Do high eff. gas furnaces vent gas?
OK, so here’s a puzzler.
Everythings been fine with the new (less than one year), 90%, combustion assisted Tempstar furnace. Zoned 4 ways, doing fine, house is warm when it’s supposed to be, gas bills are generally in line.
Came back after being away for a week over Christmas and smelled gas by the side of the house where the furnace vents out. It went away pretty quick and figured it was because the furnace had been down for a week (although why I convinced myself that would be OK is a puzzler in and of itself).
Get home late Saturday night and coming up the stairs, smelled the gas smell again. The furnace was running and the closer I got to the vent, the stronger the gas smell got.
Called the local utility, turned down all the thermostats to that unit and waited.
Gas guy showed up, we triggered the thermostat in one place, could hear the gas running through the meter—and he took out his electronic gas sniffer. Poked it all around the meter and the earthquake valve; no leak. Went back towards the side vent for the furnace, the smell and the detection tone got louder, he stuck it next to the exhaust vent and it went solid tone and bright red on the detection LED.
Went into the basement with him, he ran the detector all over the outside (sealed) cabinet of the furnace, no gas fumes in the basement at a detectable level (faint smell), looked through the port in the furnace and said “hey, it looks like it’s not burning everything; the flame looks too blue”.
We shut the furnace down for the night (1:00 AM).
Took me 24 hours to get the HVAC contractor who installed it to come around; He takes a look today for 1.5 hours. Sprays soapy water everywhere looking for leaks; Nothing. Takes off the covers for both the combustion chamber and the lower electronics bay and inspects them the burners in particular; nothing. Checks the water heaters for me gratis to see if that’s where the problem is; no problems with their pilots or burners and they vent out a totally different side of the house anyway! No hits and no replication of the strong gas smell for him (he can’t really smell well—smoker—and I was at work until the last part with the water heaters).
I get home, talk it over with him, he says he’s not sure what the problem might be; I call the utility again (figure in broad daylight and with their equipment, we might stand a better chance of tracking the problem). Furnace goes onto to his next job but leaves me his cell phone and tells me to call him if the utility guys and their sniffer equipment can do any better at finding anything.
Utility guy comes back, takes out his sniffer, goes over the gas meter, the earthquake valve, the exhaust port for the furnace (some increased tone and smell, but no solid indication this time).
Then, to check for a mainline leak, shuts down both water tank pilots, kills the furnace, even turns off my wife’s gas stove (as she’s getting ready for a dinner party—happy wife!), no gas dryer running.
With everything off and all the pilots quenched, after 5 minutes, there’s a movement in the meter that shows that somewhere there is a 1/2 cubic foot leak. He tells me that is a very small leak and that it would take a plumber forever to track it down and pretty much implies it isn’t worth finding AND it doesn’t explain the positive indication.
So, the question is:
What the heck is going on? Do high efficiency furnaces sometimes fail to ignite off their electric pilots and subsequently spew gas out the exhaust valve, shut down and recycle until they light? (Utility guy’s best guess)
OR
Is it a normal level of combustion gas odor and output (furnace guy’s guess?)
What does anyone think?
Replies
"Their best guess" could be your family's epitat!
No way would I rest until the leak was found and FIXED!
Call the installer....again!
Call the manufacturer of the furnace!
Call the mayor and repeat your story!
Remind the parties that they may all be negligent and very liable!
..................Iron Helix
What he said. Yeah, it's a small leak, but what if it accumulates, and where?
Do some thinking over everything that has changed before this gas smell - probably some clue somewhere.
Forrest - been watching Jeremy Brett as Sherlock Holmes
Initial start up up of any gas appliance will blow out unburned gas to the exhaust.
Gas has to be the right density for it to ignite, so when the gas is kicked on to the burner there is unburnt gas heading to the exhaust flue before the whole burner ignites.
Did they test against the gas control modules? I have never seen a module actually hold a test.
1/2 cubic foot in 5 min is going to be very tough to find, is all the piping exposed?
Personally I would disconnect all apliances & cap the pipe & test with valves in open posisition.
“How many observe Christ’s birthday! How few, his precepts! O! ‘tis easier to keep Holidays than Commandments.” —Benjamin Franklin
I've never heard of a 90+ designed to "vent gas." (& I try to follow this stuff.)
Sound to me like a bad valve in the furnace which isn't closing completely. Possibly an intermittent problem.
Ways to test: Best: open the combustion chamber cover and use a gas sniffer.
2: watch the light off when the thermostat calls for heat: there should not be a big whomping light-off - the flames should immediately "shoot" into the heat exchanger tubes and not change size.
