Author Topic: Gas Furnace Maintenance  (Read 295 times)

DrumAllDay

  • 5 O'Clock Shadow
  • *
  • Posts: 60
  • Location: South of Canada
Gas Furnace Maintenance
« on: October 02, 2018, 02:24:34 PM »
Does anyone here do there own yearly maintenance on a gas furnace and have any good resources or advice for doing this?

I want to keep my older furnace running for as long as possible and I want to see if I can perform some simple maintenance on it without paying a $100-$150 service call.

wheezle

  • 5 O'Clock Shadow
  • *
  • Posts: 93
Re: Gas Furnace Maintenance
« Reply #1 on: October 02, 2018, 03:07:38 PM »
Also interested. Just got a new one and was just thinking about this. It's a high-efficiency furnace, to boot, which makes me more worried about its service life and my ability to maintain it.

sol

  • Walrus Stache
  • *******
  • Posts: 7201
  • Age: 41
  • Location: Pacific Northwest
Re: Gas Furnace Maintenance
« Reply #2 on: October 02, 2018, 03:17:04 PM »
Replace your filters if they're paper, or wash if they're electrostatic.  Every six months.  That's the thing that most commonly causes furnace failures.  Ask this landlord how he knows that.

When the filter clogs, they will overheat and either melt the control board ($600) or you'll toast the blower ($200).  Some furnace systems have multiple filters, so check both on the intake vent on the wall and inside the furnace unit itself where the air return enters.

Gas furnaces are pretty mechanically reliable devices.  They're just jets and a sparker and a big fan.  The sparkers and jets don't seem to break, but I have seen malfunctions related to 20 year old thermostat wiring jiggling loose.  You should be able to visually confirm that all of the gas jets are lit, just by looking in there while it's running.

If you have one of the newer high-efficiency units, then you probably have a plastic (rather than metal) vent pipe coming out of the top, and it produces condensation.  That moisture has to be removed, and depending on the geometry of your unit you might have a gravity drain line that drips it out under your house, or a pump system that uses an electric pump to remove it.  Those electric pumps are intermittent and will typically fail years and years before the gas furnace does, which can cause all kinds of problems.  I'd find your condensate line and figure out where it goes, because that's probably the second most common failure point after the air intake clogging.

If you have a heat pump instead of a gas furnace, then you have ten other failure points to worry about.  I'd call a professional.

wheezle

  • 5 O'Clock Shadow
  • *
  • Posts: 93
Re: Gas Furnace Maintenance
« Reply #3 on: October 02, 2018, 03:24:54 PM »
When the filter clogs, they will overheat and either melt the control board ($600) or you'll toast the blower ($200).  Some furnace systems have multiple filters, so check both on the intake vent on the wall and inside the furnace unit itself where the air return enters.

...

Those electric pumps are intermittent and will typically fail years and years before the gas furnace does, which can cause all kinds of problems.  I'd find your condensate line and figure out where it goes, because that's probably the second most common failure point after the air intake clogging.
Excellent, thank you! I just opted to drain the condensation without a pump, and I'm even happier about that decision now -- it seemed like a likely and expensive failure point.

Wouldn't have thought of the filter. I do it on a window A/C all the time, but I don't yet understand the way my furnace works. I'll get there.

sol

  • Walrus Stache
  • *******
  • Posts: 7201
  • Age: 41
  • Location: Pacific Northwest
Re: Gas Furnace Maintenance
« Reply #4 on: October 02, 2018, 03:35:52 PM »
Wouldn't have thought of the filter. I do it on a window A/C all the time, but I don't yet understand the way my furnace works. I'll get there.

Your furnace is a lot more simple than your window AC unit.  It has a big fan that sucks air from inside your house into the furnace unit.  In there, it burns natural gas in a big flame to make heat, and then it blows that hot air back into your house through your ductwork.  There is no thermodynamic compression cycle, no phase changing fluids, no pressurized fluids that can leak or condensers that can crack.  It's literally just a burner and a fan, and some electronics to tell it when to burn and when to blow.

But if that air intake gets clogged, you can still break it.  I've done it twice, once when a long term tenant never cleaned the electronic air cleaner as instructed, and once when a furnace had a second hidden paper media filter inside the furnace unit.

wheezle

  • 5 O'Clock Shadow
  • *
  • Posts: 93
Re: Gas Furnace Maintenance
« Reply #5 on: October 02, 2018, 08:00:46 PM »
But if that air intake gets clogged, you can still break it.
Is it because not enough air can get in? Or does the fan try to overcompensate with higher RPM? Makes perfect sense either way.

sol

  • Walrus Stache
  • *******
  • Posts: 7201
  • Age: 41
  • Location: Pacific Northwest
Re: Gas Furnace Maintenance
« Reply #6 on: October 02, 2018, 08:08:07 PM »
But if that air intake gets clogged, you can still break it.
Is it because not enough air can get in? Or does the fan try to overcompensate with higher RPM? Makes perfect sense either way.

Not enough air gets in, or out.  The burners keep pumping heat into a closed metal box with no airflow.  Eventually something melts, usually something electronic and delicate and expensive.

wheezle

  • 5 O'Clock Shadow
  • *
  • Posts: 93
Re: Gas Furnace Maintenance
« Reply #7 on: October 02, 2018, 08:10:18 PM »
Not enough air gets in, or out.  The burners keep pumping heat into a closed metal box with no airflow.  Eventually something melts, usually something electronic and delicate and expensive.
Got it. Makes perfect sense. I'll keep an eye on those filters.