Your Wagonmaster heater may kill you

[David Tilston]

I have a blower that was actually designed for the classic Trillium gravity furnace.
http://www.fiberglassrv.com/forums/f...wer-54226.html

But I think I like Francesca's better. No power draw. How is it installed Francesca?

[Roy in TO]

Originally Posted by Francesca Knowles

Faggedoubout computer fans- they use electricity from the battery. Getcherself an Ecofan- they make their OWN electricity off waste heat from the heater!

And they're stone silent to boot.

Francesca

Eco Fans $100-200 retail depending on model.
Computer fans and switch are laying about, solar system and battery already exist. Wallet is telling me the latter prevails.

My understanding is that computer fans have very little draw and can be run for a few hundred hours before draining a battery. Switched and selectively used - much longer. They run fairly quiet. I see the benefit for when first starting to heat the trailer. Most nights after the initial heat up it spends a lot of time on pilot Maybe someone elec-trick-ly inclined can pipe in with the details.

I took this picture for the storage drawer in the Trillium closet, you can catch a glimpse of the fan on the furnace and the inlet vent below the opening for the drawer.

[Roy in TO]

Originally Posted by David Tilston

I have a blower that was actually designed for the classic Trillium gravity furnace.

I don't have a Duotherm furnace in my Trillium. The Fromme may have been an aftermarket addition.

[Roy in TO]

A quick search says that the computer fan only draws about 1/4 or so of an 1156 bulb. Can someone provide better numbers for comparison?

[Carol H]

Originally Posted by Roy in TO

I took this picture for the storage drawer in the Trillium closet, you can catch a glimpse of the fan on the furnace and the inlet vent below the opening for the drawer.
Attachment 59804

Roy was adding the inlet vent one of the items that Panda Propane suggest be added? wondered as it was my understanding that no air inlet, only an outlet was one of the big issues with the Wagon Master.

[Roy in TO]

Not sure Carol. On my furnace there were two tubes going to the outside vent. One inside the other. I thought one was the inlet and the other the outlet. Much like my fridge vents on the RM-183B.

I found similar components for the ecofan here and here maybe someone can advise us how to make our own self powered fans for a lower cost. The TEG units look to be selling on ebay for less than $30. If that is the case it would be economical to have fans for both the furnace and fridge without the need for battery connections. Anybody up to the electrical engineering challenge? I'll attempt the test installs if someone wants to tell me what I need to do.

Thermalenterprises on ebay seems to be selling the TEG units for $19.99 and up. I only wish I knew what ones would be suitable to power the computer fans. You could attach a heat sink to the side of the furnace or use the fins on the back of the fridge to attach the TEG's to and power the fans.

[Carol H]

Would indeed be cool if someone came up with a fan for the fridge that did not use power. Only time I need the fan is usually when I also need to use the Fantastic Fan a great deal as well.

[Roy in TO]

I've asked the ebay seller if one of their TEG (Thermal Electric Generator) units would power a 12V computer fan. Waiting for a reply, I'll post when I get a response. Never mentioned using one with the furnace. I assume the temperature has a lot to do with it. I would also assume that the hotter the contact surface the more the units put out. That would be beneficial for both fridge and furnace applications.

Here is their response:
You will not get 12V output from one single TEG. With our 40mm TEG modules you can expect output as follows:
FOR MODEL TEG1-12710
0.5 to 2.0 VDC
and 0 to 1.2 Amps
To obtain maximum output you would need a temperature differential in the range of 100-120 deg C
FOR MODEL HT1-12710
0.5 to
2.5 VDC and 0 to 1.8 Amps
To obtain maximum output you would need a temperature differential in the range of 120-150 deg C
If your
application requires 12V output you will need to use multiple TEG modules wired together in series.

With the temperature differential required, I see these would only be good for the furnace. One would need a motor with lower power requirements as well. I see ecofan replacement motors on ebay for under $20.

I noticed that some people are using Stirling Engines to make wood stove fans. http://en.wikipedia.org/wiki/Stirling_engine

http://www.youtube.com/watch?v=4Hn16FHElqE

[Francesca Knowles]

Originally Posted by David Tilston

But I think I like Francesca's better. No power draw. How is it installed Francesca?

They just sit atop the heater, as illustrated in the video above. Since energy production depends on the difference in temps between foot and fins, best output is achieved by keeping the fins as cool as possible. On a freestanding stove one relies on free air from behind the stove for that. In my install, I put a heat shield between the foot and the top of the fan, and feed air to the fins from behind. Here's a picture of my old install. This heater's defunct and has since been replaced- don't have a picture of the new one.

I'd thought that contact between the foot and the heater was critical, but with the recent replacement that proved impossible. The fanfoot is now "suspended" in the heat stream and works just as well as before.

Francesca

[glamourpets]

Originally Posted by Roy in TO

Here is their response:
You will not get 12V output from one single TEG. With our 40mm TEG modules you can expect output as follows:
FOR MODEL TEG1-12710
0.5 to 2.0 VDC
and 0 to 1.2 Amps
To obtain maximum output you would need a temperature differential in the range of 100-120 deg C
FOR MODEL HT1-12710
0.5 to
2.5 VDC and 0 to 1.8 Amps
To obtain maximum output you would need a temperature differential in the range of 120-150 deg C
If your
application requires 12V output you will need to use multiple TEG modules wired together in series.

It seems to me that it should be possible to get a fan to run within these specs. Sayal lists a fan that runs at 5V .24A. Its small, but how much airflow are we trying to achieve? They actually have a handful of fans to choose from 5V. Sayal is the electronic wizard's dream store.

