171BH Furnace inefficiency

[DK1]

I've spent 3 weekends solo, winter-dry camping in my 2022 171BH and 'see' a huge issue with the propane furnace. The first winter night I tried the unit (low of 18) was miserable. The furnace turned off and on all night. I didn't time it, but it seemed 10 mins on, 5 off, 10 on, 5 off, all night. I'd go from comfortable to hot, throw covers off, get cold, pull covers on, get comfortable, get hot, throw covers off, etc. I'm sure at some point I did slept but I woke up pretty much tired and miserable...


I figured I'd have to insulate a bit and so I did. I bought some 1/2" Owens Corning Formular NGX panels and created friction fit panels for the big dinette window, the window over the bed, and the window of the door. I also put the insulation under the front mattress and top, bottom, and side of mattress. I cut a panel and friction fit it against the back 'wall' where the cubicles get stored. So a few weeks a later I did another dry camp up in PA and the temps dropped to 10 degrees. This time I added a small space heater along with the furnace. It did a little bit better but I was amazed at just how cold the floor was. I wasn't smart enough to take temp readings but the air at seat level was frigid. Sitting in the dinette my feet were freezing, even in slippers. I figured cold air was pouring from the bunk area into the living area. I could feel it at the bunks. So next trip, more insulation.


I added the foam board to block off from the floor to the lower bunk and a rigid panel from the bottom bunk the upper bunk. For the upper bunk to ceiling I used Reflectix and blocked that area off. I used some cardboard uprights and dryer vent tape to connect the Reflectix. I just jammed the cardboard uprights between the mattress and the bunk frame. The next trip the temps dropped to 15 but the wind was very, very strong 35-45MPH pushing directly against the camp side... That's when I could tell, but just using my hand, how much cold air was being forced into the trailer. The stove vent bleed cold air as did the refrigerator (the lower vent inside the rig) and all along the frame mount next to the bathroom. But the biggest offender? It was the furnace. I'd put my hand in front of the grill and I could feel my hand almost being pushed away by the wind when the furnace wasn't on.


I blocked off the stove vent with a thin plastic cutting board and painters tape. I taped over the refrigerator vent and jammed clothing between the refrigerator doors and bathroom wall. I ran my space heater on high (1500 Watts) along with the propane furnace. The night was tolerable, not super great, but nowhere near as miserable as the first 'camp' and better than my 2nd experience.



I've pulled all the kitchen drawers and removed the both the grill and front fascia of the furnace. I see the problem and it seems like a big problem. There isn't a return air register(s) or return air ducts. The furnace sits at the bottom of the sink cabinet. The side cabinet of the sink cabinet joining to the stove cabinet has a ?5"-6" gap where it doesn't meet the trailer wall. The stove cabinet next to the refrigerator also has a huge gap. The refrigerator vents to outside via the enormous ?24X18" panel.


So what this means is that the furnace pulls ambient outside air as the air that's blown past the heat chambers. Yes, I know the actual unit BURNS outside air and vents the exhaust, I'm talking about air that's heated for interior use. The end result of this design flaw is that massive amounts of outside ambient temp air gets pulled into the unit. As soon as the temp rises and the unit cuts off, that cold air just POURS into the rig past the stopped fan and onto the floor. The trailer quickly cools down and the furnace turns on. It starts blowing outside ambient air past the heat chamber, ignites the propane to heat the chambers and the cycle starts all over. Hot, cold, hot, cold, ad nauseum.



To test my theory that the furnace CREATES a huge heat problem I buttoned everything up, turned the propane tanks off, turned the thermostat off and sealed up the front of the furnace with Reflectix held with painters tape. It was 35, cold and rainy yesterday, a slight wind. I remotely monitored the interior temp and turned my space heater on the low setting. I was working at my desk and kept an eye on the temp. After what seemed like a few minutes I glanced up to see the temp was 55. That didn't seem right, it was only a few minutes... I actually thought geez did I set the damned rig on fire? How'd the temp get so high so quickly? So I ran outside to check on things. Nope all was good. It seemed to me that in less than an hour it was 65 degrees and soon 72...



