bought a 15 foot endoscope camera (USB to laptop) and tried fishing it into the duct work to inspect better... Unfortunately the image quality is not what I expected, and looks more like a camera is being fished into the belly of a cow... meaning i see lots of things but cannot determine what they are.

- I have laminate floor and was think if removing it to maybe cut into the subfloor (3/4 inch plywood) but found that the previous owner who installed the flooring has glued it down. And it's not going anywhere easy.

So if someone has some advise or previous experience please share

The furnace is an Atwood 8500 series

ga traveler · 11-04-2016, 08:04 AM

I am not quite sure from your description if you have checked the ducts that attach to the heater housing. Most of the time we found the duct had slipped off the adapter to the heater housing. The fact that the over temp. is tripping is usually a indication of a blockage in the ducting. Since it has had the flooring replaced, I am wondering if he covered some outlets. At our shop when we had a camper come in with heater over temp problems, most of the time, we found the owner had covered some of the heater outlets with rugs.

ScottyBye · 11-04-2016, 06:36 PM

Yes
But there is only one duct which comes from the furnace. It supplies the above floor heat register below the kitchen sink. And it's working fine.
The rest of this units supply air is directed into the floor where I assume that the beams in the floor are performing the task of ductwork.

Pexring · 11-04-2016, 07:45 PM

Do any of the lower storage compartments feel overly warm?

ScottyBye · 11-04-2016, 08:10 PM

@pexring
Funny you should ask that because on occasion I have noticed that but only after driving for a few hrs.
No wait. The furnace wouldn't have been running while driving.
But gives me something else to check.

mhbell · 11-04-2016, 08:10 PM

Since you have a 15 foot endoscope I would put a 100 watt trouble light down each vent and then use the endoscope to try and see if there is a obstruction. You can also get an electricians fish tape and go into each vent and the main duct see if you can feel anything. Let us know what you find. I opened up a a vent and duct on a old motor home and found a Mouse or rats nest in it. managed to break it up enough with the fish tape and suck it out with a shop vac. I was able to run the length of the shop vac hose into each vent a a ways down the duct. You can't believe the crap that I sucked out.
Mel

ScottyBye · 11-04-2016, 09:22 PM

Thanks
I have tried the light and fish tape kind of,,,,,
The space betters the sub floor and bottom of the duct isn't deep enough for a trouble light.
I have used a fish tape and seems to always get stuck on something.
I also fished the hose of a shop vac in there. Some construction debris got sucked up.
I am going to try the fish tape again

mhbell · 11-04-2016, 10:02 PM

Quote:

Originally Posted by ScottyBye

Thanks
I have tried the light and fish tape kind of,,,,,
The space betters the sub floor and bottom of the duct isn't deep enough for a trouble light.
I have used a fish tape and seems to always get stuck on something.
I also fished the hose of a shop vac in there. Some construction debris got sucked up.
I am going to try the fish tape again

If the heater vents are in a straight line and the duct is in a straight line you could take smaller bare bulb and a mirror and shine the light from one vent to the other to see if you can see the light at another vent. if not then that means the obstruction is between those 2 vents. Do you know the history of the RV? how old is it and was it sitting for a long time before you bought it. Was it sitting in the open by a field. Was it in a flood zone. any sign of water damage? Maybe you could rent a endoscope that has a light on it to give you a better view. A sewer pipe cleaning outfit would have scope to check the duct for obstructions and give a better picture of what is in the duct if anything.

I just thought of something. You wouldn't by any chance have 2 furnaces? and one is not working. Do you have one thermostat or 2? Just a thought.
Good Luck.
Mel

ScottyBye · 11-04-2016, 10:21 PM

Unfortunately they are not in a straight line. That would be to simple. The history is known but no signs of water/flood damage.
It's a 2004 with 40,000 miles.
No signs of mice or any other rodents ever been seen.
Just one furnace.
2 Tstats but 2nd one is only for the rear a/c unit.
The endoscope I have had 6 led lights on the end but hard to tell what I am looking at. But I am not giving up yet.

mhbell · 11-05-2016, 10:41 AM

I would go to Monaco and see if you can get a diagram of the heating system duct work. Generally the furnace is off to one side and the floor duct work is hooked to it by a T another words the duct work goes from the furnace out to about the center of the floor and then runs in a straight line down the center with the vents in the center except for the Maybe the bathroom and kitchen under the sink. some units use a round flexible duct to run branch ducts off of the main duct work. About the only thing you can do is go through each vent with your endo scope and or a Fish tape mirror and light and try to figure out what you have. a likely blockage would be at any turns or takeoffs from the main duct work. Sorry I can't be more help. Let us know when you find the problem.
Mel

ScottyBye · 11-05-2016, 11:11 AM

Thanks for all the info.
I will contact them and see what they say.
I will also keep trying with the endoscope.
Worst case I will be ripping the floor up. After exhausting every other option first.

bigdog · 11-05-2016, 11:20 AM

Never heard of a motorhome with two tstats and only one furnace, betcha either one of two things, either you do have two furnaces and the rear one isn't working ORRrr, you were supposedd to have two furnaces and the second one wasn't ever installed.

mel s · 11-05-2016, 11:27 AM

Quote:

Originally Posted by ga traveler

The fact that the over temp. is tripping is usually a indication of a blockage in the ducting.

ScottyBye · 11-05-2016, 12:50 PM

Quote:

Originally Posted by bigdog

Never heard of a motorhome with two tstats and only one furnace, betcha either one of two things, either you do have two furnaces and the rear one isn't working ORRrr, you were supposedd to have two furnaces and the second one wasn't ever installed.

Yes
The tstat in the bedroom is only for the rear a/c. It only has a fan ON and cooling option. The a/c cycles on the tstat set point.
The one in the main living area has both heat and cool modes.