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Doug Grove's Furnace Issues


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I am having exactly the same symptoms. 

When starting from a cold temperature, i.e. more than 10 degrees below the desired temperature, everything is fine until the desired temperature is approached then the furnace cycles on and off.  The forced air stays on but it is only being heated intermittently.  Sometimes the furnace fires for just a few seconds. 

The outside temperature has fluctuated between the 19 degrees and the mid 60's.  The rear dinette is always in the bed position. 

One thing I note is that my thermostat has Bluetooth and I understand this is relatively new feature, introduced in the last few months.  I wonder if there is something different about the upgraded thermostat.

It is hot under the bed.  Which isn't all bad. 🙂

I hope we find solutions soon.

2022 Elite II, hull number 1287.  Tow vehicle Silverado 2500 (loaner). I'm shopping for a truck.

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Odds are it’s where the return air is located. I did a smoke test and the hot air is trapped under your bed and is getting sucked back into  the cold air return and over heating the furnace. Just for a test duct tape over the return air vent. Turn the defuses on the supply to face forward. Now take the front seat cover off of your dinette seat and let the return air return through the open seat and under the floor.  I think you will be surprised at what a big difference it will make. I plan to put a cold air return on the front of the rear seat of the dinette along the floor. This will draw the air from the floor back to the furnace. The new 2023 elite  II has a return in the bathroom but they leave the main return open in the back. That doesn’t make a whole lot of sense to me. You end up having an 8 x 10 inch opening right next to the return of the furnace and a 3 inch opening 20 feet away in the bathroom. I can’t see how that is going to change much of anything. Even if it did help, in a house you never put a cold air return in a bathroom. It will cause the toilet smell to be sucked into the entire trailer along with moist air from the shower and possibly cause mold to form under the floor.  


Bill & Nancy 

Holland MA
2022 Elite II  Hull #1265
2022 GMC Diesel Canyon

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I have sent and email to customer support I hope they read it.  Basically it points them to this thread I hope they read it.  This is what I told them:

I don't know if you are aware of this thread on your forum but someone should read it.  You have a lot of frustrated customers: Furnace cycling on and off every 2 minutes  I have this problem with the furnace in my trailer short cycling.
.
I have been working on this for a week now and it is driving me nuts.  When my furnace needs to heat my trailer from well below the thermostat set point everything is fine.  
 
When my trailer is near the setpoint the furnace only runs for about 2 minutes at most.  Subsequently, after a few times it may run a bit longer.
 
I have the rear dinette set up permanently as a bed.
 
I have wireless thermometers set up in my trailer.  I note that at times the temperature under the king size bed has been as high as 95 degrees.  The air in the furnace compartment, i.e. under the passenger side rear seat is always hotter then the air at the thermostat..
 
I have tried a bunch of things none has adequately improved the situation.  First I have a carboard box converted to direct the heat away from under the bed.  I have opened the compartment under the rear seat of the forward dinette, I have duct tapped the provided vent and at other times I have both open.  I have a fan running fulltime under the bed.  Since I have added the fan the temperature under the bed has dropped to between 10 degrees and 5 degrees above the set point.
 
I have some experience with control systems in chemical plants and so I have been looking to see if I could make any sense of what might be going on.  Is the fact that the return air supply is above the set point factored into the control algorithm.  I would expect the return air to be below the set point in a proper installation.  I find it odd that I have the differential set at two degrees but the furnace cycles on and off in a much tighter band of about one degree.  I am wondering if there is any kind of advanced anticipatory control being used like PD or PID.  The first factors in the rate of temperature rise, i.e. the slope of the curve and the second factors in that plus the area between the temperature curve and the set point.
 
I think you have an engineering or design problem here and maybe it is time to send this thread to your design people if you haven't already.

2022 Elite II, hull number 1287.  Tow vehicle Silverado 2500 (loaner). I'm shopping for a truck.

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So as a control I rolled up the topper mattress I had over the rear cushions and removed the inspection doors over the furnace and observed for a few hours.  I got the same or very similar short cycling as I did for all the other test I tried. 