So where does all this lead to? Well 1. YMMV but if you are winter dry camping and have electrical power, seal the furnace and just run a space heater (maybe consider sealing the stove vent and other areas...) My $0.02? Don't bother running the furnace it creates as much of a problem as it solves.


2. I'm going to test out a theory that I can block OFF the rear of the sink cabinet and allow the furnace to pull air from the front opening by temporarily leaving the fascia board off. If that works, I can cut holes in the fascia board OR cut a vent hole in the cabinet's side (where the door is) and drawn IN from within the rig and heat that air, recirculating it.





If anyone has solve the problem another way, I'm all ears!


Thanks, Dave

[RogerR]

You didn't post the model of your furnace but I expect it is the same one put on most of Jayco SLX models. Yes it does use outside air for combustion and that is a sealed cycle. Mine has an outside intake/exhaust port that is sealed and no way air can come in through that.

Have you considered adding an electric heater to save propane and help keep warm?
One of the most important mods I made was changing over to an electronic thermostat vs. the cheapo mechanical one. It keeps temps much better because it reacts more quickly to temp changes and shortens cycles and makes them closer together to avoid cold/hot/cold.

I used Reflectix to cover my windows for cold nights and to keep out UV/sun in storage and in extreme hot weather (Moab got to 108!).
I also used foamboard and panel glue under my queen bed to keep in heat and keep the mattress warmer.

[Murff]

Cool and interesting. Following this thread.


Murff

[DK1]

I can't read the model number .... the tag for that information is at the top of the unit and the lower kitchen sink shelf is right over the top the unit. However, given that Jayco says the unit is 19,000BTU the Suburban website lists ...Suburban Furnace 2504ABK 19,000 BTU (NT-20SEQ) so I'm assuming that's what I have. If you look at the pics on the Suburban site (of if you have the unit), you can see it draw air from the rear and pushes the heated air to the front of the unit.



I'm close to isolating the kitchen sink cabinet from the stove cabinet. I'm boxing in the 4"x4" hole at the rear right part of the cabinet where the drain and water lines come in. I'm using (don't laugh) cereal box cardboard to make the 'box' and then I'll fill the box with spray foam insulation. Once that is boxed in I'll have a rectangular opening to cover over (basically the gap between the rear of the cabinet to the side wall of the cabinet). This is the gap that I think basically feeds air to the fan.



I'll take a few days to get this done ... and I'll post again. I'm feeling pretty confident I can drill an air intake hole at lower part of the cabinet side by the door for air intake. I'll hold off doing that until I block the gap off and run the header without the fascia board. If I'm right (and that's a RARE thing!) then air will be drawn in from the front of the unit at either side of the sheet metal forming the box shape. (So an alternate might be just to create holes in the fascia board rather than the side of the cabinet...).

[DK1]

I've blocked off the area in the cabinet where the drain and water supply come in. All that's left is the gap between the cabinet and trailer wall. It's 3 3/4" x 12" so I'll temporarily block that with foam board or something and fire up the furnace. I'll try that today if I can. I'm planning another weekend trip to try out my other insulating measures but it won't be as cold as my other trips, just upper 20s. I'm hoping with my insulation measures and sealing off the furnace that I can use a small space heater on low an efficiently heat the unit.



Here are some pics of the drain block and the gap (if you look close you can see the Cheerios box I used to make the box...) Sorry about the pic rotation...

[DK1]

Yep I quickly added a space heater for the 2nd and 3rd camp and it helped to lengthen the time between the furnace cycling. However they ran 100% non-stop and the floor (actually anything below the knee level) was ice cold. It was that ice cold air pouring in from the furnace when it was off...

[DocBrown]

People that winter camp in trailers have been using space heaters forever. Propane heat is great in nominal weather, but yeah, the cold is too much for it.

But as you are starting to see, it's all about the insulation. You are trying to make a 3 season trailer work year round and it's just going to be an ongoing battle.

