The header says it. Somewhere I read that you should go for this if you'd be afraid to light a match in the space. Well, I don't get to that point. Woodworking does happen from time to time but most projects involve machine work and welding. Adding separated combustion adds about $300 to the cost. What do you think?
Separated combustion: worth it?
- Thread starter gregl
- Start date
pseudorealityx
Well-known member
It's got more to deal with possible things in the airstream that may ignite/explode.
HoosierBuddy
Well-known member
I assume you're talking about a furnace that brings in outside air for combustion?
The main advantage I see to a furnace that brings in combustion air from outside is that it doesn't create negative pressure in the heated space. A normal furnace that burns air from the area around the furnace and expells that air through a flue, obviously creates a natural draft out of the building. That means an equal amount of unheated air has to get sucked into the building at the same time.
This creates an inefficiency in the heating of the building that is not reflected in the furnace's AFUE. All things being equal, a furnace that takes in outside combustion air should be slightly cheaper to operate than one that pulls combustion air from the heated space.
As far as safety? I guess I could see an argument that way...but I personally have never heard of a fire caused by a furnace ingesting combustibles through the combustion air. Surely it has happened sometime...but it is probably very rare. There have most definitely been fires caused by flamable fluids getting spilled on a garage floor, running up near a gas fired water heater, igniting, and causing a major fire. But that's really a seperate issue.
Phil
The main advantage I see to a furnace that brings in combustion air from outside is that it doesn't create negative pressure in the heated space. A normal furnace that burns air from the area around the furnace and expells that air through a flue, obviously creates a natural draft out of the building. That means an equal amount of unheated air has to get sucked into the building at the same time.
This creates an inefficiency in the heating of the building that is not reflected in the furnace's AFUE. All things being equal, a furnace that takes in outside combustion air should be slightly cheaper to operate than one that pulls combustion air from the heated space.
As far as safety? I guess I could see an argument that way...but I personally have never heard of a fire caused by a furnace ingesting combustibles through the combustion air. Surely it has happened sometime...but it is probably very rare. There have most definitely been fires caused by flamable fluids getting spilled on a garage floor, running up near a gas fired water heater, igniting, and causing a major fire. But that's really a seperate issue.
Phil
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Thanks, guys. Yes, separated combustion means drawing combustion air from the outside. The Sterling Garage Guy heater comes made for that while the other brands require a different model at a much higher cost. The Sterling GG then only requires a concentric vent kit to make it separated. It's the cost of this kit that makes me wonder if the extra expense is worth it. Since I'm in Central Calif. where outside temps are not much lower than 30 in the winter, efficiency may not be that much of an issue.
t. jones
Well-known member
I worked in a dealership where they had a couple of " incidents" in the bodyshop involving an open flame heater and heavy paint vapours. Quite a bit of money was spent on a new furnace and improved ventalation. Woud you weld on a bench covered in sawdust?
Thanx Trevor
Thanx Trevor
Well, Trevor, I guess that answers the question. I guess I just needed someone to confirm what my sensible self was telling my tightwad self. Considering how much it's going to cost for the heater and related junk, underground propane run from the nearby tank, and the building insulation, I think I'll spend the extra bucks and get the whole banana.
APEowner
Well-known member
Vapors can do weird things. A buddy of mine was wiping down a motorcycle fender with paint thinner (so he wasn't using much) when the furnace fired and the fumes flashed in his face. Fortunately it was just a flash and the only damage was to his eyebrows but still.....
robortiz59
Member
- Joined
- Nov 26, 2009
- Messages
- 8
Hi everybody. I'm new to the GJ, and this is my first post. I just finished building a new 28' X 24' garage. The outside is done for now, and I'm working inside on wiring, insulation, and drywall over the winter. I plan on installing a gas heater next year, and I've been reading the GJ as part of my research. This discussion about separated combustion and flamable materials reminds me of a true story The story probably sounds a little dramatic, but it is completely true.
