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MN Renovator · 11-21-14, 07:52 AM

I just ran a little test.

There is 1 minute 15 seconds of burner run time prior to the blower starting.
Blower Time, Temp rise, percentage of max temp rise, %*57000BTUhr
1 minute, 25 degrees, 33%, 18810
2 minutes, 40 degrees, 53%, 30210
3 minutes, 50 degrees, 67%, 38190
4 minutes, 60 degrees, 80%, 45600
5 minutes, 65 degrees, 87%, 49590
6 minutes, 70 degrees, 93%, 53010
9 minutes, 75 degrees, 100%, 57000 (or about 10 minutes of the gas burner running which is actually 12 minutes of call for heat since my furnace takes 2 minutes from the call for heat until the burner kicks on)

After shutting down the furnace
1 minute, 50 degrees, 67%, 38190
2 minutes, 35 degrees, 47%, 26790

I'm not sure how to calculate all of this but if I add all of the figures together and average them I suppose I'll get somewhat close. It seems that I'm getting 67.75% of the steady state heat output in the first 10 minutes of operation including the cooldown period or about 38618 of the 57000. Which is 51.49% of the 75000 input rate. Seems a little hideous to me. What's worse is the previous owners had a thermostat that only had the gas valve running for 5 minutes which looks like an even worse proposition considering the temperature through the registers is still rising. If I take the 10 minutes and change it to 20 minutes, things look better at 91% of the heat output versus 67.75% of the 10 minute figure and 94% if we make a 30 minute run.

Granted, this math is rough but I think it illustrates the point.

11-21-14, 07:52 AM	#26
MN Renovator Less usage=Cheaper bills Join Date: Nov 2010 Location: Minneapolis, MN Posts: 939 Thanks: 41 Thanked 116 Times in 90 Posts	I just ran a little test. There is 1 minute 15 seconds of burner run time prior to the blower starting. Blower Time, Temp rise, percentage of max temp rise, %*57000BTUhr 1 minute, 25 degrees, 33%, 18810 2 minutes, 40 degrees, 53%, 30210 3 minutes, 50 degrees, 67%, 38190 4 minutes, 60 degrees, 80%, 45600 5 minutes, 65 degrees, 87%, 49590 6 minutes, 70 degrees, 93%, 53010 9 minutes, 75 degrees, 100%, 57000 (or about 10 minutes of the gas burner running which is actually 12 minutes of call for heat since my furnace takes 2 minutes from the call for heat until the burner kicks on) After shutting down the furnace 1 minute, 50 degrees, 67%, 38190 2 minutes, 35 degrees, 47%, 26790 I'm not sure how to calculate all of this but if I add all of the figures together and average them I suppose I'll get somewhat close. It seems that I'm getting 67.75% of the steady state heat output in the first 10 minutes of operation including the cooldown period or about 38618 of the 57000. Which is 51.49% of the 75000 input rate. Seems a little hideous to me. What's worse is the previous owners had a thermostat that only had the gas valve running for 5 minutes which looks like an even worse proposition considering the temperature through the registers is still rising. If I take the 10 minutes and change it to 20 minutes, things look better at 91% of the heat output versus 67.75% of the 10 minute figure and 94% if we make a 30 minute run. Granted, this math is rough but I think it illustrates the point.