So I think I am ruling out air flows at least for my case.

2022 Elite II, hull number 1287.  Tow vehicle Silverado 2500 (loaner). I'm shopping for a truck.

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Just an FYI, I've tried twice - once last winter and once this winter - to change the temperature differential control in Ollie 617 from 2 degrees to 1 degree and the circuit in the AC starts clicking and won't stop.  That indicates a controller issue.  I just gave up and left it at the default setting 🤨.

Charlie. 

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Arizona | 2020 Oliver Elite II Twin bed Hull #617 | 2021 Ram 1500 e-Hemi 4x4

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2 hours ago, CnC said:

I've tried twice - once last winter and once this winter - to change the temperature differential control in Ollie 617 from 2 degrees to 1 degree and the circuit in the AC starts clicking and won't stop.  That indicates a controller issue.

This sounds like you're attempting to change the differential setting with the thermostat mode set to something other than OFF.  The thermostat controller in the overhead has no interaction with the differential setting but it may be getting confused by the procedure to change it. 

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3 hours ago, Doug Grove said:

So as a control I rolled up the topper mattress I had over the rear cushions and removed the inspection doors over the furnace and observed for a few hours.  I got the same or very similar short cycling as I did for all the other test I tried. 

So I think I am ruling out air flows at least for my case.

You may be ruling out a return air obstruction but there is still the supply side that is more likely to be a problem with these installations.  Since the LEII duct restriction is right at the minimums for proper furnace operation, be sure the dampers in all the warm air outlets are fully open. Better yet would be to totally remove the the damper disks from at least two of the three outlets. A significant air flow imbalance could cause the sail switch to flutter, intermittently shutting down the burner and re-sequencing the operation. 

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Question from an admitted techno boob:  Is it not possible that this problem is caused on the return air vent placement?  As has been suggested in. previous post, could it be that warm cabin air drawn into furnace through return vent could be causing the unit to overheat and cycle through periods of shut-down to cool-down?  

As a qualifier, I don't have this problem.  Mine is a 2021 twin bed with Dometic furnace and thermostat.  What set ups do you folks have that are suffering with short cycling?

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On 12/7/2022 at 9:49 AM, GAP said:

previous post, could it be that warm cabin air drawn into furnace through return vent could be causing the unit to overheat and cycle through periods of shut-down to cool-down?  

I wouldn't think so.

First, there should be a clear definition of "short cycling."  When I refer to short cycling, I'm using the HVAC definition, which basically means supply air does not distribute before returning to the unit - whether that be a furnace, an air conditioner or both.

Charlie.

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Arizona | 2020 Oliver Elite II Twin bed Hull #617 | 2021 Ram 1500 e-Hemi 4x4

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On 11/28/2022 at 4:57 PM, Bill and Nancy said:

That doesn’t make a whole lot of sense to me. You end up having an 8 x 10 inch opening right next to the return of the furnace and a 3 inch opening 20 feet away in the bathroom. I can’t see how that is going to change much of anything.

From the furnace perspective, the bathroom vent into the basement does not effectively change much.

BUT, from the bathroom's perspective, if the door is closed and the fan and window are also closed, as they would be during very cold outside conditions, then effectively the bathroom long small diameter duct will not be able to move much air into the nearly closed box (bathroom).  I suspect that the new air passage from the bathroom to the basement has more to do with getting more air into the bathroom, thereby making business there more enjoyable during real cold conditions.

That said, it also gives some air a path down the street side basement which may also help keep our pipes from getting frosty.

GJ

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TV:  2019 F-150 SuperCrew Lariat, 3.5L EcoBoost, Max Tow, FX-4, Rear Locker      OLLIE:  2018 OE2 Hull 342, Twin Bed.    OLLIE DYI’s:  BB LiFePO4's, Victron 712 Smart, 350 Amp Master Switch, Houghton 3400, Victron Orion DC - DC, 3000-Watt Renogy Inverter, P.D. 60-amp Converter, Frig Dual Exhaust Fans, Kitchen Drawer Straps.    TV DYI’s:  2 5/16" Anderson System, Timken Bearings, Nitto recon’s, Firestone Rear Air Bags, Bilstein 5100’s, Mud Flaps & Weather Tech all.