Sayal

[David Tilston]

Francesca, It looks like you also don't have a Duo-Therm furnace, but in the registry images for your trailer, it looks like a Duo-Therm exhaust. ???

[Francesca Knowles]

My experience with the Duotherm was that while it was O.K. for three-season camping (which is what our trailers are really designed for), it wasn't up to winter camping demands. Too much heat wasted for the amount of propane consumed over sixteen hour heating cycles. Randy Bishop wanted an original heater for a heaterless "herd member", so I gave it to him and use a catalytic heater now.

The outside vent itself is still in use for air supply to the interior/ heater.

Francesca

[Darwin Maring]

Any combustion heater will kill you that is why you should have a Carbon Monoxide detector in the camper. I have 2 just in case one fails - Reason - You don't wake up dead because dead is dead.

[David Tilston]

I agree, the Duo Therm is a bit low on heat. I am hoping that the fan unit will help with heat output.

[glamourpets]

Originally Posted by Donna D.

It seems to me about two years ago (or maybe longer, I have sometimers disease) everyone that was a dedicated boondocker was really wanting one of these furnaces because they're gravity fed and require no power to heat the trailer. Is that right? Seems to me checking out a furnace, no matter WHAT brand is a maintenance issue and if things are going bad, they need to be fixed or replaced. So, I don't know why this furance would be any worse than any other. YMMV

These furnaces seem to get scooped up pretty fast, even now. It appears that they are still desirable. I'm surprised by the amount of money people are getting for them too. These appear to still be "hot items."

[Roy in TO]

Originally Posted by Carol H

Roy was adding the inlet vent one of the items that Panda Propane suggest be added? wondered as it was my understanding that no air inlet, only an outlet was one of the big issues with the Wagon Master.

Carol,

I just stumbled across a picture here of the inside of the component I had to replace. http://www.fiberglassrv.com/forums/f...ent-41392.html The picture shows the part from the inside.



From looking at the residue patterns on my vent from the outside I can see that the inner ring or pipe is the exhaust vent and the outer ring is for the inlet.

So you have fresh air for the feeding the furnace from outside. A leak in the exhaust pipe would be drawn back into the furnace. You would need a hole in both for the exhaust to get into the cabin.

A couple more shots of how the inlet and outlet can be seen in Con's post back in 2006.
http://www.fiberglassrv.com/forums/f...html#post61218

[glamourpets]

Tonight I took my furnace out of its storage spot and gave it a good inspection. It appears that the metal is all in good condition so there is no worry about that. Unfortunately mice decided it was a very good place to build a nest and they packed it full of pillow fibers and seeds. I ended up taking it apart, pulling out the stuffing, and spraying the thing down with disinfectant. I will put the furnace back together again tomorrow. These furnaces sure are simple. Its basically just a pressure valve, a pilot light, and a burner. There isn't much else in there.

One of the things of interest is the name plate on the furnace, which is still in good condition. Apparently these furnaces are rated at 6000BTU input and 4000BTU output. 4000BTU is plenty of heat for our little trailers. The 6000BTU input number has me curious. Would this suggest that these furnaces are 66% efficient? Compared with newer models, this efficiency is probably considered unacceptably low. Perhaps this is the reason we don't see new gravity feed furnaces? Thoughts?

Derek

[Brian B-P]

Originally Posted by glamourpets

Apparently these furnaces are rated at 6000BTU input and 4000BTU output. 4000BTU is plenty of heat for our little trailers. The 6000BTU input number has me curious. Would this suggest that these furnaces are 66% efficient?

Yes, that's exactly what it means. The furnace burns propane fast enough to make 6000 BTU per hour of heat; only 66% of that makes it through the heat exchanger to become 4000 BTU per hour of interior heat, with the other 2000 BTU per hour lost as the hot exhaust.

Originally Posted by glamourpets

Compared with newer models, this efficiency is probably considered unacceptably low

Yes. For home use, even the "mid-efficiency" (85% or so) furnaces can no longer be purchased here, because they are not efficient enough. I don't know if there are any rules for RV furnace efficiency. In the size of one of our trailers, I don't think efficiency would be my biggest concern.

Originally Posted by glamourpets

Perhaps this is the reason we don't see new gravity feed furnaces?

Especially in a house, but even in an RV, both bulk and a lack of effective distribution of the heated air are also factors... but efficiency is most of it in a house.

[glamourpets]

Originally Posted by Brian B-P

Yes, that's exactly what it means. The furnace burns propane fast enough to make 6000 BTU per hour of heat; only 66% of that makes it through the heat exchanger to become 4000 BTU per hour of interior heat, with the other 2000 BTU per hour lost as the hot exhaust.


Yes. For home use, even the "mid-efficiency" (85% or so) furnaces can no longer be purchased here, because they are not efficient enough. I don't know if there are any rules for RV furnace efficiency. In the size of one of our trailers, I don't think efficiency would be my biggest concern.


Especially in a house, but even in an RV, both bulk and a lack of effective distribution of the heated air are also factors... but efficiency is most of it in a house.

I was playing around with a few different online BTU calculators last night. 4000 BTU should give you a 20C temperature increase inside the trailer. Beyond this you are probably pushing your luck. This means that camping below the freezing mark (0C) probably isn't going to push the furnace beyond its capacity to keep the trailer warm. These are mathematical theoreticals. Has anybody tried this in practise? What is the coldest temp where these furnaces remain practical?

Derek

[Roy in TO]

Although we don't winter camp, we've camped where the water has frozen outside overnight. I'd say single digits below, never tracked it though. Pretty much stayed at a comfortable temp inside (20 deg?) with the furnace set no higher than 3.

Did you factor in the mammilian heat produced in your calculations?