Comments on: Combustion Safety 101: Three Types of Problems

By: Blake Quinton

Blake Quinton — Fri, 26 Mar 2021 17:38:00 +0000

I regularly do energy audits in Salt Lake City. During the past year I have found gas leaks in about 75% of the homes I have audited. There have been a number of times where my Bacharach sniffer doesn’t immediately find things, but my eyes are reacting leading me to keep investigating.

I find it crucial to run the gas appliances to find all the leaks. It is incredible how few installers use pipe dope on the connections inside the furnace box.

By: John Proctor

John Proctor — Tue, 22 Dec 2020 01:30:54 +0000

In reply to Brad Cook. Brad I am with you on the percentage of gas leaks. The data from the PSCo and Westside programs listed in the above Power Point presentation shows 8.1 and 7.6 percents. The 1000 furnace sample in the same presentation reports 8.3%.

By: Mark Curtiss

Mark Curtiss — Mon, 21 Dec 2020 06:54:30 +0000

Well done .
I had the gas company install contractor back out 2 hours after install for a gas leak. Back out week later. Finally gas company fixed leaks for good .
Inlet for makeup air sized way too small . Boiler been tripping out been four service calls to gas company service plan !!

Frustrated hell ya !!

By: John Vansant

John Vansant — Sun, 20 Dec 2020 15:23:15 +0000

In reply to George Shackelford.

George,
I work in Hillbilly country…….cabins, shacks and no building codes. Draft hood appliances are common in my region, consequently I recognize their benefits, but also their dangers. I think the intent of Allison’s comment concerning draft hood water heaters is that, as a rule, in following the norms of modern building science, they have no place.
In fact, careful study of draft hood appliances in general will show, that even when following “best” practice recommendations, draft hood appliances will at times, not “vent” as intended……. for evidence of this – just make a careful examination of say, a dozen operating draft hood water heaters…….

By: Brad Cook

Brad Cook — Sat, 19 Dec 2020 15:21:08 +0000

I am surprised at the statement that up to 80-90% of homes have gas leaks. I have been BPI certified (including Heating) since 2006 and have done a lot of combustion and gas leak testing. I have rarely found gas leaks in homes or small businesses here in the Central Vermont area where about 23% of homes use propane (natural gas is not available)to heat their home and a larger percentage that directly heat their hot water with propane. I would estimate only a few percent had gas leaks.
I have taken a lot of training in combustion science and heating systems and I have a lot of experience in assessing, repairing and installing heating systems. In my experience, I would put poor venting systems high on the list, especially with natural draft combustion appliances. I have many photos of such problems, such as undersized vents, no slope to vents and installations in a small room with other appliances competing for the little air available, such as another combustion appliance and a clothes dryer. The second most common problem that I see is undersized gas lines, which is a leading cause of CO in combustion appliances, especially propane ranges. That includes all of the semi-rigid copper tubing that I have found with crimps in the tubing.
As to the comment about water vapor from a flue causing water to drip from windows, I don’t see that as being a problem. Yes the flue gas from propane combustion is water vapor from the chemical process plus the water vapor in the combustion air, or >9% water vapor. It will take a lot of combustion gas to significantly raise the RH in the house, and it would be putting all of the other stuff from the flue gases into the house as well. That amount of back drafting is very rare, although that would always apply to any vent-free combustion appliance.
Where that moisture does become a problem is when a metal flue pipe goes above the roof in a cold climate. The colder it is outside, the quicker the flue gas will cool down and the more of that water vapor will condense to a liquid, which is now acidic, and run back down the flue. The cold can also cool down the flue gases so much that the appliance backdrafts into the house.

By: Brad Cook

Brad Cook — Sat, 19 Dec 2020 14:48:15 +0000

In reply to George Shackelford. Natural draft appliances vent better in the winter because of the temperature differential, which means a larger difference in density (colder air is that more dense than warmer air). Why does everyone just look at the lowest price? A natural draft combustion appliance is using indoor air for combustion and they often have a standing pilot. You have already paid to heat that air that is now drafting out of the house (including when the heater is not even heating). A standing pilot uses 2-3 gal. of propane (or equivalent gas) a month just for the pilot.

By: George Shackelford

George Shackelford — Sat, 19 Dec 2020 06:41:33 +0000

I should have added to my previous note the following caveat: it is very important to always have a working carbon monoxide detector in all levels of the house, if using natural gas heating appliances.
As long as the heat exchangers do not develop a leak in direct vent natural gas heating appliances (intake air from, and exhaust to the outdoors), it is pretty safe to use them, as far as carbon monoxide in the house goes.
If concerned about the risk of carbon monoxide from natural gas heating appliances, then electric is a safer choice.
But in my area of the country, electricity has a much higher ongoing cost per BTU, than natural gas. So many people in my area have switched to natural gas for heating. Doing so has another benefit in that if a power outage occurs, you can still have heat, as long as you have a small generator to run the furnace fan, via a transfer switch. It can get pretty cold in the winter in Northeast Ohio, and power outages have been known to last a week during the winter.
– George

By: George Shackelford

George Shackelford — Sun, 13 Dec 2020 21:43:43 +0000

Nice picture of a poorly done flue.
Question as to the statement:
“stupid building codes (e.g., allowing natural draft water heaters in conditioned space.”
In the summer, it should draft well, if sufficient air makeup is provided and the flue is designed and installed per installation manuals such as Simpson DuraVent’s manual, and in the winter, the same.
Odd high pressure differential due to high winds may cause temporary poor ventilation, but it should be very temporary, if the flue was well designed for the site.
Direct vent hot water heaters would be my preference, but the costs of those are twice the price of natural draft hot water heaters, and the warranties are worse, if you buy the better natural draft hot water heaters.
Natural draft hot water heaters also act as a way to get Radon out of a basement, unlike direct vent hot water heaters.
Do you see any progress on Direct vent hot water heaters coming down in price, any time soon?
Regards, George

By: Allison Bailes

Allison Bailes — Fri, 11 Dec 2020 19:43:59 +0000

In reply to John Proctor. John, thanks for the link. I'm not sure if I saw you present that at Affordable Comfort/ACI in Austin or not. Some of it is familiar, but not all of it.

By: John Proctor

John Proctor — Fri, 11 Dec 2020 18:32:56 +0000

Allison, I don’t know if you are aware of some of the history of combustion safety testing. Here is a summary of some of it.
https://www.researchgate.net/publication/346955263_Combustion_Safety_His…
John