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1 hour ago, Geronimo John said:

[F]rom the bathroom's perspective, if the door is closed and the fan and window are also closed, as they would be during very cold outside conditions, then effectively the bathroom long small diameter duct will not be able to move much air into the nearly closed box (bathroom).  I suspect that the new air passage from the bathroom to the basement has more to do with getting more air into the bathroom, thereby making business there more enjoyable during real cold conditions.

That said, it also gives some air a path down the street side basement which may also help keep our pipes from getting frosty.

This aptly describes our experience with the Varioheat furnace in cold overnight temps, a few times at high altitudes, during our return journey to Idaho.  With the door closed, the bathroom was nearly as warm as the main cabin, with main cabin temp at 68 F.  Also, the street side plumbing areas got no colder than 27 degrees above outside ambient temperature.  For example, when the outside overnight low was 9 degrees F, (with the main cabin temp at 68 F), the street side plumbing area next to the exterior faucet got no lower than 38 degrees F.

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Hull #1291

Central Idaho

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14 hours ago, Geronimo John said:

From the furnace perspective, the bathroom vent into the basement does not effectively change much.

BUT, from the bathroom's perspective, if the door is closed and the fan and window are also closed, as they would be during very cold outside conditions, then effectively the bathroom long small diameter duct will not be able to move much air into the nearly closed box (bathroom).  I suspect that the new air passage from the bathroom to the basement has more to do with getting more air into the bathroom, thereby making business there more enjoyable during real cold conditions.

That said, it also gives some air a path down the street side basement which may also help keep our pipes from getting frosty.

GJ

Hey John,

In addition to the 4" round vent cut from bathroom to the dinette area I also put one under the streetside bed to wall the garage and yet another one through rear wall under curbside bed, right next to the furnace.  That wall is fitted super loosely so allows a lot of air to flow past anyhow.  The plan is to partially cover some of the pre existing  8x10 return vent.  My goal is to increase warm air flow past exterior shower and the shower's feed lines which inexplicably are buried all the way in the rear of the garage.  

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On 12/9/2022 at 6:27 AM, GAP said:

The plan is to partially cover some of the pre existing  8x10 return vent. 

If you are an only cold weather camper:  Yep great way to force more air where it is needed for freeze protection below floor and throne seat comfortability..

If you are never going to be a really cold weather camper, but do occasionally camp up high were having some furnace action is desirable, not such a great idea as it will run up your propane usage keeping the floor warm from below.

HOWEVER, if you are or may be both, or just like covering all the bases, I suggest putting a damper on the 8 X 10. 

  • For extreme cold close the damper down and force air where you want it.  (Just be aware of furnace output temperatures as choking down on airflow has it's own hazards).
  • Moderate cold, leave it open to promote most efficient cabin heating and reduction of propane use.

For those of us with older trailers with the "rumpled duct" interiors, changing out the duct to the bathroom to a smooth bore one and adding the small return air path makes a lot of sense.  

GJ

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TV:  2019 F-150 SuperCrew Lariat, 3.5L EcoBoost, Max Tow, FX-4, Rear Locker      OLLIE:  2018 OE2 Hull 342, Twin Bed.    OLLIE DYI’s:  BB LiFePO4's, Victron 712 Smart, 350 Amp Master Switch, Houghton 3400, Victron Orion DC - DC, 3000-Watt Renogy Inverter, P.D. 60-amp Converter, Frig Dual Exhaust Fans, Kitchen Drawer Straps.    TV DYI’s:  2 5/16" Anderson System, Timken Bearings, Nitto recon’s, Firestone Rear Air Bags, Bilstein 5100’s, Mud Flaps & Weather Tech all.

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21 hours ago, Geronimo John said:

HOWEVER, if you are or may be both, or just like covering all the bases, I suggest putting a damper on the 8 X 10. 