[DK1]

I couldn't agree more. It's a 3 season TT for sure and while not marketed as 4 season the unit came with the 'Artic' sealed underbelly insulation. I think a few mods to manage the air infiltration and the TT will be much more capable for low temps. There are a few areas where air infiltrates and that kills any energy efficiency. If I manage the air, I think the 'stock' insulation, and what I've added will make a noticeable difference.

[Jagiven]

Thanks for posting your observations. Years ago I looked up the efficiency of my furnace. I found it rated something like 70% I find that horrid in this day in age, and to my knowledge there is no mandate to improve it. Maybe California will realize this soon and ban these low efficient furnaces soon.

Our HTT is a 2.5 season rig for most people. We commonly camp down to the mid 20's at night. We have camped down as low as 19-20 degrees. For us it is not a big deal, but for many others I can see they would not like it.

In the cooler season, we normally have an electric campsite. When we do, here are a few things we do to help.[List][*]1st we use an electric mattress pad heater, and a couple good blankets. I also add one blanket under all the bedding too.[*]We have a small 1500 watt ceramic heater. During the day it is turned on and sits on the stove, we also have a small 12v fan that helps move the heat around. At night we move the heater to the floor in front of the stove.[*]We also added a heat strip to the AC unit. It does not "feel" like it puts out much heat, because of the high air flow, but it does. Between the two heaters we can roast ourselves out of the place when the temps are above 30 degrees (remember we have an HTT with canvas bunk ends).[List\]

I find the AC unit noisy, but I actually can fall a sleep all night with it's constant hum. I find the furnace like you annoying when it cycles on and off. So we tend to keep the furnace turned off, and use the CG's electricity. On really cold nights, we may turn on the furnace for 5-10 minutes when one of us goes to use the bathroom. Or when we first get up for the day.

The floor is always cold and we wear shoes in the camper, in the cooler months.

We are looking at new campers (next year purchase??), with the goal of camping locally year round. Our temps in this area can get to -30F. 100 miles north I have seen almost -50F. The rigs we are looking at are Jayco tested to 0 degrees for 8 hours (not much of a test in my opinion). I figure I will tear it apart so we can use electric heat (CG's power verses me buying propane). We will probably still dry camp just to be safe, but we plan to be comfortable.

Keep us updated on all your mods

[Rustic Eagle]

Dave,

Originally Posted by DK1

snip....... There isn't a return air register(s) or return air ducts........

X2........,

My 24RBS furnace is located under my jackknife sofa and was starving for return air. Furnace ran hot, blower motor was working overtime, excess noise, etc..

Added a couple return air vents on the wood box covering the furnace, and installed a cold air return vent on the bedroom wall directly inline with the furnace blower vents......, resolved all my problems.

Post #220 here: https://www.jaycoowners.com/forums/f...-51005-13.html

Bob

[Marcm157]

Great write up and observations - Pretty eye opening stuff. Thank you...

[DK1]

I have completed blocking off the rear of the sink cabinet and so the furnace cannot pull cold air from that area. Per my first post, in my 171BH the furnace was pulling air from the rear of the sink cabinet, that was opened to the area under the stove top, and that area was opened to the cabinet housing the refrigerator. The refrigerator cabinet is (my words) a partial cabinet. It doesn't come down to the floor and it about a foot away from the trailer side wall. The refrigerator sits directly in front of the huge louvered ?24X16 outside vent panel. So basically my furnace was pulling frigid outside air INTO the unit from that refrigerator panel, heating the air and pushing it into the trailer. As soon the furnace turned off, that cold air would cool down the heating chambers and frigid air would migrate through the furnace and dump that frozen air on the floor. It was rinse and repeat.


The front fascia trim panel is not attached to the front of the furnace but the grill grate is. I just went outside, turned my propane on and fired up the furnace. Not surprisingly air is now being pulled from where the fascia panel would be installed. I'm monitoring the temp remotely now. I put the temp sensor in front of the furnace about 1 foot away from the furnace grate, 4" off the floor. The temp went from 36 to 78 in about 1/2 hour (it's 36 outside this morning, no wind...). I'm going to monitor a bit to see if/how the temps oscillate. (I have one of those Baldr LED display 'weather' stations).



