Natural Gas Furnace Producing a Whole Lotta Gas Smell
September 28, 2013 10:33 AM
Last night around 5 in the morning, we woke up because it smelled like natural gas--hard. After determining it wasn't coming from the oven, I remembered groggily to check the maintenance closet in our hallway, which contains two water heaters--one for our apartment, one for the apartment next door--and the natural gas furnace that heats our apartment through vents. I think something is happening to our furnace that causes it to do this, but I don't know what; I managed to stop it, but I'm not sure how.
The natural gas smell was much more intense in our hallway, and I ran into a downstairs neighbor who could smell it as well. As I moved downstairs, I definitely noticed that the smell lessened. We called our gas company and waited.
Last winter, I woke up to find the apartment very cold. I went out to check on the thermostat and found that my adjustments to the temperature weren't making it ca-chunk on or off, so I went out to our appliance closet and flipped the lightswitch-esque switch on the side of the furnace from its resting forward position, to back, to forward again. (As if I was turning a light off then on again.) When I did this, I could hear the furnace kick back in. This happened about three times over the course of a week last winter, and then I never thought about it again (a terrible idea in hindsight, I know).
Fast forward to last night: when we initially discovered it, I switched that switch in the same way I did in the winter, and then waited for the gas company's dudes to show up. By the time they got there, the gas smell had almost completely dissipated. One of the guys said he smelled it when he first came in, but not anymore--the guy with the meter never smelled it.
It seems clear to me that flipping that switch is what solved the problem. My problem is, I don't know what that switch actually does--I don't have the manual for the furnace. I'm hoping to get in touch with my building's maintenance team on Monday, but in order to help them, I'd like to figure out what exactly the problem is.
So my multi-part question:
1) What exactly is that switch doing when I flip it to off and then on? Is it some sort of pilot that's getting blown out? If so, shouldn't the gas be shutting off automatically?
2) If not, what the heck is producing/taking away the gas smell, and what can I tell my maintenance people?
P.S. the furnace is relatively new--installed two winters ago.
Thanks for any help.
The natural gas smell was much more intense in our hallway, and I ran into a downstairs neighbor who could smell it as well. As I moved downstairs, I definitely noticed that the smell lessened. We called our gas company and waited.
Last winter, I woke up to find the apartment very cold. I went out to check on the thermostat and found that my adjustments to the temperature weren't making it ca-chunk on or off, so I went out to our appliance closet and flipped the lightswitch-esque switch on the side of the furnace from its resting forward position, to back, to forward again. (As if I was turning a light off then on again.) When I did this, I could hear the furnace kick back in. This happened about three times over the course of a week last winter, and then I never thought about it again (a terrible idea in hindsight, I know).
Fast forward to last night: when we initially discovered it, I switched that switch in the same way I did in the winter, and then waited for the gas company's dudes to show up. By the time they got there, the gas smell had almost completely dissipated. One of the guys said he smelled it when he first came in, but not anymore--the guy with the meter never smelled it.
It seems clear to me that flipping that switch is what solved the problem. My problem is, I don't know what that switch actually does--I don't have the manual for the furnace. I'm hoping to get in touch with my building's maintenance team on Monday, but in order to help them, I'd like to figure out what exactly the problem is.
So my multi-part question:
1) What exactly is that switch doing when I flip it to off and then on? Is it some sort of pilot that's getting blown out? If so, shouldn't the gas be shutting off automatically?
2) If not, what the heck is producing/taking away the gas smell, and what can I tell my maintenance people?
P.S. the furnace is relatively new--installed two winters ago.
Thanks for any help.
I'm guessing the main burner in one of those appliances went out while it was operating. There is a flame detector integrated in the appliance, and when it detects that the flame has gone out, it shuts off the gas, but not before you have a big gout of natural gas spewed. That's the cause of the odor.
The switch on the side of appliances is an on-off switch, which electrically reboots the electronics in the appliance that control flame ignition. Once there has been a flameout, the electronics will not risk starting the flame again until it is reset or rebooted by the wise operator of the equipment.
You almost certainly don't have a pilot light for any of those appliances, unless they are very old. It's a waste of gas, so modern equipment uses igniters.
Call equipment maintenance. Do not let the appliance operate unattended until then. There are any number of things that can cause the symptoms you describe, and none of them are normal.
posted by the Real Dan at 11:04 AM on September 28, 2013
The switch on the side of appliances is an on-off switch, which electrically reboots the electronics in the appliance that control flame ignition. Once there has been a flameout, the electronics will not risk starting the flame again until it is reset or rebooted by the wise operator of the equipment.
You almost certainly don't have a pilot light for any of those appliances, unless they are very old. It's a waste of gas, so modern equipment uses igniters.
Call equipment maintenance. Do not let the appliance operate unattended until then. There are any number of things that can cause the symptoms you describe, and none of them are normal.
posted by the Real Dan at 11:04 AM on September 28, 2013
My wild-ass guess is that the furnace is short-cycling for some reason. It starts a cycle, tries to ignite the gas, fails in some way, and stops the cycle. Over and over again. In each cycle, it lets out a tiny amount of gas before it realizes that the flame hasn't lit.