I’ve been thinking along the same lines of having a cold (<30F) weather configuration to heat under the floor, but not moderately cold conditions.  How about putting a quiet 12V fan with a switch in the wall somewhere up under the dinette?   Leave the main furnace intake vent as is.  Turning the fan on in very cold conditions would push warm cabin air under the floor and bunks, and warm the battery box as well.  Extra vent holes inside the compartments could be created to facilitate flow.   This mod would use extra propane of course,  but would be turned on only when needed.   One advantage of a suction fan is that if using shore power, an electric space heater could be placed near the dinette.   Warm air would be sucked into the lower spaces, without using the furnace and propane.   Another advantage might be a cooling effect on batteries in high temps.   John Davies has already done a variation of this mod with the focal point being the battery box.  Ideally, the 12V fan would be powerful enough to move the air effectively, but reasonably  quiet.   This might be the challenge.  May take more than one fan, and could be mounted inside the hull space to help reduce sound.  This seems too easy, what am I missing?   

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On 12/10/2022 at 8:17 PM, Geronimo John said:

If you are an only cold weather camper:  Yep great way to force more air where it is needed for freeze protection below floor and throne seat comfortability..

If you are never going to be a really cold weather camper, but do occasionally camp up high were having some furnace action is desirable, not such a great idea as it will run up your propane usage keeping the floor warm from below.

HOWEVER, if you are or may be both, or just like covering all the bases, I suggest putting a damper on the 8 X 10. 

  • For extreme cold close the damper down and force air where you want it.  (Just be aware of furnace output temperatures as choking down on airflow has it's own hazards).
  • Moderate cold, leave it open to promote most efficient cabin heating and reduction of propane use.

For those of us with older trailers with the "rumpled duct" interiors, changing out the duct to the bathroom to a smooth bore one and adding the small return air path makes a lot of sense.  

GJ

GJ, you've offered up some great suggestions on this topic on both this chain and the 3.75 Season Trailer forum.  That said, this one really hits home.  Even though we travel with 3 30lb tanks, for both cost and convenience, I was dreading heating the belly at temps north of mid 20s where it is not necessary.  I'll switch out the 8x10 existing return air vent for one with a louvre and plan to do the same for a couple of the others vents I've cut between dead ends in the garage and basement so I can tune the system 1) to the need to share heat between the hulls and 2) adjust flow to send the most air where it is most needed.  Very helpful.  Thanks on that.

Question:  My trailer has the "rumpled" accordion, lightweight 4" foil ducts.  I notice this is super delicate and have already needed to repair with foil tape in a few spots.  You mention "smooth bore" duct.  Can you be more specific as to the type of product and why it is more efficient?  Unlike the "semi rigid" duct I've added to the streetside, I have not noticed the rumpled duct exterior heating up.

 

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On 12/10/2022 at 10:33 PM, Hokieman said:

I’ve been thinking along the same lines of having a cold (<30F) weather configuration to heat under the floor, but not moderately cold conditions.  How about putting a quiet 12V fan with a switch in the wall somewhere up under the dinette?   Leave the main furnace intake vent as is.  Turning the fan on in very cold conditions would push warm cabin air under the floor and bunks, and warm the battery box as well.  Extra vent holes inside the compartments could be created to facilitate flow.   This mod would use extra propane of course,  but would be turned on only when needed.   One advantage of a suction fan is that if using shore power, an electric space heater could be placed near the dinette.   Warm air would be sucked into the lower spaces, without using the furnace and propane.   Another advantage might be a cooling effect on batteries in high temps.   John Davies has already done a variation of this mod with the focal point being the battery box.  Ideally, the 12V fan would be powerful enough to move the air effectively, but reasonably  quiet.   This might be the challenge.  May take more than one fan, and could be mounted inside the hull space to help reduce sound.  This seems too easy, what am I missing?   

