DuoTherm furnace - Post 1: Jerry-rigged sail switch

[IdaSHO]

That said, I don't have a thermocouple. I have an electrode assembly. From what I understand, propane will not continue to be delivered to the furnace if combustion fails because of the safety mechanisms, though I could be wrong since all this is new to me.

You still have a thermocouple. Although it may be called a thermopile. The thermocouple/thermopile senses heat and forces the propane circuit for the pilot light to stay open. When the heat goes away (pilot blows out) and the thermocouple cools, the pilot circuit is closed.

Still, as I said, this isnt INSTANT. I timed the brand new valve and thermopile on my freshly restored furnace just as a test. It took nearly 20 seconds for the thermopile to cool enough to close the circuit when I blew the pilot out. During those 20 seconds propane continued to spill from the pilot orifice. This is NORMAL.

Now that I know that the issue of intermittent lighting could be altitude, I'd like to ask 1) how do I adjust the manifold pressure (actually, I need to first know where the manifold is) and 2) How do I know what size orifice to get if I decide to change it out?

I have gotten away so far with a simple adjustable regulator (on the tank). But I rarely need heat above 8k. And never above 12.
Upping the pressure a bit on mine seems to smooth the delivery of propane to the furnace, making pilot lighting much easier.


The size of the orifice will depend on your particular furnace and the valve it uses. Best bet would be to take the thing into a heating shop. The valves themselves are actually pretty generic.

 

[IdaSHO]

I picked up a nice non-electric propane furnace from a sale at Lowe's in the spring a couple of years ago - works really well for heating a loft apartment space in a shop building I have.

Its a direct vent type unit - so the burner's intake and exhaust are sealed off from the inside air and go through a single "coaxial" pipe through the wall. Doesn't add moisture to the interior air and should be safer - less chance of CO poisoning.

I think it would be a good option to consider for a camper since it uses no electricity. One nice feature on the one I have is that the burner turns down to a lower level before going to pilot only so it cycles on and off less. Mine has only been used at low elevations so I can't say much about high altitude operations unfortunately. I did have the pilot clog once due to foreign material getting into the propane line - so a filter by the furnace is a good idea to consider - especially if the propane line is disconnected when not in use - it will save a lot of time messing with it trying to get it to light or stay light on the pilot...

It is a gravity furnace, functionally no different than the furnace I posted a photo of. It probably even uses the same valve mine does.

Though any household furnace like that you will probably have to do a LP conversion to run on a camper. Most come standard to run off of natural gas.


This is the valve I put in mine. They cost about $200

But again, they come standard to run off of natural gas. So you will have to do a conversion.

The conversion basically consists of just a different regulator coil spring to adjust the pressure.

 

[IdaSHO]

What search words have you found to be successful?

How wide are these type furnaces?

keywords "camper, furnace, heater"

And look at each and every listing. Most people dont know what they have when they have it, and consider it junk. You have to look at the pictures. If it doesnt have a blower, its probably a gravity furnace.

Funny thing though, these furnaces also came with blowers. So you really just have to know what you are looking at.

They seem to some in all shapes and sizes.

This is one of my other furnaces, that came with my old crappy 1971 Bell camper. It is a Carlson

Same style valve that the Hydroflame came with, but a significantly different burner. This one is cast iron vs the stamped steel burner on my hydroflame

 

[Stereo]

Catalytic heater option

As I was trying to learn more online about the gravity heaters, I came across a catalytic heater that a lot of people really like (though some got a dud, so be sure to have a CO detector). I especially like that it has no fan. Our current heater is LOUD.

Note that it is NOT a vented heater though it is rated for RV use. We always crack our ceiling vent at night anyway to deal with condensation. I could also put in in the cabinet with the vent for the battery to provide combustion air.

I'm spoiled currently; we flip a switch to turn on our furnace before we get out of bed. I would think it's possible to wire up a remote switch on this unit, though.

It's supposedly rated to 10,000 feet because it doesn't have an oxygen sensor.

