Natural Gas Furnace ... Maximizing the Efficiency.

[Robert Morris]

Greetings all.

Let me start by posing a hypothetical scenario... I want to maximize my furnace efficiency in my home. I have already performed the following but would like to do more.

Currently a 3 level home with 2 zones/2 thermostats (Honeywell Visionpro 9000). Natural gas furnace in attic.

1. Thermostat - cycles per hour = 1 (still very comfy and minimum wear/tear. Also ductwork is in the attic so to me more cycles means more times per hour cool air gets pushed through at startup .)

2. Ductwork - Bypass damper: spring added to make it unused unless a very abnormal pressure situation is encountered.

3. Furnace - Reducing the inducer cfm by blower speed reduction or physical plate[/U]. I know this one sounds crazy but stick with me. The furnace is <80% efficient yet its BTU rating for the situation makes it rather oversized. I have already turned down the flame such that it sips the gas but still maintains a safe and constant flame (heat recovery on cold days has suffered some but it's certainly not unreasonable). I feel that the flame could be reduced even more to maximize efficiency but with the factory set inducer draft cfm this would run the risk of an unstable flame with the likelihood that all the gas may not fully combust. Theoretically if one could slow the inducer fan and reduce the flame considerably, could the efficiency be brought to 90+ percent ? (with the overall BTU/hr capacity of the system diminished of course).

Let me know your thoughts! Thanks.

[ammoniadog]

Flue gas starts to condense at any efficiency over about 80%. Furnaces need to be specially designed and built to handle this condensation, otherwise the heat exchanger and/or flue pipe can quickly rot out and cause a very unsafe situation.

This isn't stuff that you should be playing with if you don't know exactly what you are doing. Please set the gas pressure back to factory recommended settings and don't mess with it any more. If you don't have the proper tools to do this, please get help from someone who does.

[kdean1]

You MUST use a combustion analyzer when setting it that far from the factory settings.
You are correct that the heat will either go into the air in the house or out the vent, but just fiddling with it will not yield safe or satisfactory results

[pecmsg]

Please get a factory authorized tech out to reset all the pressures and check the entire furnace.

What you've done is potentially dangerous to your family and damaging to the equipment

[beenthere]

First. If you made an 80% furnace 90% deficient. You would rot out the heat exchanger.
Second. You have actually so far reduced the efficiency of your furnace.
Third. This is not a DIY site, and what you want info on is far more then our site rules permit.

Thread closed.