Sounds like some good ideas there.  Have a couple of thoughts.  If the fan is itself under the dinette, where would you be drawing warm air from tho heat between the hulls?  On the newest trailers (and mine after tweaking last season) there is a vent cut from bathroom to under the dinette.  Using the fan would work well in that circumstance but, if you have a composting toilet, could reverse the flow of the air through the solids box = sad faced smell.  Another option would be to cut a small louvered vent under the forward dinette seat so the warm air could be drawn from the cabin. 

You are spot on about opening the internal dead ends.  There are walls  between basement and garage under streetside bed and another behind the furnace which prevent warm air from getting to the rearmost water lines.  It's a shame otherwise to heat the garage but those lines (that feed the external shower) are the most vulnerable in the trailer.  

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1 hour ago, GAP said:

If the fan is itself under the dinette, where would you be drawing warm air from tho heat between the hulls? 

The fan suction vent would be under or near the dinette somewhere, and draw warm cabin air in and push it between the hulls.   If on shore power, an electric space heater could be placed near the fan vent, drawing warm air and saving propane.   You’re right, this wouldn’t be a good idea on the new designs with a return vent in the bathroom, and seems like it’s not needed with the Truma VarioHeat.   John Davies has already done this, I’m just thinking about a slight variation on his design.   Check it out here.

Lithium Powered Vent System

 Overland had some good ideas along these lines, can’t find the link.  Just brainstorming here, I am not ready to cut any holes any time soon! 

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  • Moderator+

This thread has been split from Bill and Nancy's Furnace is cycling on and off every 2 minutes.

There WILL be some apparent discontinuity issues as a result

Steve, Tali and our dog Rocky plus our beloved Storm, Maggie, Lucy and Reacher (all waiting at the Rainbow Bridge)

2008 Legacy Elite I - Outlaw Oliver, Hull #026 | 2014 Legacy Elite II - Outlaw Oliver, Hull #050 | 2022 Silverado High Country 3500HD SRW Diesel 4x4 

 

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Moderators:

Thank you for separating the two competing threads and creating Doug Grove's Furnace Issues thread.  That  done, in DGFI's thread we "appear" to have therein really two topics:

  • How to fix Doug's furnace
  • Modifications for Extreme Cold Weather Heating Performance

I would like to "get into the weeds" on the extreme cold weather topic, but don't want to further confuse readers on how to fix Doug's issue... nor do I desire to start a new MfECWHP thread without all the great thoughts already presented therein.  

Should you agree that we have successfully trampled the first topic with the second topic, I respectfully suggest separating them accordingly.  Should you not agree with my assessment, and that would be totally cool, then I will get into the weeds on the topic of extreme cold weather modifications in Doug's furnace fix thread.  Totally your call.  

Please advise all.  Mahalo,   GJ

TV:  2019 F-150 SuperCrew Lariat, 3.5L EcoBoost, Max Tow, FX-4, Rear Locker      OLLIE:  2018 OE2 Hull 342, Twin Bed.    OLLIE DYI’s:  BB LiFePO4's, Victron 712 Smart, 350 Amp Master Switch, Houghton 3400, Victron Orion DC - DC, 3000-Watt Renogy Inverter, P.D. 60-amp Converter, Frig Dual Exhaust Fans, Kitchen Drawer Straps.    TV DYI’s:  2 5/16" Anderson System, Timken Bearings, Nitto recon’s, Firestone Rear Air Bags, Bilstein 5100’s, Mud Flaps & Weather Tech all.

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On 12/12/2022 at 4:21 AM, GAP said:

Can you be more specific as to the type of product and why it is more efficient?  Unlike the "semi rigid" duct I've added to the StreetSide, I have not noticed the rumpled duct exterior heating up

DUCT TEMP: The rumpled uninsulated thin aluminum spiral air transfer duct gives up a lot of heat right at the furnace.  Compare the surface temperature of it under the bathroom sink and say a foot from the furnace itself.