Here's what is said about the Camco/Olympian Wave catalytic heater which comes in 3k, 6k or 8k btu options: "If you're interested in a propane RV heater that has bulletproof reliability, I'd like to put in a good word for Camco/Olympian Catalytic Heaters. Most models don't require any battery power (won't leave you in the cold when your house batteries run down), don't have any complex electronic ignition, don't have a blower (are completely silent in operation), and produce a very pleasing radiant heat that warms objects rather than air (feels like sunlight). It is especially great for boondocking. Because it is so efficient, you can run it from a standard 20-pound tank."

The big A carries the 3k burner for $200 with free shipping, the cost of just the gas valve IdaSHO mentioned.

Thoughts?

 

[Stereo]

This one is cast iron vs the stamped steel burner on my hydroflame[/IMG]

Yikes! That looks to be twice the size of my current furnace. Is the tall ducting required? I only have a space of 12 x 12 x 22 deep to work with.

 

[IdaSHO]

Lots of people run them.

I refuse to. I like knowing that the air used comes from outside and the exhaust emitted is forced outside.



Im one that is pretty sensitive to odors. And propane odors are at the top of the list. I hate it, and it gives me headaches.


Not a chance in hell would I survive a trip with a catalytic heater.

 

[Stereo]

Im one that is pretty sensitive to odors. And propane odors are at the top of the list. I hate it, and it gives me headaches.

I hadn't considered that. I tend to get headaches pretty quick from noxious odors too. However, in reading over 100 Amazon reviews, good and bad, not one person mentioned odor.

 

[uriedog]

I have seen vented catalytic heaters, although pretty spendy compared to the Wave. I personally don't like them for RV use, although I will say the heat off them is very nice.

I have gravity heaters in both of my campers. 7000BTU's in the summer trailer, 10,000BTU's in the winter camper. Best most reliable heaters ever. Silent and easy to service on the fly. I can run 4 days/nights on a 20lb tank in -20'c weather the camper sits at a comfortable 20'c

Is that sail switch like an air proving switch? May be and idea if you cant find a replacment

 

[Stereo]

Need gravity heater dimensions

I have gravity heaters in both of my campers. Best most reliable heaters ever. Silent and easy to service on the fly.

How much area do these gravity heaters take up including the venting? From the few pictures I've seen, it looks like the vents are relatively tall to allow cool air to come in at the bottom and warm air to rise up and out? In my pop-top, slide-in camper, I only have an area 13 wide x 14 tall x 22 deep.

I totally understand people's misgivings about having an unvented heater in the camper but we never run our heater while sleeping; we just flip it on for a short while to heat things up in the morning and to stave off the cold at night until we crawl under the down. We only summer camp (though it does get cold at 10,500 feet). We also have a small, always-open vent for the battery and crack the roof vent to help limit condensation. There's great appeal in the 10 x 12 x 3.5 size and low weight of the catalytic heater.

However, if we can fit it, I'd prefer to go with a gravity heater so I'd really appreciate getting some dimensions.

 

[IdaSHO]

No matter how you do it, a gravity furnace will will never fit within the opening of a forced air unit.

Gravity furnace needs height for the convection aspect to work. Forced air units are like large shoe-boxes.


None of my gravity furnaces are deeper than 8 inches or so. But they are tall.

 

[Herbie]

View attachment 219292

View attachment 219293
What's on there now is a 3 amp switch made by Cherry Electric. I believe the part No. is E22. The mount holes were not altered but the arm's been bent and the flag has glue on it now that I removed the extension (which I thought was just pinched on). So I need a new flag switch.

OK, I don't have an answer for you, but I can get you close, so some more catalog digging, etc. should get you the rest of the way there.

The switch is part of the "General Purpose E-line" of Cherry Snap Action Microswitches:
http://cherryswitches.com/product/general-purpose-e/

The E22 designation just sets the current handling, etc., you can see the general specs in this version of the datasheet. The good news with that is that any higher rated switch should also work. All the switches in the E-series should have the same form factor, I think, so will bolt to the bracket
http://www.mouser.com/ds/2/71/E21_Series-187037.pdf

The tricky bit is what you call the "flag". Cherry calls these "actuators", and they make a HUGE number of different levers, roller levers, etc. for a variety of applications. They seem to have a separate part number or at least part suffix for the actuator, which makes sense. I haven't found the exact actuator, but I also haven't found a full "catalog" of actuator types - you will probably need to continue poking around for that. I suggest checking newark.com, mouser.com digikey.com and any other such places you can find. Cherry also has a downloadable interactive catalog that might have more detailed information on actuators, so check that as well.

