Thread: Open flue

I had a gas fireplace the other day that was a vented gas log. There was a metal plate hanging down from the upper wall that blocked a direct view up the flue. I used a mirror and seen that it was open all the way up the chimney. There were no doors installed on the front opening, just a metal chain screen. When the log was ignited and running, I noticed the flames extended past the firebox. I called out the unit as being unsafe, called for further evaluation by a qualified chimney contractor and recommended that doors be installed to keep the heated and cooled air from going up the chimney. Chimney contractor came and said I was an idiot for calling the unit unsafe. He said the log just needed adjusted so that the flames would not extend out too far. He also repositioned the ceramic log in front to deflect the flames back towards the log. He also stated that the opening does not need doors as there is no air going up the chimney due to drafting. He stated that an supply vent would have to be within 8 feet of the opening for it to go up the chimney. I am of the understanding that if you have a hole in your house, then heat rises and will find that path to the exterior. Also, putting the ceramic log in front of the flames like that is not good. This causes black soot buildup and possible carbon monoxide. Your comments are greatly appreciated.

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Jody some clarification and correct terminology might help here:

Is this a masonry fireplace or a factory built fireplace?
If factory built, what is the make and model #?

If it is a factory built fireplace, is it a woodburning factory built fireplace with vented gas logs installed versus a self contained unit?

Providing the ANSI or UL listing would clarify these issues.

As for the chimney contractor calling you an idiot, why did he need to make adjustments if everything was acceptable?

The comments about air not going up a chimney make no sense whatsoever. If the damper is open, then air will draft up the chimney. If this is a sealed combustion direct vent, then that air will come from outdoors and not affect the indoor air. Otherwise, if the fireplace is vented, then certainly room air will be exhausted up the chimney to the tune of several hundred CFM.

Do you have any pics?

Please try to break your posts up into several paragraphs--it is hard reading as is.

HTH,

Originally Posted by Jody Humbert

I had a gas fireplace the other day that was a vented gas log. There was a metal plate hanging down from the upper wall that blocked a direct view up the flue. I used a mirror and seen that it was open all the way up the chimney. There were no doors installed on the front opening, just a metal chain screen. When the log was ignited and running, I noticed the flames extended past the firebox. I called out the unit as being unsafe, called for further evaluation by a qualified chimney contractor and recommended that doors be installed to keep the heated and cooled air from going up the chimney. Chimney contractor came and said I was an idiot for calling the unit unsafe. He said the log just needed adjusted so that the flames would not extend out too far. He also repositioned the ceramic log in front to deflect the flames back towards the log. He also stated that the opening does not need doors as there is no air going up the chimney due to drafting. He stated that an supply vent would have to be within 8 feet of the opening for it to go up the chimney. I am of the understanding that if you have a hole in your house, then heat rises and will find that path to the exterior. Also, putting the ceramic log in front of the flames like that is not good. This causes black soot buildup and possible carbon monoxide. Your comments are greatly appreciated.

Jody....

I think I would have stuck with the facts which (the best I can determine) are: The flame was extending out past the front of the firebox and you could not see the entire chimney. These two problems are enough to get a fireplace/chimney guy involved.

Thanks guys. Bob, I only have one photo. The fireplace I believe is factory built. Not a wood burner. There is no closing damper. Only that piece of square metal hanging down about 6 inches and blocking view up the flue. It is attached to the top of the firebox. I had a photo of the flames protruding past the firebox wall but apparently cannot locate it. Do not have model number.

Is the grate listed? The log set may be affecting the burn.

A little hard to tell but it looks like the log set is too large for the firebox. Log sets are sized according to the dimensions of the box, oversizing them may well result in flames, sooting, particulates and Carbon Monoxide entering the inhabited area. Also looks like the gas shut-off valve is inside the firebox.

Other thaan cosmetic purposes, glass doors are really only necessary to help prevent inside room air (warmer) escaping via the flue and open damper when the fire is un-lit. They should not be closed when the fire is in operation. Seeing that the view up the flue was blocked it appears that a damper may well be installed and is partially closed (open), as it should be. With a manufactured fire-box, as this appears to be, there should be a lever arm which controls the damper operation and a 'damper stop' attached to the damper plate to prevent its complete closure.

If the damper was present and closed, glass doors would not be needed, nor required.

.

Originally Posted by Ian Page

A little hard to tell but it looks like the log set is too large for the firebox. Log sets are sized according to the dimensions of the box, oversizing them may well result in flames, sooting, particulates and Carbon Monoxide entering the inhabited area. Also looks like the gas shut-off valve is inside the firebox.

Other thaan cosmetic purposes, glass doors are really only necessary to help prevent inside room air (warmer) escaping via the flue and open damper when the fire is un-lit. They should not be closed when the fire is in operation. Seeing that the view up the flue was blocked it appears that a damper may well be installed and is partially closed (open), as it should be. With a manufactured fire-box, as this appears to be, there should be a lever arm which controls the damper operation and a 'damper stop' attached to the damper plate to prevent its complete closure.

If the damper was present and closed, glass doors would not be needed, nor required.

.

I would agree with Ian. My first thoughts would be the gas shut-off valve is inside the firebox.

I did mention the shut off valve inside the firebox. There is no damper and no handle. I'm just not agreeing with the contrator that there is no loss of heat when there is no damper door or front doors to close.

Originally Posted by Jody Humbert

I did mention the shut off valve inside the firebox. There is no damper and no handle. I'm just not agreeing with the contrator that there is no loss of heat when there is no damper door or front doors to close.

Since that is not a part of the inspection (at least it would not be in NC) I would not loose any sleep over what the contractor says. Your opinion is in writing it sounds like and I bet he is flapping his gums and would not put what he is saying in writing.

If the firebox is a factory manufactured unit then it will almost certainly have come with a damper and control mechanism. If it didn't then the whole unit may not be UL listed, probably does not meet code requirements and may be hazardous (even more so with an over-sized log set). The chimney guy should be aware of that. I can't imagine that someone would have removed the damper before, during or after installation, especially in a pre-fabricated unit. That makes no sense and serves no purpose to do so. If originally installed but now missing, the control lever would likely have to be hacksawed through to effect removal.

Either way, there most certainly will be a loss of room temperature air rising through the firebox draughting upwards through the flue. Something to make your clients aware of.

It's a heat shield, designed to increase heat efficiency without compromising draft and venting. . . and they don't put dampers on vented gas appliances.

It's still too hard to tell what we're dealing with from the one photo. That front grate/ fender is typical of a generic one used on vented gas logs such as ANSI Z21.60 or Z21.84 . The gas line appears to be spliced flex connector which is not allowed. A shutoff can be located inside a firebox if so listed but it would be better to have one outside the firebox within 6' or, if under the IFGC, meets the 3 criteria.

Note that there are listed factory built woodburning fireplaces that are approved by the mfr. for vented gas logs, some approved by the Fp mfr for ventfree logs whether it is listed for VF or not, then there are some factory built boxes that appear very similar to woodburners except they have built in gas controls and are vented with B-vent instead of stainless factory chimney. These units are typically open without glass doors, often have a deflector/ shield located much as you describe, sometimes have a bimetallic damper tucked up in the flue, and cannot be converted to burn wood. Again, as with ALL factory built fireplaces and ALl combustion appliances, you should take several pics and record the make, model, serial # and fuel setup for that appliance.

The logs in this unit do appear to be oversized as they are way too far out front. Note the heat damage to the top of the firebox paint. If this area saw too much heat, what about the combustible header in the wall above it?

Recommed do not use until inspected and approved for use by a qualified professional including a level II and possibly a level III inspection. Done.