SMOOTH BORE DUCTS:  Think of it as the difference between a rifle and a shot gun.  For moving air efficiently a smooth bore allows for more laminar air flow vs. the rumpled flex duct.  Here are two smooth bore ducts and below a compromise duct with a smoother bore.

image.png.a21121b94b72551ff90d0e1b66efd01f.png

image.thumb.png.1b9cb5ada7a13426cc9e791f1b5089b7.png

image.thumb.png.9a472067dd3f27b55995a44aef74eedb.png

Every product has it's pro/cons.  Uninsulated or poorly insulated ducts in our hulls lose heat as they travel across the hull.  This for moderate temp camping is wasted fuel.  But for COLD weather camping, it is a good thing.  Point is that well insulated ducting is not for everybody.  

For the cold weather campers, I really like Hokieman's concept of using a fan to push air from the dinette foot area into the street side basement.  And as suggested using an electric heater by the fan, and air transfer holes in the various walls creating a heated  air return path down the street-side, basement and back to the furnace.  The concept  would be easy to do, and when not needed (as suggested) just turn it off. 

However, my concern is actually with getting  warm air movement at the rear shower area for an un-ducted air flow path.  It's a long way with many air leakage opportunities and the freely moving air would likely be giving up it's heat long before it got to the most important target.... the aft shower plumbing area.

To optimize Hokieman's concept:

A.  I suggest using a duct fan and lightly insulated 3" round duct.   (Maybe DWV plastic???) Doing so would significantly improve the odds of getting warm air onto the aft shower plumbing area.  By using lightly insulated duct, it allows for some heat transfer along the street-side basement to the primary target area.  The duct fan needs to be very quiet.  My suggestion is to get a 2" fan and run it in 3" duct.  Only need say 20 to 35 CFM range.

B.  For the duct fan control, I would use an Off/On/Auto switch.  The Auto would be tied to a normally open thermal switch located at the most cold exposed surface of the aft shower area plumbing.  The switch should close when the temp in the area falls below say 30 degrees F.  They cost less than $10.  WHY?  So for example, if your are away from the trailer and bad conditions hit, or if you just forget to switch it on, if you have left it in "AUTO", you are still "somewhat" freeze protected.  (NOTE:  Somewhat because i would not recommend leaving an free standing electric space heater running while you are gone.)   "ON" turns on the fan and leaves it on.  "OFF" is off.

Hope this helps.

GJ  

TV:  2019 F-150 SuperCrew Lariat, 3.5L EcoBoost, Max Tow, FX-4, Rear Locker      OLLIE:  2018 OE2 Hull 342, Twin Bed.    OLLIE DYI’s:  BB LiFePO4's, Victron 712 Smart, 350 Amp Master Switch, Houghton 3400, Victron Orion DC - DC, 3000-Watt Renogy Inverter, P.D. 60-amp Converter, Frig Dual Exhaust Fans, Kitchen Drawer Straps.    TV DYI’s:  2 5/16" Anderson System, Timken Bearings, Nitto recon’s, Firestone Rear Air Bags, Bilstein 5100’s, Mud Flaps & Weather Tech all.

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17 minutes ago, Geronimo John said:

DUCT TEMP: The rumpled uninsulated thin aluminum spiral air transfer duct gives up a lot of heat right at the furnace.  Compare the surface temperature of it under the bathroom sink and say a foot from the furnace itself.

SMOOTH BORE DUCTS:  Think of it as the difference between a rifle and a shot gun.  For moving air efficiently a smooth bore allows for more laminar air flow vs. the rumpled flex duct.  Here are two smooth bore ducts and below a compromise duct with a smoother bore.

image.png.a21121b94b72551ff90d0e1b66efd01f.png

image.thumb.png.1b9cb5ada7a13426cc9e791f1b5089b7.png

image.thumb.png.9a472067dd3f27b55995a44aef74eedb.png

Every product has it's pro/cons.  Uninsulated or poorly insulated ducts in our hulls lose heat as they travel across the hull.  This for moderate temp camping is wasted fuel.  But for COLD weather camping, it is a good thing.  Point is that well insulated ducting is not for everybody.  

For the cold weather campers, I really like Hokieman's concept of using a fan to push air from the dinette foot area into the street side basement.  And as suggested using an electric heater by the fan, and air transfer holes in the various walls creating a heated  air return path down the street-side, basement and back to the furnace.  The concept  would be easy to do, and when not needed (as suggested) just turn it off. 

