Thread: gas logs

We just moved into a house that has gas logs in the fireplace . when burning the gas logs , do i need the damper open or closed . i could not find any info on the logs at all. i dont know if they are vented or not.

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Damper should be open. Burning natural gas produces combustion exhaust gases, such as carbon dioxide and carbon monoxide, which should be vented to the exterior of the house.

Typically, with a gas appliance in a fireplace, the damper should be fixed so that it does not close fully. Typically, a c-clamp is used to prevent the damper to remain open enough to vent these combustion gases to the exterior.

Originally Posted by Randy Gregg

We just moved into a house that has gas logs in the fireplace . when burning the gas logs , do i need the damper open or closed . i could not find any info on the logs at all. i dont know if they are vented or not.

Hopefully your home inspector gave you the poop on your gas logs in the report. Vented or unvented.....etc.

Burning gas produces 2 by-products: water vapor and carbon monoxide. The only variables are how much. Even if you read the manufacturer's specs on vent-less appliances, somewhere they'll likely recommend some form of venting.

JLMathis

Originally Posted by Jeffrey L. Mathis

Even if you read the manufacturer's specs on vent-less appliances, somewhere they'll likely recommend some form of venting.

Usually such as 'Open window(s) and/or door(s) when fireplace is in use', and sometimes they may even put in a qualifier such as 'open at least 2 inches' or some specific minimum amount.

So, let's see, you use the ventless appliance for heat on a cold day and ... you have to open a window or two? Does not make a lot of sense, does it?

And all so they can save the cost of installing the vent for a vented model.

If there is no rating plate the appliance should be removed. The fireplace should have a level II inspection irregardless.

FYI, normal combustion of NG and LPG produces heat, light, carbon dioxide and water vapor. Carbon monoxide is produced by incomplete combustion. Recent studies revealed VF logs produce much more NOx than previously thought. If the logs are dirty or out of placement even by a hair or if there is a stray air current such as caused by foot traffic, open dampers, forced air registers, fans, etc., you can get CO, aldehydes, NOx, etc.

I shut down another VF log last weekend that was producing >100ppm CO just from the pilot burning.

I have seen plenty of VF logs that were properly installed but never found any properly maintained. I have also seen plenty of VF improperly sized or installed.

There is very little room for VF logs within the 2009 IRC even if your State allows them.

The BPI Stds for energy rating call for their removal as part of a whole house survey and weatherization plan.


Gunnar is correct on vented logs.

As to JP's point, he is also correct. What is the true efficiency if you have to open windows to ventilate these logs? Also, if you open a window, does fresh air infiltrate or room air exfiltrate and how does it know which way to go? The answer is pressures. Open windows were proven by ASHRAE to be totally unreliable for ventilation.

HTH,

Does the requirement that the damper above gas logs be removed or locked open include a cable operated "chimney top" damper?

I ask because I just saw one that closes completely, in a fireplace that had recently been serviced by a well-regard local sweep.

So now I'm wondering if this is an exception... that does not make sense to me, but this guy ought to know what he is doing....

Regarding gas appliances in fireplaces:
IRC 2432.1 Maintain open vent (block damper in open position)

Probably not an exact quote, as this is from Code Check, but if you have a copy of IRC...

To me, it doesn't matter where the flue is blocked, it's blocked and dangerous!