OIL FURNACE HELP

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WAYNE0

WAYNE0

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Wasnt sure where to post this. Who here knows about oil furnaces ? Here is my issue- unlike last winter i was able to paint in my one bay garage with the oil furnace running. Not this year. Not sure whats different. Any ways- my garage is 16 x 30 & i do body work & paint work in the same bay. I have an exhaust fan at one end & i have intake filters on the garage door at the other end where the windows were. Just 2 The furnace is in a small room just about double the size of the furnace & thats where the walk in door is. I also have a whole in the wall with a filter a the size of a plastic bucket right beside the furnace for fresh air from outside. When im spraying i also have the walk in door cracked a bit for fresh air for the furnace. Now twice this year as im spraying with the furnace on & when it kits on it will make a big bang & blow the chimney off. It did it twice & both times i had the exhaust fan running. With the walk in door cracked in which is right in front of the furnace & the whole in the wall to the outside i cant believe the furnace isnt getting enough air. Sorry so long. Thanks
 
Sounds like the exhaust fan you're running for the spraying is probably pulling a draft back through the chimney. Could be dangerous. To get the pressure inside and out to be more equal you either need more air intake or less air being exhausted. You could put some yarn strings near the furnace door or the hole in that door to see which way the air is flowing when your exhaust fans are running.

Personally, I'd either isolate the furnace from the ventilated space you're painting in, or turn off the furnace while the exhaust fans are running.
 
Unless you're drawing combustion air in DIRECTLY (via a sealed venter) from outside, you're asking for a BIG bang and fortunate so far that you're only getting a slight "warning" at this point. Same reason the old rule was an ignition source had to be 24" off the floor in a shop.
 
Sounds to me like you've been lucky so far. You could have soot all through the shop, or worse. Sounds like it is drafting paint vapors in until the furnace burner tries to light them, the mixture is wrong and you get the big bang.

Somebody else mentioned what we always known as "outside air for combustion". Really, a combustion device should NOT be anywhere near a painting area, either gas, LPG, oil, or any other, including wood.

Depending on where it's located, you might want to consider sealing the furnace off from the shop, and provide some screened grills in from the outside. You want one up high above the furnace, and one down low. There should be info online for minimum sizing.

I used to maintain this stuff, for about a dozen years. Worked on heat pumps, LP and nat gas, and oil.
 
Good advice above from Del as usual.

The exhaust fan is pulling air out of the shop, and so is the burner. You need direct vent make-up air or powered make-up air to equal the air leaving the shop. Natural draft make-up does NOT equal powered exhaust. When was the burner fan, oil filter, pump screen, electrodes and pump pressure check - last serviced?
 
I had the exact issue. Seal the furnace room from the shop when spraying and only draw air from the outdoors. Many people I know use a mobile home heater. They draw the burner air through the double wall roof jack.
 
Demonic said:
Good advice above from Del as usual.

The exhaust fan is pulling air out of the shop, and so is the burner. You need direct vent make-up air or powered make-up air to equal the air leaving the shop. Natural draft make-up does NOT equal powered exhaust. When was the burner fan, oil filter, pump screen, electrodes and pump pressure check - last serviced?
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Every thing was gone over before the furnace was started this year.
 
Oldmanmopar said:
I had the exact issue. Seal the furnace room from the shop when spraying and only draw air from the outdoors. Many people I know use a mobile home heater. They draw the burner air through the double wall roof jack.
Click to expand...
This furnace gets its fresh air from the bottom side of the furnace. I do have a whole in the wall of the garage a size of a 5 gal. bucket & the bucket is what i used in the whole. I cut the bottom out of the bucket stuck it through the whole & put it up against the furnace where it gets its fresh air. On the outside of the garage i nailed screen so nothing could get in.
 
Sounds like you're lucky you haven't blown yourself to heck and back.
 
It sounds like you've tried to make sure the furnace gets air.