My brother-in-law was working as a mechanic in a local auto repair shop with 3 or 4 bays a few years ago. He had to drop a fuel tank from a car - don't remember why. As part of prepping the car he had it on a lift and was draining the fuel into a drain pan. It was the type you typically drain oil into: bowl on top that adjusts up and down and has a big can on the bottom. Before he could finish draining it there was a huge whooshing explosion, and the entire shop erupted into a ball of flames. Everybody ran out immediately, and nobody was hurt. But the shop literally burnt to the ground in minutes. The fire was so intense the the mechanics ran out without their tools. Their toolboxes were all destroyed. And, while some of what was in them was salvageable, much was destroyed. Those of us who have made our living with our tools can appreciate how devastating this was.
This was a front page story in the local newspaper for a few days. He was really villianized in the local press for a few days. They basically suggested his negligence somehow caused the fire .
A formal investigation determined the fire was caused when the vapors from the draining gasoline, which I assume were pooling near the floor, were drawn through a vent in the lower part of a door for the room/closet where the building's gas hot water heater was located. The burner or pilot light ignited the vapors. He did nothing wrong. As I understand it, the room should have been sealed, and the venting should have been done to the outside. He was new there and didn't even know the boiler was behind the door.
I guess my point in relating this story is the potential for fire is pretty significant if you are working with flamable or combustible materials. In his case all the variables (i.e., the boiler was on the floor, it was in very close proximity to where he was working, and there was likely a very significant of gasoline vapors) worked against him. You may not have the same combination or magnitude of risks. But, it can happen. I plan on installing heat in my new garage next year. I think it will be worth the extra expense to get sealed combustion for the added safety value alone. The efficiency of not drawing cold air into the garage to displace the air venting out through the flue when not using sealed combustion seems like an economic bonus on top of the additional safety.
Rob
My brother-in-law was working as a mechanic in a local auto repair shop with 3 or 4 bays a few years ago. He had to drop a fuel tank from a car - don't remember why. As part of prepping the car he had it on a lift and was draining the fuel into a drain pan. It was the type you typically drain oil into: bowl on top that adjusts up and down and has a big can on the bottom. Before he could finish draining it there was a huge whooshing explosion, and the entire shop erupted into a ball of flames. Everybody ran out immediately, and nobody was hurt. But the shop literally burnt to the ground in minutes. The fire was so intense the the mechanics ran out without their tools. Their toolboxes were all destroyed. And, while some of what was in them was salvageable, much was destroyed. Those of us who have made our living with our tools can appreciate how devastating this was.
This was a front page story in the local newspaper for a few days. He was really villianized in the local press for a few days. They basically suggested his negligence somehow caused the fire .
A formal investigation determined the fire was caused when the vapors from the draining gasoline, which I assume were pooling near the floor, were drawn through a vent in the lower part of a door for the room/closet where the building's gas hot water heater was located. The burner or pilot light ignited the vapors. He did nothing wrong. As I understand it, the room should have been sealed, and the venting should have been done to the outside. He was new there and didn't even know the boiler was behind the door.
I guess my point in relating this story is the potential for fire is pretty significant if you are working with flamable or combustible materials. In his case all the variables (i.e., the boiler was on the floor, it was in very close proximity to where he was working, and there was likely a very significant of gasoline vapors) worked against him. You may not have the same combination or magnitude of risks. But, it can happen. I plan on installing heat in my new garage next year. I think it will be worth the extra expense to get sealed combustion for the added safety value alone. The efficiency of not drawing cold air into the garage to displace the air venting out through the flue when not using sealed combustion seems like an economic bonus on top of the additional safety.
Rob
shocksystems
Well-known member
I have radiant heat with a boiler. I chose a sealed combustion unit and also elevated the boiler off the ground through the use of cement blocks. If I recall correctly the recommendation is to keep it elevated at least 18" from the ground to avoid combustible gasoline vapors.
Here is a link to a discussion about the 18" elevation.
http://www.inspectorsjournal.com/Forum/topic.asp?TOPIC_ID=2879
Cheers!
Jim
Here is a link to a discussion about the 18" elevation.
http://www.inspectorsjournal.com/Forum/topic.asp?TOPIC_ID=2879
Cheers!