However, my concern is actually with getting  warm air movement at the rear shower area for an un-ducted air flow path.  It's a long way with many air leakage opportunities and the freely moving air would likely be giving up it's heat long before it got to the most important target.... the aft shower plumbing area.

To optimize Hokieman's concept:

A.  I suggest using a duct fan and lightly insulated 3" round duct.   (Maybe DWV plastic???) Doing so would significantly improve the odds of getting warm air onto the aft shower plumbing area.  By using lightly insulated duct, it allows for some heat transfer along the street-side basement to the primary target area.  The duct fan needs to be very quiet.  My suggestion is to get a 2" fan and run it in 3" duct.  Only need say 20 to 35 CFM range.

B.  For the duct fan control, I would use an Off/On/Auto switch.  The Auto would be tied to a normally open thermal switch located at the most cold exposed surface of the aft shower area plumbing.  The switch should close when the temp in the area falls below say 30 degrees F.  They cost less than $10.  WHY?  So for example, if your are away from the trailer and bad conditions hit, or if you just forget to switch it on, if you have left it in "AUTO", you are still "somewhat" freeze protected.  (NOTE:  Somewhat because i would not recommend leaving an free standing electric space heater running while you are gone.)   "ON" turns on the fan and leaves it on.  "OFF" is off.

Hope this helps.

GJ  

Lots of great stuff there Gj.  I am especially interested in the insulated flexible vent duct options.  I'd like to replace sections of duct close to the furnace as that is an area least in need of heating that runs super warm because of heat loss through the duct itself.  I've replaced the duct line that feeds the cabin mid way under the curbside bed.  Ran the new duct to a spot opposite the existing vent under the galley so now there is one close to the battery compartment.  I used semi rigid duct which gets hot so it has heated the compartment surrounding the exterior shower and opened a vent through to the garage to share heat with pex lines run through there.  insulated (with reflectix) areas close to electronics to protect that stuff.  Will add some of your suggested insulated duct from the furnace till the duct comes out under the streetside bed as to minimize heating areas where not needed.  

The ideas about running a fan and portable AC powered heater sound like smart thinking but I have yet to winter camp somewhere with access to shore power so may be a project for next summer. 

Thanks much for sharing.  Very helpful stuff.

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1 hour ago, GAP said:

Will add some of your suggested insulated duct

Do some searches on this as likely there are other similar products at a less expensive cost. 

 I do suggest that you ensure your selection is rated for the temperature you expect it to be utilized.  

Good luck,

GJ

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On 1/2/2023 at 2:44 PM, Geronimo John said:

However, my concern is actually with getting  warm air movement at the rear shower area for an un-ducted air flow path.

I agree GJ, good ideas, I think we are on the same page.   I’m also concerned about fan noise, which is why I suggested one or two fans mounted internally.    These could be connected to ducting like you mentioned.

On 12/10/2022 at 10:33 PM, Hokieman said:

Ideally, the 12V fan would be powerful enough to move the air effectively, but reasonably  quiet.   This might be the challenge.  May take more than one fan, and could be mounted inside the hull space to help reduce sound.

Ideally, this system would also vent the battery box, keeping it warmer in extreme cold and extreme heat, to avoid BMS cutoff and optimum lithium battery performance.   In this link, @NCEagle describes dual systems, both a battery compartment fan and a basement fan.

Lithium Powered Vent System

@NCEagle’s battery compartment mod uses a 120V duct fan with ducting.  I can’t find a post with his basement fan mod, but my guess is that it’s similar and is designed to heat those critical plumbing areas.    I’ve been unable to find a 12V duct fan, other than marine bilge blowers, which I worry are too noisy.  @Overland proposed a nice battery compartment fan mod (same link) with a quiet fan and plastic ductwork that mounts directly to the fan, with a thermostat.   

Keep the ideas coming.  I’m still looking for the ideal system before I cut any holes! 

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