Further extending the guess, I would bet that it's one of these two things:
1- The flue is blocked somehow. Either a physical obstruction like an animal's nest, or something structural like an improper cap on the end of the pipe, or some kind of backflow that happens when the wind blows in a certain direction. (Or some kind of restriction in the makeup air for the burner.)
2- If there is a burner fan (a smaller one that provides air for the flame, not the one that circulates the air in the building), it is failing in some manner. Spinning too slowly, or not starting up every time.
posted by gjc at 11:06 AM on September 28, 2013
Further extending the guess, I would bet that it's one of these two things:
1- The flue is blocked somehow. Either a physical obstruction like an animal's nest, or something structural like an improper cap on the end of the pipe, or some kind of backflow that happens when the wind blows in a certain direction. (Or some kind of restriction in the makeup air for the burner.)
2- If there is a burner fan (a smaller one that provides air for the flame, not the one that circulates the air in the building), it is failing in some manner. Spinning too slowly, or not starting up every time.
posted by gjc at 11:06 AM on September 28, 2013
2) If not, what the heck is producing/taking away the gas smell, and what can I tell my maintenance people?
Hopefully you can tell them what has happened, just like you did here, and let them work it out.
posted by jon1270 at 11:08 AM on September 28, 2013
Hopefully you can tell them what has happened, just like you did here, and let them work it out.
posted by jon1270 at 11:08 AM on September 28, 2013
The switch likely controls electrical power to the furnace. The switch completely disables the furnace and turns off the gas regardless of the setting of the thermostat.
Older furnaces had a pilot light that was permanently on. The pilot light was used to ignite the main burners when the furnace controller turns on the gas. But most more modern furnaces don't have a permanent pilot light. They have some sort of electronic igniter that is activated when the controller turns on the gas and this ignites the gas burner.
There is a safety circuit that detects if the gas burner ignites properly when the gas is turned on. If a flame is not detected in three or four seconds, the circuit automatically turns off the gas for safety. The controller may try this ignition cycle a couple of times before giving up. So each time it tries to light and fails, there will be some unburned gas released which you can smell.
Although you can smell the gas, it is not at unsafe levels and quickly dissipates. When you flip the switch on and off again, the controller resets and will attempt to light again and maybe the dodgy igniter works this time and everything is fine.
So what I suspect is that the furnace igniter is becoming unreliable. Sometimes it works and sometimes not and when not, it releases some puffs of gas. Igniter failure is a very common thing -- they just wear out. The repair is fairly simple. You can do it yourself if you are inclined or should call a repairman.
posted by JackFlash at 11:10 AM on September 28, 2013
Older furnaces had a pilot light that was permanently on. The pilot light was used to ignite the main burners when the furnace controller turns on the gas. But most more modern furnaces don't have a permanent pilot light. They have some sort of electronic igniter that is activated when the controller turns on the gas and this ignites the gas burner.
There is a safety circuit that detects if the gas burner ignites properly when the gas is turned on. If a flame is not detected in three or four seconds, the circuit automatically turns off the gas for safety. The controller may try this ignition cycle a couple of times before giving up. So each time it tries to light and fails, there will be some unburned gas released which you can smell.
Although you can smell the gas, it is not at unsafe levels and quickly dissipates. When you flip the switch on and off again, the controller resets and will attempt to light again and maybe the dodgy igniter works this time and everything is fine.
So what I suspect is that the furnace igniter is becoming unreliable. Sometimes it works and sometimes not and when not, it releases some puffs of gas. Igniter failure is a very common thing -- they just wear out. The repair is fairly simple. You can do it yourself if you are inclined or should call a repairman.
posted by JackFlash at 11:10 AM on September 28, 2013
When you smell a lot of natural gas, the first thing you do is open a lot of windows. Even if it's cold!
posted by Chocolate Pickle at 11:21 AM on September 28, 2013
posted by Chocolate Pickle at 11:21 AM on September 28, 2013
Something I forgot to mention: when this happened last night, the furnace was not in use (that is, our thermostats was set all the way down so as not to activate, because it is currently warm where we are). I don't know if that matters. Thanks for the answers so far.
posted by stresstwig at 11:27 AM on September 28, 2013
posted by stresstwig at 11:27 AM on September 28, 2013
Call the gas company. They will send someone to your house within hours to look for any leaks. Tell them exactly what you said here.
