furnace mounting - blowing air at the water tank & lines

[Vic Harder]

Since I have the option of where to mount my furnace when I get to that stage, I'm aware that when winter camping the lines can freeze up. Lots of good discussion here before.

I am most intrigued by the ideas of:
1) a small 5w pad heater under the tank
2) blowing the air at the lines

The latter would be easy to arrange since I am still in the building cabinets and layout / design stage, and will be using a Propex 2000 heater for size and placement advantages.

Question, would the heater output if blown directly at the water tank lines be hot enough to have to worry about melting them?

 

[Taku]

I doubt it. We have about a 12" run of duct pipe to our outlet with our Propex and it is hot, but not that hot. Maybe if the lines were right up against it, but even then I doubt it would melt water hose.

 

[Vic Harder]

I doubt it. We have about a 12" run of duct pipe to our outlet with our Propex and it is hot, but not that hot. Maybe if the lines were right up against it, but even then I doubt it would melt water hose.

Good to know. And from a Propex user no less. Thanks Taku!

 

[nikonron]

Be difficult to melt the lines with water being in them. Ron

 

[DanoT]

When one considers that the low setting on most electric space heaters is 500 watts, it seems unlikely that a 5watt heating pad is going to keep anything from freezing while camping in Alberta in winter.

As an experienced winter camper, what I do is not use my water system in winter. Instead I pack water in 4 gallon containers, heat water on the stove and shower using a portable shower.

 

[rando]

I used a Propex HS2000 in my last camper (excellent heater!) and would agree that the outlet air is not hot enough to melt your lines. The grill they provide for it is thermoplastic and has no issues. You could split the outlet ducting with a Y and provide one duct straight into the camper, and one with a damper into your utility space.

I also would agree that 5W is not going to do much for your water tank. The heat capacity of water is 4.2J/gram-C. Given a small 20L water tank a 5W heater would only raise the temperature 0.2C per hour, assuming no losses. I think you would need more like a 100W heater to make any sort of difference. Much better idea to use your furnace to keep the ambient temperature around the tank and plumbing warm.

 

[Vic Harder]

I used a Propex HS2000 in my last camper (excellent heater!) and would agree that the outlet air is not hot enough to melt your lines. The grill they provide for it is thermoplastic and has no issues. You could split the outlet ducting with a Y and provide one duct straight into the camper, and one with a damper into your utility space.

Sounds like this is what I will do, since it appears simple and no snags have been mentioned yet. Thanks!

 

[Vic Harder]

I installed my Propex this spring, and thought I would update this thread with my install. First, when I built out my shell last year, I was already thinking that I would use the Propex vs the Attwood. So my cabinets are actually too short to install an Attwood. The Propex fit was tight, but I had left the perfect spot for it, just above my water tank/pump in a cabinet that also housed the water lines coming in from outside and to the faucet. Here is a trial placement:

It didn't end up facing that way. I flipped it over so I had easier access to the propane fitting, and the electronics access panel on the Propex. The big water line is for filling the tank, the smaller water lines go to the city connection and faucet. The big brown tube is the heat output from the heater, which feeds down and blows on the water pump and connection lines of the water tank. The red (and black) electrical wire is for the external solar connector which is at the front of my camper. Kudos if you can make out an AC wire too, that goes to the external AC plug which ONLY feeds my NOCO Genius 7200 for the rare times I made need to charge the batteries that way.

Here is a pic of the crazy number of fittings I had to use to get the propane line to connect to my 20# horizontal tank

And one mundane one of the routing of the propane line

In this pic you can see the short stubb of another big brown tube that comes up at the back. This is the air intake line for the heater

With the divider in place, it looks like this:

About that divider... I puzzed over ways to solidly mount the unit, as the space was tight, and the supplied mounting gear wants you to mount the heater with small exhaust and combustion intake lines facing down. I used a divider board, some T-nuts and universal 1/4" threaded bar to go through the wood of the camper. Not only do I get a divider so I can still toss light stuff into this space, the heater is very solidly mounted.

Combustion and air intake lines route down through that same area of the camper and are secured against the side of camper wall, facing in opposite directions and far enough apart so as not to interfere with each other as per the install guide.

This is what it looks like now if you open the cabinet door

From the top without the top of this cabinet mounted. This pic shows the air intake vent I installed. The air flows in their and then via the big brown tube (previous pic) into the heater.

No pic for this, but I mounted the thermostat at the foot end of the bed, so it can be reached in the morning to crank up the heat. The fan is a bit louder than I expected, but I'm sure we will like the heat, regardless.

 

[wuck]

I installed my Propex this spring, and thought I would update this thread with my install.





Combustion and air intake lines route down through that same area of the camper and are secured against the side of camper wall, facing in opposite directions and far enough apart so as not to interfere with each other as per the install guide.

Yay! Heat! We've not used our Hawk much in the summer, mainly spring and fall. And, even here in California, heat is nice.
Our old Suburban furnace is pretty loud, so we usually keep it down around 50. I've turned it up a few times in the morning, but then boiling water for coffee makes it way too warm in there!

I'm not at all familiar with the Propex unit, but I'm wondering how hot that exhaust gets?

 

[Vic Harder]

Not very, surprisingly.

 

[Thevulture]

I’m getting ready to install a Propex on my Eagle. Have you noticed any issues with your exhaust going into your truck bed? Or do you think there’s enough airflow?

 

[Vic Harder]

not yet, since it’s warm outside

 

[Thevulture]

Thanks.

 

[Vic Harder]

Update time. We have been out a few times in cooler weather, so have had a chance to check out the Propex furnace.

