Draft set too high for air furnace?

RascalOrnery

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Hi everyone,

Our church furnace seems to run a lot for the area it heats and the bills seem to me to be a little on the high side. This is serviced by the oil supplier. According to the barometric damper setting it looks like they have it set to heat the outdoors, whereas the label specs out .04-.06.

Is it possible this is an oversight or misadjustment? The furnace is in a pretty small room (maybe 4 x 10) and the chimney is stainless steel I believe probably only about 12'-15' total height from the top of the furnace. Would these affect the actual damper setting? I have a magnehlic I could take and check it with but not sure where the point of measurement would be.

I certainly don't want to go fiddling with ANYTHING but am wondering if we should be using a third party servicing company.

bburd

The barometric draft regulator appears to be set higher than the furnace manufacturer's flue draft specification of -.04 to -.06. The only way to set it correctly though is with a draft gauge, a combustion analyzer and the training to use them correctly.

EdTheHeaterMan

There may be a slight savings available if you can get the service company to properly adjust the burner so there is about -0.01"wc over the fire and -0.03 at the breach. Then adjust the flame to a zero smoke with about 10 to 12 percent carbon dioxide. Depending on the stack temperature, that will get your combustion efficiency up to about 81% to 84%.

HVACNUT

I'd be more concerned with the temperature in the drafty flue. Is there combustion air for the burner when the door is closed? Is draft affected when the door is closed?

techforlife

Point to consider; When draft damper is open it is sucking room air you paid to heat up the chimney. This forces infiltration of cold outside air to enter the building wherever it can making the burner run more.

mattmia2

https://forum.heatinghelp.com/discussion/comment/1841728#Comment_1841728

that is unavoidable unless you can reduce the draft of the chimney. you can provide outside makeup air at that point so that is what is drafted up the chimney.

the draft regulator is there to provide a constant draft within the appliance. it does that by letting room air make up any excess draft in the chimney

RascalOrnery

Thanks everyone! So does this seem like a situation where it would justify a maintenance service call or is the savings of a draft adjustment going to be not noticed even if it's off?

The furnace room has three doors in it, one which leads outside, it is not a very tight building.

So does it seem like this high of a damper setting is more on the normal side or abnormal side?

bburd

Abnormal. Greater draft than the manufacturer's specification can result in flue gases being pulled too quickly through the furnace to transfer most of their heat to the building. The usual symptoms are high stack temperature measured at the breech, before the draft regulator; and high fuel consumption.

Whether adjusting this properly would be worth the cost of a service call in fuel savings is another question which we don't have enough information to answer. It might make more sense to leave it alone for now if it is running well, and mention this at the next regular service call.