Really. Gas company, please call them.
posted by 26.2 at 11:33 AM on September 28, 2013
Really. Gas company, please call them.
posted by 26.2 at 11:33 AM on September 28, 2013
How low did you set the thermostat over night? 5 AM would be the coldest part of the night. Is it possible that the house cooled down enough to trigger the furnace on?
posted by JackFlash at 11:37 AM on September 28, 2013
posted by JackFlash at 11:37 AM on September 28, 2013
We did call the gas company; they detected nothing. The thermostat was not set, and we were sleeping with the windows open.
posted by stresstwig at 11:39 AM on September 28, 2013
posted by stresstwig at 11:39 AM on September 28, 2013
...the maintenance closet in our hallway, which contains two water heaters--one for our apartment, one for the apartment next door--and the natural gas furnace that heats our apartment through vents.
With three major gas-burning appliances in it, that had better be a hell of a well-ventilated closet-- and a pretty breezy hallway to boot.
Incomplete combustion of the natural gas would mean incomplete combustion of the odorant too, I'd imagine.
You may have fixed things by opening the door of the closet and the door of your apartment.
Ask the gas company about a CO detector. They might let you use a good one on a temporary basis for free.
posted by jamjam at 11:58 AM on September 28, 2013
With three major gas-burning appliances in it, that had better be a hell of a well-ventilated closet-- and a pretty breezy hallway to boot.
Incomplete combustion of the natural gas would mean incomplete combustion of the odorant too, I'd imagine.
You may have fixed things by opening the door of the closet and the door of your apartment.
Ask the gas company about a CO detector. They might let you use a good one on a temporary basis for free.
posted by jamjam at 11:58 AM on September 28, 2013
Did they use one of those handheld scanners that clicks and beeps when it detects gas? If they did, then you can probably trust that there is indeed no leak. They are very sensitive; they will scream when you can barely smell the gas.
If there is no external leak in the piping, that's good.
I would not necessarily say that flipping the switch solved the problem. If everything is plumbed and wired up right, it should NOT solve the problem. The switch on the side of the furnace should only control the furnace. I would say that it is more likely to be coincidence, or some other thing, that solved the problem. For example, opening the door.
(There is one slim possibility that I can think of: there is some kind of damper on the flue or the make up air supply that opens when one of the appliances is firing, and shuts when it shuts down. In that case, it might be controlled off of the furnace's power, and resetting the power resets it.)
So, what you probably need to do now is just wait for an appliance repair person to show up and diagnose.
posted by gjc at 1:13 PM on September 28, 2013
If there is no external leak in the piping, that's good.
I would not necessarily say that flipping the switch solved the problem. If everything is plumbed and wired up right, it should NOT solve the problem. The switch on the side of the furnace should only control the furnace. I would say that it is more likely to be coincidence, or some other thing, that solved the problem. For example, opening the door.
(There is one slim possibility that I can think of: there is some kind of damper on the flue or the make up air supply that opens when one of the appliances is firing, and shuts when it shuts down. In that case, it might be controlled off of the furnace's power, and resetting the power resets it.)
So, what you probably need to do now is just wait for an appliance repair person to show up and diagnose.
posted by gjc at 1:13 PM on September 28, 2013
My wild-ass guess is that the furnace is short-cycling for some reason. It starts a cycle, tries to ignite the gas, fails in some way, and stops the cycle. Over and over again. In each cycle, it lets out a tiny amount of gas before it realizes that the flame hasn't lit.
In my experience, this behavior is also associated with a cracked heat exchanger, which is essentially a big exit-into-the-human-space for the natural gas.
Needs fixing, sooner rather than later, if this is the case. Also, likely expensive.
Here's another thing that I see all the time on "Home Inspection Nightmares" types of photo collections: DIY/non-professional venting solutions where a gas appliance like ... a water heater ... is incorrectly piped into a chimney for a gas furnace. This can lead to a backflow? flowback? situation where the CO comes back into the living space. The good thing here is that you're smelling actual natural gas (with the odorizer), rather than NOT smelling and having headaches (which is what you get with a CO venting problem, if you survive the ordeal).
Anyway, in either case this isn't anything to mess around with. Unless it's in your lease, though, I would fully expect this to be 100% on the landlord to fix (using certified contractors) and pay for.
posted by dhartung at 3:40 AM on September 29, 2013
In my experience, this behavior is also associated with a cracked heat exchanger, which is essentially a big exit-into-the-human-space for the natural gas.
Needs fixing, sooner rather than later, if this is the case. Also, likely expensive.
Here's another thing that I see all the time on "Home Inspection Nightmares" types of photo collections: DIY/non-professional venting solutions where a gas appliance like ... a water heater ... is incorrectly piped into a chimney for a gas furnace. This can lead to a backflow? flowback? situation where the CO comes back into the living space. The good thing here is that you're smelling actual natural gas (with the odorizer), rather than NOT smelling and having headaches (which is what you get with a CO venting problem, if you survive the ordeal).
Anyway, in either case this isn't anything to mess around with. Unless it's in your lease, though, I would fully expect this to be 100% on the landlord to fix (using certified contractors) and pay for.
posted by dhartung at 3:40 AM on September 29, 2013
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You might search for a manual of the furnace online (that's how I learned to understand the workings of the heating system in my flat in Britain).
posted by Namlit at 10:49 AM on September 28, 2013