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Old 01-09-2017, 10:11 AM   #1
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Furnace Issue

I have a new 2017 Sierra 381 RBOK 43', only 3 weeks old. When the temperature gets around the low 20's, the furnace can only bring up the inside temp to about 62 and it seems to struggle to get there since it is constantly running to reach that set temp. It is a 35k furnace. I checked the return air temperature at all vents in floor and they all average around 110 degrees. Now the return air flow in the front bedroom and bathroom of the 5th wheel is strong. As you go towards the living room it gets noticeably weaker and even weaker, almost non existence, as you get to the back bunkhouse. Is this an issue with my furnace or is it just an issue of the furnace being too small and not able to keep up with my size of 5th wheel?

Also I have noticed that since the return heat flow is so weak towards the back of the 5th wheel, the water lines will freeze up. The waterlines in the front bathroom don't freeze up though since the return flow is strong.
My furnace is a SF-35, propane is filled, fan is on auto.
Some help would be appreciated since we just bought this trailer and it is winter time.
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Old 01-09-2017, 10:18 AM   #2
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Welcome!

There is lots of discussion on your dilemma here on the forum.
It doesn't just pertain to your particular unit. it stems from the fact that the heat ducts often get crushed during assembly, they are uninsulated or simply don't flow well with long runs of collapsible type ducting.

Do a forum search and you will find plenty of discussion and opinions, as well as tips others have used to help the situation.
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Old 01-09-2017, 10:25 AM   #3
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Check the heat ducts going to the bunk house they could be crushed or smaller. The ducts to the bedroom in our TT are only 2" despite the fact that they enter a 4"vent cover. You can look into the vents in the bunkhouse to see what size the ducts are. If you do not have them, you can get vents that have adjustable louvers so you can partially reduce the flow into one room in and effort to direct it to another. Be careful with this as restricting too much can cause the furnace to overheat and shut down. Unless you have a winter package, you can not expect an Rv to be anywhere close to a house as far as retaining heat. Too many openings and too little insulation and single pane windows.
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Old 01-09-2017, 10:25 AM   #4
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One thing you can do is add a skirting kit to the trailer, you could also cover any unused windows with aluminum foil to reflect the heat inward.

The R-value of the walls are next to nothing the roof and floor are little better.

You can use an electric space heater to supplement the furnace.
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Old 01-09-2017, 10:38 AM   #5
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How would I go about checking the duct to see if it is crushed? And if it is crushed, how would I go about fixing it or would I have to take it in?

We had a TT and were staying in the same park with these temperatures and we had no issues with the heater. We just upgraded to the 5th wheel and wasn't expecting to have heat issues.
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Old 01-09-2017, 10:38 AM   #6
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Reading the other day that ducts should be as short and straight as possible. I had low air flow to 2 ducts in the living room. The one on the side of the island had a very high flow. Upon inspecting each duct I cut at least 2 feet from each and reattached. That totaled 8 feet removed.
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Old 01-09-2017, 10:53 AM   #7
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Quote:
Originally Posted by bburris View Post
How would I go about checking the duct to see if it is crushed? And if it is crushed, how would I go about fixing it or would I have to take it in?

We had a TT and were staying in the same park with these temperatures and we had no issues with the heater. We just upgraded to the 5th wheel and wasn't expecting to have heat issues.
You are going to have to do some exploring.
They run these ducts during assembly and build around them. (often why they get damaged/smashed/even completely disconnected)

Possibly pull out panels in the basement or drawers/panels inside or anywhere the ducting runs are located.
Some units the ducting runs are in the enclosed underbelly. (coroplast)
Folks that have had to pull the belly off find lots of stuff (wiring/plumbing/ducting/etc.)mis-routed and not secure in there!
Out of sight... out of mind!
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Old 01-09-2017, 05:04 PM   #8
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The biggest difference between your tt and 5th wheel is the ducts and ceiling height. Normally a tt has direct piping from the furnace to the register. The 5th wheel has ducts they try and run 2 4" ducts to heat the whole main floor of your camper. In my 5th wheel I block off the upstairs vents and crack the vent in the living room. I try and get as much heat as possible to the bunk house. I also ran another duct to one of the air return vents in the stairs. This vent heats the living room.

If you have hookups a 1500 wattelectric heater will help a ton. Rv furnaces are terrible. While it's running go put your hand over the exhaust if you want to see where all your heat is going.
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Old 01-12-2017, 06:25 AM   #9
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Originally Posted by bburris View Post
I have a new 2017 Sierra 381 RBOK 43', only 3 weeks old. When the temperature gets around the low 20's, the furnace can only bring up the inside temp to about 62 and it seems to struggle to get there since it is constantly running to reach that set temp. It is a 35k furnace. I checked the return air temperature at all vents in floor and they all average around 110 degrees. Now the return air flow in the front bedroom and bathroom of the 5th wheel is strong. As you go towards the living room it gets noticeably weaker and even weaker, almost non existence, as you get to the back bunkhouse. Is this an issue with my furnace or is it just an issue of the furnace being too small and not able to keep up with my size of 5th wheel?

Also I have noticed that since the return heat flow is so weak towards the back of the 5th wheel, the water lines will freeze up. The waterlines in the front bathroom don't freeze up though since the return flow is strong.
My furnace is a SF-35, propane is filled, fan is on auto.
Some help would be appreciated since we just bought this trailer and it is winter time.


If you read my post in the Sierra forum you'll see I'm having the same issue. Some great suggestions some of which I'm heading to VT to fix right now as the BH lines thawed yesterday and one of the kids (or me) left one of the shower faucets opened. Flooded bathroom, as gray valve was closed cuz it too was frozen. Looking into skirting in next few weeks, installing pipe heaters today when I drop bellow to assess any water damage and dry it out before temps plummet into Friday. We use 2 low profile DeLonghi oil-based radiant space heaters and I've installed the nice bronze metal adjustable registers in MBR and MBath...these are preferred because duct is not deep and the standard metal registers hit the duct work and therefore don't divert//block air very well or at all. Will also take note of duct condition when I open belly...love the idea of using one of the stair returns as another duct...brilliant.

I also put insulation pillows in all the ceiling vent/fans and shrink wrapped all the AC vents as if you put your hand up to one you will either feel cold air blowing or warm air escaping. Going to do the same to all the windows. Also plan on using the double bubble foil insulation to insulate every inch I can reasonably get to starting with the belly....hope this helps.
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Old 01-12-2017, 07:02 AM   #10
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See if you can get a roll of clear plastic visqueen to use as skirting, painters tape may hold it to the wall and not make a mess or rip the decals off.

It will hold in some of the heat and allow some light to come thru you can use 2X4's to hold it on the ground.
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