3: measure CO in the flue gases at light off (shouldn't go above 300 ppm, although it's not unusual for 90+ to go a few hundred higher at lightoff) AND as and after the burner shuts off - if CO spikes after shut-off, the valve isn't closing properly.
In my opinion, there's no such thing as a "small" gas leak.
Get/try a new HVAC guy, I think this should have occured to the one fellow. (I wasn't there though.)
Look for one who has ben trained by Jim Davis at the National Comfort Institute (or check at http://www.NationalComfortInstitute.com 's find a contractor page.)
BTW, in your installation, are there both a flue and an outside air intake? Are they separate outside (2 pipes?) If so check for gas at the lower pipe (which is supposed to be the air intake - it is the one that leads to the top of the combustion chamber.)
Some installations use "integral" exterior ports: the exhaust 'shoots' out, the air intake is on the "backside" close to the wall.
I'll betch ya the gas is coming thu the air intake (although that doesn't reall y change anything.)
BTW >>"hey, it looks like it's not burning everything; the flame looks too blue".
Flame color doesn't tell you squat about the combustion process - old "wive's" tale (from the days before we had CO and COmbustion analyzers.)
Also BTW, If it isn't burning everything, it'll be producing excess CO (>100 ppm) throughout the burn.)
What made the teaching of Jesus different and apparently so hard to accept then as now, was that it required a critical reassessment of the structures and values and attitudes of human society as his listeners and followers shared in it.
- Monika K. Hellwig
from Jesus: The Compassion of God (The Liturgical Press, 1983)
Uh oh.So, as to what has changed before the leaks and now, there were 4 small earthquakes in the region, all of which rattled the house"BTW, in your installation, are there both a flue and an outside air intake? Are they separate outside (2 pipes?) If so check for gas at the lower pipe (which is supposed to be the air intake - it is the one that leads to the top of the combustion chamber.)"Yes, there are two pipes; there was no gas at the intake.Hmmmm.We'll, now I've got a problem.The Utility doesn't want to trace the problem and the furnace guy says the problem isn't the furnace.Argh.BTW, to check the gas leakage level, the utility guy:
1) Killed the power to the entire furnace
2) Killed the water heater pilots and turned them off
3) Turned off the wife's range (and sniffed behind and around it for a leak---nothing)
4) and took the thermostat on the upstairs unit down to 50 (taking it out of the equation)This is frustrating...
And scary, a bit.Thank you to one and all for your help on this; of course, Breaktime has once again helped get me on the right path.I think I need another service call from the utility with their sniffer.It's possible it was a combustion gas smell; but if so, why did the sniffer go off the first night?Thanks!
NotaClue
>>It's possible it was a combustion gas smell; but if so, why did the sniffer go off the first night?Depending on the type of sniffer -some will detect carbon monoxide at very high levels (1,000 ppm + for the TIFF 8800)
What made the teaching of Jesus different and apparently so hard to accept then as now, was that it required a critical reassessment of the structures and values and attitudes of human society as his listeners and followers shared in it.
- Monika K. Hellwig
from Jesus: The Compassion of God (The Liturgical Press, 1983)
Of course, a properly functioning furnace shouldn't be producing much carbon monoxide.
Half of the harm that is done in this world is due to people who want to feel important. They don't mean to do harm but the harm does not interest them. --T.S. Eliot
Well, I'd suggest you repeat that leak test procedure, just as before.Oh, and wait 5 minutes before checking the meter the first time, to give the temperatures a chance to stabilize in the pipes. Only if it continues to move over the second 5 minute interval should you be suspicious.If you still detect a leak (meter motion), go to the furnace and turn off the gas at the external valve. Then see if the meter's still moving. If the meter stops then the valve inside the furnace is bad.If the meter STILL keeps moving, turn off the external valves at the other appliances. STILL moving?? Turn off any valve there may be on the outlet side of the meter. STILL moving?? Meter's defective somehow.(Of course, you indicated the house had been unocccupied for awhile. It's not unheard of for a neighbor to tap into someones gas line -- been one or two incidents of it turning up here, and folks here are pretty law-abiding for the most part.)
Half of the harm that is done in this world is due to people who want to feel important. They don't mean to do harm but the harm does not interest them. --T.S. Eliot
BTW - please let us know the final solution
What made the teaching of Jesus different and apparently so hard to accept then as now, was that it required a critical reassessment of the structures and values and attitudes of human society as his listeners and followers shared in it.
- Monika K. Hellwig
from Jesus: The Compassion of God (The Liturgical Press, 1983)
> Do high efficiency furnaces sometimes fail to ignite off their electric pilots and subsequently spew gas out the exhaust valve, shut down and recycle until they light? (Utility guy's best guess)
That does sometimes happen. Shouldn't happen very often, though.