The problem is though, if your exhaust fan is doing its job (and it sounds like it is), then every opening or air leak connected to the garage has a draft going toward your exhaust fans.

Think of it like a hose with a bunch of different sized holes in it, leaking. Small ones leak less, but they still leak. It's just like that, but in reverse.. There's no way to get any of those air holes to flow zero even if they flow less than the big vent/fan or less than the big open windows with the filters. This is why the furnace needs to be absolutely isolated from any low-pressure area.

Sounds like a sealed fire rated door (they have seals) could be installed between the entry and the garage, making a mud room in effect, to help isolate it? Hard to suggest anything detailed without a floorplan or something, but you sound capable of figuring something out.
 
WAYNE0 said:
This furnace gets its fresh air from the bottom side of the furnace. I do have a whole in the wall of the garage a size of a 5 gal. bucket & the bucket is what i used in the whole. I cut the bottom out of the bucket stuck it through the whole & put it up against the furnace where it gets its fresh air. On the outside of the garage i nailed screen so nothing could get in.
Click to expand...
OK but is it sealed in it's own space? Sounds like "not." Also stuff like the exhaust fan may be reducing the draft--you HAVE to understand pressure. When you have a combustion appliance in a space, and an exhaust fan, depending of course on how large, the fan depressurizes the room, AKA causes a low pressure area. I've seen buildings with SEVERE exhaust fan (or commercial range hood) problems where the building is actually under a VACUUM. This will reduce the burner draft to zero or negative, ---and the burner will attempt to "draft" right back out the burner inlet

Also, forgetting that part completely, an oil burner that has problems, wrong/ dirty nozzle, wrong fuel pressure, and adjustments, or even just run "too cold" --such as starting in a cold space and never fully warming--can cause the heat exchanger and stack to soot up and THAT will reduce the draft.

There is only one way to properly tune a pressure burner, and that is with instrumentation. And knowledge. You need at minimum, a draft gauge and stack thermometer, and some sort of combustion analyzer to measure CO2. You need a pressure gauge for the burner and be able to clean and replace the in-burner filter if there is one, adjust the electrodes and so on

And you have to have the knowledge to recognize various burner problems.

I haven't touched a gun burner since the mid 90's and If I could not adjust it in one try, simply, AKA if it seemed "not right" I would call a current qualified burner man. And I used to maintain them.
 
The worst building dpressurization I've seen was a big huge high pitched roof wood building that was a multi-purpose area for an RV park. Lounge, snack bar, video rentals, laundry, and a huge pool. The kitchen range was not properly equipped with make-up air, and the range would cause a vacuum in the building. Upstairs had been remodled, and there was a small area, altho open to the rest of the building, with a hanging unit heater. They had about 4 boilers for pool heaters. The building forced air heating furnaces were externally provided with combustion air as they were 90% plastic vents, so they were not an issue.

The range hood cause all natural draft gas appliances including the water heater, the unit heater, and the pool boilers to VENT BACKWARDS DOWN THE VENTS and into the building. The pool heaters had operated that way enough, that the vent products--largely water vapor--had gotten up through the attic access, SOAKED the fiberglass bats in the rafters, and the glass bats were falling down FROM THE WEIGHT of the water.

This was a building that had had an architect involved, and it was a complete mess top to bottom. I left the outfit I worked for (Lennox dealer and off to Motorola) right in the middle of this, but I had advised them to hire a mechanical engineer either through the outfit I worked for, or their own, and get it re--designed for the building mechanicals. I also told them that if they didn't do something drastic, that building would not be there in 20 years.

WHAT IS THE POINT of all this? It is that you can get your *** in a huge sling over something as simple as the draft and venting on combustion appliances
 
I re-read the original post. If the furnace room has a hole in the wall to outside, close the door between the furnace and the shop. Better to pull all outside air than any air laden with pain vapors.
 
Sounds like i should just bite the bullet and build a small addition on for the furnace. Thank you all for your input and advice
 
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