How dumb is an indoor LPG furnace..?

So we're balls deep into winter in my neck of the woods and have been contemplating building a new "ultra" low mass furnace for indoor use. The obvious option is an electrical approach. However I don't have any of the heating element to build with and have pretty much everything for a propane build or natural gas for that matter

What I'm trying to sort out is how intensely do I need to vent the LPG furnace...? Passive hood or something with a blower to pull the output of the furnace to the outside. ...Or, is it just a straight up dump idea...?

The intended space is my garage, and I'd be willing to punch a hole in the outside wall to accommodate the vent, which should double as a fume extractor for a welding bench and spray painting area.

Thoughts...?

 

Intensely!!!
Me think you need to run it outside unless you have a death wish.

Just hug the furnace occasionally to warm up, you’ll be fine.

 

My moneys on death wish. Carbon monoxide and CO2 like to sink to the lowest spot as well so even with a vent you'll be breathing that stuff in large quantities. Can't you build a shelter outside to shield you from the wind? Maybe reflect some of that furnace heat back at you?

 

Funny... OCD and I were just talking about this. I bought a 30000btu gas heater for my garage. It is arriving this wednesday and the forecast is calling for temps in the 70's
CHEAP AS CHIPS! 105bucks free shippingg! Requires NO ELECTRICITY and will run on propane AND NG! Told the wife if we ever lost power and it was cold,we are screwed.
https://www.houzz.com/product/95577...u-model-mnsd300tba-contemporary-space-heaters

I have a 2 car empire of dirt. Pretty sure 30k btu will be plenty to take the chill off. Not looking to make it 80 in there. If you have NG, it will cost pennies per hr to run this thing.

 

LMAO... I thought he was cold. Not melting metal INDOORS!
I think the cold weather is starting to get to me... Or it's the dogs next door constantly BARKING.

 

Guys are doing it and living to tell about it. Robert has a great thread on AA about 3 pages into his recent threads. Check out Ron Reil's site. It looks like he forges in his parlor. Both appear to have significant investment in their ventillation and used well informed designs and testing. Wargrade did it with oil in a shipping container, but he's disappeared and may be taking a long nap in there for all I know.
As someone whose dealing with 5F temps and 2 feet of snow everywhere I can certainly see the appeal but now we'd be pouring inside too and that brings concerns of its own.

Pete

 

IFI and a good portion of it’s members are living proof LPG forges are operated indoors.


Spaz out when the simplest of questions are asked,
Ban people for it as well......
............................
Nope, nothing wrong with them.

 

I've seen a few guys doing some stuff truly "indoors" with just some ventilation, but wasn't sure where the line gets crossed when it comes to burning LPG. Hell my gas stove runs hours at a time with zero venting to the outdoors and no one has taken a dirt nap yet. Is it just a matter of volume..?

I'm not trying to kill myself. Just wondering the practicality...

We just came out of stretch of ~ -35C weather (that's -31f for our American readers). I don't expect much more of that level of deep freeze but it does put things into perspective I think...lol

Good question... Didn't get much passed whether I should do it...lol.

Well, I wouldn't consider going beyond small Aluminium melts. At the most maybe what it takes to fill an A10 crucible. Definitely within the realm of what a simple electric furnace could manage in reasonable time I would think.

 

Right now I couldn't, but that definitely is the right course of action moving forward. I have enough space that I could allocate a designated "weather protected dirt" area to keep my outdoorsy stuff in, and utilize as a true "foundry" space.

Maybe one of those cheap half circle drive sheds. Would just need to run power out there for the beer fridge

 

I have considered using my small hard-brick furnace indoors with a propane burner, and just opening the door a bit, but then again I don't have a death wish either.

I think it could be done, but it may get a bit breezy introducing outside air into the shop.
You only need enough outside air to keep the oxygen level up to breathable levels.

I would definitely use a carbon monoxide detector, or perhaps two.