You can also get a faint odor in the combustion gasses, especially right as the furnace starts up, and especially if the unit hasn't been running for awhile. This isn't exactly the same as a "gas" smell, but similar enough that they can be confused.
I'd agree that if there's a leak big enough to cause detectable motion in the meter in 5 minutes, that needs to be found and fixed.
Question: When the utility guy shut everything off, did he shut them off with the cutoff valves in the pipes, or just turn them off? If the furnace was shut off at the cuttoff valve then a leak through the valve inside the furnace could not have caused the meter motion. If the furnace was simply turned off, though, I guess I'd suspect the furnace's internal valve is leaking sometimes.
Dont have NG myself, but this sounds like a great opportunity for you to go buy a new tool, esp if the utility does not want to come out again.
Just did a quick ebay scan for gas detectors, the semi-pro type models yu would need for your leak are going for as low as $150 used. The utility guys meter probably is a $3000 calibrated model, but the 50 ppm +/- 20% type few hundred $$ meter should work for you and provide 24/7 testing until you find the leak.
"Well, I'd suggest you repeat that leak test procedure, just as before.Oh, and wait 5 minutes before checking the meter the first time, to give the temperatures a chance to stabilize in the pipes. Only if it continues to move over the second 5 minute interval should you be suspicious."Shoot, I should I have thought of that too.
Thanks!
This happened to me 3-4 years ago. I bought a house and the home inspector "got a hit" with his detector when he took readings beside the furnace and in the utility room where the furnace is located.
He said "call the utility co - they have more sophisticated and more expensive detections equipment"
I did so and an old timer from the utility co came over and spent quite a while at my house and he got no readings with his detector.
He said "I'm not finding anything" and left.
A year or so later my water heater went kerfluey and I replaced it.
It's beside the furnace.
I removed the old one and inspected the old galvanized three inch flue pipe and found holes rusted in it.
I'm guessing the water heater flue pipe leaked while the home inspector was there and then didn't leak with the utiilty company inspector or the water heater wasn't heating and operating while the utility company guy was there.
The rusted part of the flue pipe was in the utility room and not in the attic.
^^^^^^
S N A F U (Situation Normal: All Fouled Up)
Were they testing for natural gas or carbon monoxide?BTW, the combustible gas detectors are prone to fals positives - including pipe dope! Telling someone "This newly installed gas line is leaking at every joint" based on a TIFF or other sniffer is a great way to pizz a lot of people off.Believe me!
What made the teaching of Jesus different and apparently so hard to accept then as now, was that it required a critical reassessment of the structures and values and attitudes of human society as his listeners and followers shared in it.
- Monika K. Hellwig
from Jesus: The Compassion of God (The Liturgical Press, 1983)
Well I've got two stories for you:
We were working on a home this summer and every time I went near the gas meter, I could smell gas. I finally got out the soap suds and checked all the fittings and found a small leak on the gas companies side of the meter. The gas co. comes over and fixes the leak and then tells me that a lot of their meters leak .
He said they added too much stinky stuff to the lines one time and they got over a hundred calls in one night from people who smelled gas. They all had leaks, but had never really smelled it before. Now that's a comforting thought!
I started a job yesterday at a home with a 90% FA propane furnace. The minute I walked up to the house , I could smell propane coming from the exhaust of the furnace. It was very noticeable. I have watched it for two days now and it smells some times and other times there is no odor. It sounds like it's doing the same thing yours is.
Is your meter near the air intake and exhaust pipes? If so, you could very likely have a leak in a meter connection. I would get the soap suds out and check it if the meter is anywhere near where you smell the gas.
Your Tempstar furnace should not have any NG smell when operating properly.It will smell if it dosn't liteoff on first try, gas valve will open for 5 sec. if no flame detected will shut down and try again usually 3 times before lockout. Sounds to me like it dosn't take on the first lick every time. don't know why.
That sounds like what the Utility guy said too.There hasn't been any gas smell so far this week (so far.......), so I'm puzzled.I have a sort of hypothesis though; that the furnace guy came out and saw something and fixed it, but either didn't think it was the cause/important enough to tell me about (but it did fix it) OR came out and found something that he immediately knew they had screwed up on when they installed it---and fixed it and decided not to tell me...Argh.
NotaClue
Nice name.
Don't tell me your one of those educated plumbers out there, that actually know the history of our trade.
Welcome to Break Time aka BT.“How many observe Christ’s birthday! How few, his precepts! O! ‘tis easier to keep Holidays than Commandments.” —Benjamin Franklin