This is something to keep in mind the next time (or hopefully before) you
have problems with a high efficiency gas appliance.
Our area was impacted by Winter Storm Vulcan last night, which left us with
lots of drifts due to the high winds.
A co-worker came in this morning and told us that his on-demand water
heater didn't work this morning and that they smelled gas in the basement.
He got everyone out of the house and called the gas company. They came
over, checked for leaks (said that they were required to) and then trudged
through the snow to the back of the house to check the vent.
The snow had drifted up high enough to block the vent. The water heater
would come on, try to blow the exhaust out and then shut down. Once the
vent was cleared, everything worked fine.
About a half hour later, another co-worker came in and told us that her
furnace stopped working just before she went to bed. Her husband checked a
few things in the basement and then went outside to check the vent. Again,
the snow had drifted up high enough to block the vent. Once he cleared the
snow, they had heat again.
We should all remember that during a significant snow event we should keep
an eye on the exhaust vents for our furnaces, water heaters, dryers, etc.
If you are going on vacation, instructions should be left with someone to
have them check the vents if you think they are low enough to be impacted
by drifting snow.
Good point of emphasis, I hate the horizontal at the ground exhausts for
such reasons as well as aesthetics. I tried like the dickens when we
put the new furnace in to figure out a way to get the stack out the roof
but just was no way and the cost of the approved piping in the chimney
was prohibitive so let him do that for the main floor unit.
There shouldn't have been any gas, though...it should've known not
enough airflow to prevent trying ignition. That sounds like a failure
in control logic to me.
Luckily for me, my vent is located in an area that collects very
little snow, but if any did accumulate, I'd spot it immediately.
It's not just the furnace and water heater vents you have to monitor,
it's the pressure regulator vent on the gas meter as well. It's very
small, so piled up snow or ice on the meter could block that vent.
When that happens, either the gas service will shut off or, more
dangerously, you can get gas accumulating indoors. For that reason,
our local utility installs small roof-shaped caps on their meters to
prevent snow or ice accumulation on the pressure regulator vent. Even
then, we are cautioned to keep the gas meter shoveled out as
It's not always that easy, especially in an older residential building. For
example, my house was built in 1956. Back then the plans were drawn up to
account for the furnace and the chimney, maybe even the water heater.
Window placement, siding, etc. didn't need to be taken into account since
everything vented through the chimney.
Fast forward ~40 years and I decided to put in a high efficiency gas
furnace. The furnace has to go in the same spot as the old one - unless I
want to have all of my ducts redone - but now we have to vent it through
the basement wall - unless I want to have my chimney relined.
Now we have to deal with proximity to windows - unless I want to have my
windows moved - and any other code related issues regarding the placement
of the vent - unless I want to alter other physical aspects of the house
just to accommodate the vent.
In my case, the vent ended up high enough not to be an issue with snow
since I have a walk out basement, but we did have to take the kitchen
window into account and angle the pipe away from the furnace so it came out
of the house far enough from all windows to meet code.
When a house is designed with the furnace, water heater, dryer, etc.
initially accounted for, the code requirements, aesthetics, etc. can be
built into the plans. In an older home, the retrofit can be problematic.
Many times, with your typical below grade basement, the vent ends up very
close to the ground not only because that's where the rim joist is, but
also because of windows, doors, etc.
When our furnace got upgraded, only thing chimney is venting is water
heater. Code required B-vent liner from heater to the top end of chimney
whose opening got much smaller now. They had to push down the one piece
liner from the roof all the way down to basement.
If you have a "condensing" water heater and a "condensing" furnace,
both can vent separately through the chimney.. You cannot share a
condesing (forced draft) and a non-condensing device in the same
chimney. With a non-condensiong (medium efficiency) furnace and a
regular water heater they can chare a "b-vent" liner in a chimney.
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