Jim
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texasOFT
Well-known member
Another way to do it is to move the forced air furnace to the outside of the shop. Then duct the return air from the building into the furnace and duct the heated air back into the shop. We had this type of heating system in a chemical storage/loading dock building with lots of flammable vapors. Never had a problem. Had to heat the building to keep some of the chemicals liquid.
The furnace was mounted about 6" away from the outside wall in an enclosure similar to a closet but vented to allow combustion air into the furnace. the ducts were insulated to help prevent heat loss from the unheated enclosure the furance was in.
The furnace was mounted about 6" away from the outside wall in an enclosure similar to a closet but vented to allow combustion air into the furnace. the ducts were insulated to help prevent heat loss from the unheated enclosure the furance was in.
ovilla
Well-known member
Does anyone with a non-seperated combustion heater store gas in their garage, in a 5 gal gas can or in a mower or anything else (and have any concerns about blowing up the place)? I'm thinking of getting a regular Hot Dawg heater and am curious as to what all of you do with your gas cans. Thanks
regguy1
Well-known member
Seperate Combustion units scroll down on page
MODINE LOW PROFILE SEPARATED COMBUSTION UNIT HEATER - THE "HOT DAWG"
http://www.djsonline.com/modineunitheaters.htm
MODINE LOW PROFILE SEPARATED COMBUSTION UNIT HEATER - THE "HOT DAWG"
http://www.djsonline.com/modineunitheaters.htm
oldgoaly
Well-known member
bringing in clean outside air means you won't have burners getting dirty as fast.
jklingel
Well-known member
Only the ones who want a new garage. No way in the land should anyone store gasoline, starting fluid, acetone, etc, anywhere near a fire, confined or not. That is my take on the deal. Put the gas outside in a shed.
dodgeram2500
Well-known member
You can not just run a separate pipe with Sterling GG Heaters. The vent kit comes with various gaskets etc for the unit which make it true sealed combustion.
D.J.
Well-known member
Bump. This old thread is still very relevant to myself and others I'm sure.
Personally I'm just trying to justify spending more money on venting parts for my Beacon Morris 45k than I paid for the heater. Also, installation looks a bit more complicated.
I would like to vent the heater horizontally at a 45* angle and do it properly with cat III pipe, sealed combustion or not.
Sealed combustion parts/pipe for my application: about $470
Standard combustion 45* pipes/kit: roughly $200-250
Is spending the extra $200+ worth it for benefits? I'm not really too concerned with heater life expectancy. Safety and efficiency yes. I do occasionally deal with gasoline in the space to be heated and occasionally park a small engine inside with a potential small fuel leak. I rarely deal with paint fumes. I have worked in automotive shops with older hanging, non-separated combustion heaters for years with zero safety issues. Space will be fully insulated, not sealed up super tight.
I'm leaning towards the concentric venting but cheap, safe, and practical ok.
Opinions appreciated!
Personally I'm just trying to justify spending more money on venting parts for my Beacon Morris 45k than I paid for the heater. Also, installation looks a bit more complicated.
I would like to vent the heater horizontally at a 45* angle and do it properly with cat III pipe, sealed combustion or not.
Sealed combustion parts/pipe for my application: about $470
Standard combustion 45* pipes/kit: roughly $200-250
Is spending the extra $200+ worth it for benefits? I'm not really too concerned with heater life expectancy. Safety and efficiency yes. I do occasionally deal with gasoline in the space to be heated and occasionally park a small engine inside with a potential small fuel leak. I rarely deal with paint fumes. I have worked in automotive shops with older hanging, non-separated combustion heaters for years with zero safety issues. Space will be fully insulated, not sealed up super tight.
I'm leaning towards the concentric venting but cheap, safe, and practical ok.
Opinions appreciated!
Using outside air improves the reliability of your heating unit. The combustion chamber stays cleaner, longer. It is absolutely safer. Using the concentric pipe pre-heats the combustion air going to the unit, slightly improving. You cannot overlook the “peace of mind” side of things. Wondering if something you are doing is goin to potential create a “flame event” is no fun. Spend the money. Do it right the first time.
TTA89
Well-known member
As some of the 8 year old replies mentioned above, it's going to be more efficient since the air is being equalized as it comes in and goes out. If you pull air from the inside then the building will create negative pressure and draw cold air in from the outside.
