operated damper in place, closing it, then venting a quantity of vapor
and attempt to detect back pressure. If only atmospheric pressure in 5
seconds after release, then open damper and allow furnace to run. Need
a largish supply of compressed air or an air compressor and a bottle to
store the gas.
This system would add at least $500 to the cost of the furnace.
Most likely. The exhaust inducer has a pressure switch to monitor performance
and also shut down the furnace if there is an exhaust problem. The computer in
the furnace will attempt to check again (without lighting the burners if it
fails) to clear the fault. If not, an error code is stored.
For reference some of the better oil burners have similar features. Side
power vent kits which can be used with any oil burner also have this
feature where if there isn't airflow they lock out the burner.
There are draft sensors that could detect blockage, but they are not
generally used. The much more common CO detector would detect such
conditions if properly installed and maintained.
Unfortunately some people install CO detectors right next to the furnace
and then eventually unplug them after too many false alarms due to
momentary back drafts from wind gusts. They need to be installed a
sufficient distance away so those non-threat conditions do not give
They are just about always used on a modern efficient (greater than 90% AFUE)
furnace that has direct vent.
Everyone with an attached garage or interior combustion device should have CO
detectors, at least on every level. They aren't expensive and some states are
mandating them, just like smoke detectors.
Wind gusts? Back drafts? Yikes! Isn't your oil burner using sealed combustion
to prevent inside air from ever touching the combustion chamber of the furnace?
It would be a shame for the furnace to consume heated house air.
Correct, however they haven't really found their way into non-direct
vent furnaces yet.
Right and if you have gas you can get the combination explosive gas
(nat. gas or propane) and CO detector. Note that with these you have to
mount them high to detect nat. gas and low to detect propane since nat.
gas rises and collects ceiling down and propane sinks and collects floor
up. I think most states have CO detectors mandated in rental housing
Only a small percentage of furnaces oil or gas are sealed combustion at
present. The Riello burners are particularly nice in a sealed combustion
configuration with their pre and post purge cycles.
Oil furnaces are more prevalent in the northern climates where gas
service is spotty and backup more critical. In those areas they are
typically in basements to they are not consuming heated air.
Anywhere outside urban and close suburban areas. There are vast areas
without nat. gas service and many of those areas are also in colder
climates where backup is more critical. There wasn't gas service where I
was in CT and there isn't gas service where I am now either.
To a large extent yes. Warm air also rises so you aren't going to get
warm air from upstairs going downstairs. Indeed waste heat from the
furnace is rejected into the surrounding area and that warmer basement
air will rise and warm the floors above slightly.
Well obviously if there is no nat gas service and propane isn't feasible, oil
would be a way
to go in climates too cold for heat pumps to work well. Oil. Cleaner than Coal.
Wow! I've never seen a house where the basement air was sealed from the house
nice to know that the air "consumed" into the oil burner wouldn't need to be
made up from
air leaking into the house via window gaps, exhaust fans, cracks etc.
Propane is even more dangerous than nat. gas. Because it is heavier than
air it is even less likely to dissipate from a leak in a house. Because
it is not a pipeline service you have to store a large quantity on-site
in a tank that you can't smoke/grill/whatever around and that has to be
outside where it is exposed to the weather and more likely to rust than
an oil tank in a basement.
Air typically leaks into basements just fine through garage doors which
are damn near impossible to seal, utility penetrations, dryer vents and
other basement openings. You won't generally see a draft sucking under
the gap at the bottom of the one basement door.
Wow! You can't grill near a natural gas tank! I think you just ruined a lot
Labor day parties.
Well my garage IS quite sealed from my basement, with a tight fireproof door
with lots of weather
stripping. Of course it's a moot point for the furnace discussion,since the
natural gas furnace
uses outside temperature air (colder air contains more oxygen too :) which it
inside for its use.
You have a nat. gas tank? You have your own refrigeration and
liquification facilities too?
The reference is to the large "hot dog" propane tanks of several hundred
gallon LP capacity. They can and do vent some gas while roasting in the
hot sun so you aren't supposed to smoke/grill/whatever near them.
And your point is? Oil furnaces can and do use sealed combustion as
well. Neither gas nor oil furnaces used sealed combustion until fairly
recently and both are able to use it currently. No real difference.
Chimneys? Modern efficient gas furnaces do not require "chimneys." They use
ordinary piping to bring fresh outside air in (so you're not sending your heated
home air into the combustion chamber to throw away) and remove exhaust.
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