Backup Propane Heater for Offgrid house -- recommendations?

[PorkChopsMmm]

Our primary heat source is our wood stove. I want to install a wall mounted propane heater for backup use while in the house, but more importantly, for a heating source if we are away from the cabin for more than a few hours. I am wondering how well the thermostat works on a unit like the one linked below and if you would have any other recommendations? Our cabin is ~768sqft on the 1st floor and ~1200sqft total. I would just be looking for this to keep the cabin around 50 degrees so pipes don't freeze. This would be assuming we would leave the cabin at 65 to 70 degrees when we left.

http://www.amazon.com/Mr-Heater-Propane-Flame-VF30KBLUELP/dp/B000UPR5TY/ref=sr_1_4?ie=UTF8&qid=1345559333&sr=8-4&keywords=propane+heater+thermostat


Thoughts? Thanks!

[Squirl]

Do you have a CO detector?

If you have an airtight house, I would normally pass on the direct vent.  They use oxygen from the house to heat it and propane can release a little bit of water vapor when it burns.

I was able to pick up a direct vent heater off of craigslist for $175.

[PorkChopsMmm]

We do have a CO2 detector and I am open to using a vented heater. My concern is more on it regulating it's own temperature. I would prefer the unit keep the pilot lit but turn up or turn down the gas based on temperature. From the looks of it, these can handle that requirement.

I just wonder what other heaters you all are using?
This one also looks like a good one, although it is not vented. I am struggling to find an exterior wall in the house that has the clearances needed for a heater. I can easily mount a non-vented model on an interior wall -- however.
http://www.northerntool.com/shop/tools/product_200485121_200485121

[flyingvan]

I'm using the Williams 35,000 top vent model.  It's mounted in the center of the house.  The chimney chase has a stud bay and the flue runs up that, then a couple of angles in the attic made the terminal cap the correct distance from the chimney cap.





   The flue assembly is designed to run up a 2x4 wall so there shouldn't be much problem mounting it somewhere in the interior where it belongs.  I added the blower that mounts on top, which is optional.  The wall heater will work without any electricity, the thermostat is a millivolt type and can mount anywhere (like whatever wall your pipes are in)

   The (direct vent) CORRECTION NOT DIRECT VENT.  I MEANT VENT FREE OR VENTLESS heaters are OK for garages or ice fishing lodges, or drafty old homes, but a bad idea for a well built living space.  35,000 is the correct size for your cabin.  Don't make the mistake of undersizing it thinking you only want to 'take the edge off' the cold----it will run more often than it is designed to and fail prematurely, and a 35,000 doesn't cost much more than a 25,000 any way.  I don't know your elevation there but if you're over 2,000' get the correct orifice size (reduce by 4% for every thousand feet over sea level)

[PorkChopsMmm]

flyingvan -- thanks for the heads up. I thought I heard of such heaters before but have not found them in my searches. That unit looks great but I am scared by 2 things -- the cost (looks to be between $500 and $700) and the install with piercing through the roof for the chimney. The wall vented install looks so much easier but I can see why the Williams heater, when installed during rough-in, is popular.

[Squirl]

Do you have a CO detector?

If you have an airtight house, I would normally pass on the direct vent [wrong].  They use oxygen from the house to heat it and propane can release a little bit of water vapor when it burns.

I was able to pick up a direct vent heater off of craigslist for $175.

I am sorry. I misnamed that.  I meant ventless. I always mix those up. Direct vent is the kind that uses the outside air and vents to the outside of the house.  That is the kind I opt for.  Sorry for the mixup.

http://www.northerntool.com/shop/tools/product_200362088_200362088

I did mean carbon monoxide (CO) vs. carbon dioxide (CO2).  I don't know if they have those in the same detector.

[MountainDon]

We have a wall mount direct vent from Northern Tool. It's an inexpensive model as those things go, although I did get it on one of their sales for $400 a few years ago 18K BTU rating and derated for altitude it is less.  It is capable of maintaining a comfortable warmth without having to run too often and without overshooting the thermostat set point.

The one we have has a built in thermostat with no remote capability. It does work well once I figured out where to set the uncalibrated dial. I made my own marks. A unit with a separate wall mount thermostat will cost more. This is one of the things that sets it (a Housewarmer brand) apart from the parent company's nicer looking Empire brand.

I do not like the non vented or so-called ventless or ventfree types. I simply do not want the products of combustion in the air I breath inside. Note that one of the products of combustion is water vapor; not necessarily a bad thing in wintertime, but it is too easy to get too much of an otherwise good thing when the heater adds moisture everytime it goes on. I forget the actual figure but there is a surprising amount of water produced for every pound of propane burned.

The Housewarmer ones will function with no electricity at all, though we do have a blower to assist with air circulation on ours. Some brands of direct vent require power.

On the subject of proper venting for a direct vent heater....  it can be difficult to position the heater with all the various clearances that are recommended. However, that should make one think. Some of the clearances are because it is desirable to keep the exhaust far enough away from a window to prevent any exhaust from entering the building interior if the window is opened. They must think there is something in the exhaust that is not good. Makes me wonder about the safety claims that are made by the sellers of ventfree designs.