I think my beacon morris instructions said it was 10-20% more efficient to use the concentric vent kit. I installed mine a few months ago.... In the grand scheme of things... whats another few hundred bucks? I would just do it (and I did).
h1 by MikeTTA89, on Flickr
h2 by MikeTTA89, on Flickr
I think my beacon morris instructions said it was 10-20% more efficient to use the concentric vent kit. I installed mine a few months ago.... In the grand scheme of things... whats another few hundred bucks? I would just do it (and I did).
h1 by MikeTTA89, on Flickr
h2 by MikeTTA89, on FlickrBretny
Well-known member
By separating combistion your actualy pulling air from outside and not every crack in the building. Building stays warmer, you wont blow up and your insurance company will be happy.
They wouldnt allow me to park a vehicle in my garage with a normal heater.
Also i put one of these outside air kits on my homes wood stove. I saw a significant benefit. Warmer house and burn less wood. 4cords to about 3..with a warmer house.
They wouldnt allow me to park a vehicle in my garage with a normal heater.
Also i put one of these outside air kits on my homes wood stove. I saw a significant benefit. Warmer house and burn less wood. 4cords to about 3..with a warmer house.
As far as gasoline in heated garage/shop.................Many of us have heated garage-shops with collector cars and motorcycles plus power equipment all with gasoline in them. Then there are the people that have daily drivers and boats in heated garages ............so guess we all have a evaluate the risks.
Part of the reason heaters are not allowed to mounted at floor level in garage spaces.
Part of the reason heaters are not allowed to mounted at floor level in garage spaces.
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Christheguitarmaster
New member
Did you have to use a thimble going through the wall for the concentric kit or does the intake pipe stay cool enough to act as a thimble? I am looking to install and have a question on this. I have 5/8 Firecode Sheetrock / Fiberglass Insulation / OSB / Vinyl Siding to go through.
driftpin
Well-known member
Not necessarily about heating, but years-ago, a south Florida tire shop had two people killed when a propane tank leaked, and welding being done ignited the fumes. It destroyed the building in an explosion that was heard for miles.
HoosierBuddy
Well-known member
As I posted back in 2009 the outside/inside combustion air being a safety benefit is a bit of a red herring in my opinion. None of these units are intrinsically safe. They are all ignition sources for any combustible mixture of gas/air.
To the OP...when faced with the same choice on my home furnace...it could be installed either way per the manual....I went ahead and brought my combustion air in from the outside for efficiency reasons.
To everyone concerned about safety....my garage is heated by a wall boiler that has a concentric vent kit (pulls in outside combustion air). My lift is within 10 feet of that boiler so when I work on a fuel line, fuel pump, fuel tank, etc....I simply walk over and shut off the power to the boiler. Is it going to blow up if gasoline runs out on the floor? No...probably not....but now that the power is off...it just adds another layer of safety.
Also...my gas cans get stored in my unheated barn.
Finally....when you need to refill your mower or generator or chainsaw...take it outside to do it. We try to be careful, but you eventually spill some gas on the ground. Better for that to be outside than inside. Even if you don't spill enough to be dangerous...who wants to smell gasoline inside for hours. Safer outside.
Phil
To the OP...when faced with the same choice on my home furnace...it could be installed either way per the manual....I went ahead and brought my combustion air in from the outside for efficiency reasons.
To everyone concerned about safety....my garage is heated by a wall boiler that has a concentric vent kit (pulls in outside combustion air). My lift is within 10 feet of that boiler so when I work on a fuel line, fuel pump, fuel tank, etc....I simply walk over and shut off the power to the boiler. Is it going to blow up if gasoline runs out on the floor? No...probably not....but now that the power is off...it just adds another layer of safety.
Also...my gas cans get stored in my unheated barn.
Finally....when you need to refill your mower or generator or chainsaw...take it outside to do it. We try to be careful, but you eventually spill some gas on the ground. Better for that to be outside than inside. Even if you don't spill enough to be dangerous...who wants to smell gasoline inside for hours. Safer outside.
Phil