Furnace question


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Old 01-26-15, 03:55 PM
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Furnace question

I live in a 75 yr old house and have been working recently in my basement sealing up a lot of air leaks with spray foam. I actually foam sealed all the rim joists shut to get rid of draft, but I now found they were a source of ventilation in the basement because this is a balloon frame house so the rim joist cavities run all the way to the attic. Well our Furnace has been acting strange since I did this work and it made an extremely odd noise today along with smoke smells upstairs. We had an HVAC look at it today and he said by tightening up the basement air leaks(specifically the rim joists), we were not allowing the furnace to breath. Could this also cause sediment or build up in the oil line if the furnace was working harder to operate because he said there was a restriction and oil was not flowing well. We did have an oil delivery two weeks ago so maybe that stirred up gunk in the tank.
So he recommended finding a new source of ventilation such as putting an open vent in the basement stairs door but I'm wondering if that alone will solve any further issues. Thanks for the replies.
 
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Old 01-26-15, 04:43 PM
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The sealing has absolutely nothing to do with the fuel system unless the oil tank is vented into the basement.
With old tanks the best solution, short of replacing the tank & lines, is to install a single line off the top & a Tigerloop.
 
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Old 01-26-15, 11:22 PM
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Im not sure what you mean by a tiger loop. The fuel line already comes out of the top of the tank, although it has about 20 feet to run before reaching the furnace.
 
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Old 01-26-15, 11:41 PM
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I agree with Grady, there is virtually no connection between the fuel side and the combustion air, assuming you haven't absolutely sealed that basement and being 75 year old construction, that would be difficult.

You mentioned balloon construction, did you seal all wall cavities that run from basement to attic? That is necessary, but you should be using a fire block, like a 2x something piece of wood.

Assuming you have greatly reduced the fresh air flow from outside, the furnace will still draw through the floor and from the house. But the pressure required to get that air may exceed the draft pressures the furnace can tolerate. Opening a basement window for a day or two would tell you if your air sealing was the cause of the problem or if the fuel delivery stirred up enough sludge to clog your filter.

Let me know if those balloon paths are still open or now sealed?

Bud
 
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Old 01-27-15, 08:37 AM
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You can learn about Tigerloop here: Tigerloop
I have one on my own system & install a few each year.
 
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Old 01-27-15, 10:22 AM
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Bud, I talked to you on another thread about this. I did seal up the rim joists, and I understand the should be fireblock 2x's in the balloon cavity, but I thought that couldnt be done from the basement. Everyone I talked to said you have to open the first floor and\or second floor walls to access and do it properly, and thats not gonna be possible right now. Regardless, the
rim joists are sealed with rigid and spray foam now.
 
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Old 01-27-15, 10:56 AM
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I believe fire blocks need to be every 8 or 9' so a two story would indeed need some solution half way up. However, if that isn't going to happen soon, a fire block at the rim joist would still be good and may actually be required, I'm guessing.

But what I was trying to determine is how well that basement is connected to the attic. If those balloon channels are still open to the attic then it will make the basement more negative. If they were connected and now are not, then the basement should be more positive. I'll have to ponder what effect that would have on combustion air.

Bud
 
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Old 01-27-15, 04:46 PM
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Bud, if you remember(I know you answer a lot of posts) I previously discussed with you about how my Hot water radiator Pipes run up through the rim joist cavity to the second floor and when I recently rigid foam sealed the rim joists around the pipes, I noticed Hotter radiators upstairs. Someone thought that was because their was less draft in the cavity and up against what are likely bare pipes in the walls, although I didn't seal the top end rim joists in my ice cold attic. I did notice OLD Batt insulation in the basement rim joist area before sealing it and some insul in the attic joist but I don't know how far that extends. I doubt they would have insulated the entire length of the cavity when building the house in 1940 right? Either way, that batt insulation would not have stopped air flow in a vertical fashion from attic to basement. There is already a noticeable difference in temperature in my unfinished basement with the little I've done, and that says a lot considering the bare block walls and concrete floor. My goal is to rigid foam board the walls in the near future but my priority is getting two crawl spaces in shape first.
 
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Old 01-27-15, 05:20 PM
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Where a house rests on the foundation can account for a significant amount of air leakage. I have investigated with an infrared camera and found wife open spaces. Once all of that is sealed, as you are experiencing, it can make a big difference.

What I'm trying to isolate is the smoke issue being a combustion problem or a backdraft problem. The "open a basement window" suggestion from before was intended to eliminate a backdrafting problem caused by a now restricted air supply. But first another issue.

If you have reduced the available air supply for the basement there may be another related problem, a leaky return side of your furnace. If the furnace can draw lots of its air from the basement (instead of the return ducts) it may have been getting much of that from where you air sealed. But now it simply pulls the basement negative and interferes with the draft trying to go up the chimney. The open a window suggestion above (a test only) could make that problem go away, but that would not necessarily mean it is a combustion air problem, just a pressure imbalance from a leaky return side of the furnace.

Air sealing all of the ducts in the house is always a good improvement, but look for an imbalance where the basement needs more air when the fan is running. On some furnaces you can force the fan to run without the combustion. Do that and then crack the basement door open and feel for a draft, or carefully do a smoke test.

Bud
 
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Old 01-27-15, 06:05 PM
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Bud, as mentioned..this house has pipes, not ducts. It is an oil fired boiler furnace. No fan. Two zones with circulator pumps.
 
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Old 01-27-15, 07:32 PM
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OK cancel that thought.

Most naturally drafted boilers will back draft (spill) for a short period of time while the chimney warms up. If you have a barometric damper you will see it quickly close as the boiler fires up. But it isn't a perfect seal so some combustion gasses will enter the basement. If you watch this cycle, the damper (assuming you have one) should begin to open in less than 30 seconds. I'd have to look up the exact allowed time. If much longer than there could be a draft problem.

If, when the boiler ignites there is smoke puffed back through the air intake, then you have an ignition problem unrelated to the small pressure changes that may have resulted from the air sealing.

It is unfortunate that the testing for worst case depressurization is not part of the HVAC work scope either during installation or anytime there after. At leas as far as I have experienced it.

Are you still experiencing the smoke and smell?

bud
 
 

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