First - it works! Noisier than I had hoped. Can't compare to much of anything else though, since the other noisemakers in the camper are only the 130L Truckfridge (near silent) and the Fantastic Fan (noisy!).

Second - I had to tweek my install. I had a problem with the furnace not lighting, (turns out to have been user error, as I didn't tighten the propane hose onto the tank tight enough to open the valve - small burr had me thinking it was "on", had to push past that resistance to really get it on), and learned a few things from the excellent support folks at Propex Canada (Chris Ball).

- The exhaust hose gets really hot (250*) and needs to be protected. These units normally go into "Caravans" with metal bodies/floors. When installing in a wooden camper, we need to take extra precautions. Also, I mounted mine in a really tight spot, so need to take extra extra precautions! See more info below...

- There is a fuse on the circuit board! This can be really hard to get at, depending on how the furnace is mounted. Take a look at it when you are connecting the wires and have the cover off. JPG attached with details here:

I got this PDF from Propex Canada, when we were troubleshooting why the furnace wouldn't light up. The fuse on mine was not blown, but it was good to find out where it was.

So I made a few mods to ensure the hot stuff on the heater does not get in contact with wood. I had initially routed the flame exhaust like this:

It now goes through an aluminum plate, with the hole just big enough for the supplied silicone rubber sleeve to fit, and sealed with red high temp silicone for use on engines and other super hot items. The hole behind the alum has been enlarged to 2", so there is lots of room around the exhaust hose.

I also added another hose clamp to secure the hose and keep the down angle consistent (for condensation drainage) and added some 1" long metal stand-offs to keep the hose away from the camper's wooden surfaces.

Finally, I added a piece of angle alum inside the camper, to shield the hot air hose from the hot exhaust hose. There is about 3" clearance there, and the hot exhaust hose rests on top of the alum angle. I could also add a sheet of silicone rubber on top of the angle alum at some point, as the alum angle still gets pretty hot.

Also, the way I had the hot air exiting and blowing onto the water pump, and hose fittings on the end of the water tank, meant that there wasn't a lot of air flow coming out of the heater. Too many obstructions as you can see in the image below. So I am going to be adding some more length to that hose and running it beside all those components, and still exiting down low as planned, but with a hose to run through the whole way. Gotta go to HomeDepot and grab some dryer vent hose for that.

The next project is adding a better thermostat. We tested out the existing one last weekend, and on the lowest setting it heats the camper to 15*C. Too warm for me at night. I'd like to get a "freeze protect" setting of around 5*. I got this info from Propex Canada and need to splice in a thermostat to give me finer control.

Ideas on how to do that would be appreciated. There are a few links out there, (this is a great general install page https://faroutride.com/propex-install/ )
but nothing super clear on how to wire in an additional thermostat.

 

[DanoT]

I have found that for winter camping the position of the thermostat can be critical. The factory thermostat position in my Phoenix camper was too close to the furnace and in really cold temps caused the furnace to shut down before things got very warm. So I re positioned the thermostat farther away on the side of a cabinet but this time the furnace would not cycle off when I wanted it to. So the 3rd thermostat position (front of the cabinet) was finally the charm.

 

[larryqp]

When I installed my propex heater, wrapped the exhaust pipe with automotive exhaust header wrap.The ends of the header wrap are secured with a hose clamp.
It's available at any auto parts store. I can wrap by hand around the exhaust pipe when its running and it's not hot at all. It may be overkill, but I didn't want to worry about it. I think a roll of the exhaust header wrap was about $50. Cheap enough for mental wellness.

 

[rando]

The arrangement of your exhaust tube may be a little concerning. When I installed a Propex on my pop-top land cruiser, the advice I was given was that you had to be careful routing the exhaust near flammable materials (which you have addressed), but also that the exhaust needs to extend out from under the vehicle to make sure you were exhausting away from living spaces. Dumping the exhaust gases into the space between the camper and truck seems a little risky, given these campers are not very well sealed. Can you run the exhaust out to the edge of the camper and into clear air?

Wiring in a new thermostat is a little tricky - you will loose the status LED, which is useful for trouble shooting as it blinks out error codes and possibly the fan control too depending on your thermostat. An easier solution maybe to modify the stock Propex thermostat to have a lower range:
https://www.thesamba.com/vw/forum/viewtopic.php?p=6630782

 

[Vic Harder]

Dumping the exhaust gases into the space between the camper and truck seems a little risky, given these campers are not very well sealed. Can you run the exhaust out to the edge of the camper and into clear air?

Wiring in a new thermostat is a little tricky - you will loose the status LED, which is useful for trouble shooting as it blinks out error codes and possibly the fan control too depending on your thermostat. An easier solution maybe to modify the stock Propex thermostat to have a lower range:
https://www.thesamba.com/vw/forum/viewtopic.php?p=6630782

Thanks for these insights rando.

I'm pretty sure that the CO can't get into the camper. I saw those same instructions, and I wonder about the wisdom of it, since CO is supposedly lighter than air, so I am not sure how dumping it below the truck would help, it would rise up anyway.

That link looks interesting! I had thought of keeping both the existing Propex thermostat so as to get the blinking lights, etc... by splicing into the temp sensing line and inserting another thermo in there.

 

[Vic Harder]

Hmm... that article talks about the older version of the thermostat. The new one looks very different and may not work the same.

 

[rando]

I am going to guess the new one works the same way - temperature is sensed by a thermistor (resistor that changes resistance with temperature) and a second in series with the thermistor that turns the variable resistance into a voltage. This the resistor you want to change to move the range of the thermostat (R7 in the previous version of the thermostat). If you post a close up photo of the board inside the thermostat, I can probably tell you which resistor you would need to change.