I've just about completed the insulation. i have one more area I want to do. Hopefully I can do that later this afternoon and overnight in the driveway tonight since it's going down to 22 degrees tonight. (it's been very mild here so this is the coldest we'll see in a while). The area I want to insulate is the 'headboard area'. My plan is to insulate with 1/2" rigid panel. A layer underneath the top board and a layer against the thin panel at the top / side of the bed. That would leave the box area by the front door to do but that requires removing the panels under the front bed and so I'll hold off on that until later. Still all told I've used 3 1/2 sheets (4'X8') of insulation or about 112 sq ft of rigid board.


I'm heading to Western MD for this weekend to dry camp again. The forecast for the weekend is a low of 28 (Sat) and 30 for Sunday morning. I'll have electric at the campground. I don't know if the restrooms are heated or not... I'll block off all windows with the foam panels I've cut at night. I'll block off the hood vent and most of the refrigerator panel at night. There's nothing scientific about all this, I guess I'll see if I think the mods make the unit more comfortable. Given how small the unit is, I'm hoping I won't be wasting a bunch of energy. If it seems better than the original configuration, my plan would be to cut a 6X6 hole in the kitchen cabinet side wall (closest to the door) as the 'cold' air return and put the fascia panel back in place as the permanent solution.

[DK1]

Man am I humbled and impressed!!! Excellent work-person-ship throughout. Clearly you've solved a gazillion issues and made many mods. From Bill & Ted's Excellent Adventures - I'm not worthy, I'm not worthy!!!

[Rustic Eagle]

Originally Posted by DK1

snip....... I guess I'll see if I think the mods make the unit more comfortable. Given how small the unit is, I'm hoping I won't be wasting a bunch of energy....snip

Dave,

Everything you are doing will pay dividends..., especially when dry camping.

I'm presently wintering in Texas and it's been a cold (20's at night), windy winter here in the Hill Country. The 'insulation' and furnace 'performance' mods I incorporated make for a comfortable camping environment.

Bob

[DK1]

My daughter and SIL just moved from Dripping Springs back here to Md a few months ago. His father has some property in Hill Country. We used to visit and I remember it getting quite cold (and in summer sweltering hot!) in both Dripping Springs and in Hill Country.

[DK1]

I spent the night 'dry camping' in the driveway before my trip this weekend as the forecast is only for upper 20s and I want to test my handiwork. What a difference! I couldn't be more pleased with the thermal performance of the trailer. I awoke this morning at 6:30 AM to 17 degrees amazed at the difference some 1/2" foam board, spray foam, Reflectix, and insulating foam tape could make in the little 171BH. The difference is night and day, or metaphorically, 'nice fall day .vs. freezing winter'.

I just didn't have time to insulate under the head board yesterday so put a folded fleece blanket on it. I did put foam tape on the lower cabinet doors so when they close, they seal completely. I also found an opened roll of 1/2"X1/8" open cell foam tape left over from a home improvement project and used it to seal off the gap around the top and side of the refrigerator mounting flange. I left the paper tape on the foam and just slid the tape into the gap. The mounting flange is about 3/8" wide and so you can barely see any foam protruding. I also made a small Refectix
'pillow' to block off the stove outside exhaust vent. My final tape job was to temporarily tape over most of the refrigerator inlet screen on the outside. I probably left in total about 8 inches of opening to allow air into refrigerator. I'm not telling or suggesting anyone do that, but it's what I did. I figure given how cold it was and was going to be, the refrigerator wasn't going to need a great deal of outside air to do its job. I did not tape over the refrigerator exhaust grill below the refrigerator door (inside the unit).

I went to the trailer around 9:30PM last night. It was 33 degrees outside at that point. I had left the furnace on from doing work earlier in the evening and so the trailer was comfortably warm. I went to bed, no PJs or other winter clothing and just a single synthetic down blanket. I didn't fall asleep immediately and was surprised that in the 20 minutes since I had entered the trailer the furnace didn't kick on. Just as I was thinking that, it did, but I soon went to sleep despite the fan drone (which I might be able to attenuate...). I awoke at 2:00AM thirsty. It was 22 outside, I think the humidity was 17% inside... The furnace had just kicked on. I decided to get out of bed and walk the length of the trailer in bare feet. I have an old carpet runner 'donated' by the CEO so I wasn't walking on bare vinyl but I'll tell you the floor wasn't ice cold. Previously stepping on the floor was like walking barefoot on a glacier at Mt Everest in winter.
I stepped off the carpet runner onto the bare vinyl and although certainly not warm, is wasn't ice cold either. So basically now my floor is winter tolerable with just socks.