Hope that helps.

 

[Stereo]

some more catalog digging, etc. should get you the rest of the way there.

I will definitely see what I can find. My worry is that the switch that's on there is not the original, thus the need for the extension. I would love to get my hands on the manual for the motor to be sure, assuming it has parts information (though even then, it will probably only give a part number rather than the specific make, voltage, configuration, or whatever else needs to be known). However, if I can find the right Cherry switch, I'm sure it will be inexpensive enough to give a new one a try.

Thank you for giving me something to go on.

 

[Stereo]

None of my gravity furnaces are deeper than 8 inches or so. But they are tall.

How wide are they and how tall is "tall?"

 

[Stereo]

Found sail switch for DuoTherm 66012 heater

RV Parts Center had my sail switch. They emailed me a section of catalog that showed that all models in DuoTherm's 66012 line of heater with either a pilot light or DSI (direct spark ignition) use the same switch. Mfg Part No. 315269.000. In-house PC #23984. $16 plus shipping. By the looks of the photo of the part, the sail switch I currently have is not a DuoTherm switch.

I'm going to put my heater back together with a larger orifice (size still to be determined) and get an adjustable regulator per IdaSHOs recommendations.

The gravity heaters appear to be too big for my small pop-up and I don't think the butane heater is a good fit either. I'll reveal the reason why in the next post to make it easier to find for people considering the Camco catalytic heater.

 

[Stereo]

Olympian/Camco Wave catalytic heater

In my search for information about gravity heaters (which have great appeal if you have the room for them), I came across lots of posts lauding the benefits of the Olympian/Camco Wave catalytic heater. It comes in 3k, 6k, and 9k btu sizes and it's pretty small. The 3k is only 10 x 12 x 3.5" deep, weighs about 6 pounds. The heater can be wall-mounted horizontally or placed on an optional stand (which reviews suggest is pretty flimsy). The 6 and 9k models can be inset with an optional inset kit (or line the inset with non-combustible material). One owner used a "rubber" gas hose so he could move it to different locations. It currently costs $200 with free shipping through Amazon. The heater has a 3-year warranty. Camco has shipped some of its manufacturing to China.

The heater has a 3/8 SAE flare connection to link to your propane gas supply line and it's said to be very miserly with fuel. (Don't use it with the small Coleman bottles even though it's technically possible with an adaptor.) There's no complex electronic ignition.

The heater is rated for indoor use with adequate ventilation. It works at altitude (rated to 10,000 feet) because it doesn't have an oxygen sensor. (I'm amazed a sensor is not required given that the major safety concern with catalytic heaters is the possible over-consumption of the oxygen we humans need for life. However, this should not be a risk with adequate ventilation.)

It provides radiant heat that warms objects in its path (including humans). The objects then give off heat to the air. It has silent operation because there's no noisy fan which means it also doesn't require battery power. Some people have added an Ecofan to help circulate the heat without power.

I didn't find any reviews mentioning any odor.

I emailed Camco with many questions and they were pretty quick to get back with me. Several reviews suggested that customer service is responsive. Here's some additional information I received:

There are no Camco accessories to wire a remote switch or a thermostat to the heater, nor is there a quick gas connect, though they're working on one. (I'm sure you handy people could create any of these functions with off-the-shelf hardware).

Rough roads don't pose a danger for it but dust can be a problem. Camco recommends their optional dust cover. One poster cautioned as follows: 'As the propane in the tank is consumed, the mercaptan odorant is concentrated somewhat in the remaining liquid propane in the tank. As the tank runs dry, the mercaptan (containing sulfur) comes out much more concentrated in the propane gas and is bad for the platinum catalyst in the heater. Just a one-time exposure could poison the pad in the heater.'

Some people complain that condensation is a bigger problem with these heaters. Water is a bi-product of combustion and with a catalytic heater, combustion takes place within the interior of the heated area rather than inside a heat exchanger which vents to the outside.

Clearances: 4" on either side, 4" from the floor or other horizontal surface, 18" above, 0" in the rear, and 30" from the front. This last measurement is what made the unit untenable for our pop-top truck camper. With two people and a dog, it would be hard for us and other surfaces to stay far enough away from it to be safe.