[flyingvan]

http://www.google.com/products/catalog?q=williams+top+vent+wall+furnace&hl=en&rls=com.microsoft:en-us:IE-SearchBox&rlz=1I7GGLL_en&prmd=imvns&bav=on.2,or.r_gc.r_pw.r_qf.&biw=1280&bih=819&wrapid=tlif134558717412510&um=1&ie=UTF-8&tbm=shop&cid=2409355619246076124&sa=X&ei=7Ac0UMzDGKGGiQLRhoHYCA&ved=0CFoQ8wIwAQ

   Oops I made the same mistake----ventless, not direct vent.  My only issue with direct vent (out the wall) is that I'd rather have the heat source in the center of the house for more even distribution of the heat.  Also I know fireplace chimneys draft better if not located on an outside wall, so I imagine same is true for wall heaters.

   The picture I posted is the same model (except LPG) the cover is off though in the picture because I didn't want to get any grout on it.  I might get the cover powder coated the same white as the rest of the interior.
   It really isn't a big deal to run a vent through an existing roof.  I've never done it through a metal roof though, just composition, and spanish tile

  Also---a little off topic but I really wanted to install this unit
http://www.bensdiscountsupply.com/williams-3509621.6-Fireplace-in-a-furnace-propane-monterey-sro-top-vent.aspx
   It's a wall furnace but you see the flames through a glass cover.  Why not get some warm ambient light along with your heat?  My plans called for 35k btu though and this one's only rated at 32k.  I asked my inspector (who is very reasonable) and he said I'd have to get my plans re-drawn and re-approved.  Over time if I feel like I don't need that extra 3k btu and this furnace fails, maybe a retrofit

[PorkChopsMmm]

Those are some nice propane heaters. The heater I am looking for will be more of a back up unit for when we are out of town versus our main furnace. We have friends on a nearby lake with a very similar wall propane unit -- but that is also their only means of heat. Our main heat source is our wood stove with looks very nice and, as my wife says, is the focal point of our living room. We want to heat with as much wood as possible because we live on 20 wooded acres and propane can be expensive. If the unit is too nice or could heat the place too easily I am afraid we would get lazy and use it more than the wood stove.

[flyingvan]

I understand that sentiment....When I'm home I keep the fire going.  When the fire goes out on a cold night the heater takes over just before dawn.  If I'm at work for an extended period and my family's home with snowy weather, it's nice to know they have heat...The other issue for us is, sometimes we have very high fire danger when it's very cold, dry, and windy so we stick with the propane heat

[craig]

We have the same 20,000 BTU model from Mr. Heater in our 14 X 24 cabin, open ceiling, poorly insulated. It works good. Our cabin is not "tight" construction and we have 2 CO monitors and even with windows cracked this heater keeps cabin temperature at 68 DEGF when outside temperature is 20 with heat setting on 2 of 5. With regard to the thermostat, the thermostat is in the unit so the temperature near the thermostat tends to be warmer than real room temperature so the far side of the room is cooler. A small fan works well in this case.

[zion-diy]

I've been using a heater like that for 6 years now along with my wood stove. works fine. I lost the legs so I made some out of 4x4 brackets 
And yes, Co2 detectors are a must.

[zion-diy]

We also have wood heat and love it. FYI, I also installed a small 220 electric wall heater for those times when I just get lazy or leaving the house for, say, 6-7 hours and don't want to stoke up a big fire. So, now I have wood, electric, and propane. should about cover it don't you think?

[flyingvan]

Why would you need co2 detectors?

[MountainDon]

I think there is simply some confusion about correct terminology; for some reason it is quite common for people to confuse or mix up the two.

CO, Carbon Monoxide, is the dangerous product of incomplete combustion. We all breath out CO₂, Carbon Dioxide. No need to detect CO₂, but as CO will readily and silently kill us, a working CO detector/monitor/alarm is a good, maybe indispensable, tool.

[flyingvan]

Whenever people talk about CO2 detectors I start thinking they take Al Gore too seriously....(I knew Dr. Revelle, the professor Gore studied under, from a group at UCSD I was involved with.  He disagreed with Gore saying the temperature fluctuations are all within the parameters attributable to natural occurrences)

Ideally in combustion of hydrocarbons you'd end up with water and CO2---Perrier, basically.  Buy cheap gas, get the mixture wrong by ignoring altitude differences, let stuff get dirty---now you're going to end up with more CO.  Nature knows exactly what to do with CO2 and there's an ignored macro carbon cycle (we're actually in a deep CO2 deficit compared to the cambrian explosion) and that cycle is deeply dependent on CO2.
CO serves no practical purpose I know of in our atmosphere and is bad inside---hemoglobin has something like 470 times the affinity for it over oxygen so it'll accumulate and displace oxygen until you get dead, and hyperbaric chambers aren't a DIY proposition 

[considerations]

Like Mountain Don I have an 18K Housewarmer brand direct vent.  My cabin is smaller than yours 14 x 24 with a loft.  The propane heater does a great job. The heat adjustment is manual, but it has done a wonderful job so far (less to go wrong, IMO).  They come in different output sizes, bigger mostly.  This is my backup heat and I have nothing but good things to say about it, after a first winter without one.  Very cost effective.