An amazing difference. That's what it should be, after all I have the stock 'Glacier' underbelly package. I don't know the construction per se, but the frame rails of the trailer look to be 5 inches. There's foam sprayed underneath and a corrugated panels even with the lower level of the frame, so that's ? 5" of sprayed foam? Assuming R5-6 per inch
that could be R25-R30 under the floor. It shouldn't be ice cold and now, is NOT.

I no longer have winter antarctica from seat level to floor. Before there was 3 zones. Freezing code below the knees sitting at the dinette, comfortable at the waist, but it you stood up in the trailer you'd say it's hot at shoulder level and higher. I'm sure there's a temperature gradient from floor to ceiling but it's not a pronounced as before.

I decided to supplement the furnace with my space heater and so at 2:00AM I turned it on to low heat setting (which I think is 750watts power draw) and went back to sleep. So far as I know the furnace did not
turn on until I got up at 6:30AM to find the outside temperature was 17 degrees.

I couldn't be more pleased now with the thermal performance of my 171BH. I think I can yet make incremental improvement by insulating the headboard area and the boxed area at the foot of the bed by the door. For camping here in Md or the surrounding areas I can't see that there's no winter event it can't do. I completely understand 17 isn't single digits
or below zero, but it's rare for our area to get below zero. I would have no issue trying to dry camp down to single digits in the trailer now. But winter (I think) is just about done. I figure we'll see some 20s but I think our area has seen the worst of winter (which actually has been pretty mild...).


I'm claiming success!

[DK1]

The insulation mod, especially blocking off the air supply behind the furnace made a huge difference this weekend. It was relatively mild this past weekend, 27 on Saturday morning and I think 39 on Sunday AM. On Friday night I ran just the furnace early on to see the thermal performance. I didn't time the on-off cycle but it seemed the furnace was on for 4-5 minutes and off for 15 or 20 minutes. I let it go a few hours (I guess it was 30 degrees at that point) and just decided to go with the space heater on low and turned the furnace off. Even with the space heater on low the TT got too hot, 74, and so at one point I just had to turn it off later in the night, switching back to furnace.


Saturday the temps reached the 60s and the night was relatively might. The space heater, even on low was just too hot and so I just had to deal with the furnace fan noise every 15-20 mins, but I was so tired from a mega hike I slept through the noise... I think a great deal of the fan noise is the vent at the front of the unit. I'm going to try to remove it night and let the fan run without it. I think the aggressive downward angle of the vent plates creates a great deal of noise...



In any event, I certainly haven't turned the TT into a 4 season unit, but it's way, way better than 'as delivered'!

[TomC_AZ]

DK, can you please make a bulleted list of the mods you did that helped? It seems like a lot of trial/error and was not clear on what exactly worked and what didn't.

Also on the furnace, so it was pulling in cold outside air? Did you figure out exactly where that air source was?

We have been in weather down to 23ish and it got cool but the floor was not cold and we have not had the same "layer" effect of coldness. But the furnace does seem to be a bit deficient. I have looked and seen some spaces that go down to the tanks below etc that are not sealed. I have questioned if I want to or not as it might impact any work in the future if any was needed. I also thought it might allow some heat to possibly go down to the tanks to help with freezing.

[Bugman]

Saw on another RV forum that the wall had a large opening where the thermostat was attached. Lots of air could come up behind the thermostat and really mess with the settings. He cut a small patch of foil insulation and stuffed it in the hole and sealed it up, allowing only the wire to come through. Not familiar with your model, but any hanging curtains close to the thermostat could disturb the airflow around it.

[garywilson]

I guess you haven't tried using the outside shower yet?