1995 Pulse furnace

And I inspect the heating coil return bends for leaks every year. Mine is the model that had the improved brazing material.

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By "purge blower" I presume you mean the blower which blows air into the combustion chamber. What happens when it "tries to fire"? Does the hot surface ignitor glow, and the gas valve open?

So, you say that when you turn the thermostat up hard and far, the furnace runs?

Of course, there are two fans. One to supply air to the fire. And one to blow heat into the building. Some of the more complicated furnace use a timer, to turn on the blower fan that blows the heat into the building. I can't comment on the Lennox, never worked with that brand. Others use a heat sensor, or other device to know when to turn on the hot air blower.

A tech with Lennox experience would be more help. Too much electronics.

On 2/25/2010 6:16 PM, acbysean wrote: > acbysean had written this in response to >

There is no filter to the air box. Only a muffler on the intake pipe. I suppose some of the grime on the air flapper could be from the fiberglass insulation panels inside of the airbox. The purge blower also runs to evac the burner chamber in case of a no fire. A spark plug starts the pulse ignition and a heat sensor plug determines if the pulse is self sustaining and turns the spark off.

The thermostat is as old as the furnace. I will probably change it out first and see if that's the problem. Otherwise a furnace tech is going to make some money. That's alright as long as I can't do it myself.

Natural gas buzz-bomb pulse-jet engine process. If it needs much in the way of repair you are likely farther ahead to replace it. A very large percentage of the original pulse furnaces have gone to the great scrap yard in the sky.

Was anyone playing with the thermostat and changed the "heat anticipator" setting? For that matter, is the t-stat mechanical or electronic?

If it works fine and cycles fine set at 75 but not 68, replace the thermostat

If it is a pulse type, trash it. My neighbor's only lasted about 3 years before he had to replace it.

I still have an old 1965 gas-fired furnace where the flame is ignited by a pilot light and burns inside a great big can. It may be old, but I have never had any problems other than oiling the blower motor and changing the filter. I also filled in the gas nozzle and then drilled it out with a smaller size drill so the gas flow is about half of what it used to be, so it doesn't burn as hot and I put less heat up the chimney. I have the blower temperature sensors set low so the blower comes on at a low temperature and runs until the air is down to about

Well yeah. A bunch of them did. Mostly because a bean counting engineer decided to save a few pennies per unit by using a lower silver content solder in the coil brazing process. I think you'll find that most of the bad ones were of the G-14 model. That problem had been mostly solved in the G-21 model. That destroyed the rep of a finely engineered and built furnace. Still the most efficient furnace around. Soon may be a problem with getting parts but I'm going to keep her as long as possible. If the heat exchanger does go bad, lifetime warranty. Either a new heat exchanger if available or a new high efficiency furnace (which efficiency would be lower than the pulse.).

I hate to be one of those guys but I need to disagree with you. I've had this for 15 years now and very little trouble. When I installed it my gas bill was cut in half. Mine is very efficient, quiet (relatively), and reliable. I also like the feel of the heat. Not too dry. It is also the first furnace to use coil technology for higher efficiency. You might say it was a pioneering furnace for high efficiency. I do keep a carbon monoxide detector though.

If you take a certain amount of air and its water content and heat it by blowing the air over my can or over your coils, that does not change the moisture content unless the air is exposed to some open flame, so how can the tyoe of furnace make a difference in how the heated air "feels"? Maybe the blower/air speed changes how the heated air feels, but the type of heating does not change things at all.

My G14 is now 34 years old. Heat exchanger was replaced on recall when a couple years old. Circulating blower replaced once. Purge blower still original. Flapper valve replaced once. Just today it began short cycling.... just as weather is getting colder....might be the end???