I knew an engineer one time who went up to the top of a factory that was combusting something, and he got into either a low-oxygen area, or a high-carbon monoxide area and passed out.
Some of the workers just happened to find him and drag him out before it was too late. He got very lucky.
But don't count on luck, be sure you have enough fresh outside air.

 

OK in the Navy we melted indoors, but our ventilation was awe inspiring, with only the exhaust on you could not open the doors, the supply ventilation had to be turned on to get the doors open or the exhaust turned down, we had 3 exhaust systems, and 2 supplies so we could move air from exactly where we wanted, unless it was cold or humid we would open all the doors and turn the ventilation on full blast... each system could cycle all the air in our space 3 times per minute easily, and it was tested regularly, so with everything running we could vent the space completely in under 10 seconds

V/r HT1

 

I wasn’t saying it can’t be done.
It can be done but with a hefty price tag and once you go there I don’t consider that as backyard foundry hobby metallurgy but commercial/industrial.

Anything can be accomplished as long as you have the cash to fund it.

 

Screw venting it. As long as you have blue flames, I wouldn't be too concerned with carbon monoxide. Look at my little junk 100buck heater. NO VENT, built to run INSIDE the house burning propane or NG. Keep the flames blue and you shouldn't take a nap in the ground. (At least this is what I was taught. Your mileage my vary)

Some helpful numbers for this is 24:1 propane to air and 10:1 for NG. This should minimize the risk.

Hey J... Is that your little quonset hut? I like those. Cheap and cheerful. You can throw up one of those in a weekend.

 

No I wish... Just something I found through google to illustrate what I was thinking about when I mentioned a shed for protecting the dirt from the elements.

I did a little digging on the cost of those quonset huts and the price isn't very cheap at all. Well at least not what I consider cheap. Found a couple "new/unassembled" that would measure out to ~25x20x13' wehn assembled and the asking is right at $16k, (<-- yes the 'k' denotes a multiple of 1000!). ...and at that price you still don't get the front/back walls....???

https://www.kijiji.ca/v-buy-sell-ot...b-steel-shed-garage-shop-850-sq-ft/1270963997

 

I fire my small furnace 80 kbtuh inside the 2 car garage without worrying about ventilation remember that a garage is not air tight and probably leaks 5 to 10 air changes per hour.

a normally insulated house leaks 3 to 4 air changes per hour.

When i am running my tilting furnace on waste oil 500kbtuh I open the garage door and turn on the exhaust fan, the fan is 2000 cfm removing any no problems with Co or Co2. C0 is a fuel and ignites and burns at any temp above 1040. f. as long as the fuel isn't exiting the furnace there is very little Co at the temps that our furnaces run. as long as there is sufficient air to the burner Co isn't an issue. running a car engine inside a garage is more dangerous then our furnaces ever thought of being. Use the same ventilation as you would if you were working on a car engine and you will be safe.

 

Yes but don't forget about low oxygen.
I sometimes have to enter confined spaces for work, and you have to sense several things, such as chemicals, carbon monoxide, and low oxygen.
No oxygen = no life.

 

I have seen photos of two furnaces in the UK that appear to be in sheds/workshops behind the house, and they exhaust their furnace out a hole in the refractory near the top sidewall, with a solid lid with no opening.
The exhaust goes up a tall stack to above the level of the shed and sometimes up at the house roof line.

So it is definitely done, but I am not sure the flue would stand up to iron melts without doing something special to cool it.

 

These photos belong to Rob Wilson, not to me.
Fair use policy for non-profit educational use only?

I think he does have a hole in the lid of his furnace, but it appears to be somewhat small, and he probably blocks it while he is using the furnace?

You still need to introduce both combustion air and ventilation air into the room, and the combustion air would be equal to the output of your blower, in my current case a leaf blower, which by itself is a lot of cold air coming into the room, but it could be done, and is done by some.

Would I do it in my shop?
Given my southern location in the States and the mild/short winters we have, no, I probably would not do it.
If I lived in the GWN (great white north) as some do, yes, I would do it, but not tell the wife what I was up to.