View Full Version : Fire rate in a furnace

01-10-2011, 04:40 PM
Just curious, was talking to a HVAC guy at work and he mentioned there is a way to make the flame higher in a gas furnace. When I heard this, I thought he was crazy. I had thought the gas burner were all firing at a steady rate and only the fan speed ajustment allows you to feel the difference in heat coming out of the registery.

He mentioned you can ajust the flame level like you do on a hot gas water heater. Is this true???

01-10-2011, 07:07 PM
There may be a way to adjust the fuel/air mixture, but this is not for adjusting the amount of heat.

01-10-2011, 07:24 PM
THe air/fuel mix can be adjusted for optimum efficiency and minimum emissions. I think changing the regulated gas pressure for a bigger flame is asking for trouble. THe burner is rated at X many BTU. Trying to coax more out can cause problems.

01-10-2011, 08:53 PM
Oh I absolutely wouldn't try to adjust the flame level. I was curious after listen to the HVAC guy talking earlier today at work. I know my gas hot water tank, there is a lever at the bottom where I can adjust how warm I want my water coming out of the faucet. I can adjust betwen VACATION, MEDIUM WARM, high WARM, HOT, and MAX. Mine is set at high warm. And just wonder if same can be done on the furnace as you can do it on a gas stove.

01-11-2011, 07:22 AM
OK, that is a different question. I do not know of any way to do that with your existing furnace. Today's very high efficiency models have what is often called a multi-stage burner. I think in most cases there are groups of burners, and they use switching at the gas valve to use one or more burners as necessary. For example, in the am, after the night setback, all burners might come on to quicly get the house warmed up. Then one or more groups would be switched off, using just a smaller amount of fuel to keep the house warm. Oftern you will see variable speed blowers used in such a system.

If you are in a very cold climate, with high fuel costs, it might pay to look at investing in a new furnace. Otherwise, just wait until this one wears out

Rich B
01-11-2011, 08:25 AM
My Rheem furnace has a 2 stage burner. It has a 2 stage gas valve........This is not adjustable other than for efficiency of the flame. My furnace can be controlled by a 2 stage T-stat or a 1 stage T-stat. It runs the burners rate of fire by way of the PC Logic board. I have it controlled with a 1 stage T-stat mostly because I never got around to installing a 2 stage t-stat yet. It runs at low fire for a set amount of time.......8 minutes I think it is.....if the t-stat is not satisfied by then it goes to high fire and runs at high fire untill the heat call is satisfied. If it has a 2 stage t-stat it changes the timing sequencing of the fire rating.......I would not mess with the burner adjustment.....get someone from the gas company....they can adjust it and check to make sure it is burning efficiently.........

My old gas furnace was 20+ years old and I never touched it other than changing filters and clean it out of any dirt or debris in there.

My new one is about 5 years old.....same deal...

01-11-2011, 02:21 PM
The wh knob is a thermostat. No effect on the flame size, just duration.

01-11-2011, 06:03 PM
I see. thanks!