Plug fireplace basement cleanout?

[Fod01]

Hi. We installed a VC Montpelier insert last season into a fireplace with a basement cleanout. The flue is fully lined with SS.
Is there any reason to plug the cleanout in the basement? The cleanout door in the floor of the fireplace was not sealed.

Thanks,
Gabe

 

[DBoon]

I installed a Lopi Answer free standing stove in a fireplace opening. I used the cleanout/ash dump as the source for the combustion air. I keep the cleanout door permanently open. This works great - combustion air is drawn from the basement (which, by nature, is far leakier than the house), and it keeps the basement air from getting stale or musty. It did keep my basement about 2-4 degrees cooler than it would otherwise be, I believe, which I don't mind at all. Basement is typically between 45 and 50 degrees in the winter.

If you do this, make sure you give the cleanout area a good cleanout before you install everything.

 

[Fod01]

There's the question.. we have a half finished basement. My son is usually down there in the evening hours, and he's ok with it being cooler. The cleanout door (unfinished side) is closed, as is the flip-up door under the insert. Could the insert be pulling enough air from the basement to make a difference in temp? Even though the thermostat was set to its lowest setting, I thougth the basement zone kicked on more than it should have.

 

[johnn]

My set-up similiar to yours,, 1/2 finished basement except clean out is on finished side (no zone heating) unless we build fire in basement insert. Sure your sons ok with it being cooler? Maybe he takes the chill off ocasionally. I cant see with the clean-out door being closed and your insert upstairs sitting on top of the louver, and this being on the unfinished side of a "heated zone",,,being a draft problem which would effect temps on the finished side

On my 1/2 finished side, we do have registers and a large return 14x25 supply. This supply ,being the closest to furnace will really pull air, so during winter I block it off with cardboard so the furnace utilizes return ducts from upstairs. That large of a return in the basement is going to draw air from cracks that didnt really want to leak in the first place. Not sure what your set-up is like.

 

[Fod01]

We run hot-water baseboard. You're right, not much draft should be affecting the heated side.

It rained all weekend so I couldn't play with my woodpile. Probably thinking way too much.....

 

[begreen]

On my 1/2 finished side, we do have registers and a large return 14x25 supply. This supply ,being the closest to furnace will really pull air, so during winter I block it off with cardboard so the furnace utilizes return ducts from upstairs. That large of a return in the basement is going to draw air from cracks that didnt really want to leak in the first place. Not sure what your set-up is like.

Unless I am mis-understanding something (totally possible), this appears to be a false assumption or perhaps a bad system design. If this is a zoned system, the basement zone should be balanced so that the supply side roughly matches the return side. If so, it should have relatively neutral pressure while the furnace is running.

The concern is that if there is a large, negative pressure zone in the basement, the result could be a furnace fire starving for air unless it has an independent, outside air supply. And, blocking a return can cause the fan to run too fast, shortening the long-term lifespan of the blower motor. Have you reviewed this with your HVAC system installer?

 

[johnn]

BeGreen,,Thanks so much for the insight. I really dont want to highjack this thread, however I have tried to get hits before on "CFM blower question" and "hvac vent replacement"?? without much feedback. Double flues,same chimney ,basement fireplace, first floor fireplace above it with insert. The basement remodel was done during the 70`s (yuk) where they tapped into a supply for upstairs office with two small supply vents, and also installed the large return duct. Office always hot or cold and suspect its not a balanced system. The basement is not a seperate zone, only thermo. is upstairs which seldom comes on once we start burning. the registers are the old flapper style which really pump out the air and are difficult to control. I feel they need more modern insert dampers to help control air flow. Blower cycle times always seemed too short during winter and I was trying to learn about using a slower blower speed which is sometimes recommended during winter months, but didnt get much feedback. The main reason I blocked off the return was that it pulled so much air, that if all conditions were right, sometimes it would pull smoke down from the neighboring flue, and fill house setting off alarm. I certainly need a review,,thank you

 

[begreen]

There's the question.. we have a half finished basement. My son is usually down there in the evening hours, and he's ok with it being cooler. The cleanout door (unfinished side) is closed, as is the flip-up door under the insert. Could the insert be pulling enough air from the basement to make a difference in temp? Even though the thermostat was set to its lowest setting, I thougth the basement zone kicked on more than it should have.

If I am understanding the installation correctly, this is a sealed liner going from the insert all the way to through the chimney cap, correct? If so, unless the insert is pulling fresh fire air through the basement cleanout door, there shouldn't be much negative draft at the cleanout door. An easy way to check is get a good fire going upstairs in the insert, then hold a candle or a smoking incense or punk stick near the edges of the closed, cleanout door. If the smoke get sucked right into the edge of the cleanout door, then the insert's pulling some air from the basement.

Basements are notoriously chilly places unless well insulated Is your son in an isolated room there or is it a large family room? If small room, maybe consider an electric space heater for the room?

 

[Fod01]

ml - hijack away. No worries.

BeGreen - yes, full SS liner. I 'meant' to hold an incense to the cleanout door.... just never got around to it.
Regarding the electric heater- the space is small enough, but I'd rather have the baseboard cycle on the really cold days than worry about a heater being left on. Plus my wife would never go for it.

Thanks for the input.

 

[oconnor]

One simple reason for your cooler basement could be stack effect - as you heat the air upstairs, you will tilt the pressure gradient in favor of higher pressure upstairs (increased pressure, and relative positive pressure compared to outside air pressure), and air will start to migrate out of the house. This air will need to be replaced, and given that basements are usually the leakiest part of the home, and that they are usually an area of negative pressure in comparison to the outside pressure, then air will be drawn in where able.

As well, trying to draw combustion air from this basement negative pressure zone isn't always a good plan (I note one mention above of this), as there is a good chance of pressure differential at some point overcoming the draft of a cooling flue in the late stages of a coaling fire. If you have isolated the combustion air to the basement, you have essentially moved the stove to the basement (as far as it's performance in changing pressure situations goes) and you have to observe the issues that a basement stove can endure - cold flue reversal being one of them.