DIY Hot Air Furnace Maintanience

I thought this might amuse a few reader:

It’s cold out today and I’m happy to have just experienced the 44th successful re-start (during my ownership) of the c. 1965 Lennox forced hot air system that the previous owners had installed to replace the original 1899 gravity hot air monster that must have filled the cellar.

When I first bought my house a Brooklyn Union Gas Co. technician showed me how to service the thing. It
s very simple:

Hose down the old-fashioned tent-type fiter. I used to change a fiberglass sheet filter, attached to the tent frame, but when I could no longer locate those I found a washable sheet at an industrial heating place in Gowanus. Now the disposable filter rolls are available on Amazon, but I don’t see the point–I HATE handling fiberglass!

The B.U.G. tech told me that th e furnace was absolute top of the line and might last “forever” as long as I don’t turn the pilot light off over the summer. You can shut the main gas valve and leave open a smaller one for the pilot. The slight heat helps keep the heat exchanger from rusting out, which wo uld be the end of the furnace. The thing is less efficient than a more modern unit, but I had it tested years ago; it’s 74% efficient which isn’t all that bad. My heating bills are lower than most of my neighbors.

The service procedure is VERY simple:

•remove the back cover
•Check the fan belt; I’ve had to replace it once, long ago
• Remove and hose down, or change the filter hosing it down outside, of course
•Put a drop of SAE 20 oil in each of the 5 oil holes–the can of oil I bought in 1974 was finally empty, thus a trip to the hardware store
•Remove the 2 grease cups to see if they have enough grease in them. If the do, put them back and tighten them; if not, add some. The one pound of grease I bought on Chambers Street in 1974 is still almost full.
•Put back the filter and back cover
•Remove the back cover and re-open the main gas valve
•Go up to the thermostat and turn it on
•Hold your breath and wait for the wonderful acrid small of heating dust in the 119 year old ducts.
•Hold your breath some more, until the fan starts.

FWIW hot air furnaces DO produce heat that’s a bit less comfortable than a good steam of hot water boiler with radiators. However they are SO easy to maintain. The heat is uneven since the hot air registers heat up and cool off virtually instantly. There was a big improvement when I replaced the old electro-mechanical thermostat with a digital one. The old thermostat, with it’s mercury switch, let the heat go a few degrees over the setting before shutting off and waited until it got a few degrees below the setting before going on again. The digital thermostat makes the heat ALMOST as even as hot water radiators. There’s still more dryness, but I can live with that. There IS a humidifier on the return duct, but I disconnected it LONG ago, for fear of microbes growing in the water tank.

My service contract would cover all of this for free, but I’d have to request service weeks in advance and wait around all day for a technician to show up. Also, my furnace ids older that any technicial who’d service it and, I fear they might screw it up. As I age it’s getting more and more painful to squat in the small space behind the furnace. Some day I’l have to have someone else do it, but NOT this season.

RobertGMarvin

in Heating and Cooling 6 years and 11 months ago

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RobertGMarvin

in Heating and Cooling 6 years and 11 months ago

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I was able to buy a large sheet of washable filter material, big enough to cut into four filter sheets to attach to the filter holder. I stupidly discarded the first, after one season. I’ve washed the second several times, with no sign of deterioration, leaving two more in reserve.

RobertGMarvin

in Heating and Cooling 6 years and 11 months ago

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Most people use disposable filters–there was just a time when I was unable to find the large rolls of filter material I needed for my old furnaces tent-type filter holder.

SoSlope | 6 years and 11 months ago

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Very helpful. I have found our forced air furnace to be extremely simple and easy to maintain. The only repair we have made in the past 10 years is to replace the hot surface igniter, which cost a few bucks and took a few minutes. I also installed a humidifier (actually two since the first one was not at all effective, so I replaced it. The second is only marginally more effective. We still run room humidifiers throughout the house in the winter.)

We do use disposable filters rather than hosing off the old filter and replace them somewhat frequently.

RobertGMarvin

in Heating and Cooling 6 years and 11 months ago

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Thanks NP; of course other hot air heating systems probably differ a bit.

yudashasom | 6 years and 11 months ago

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Good tips – thanks for sharing.