New furnace savings minimized by energy efficiency upgrades

[martik]

After upgrading insulation and windows and replacing a 30 year old 120k NG furnace with a 75k 92% unit, my calculated heat loss went from 110,000 to 32,000 btu/hr. At a setpoint of 19C with outside temp of 5C the house will maintain 18.5-19 for several hours. The furnace cycles TWICE a day for,20-30 mins in the morning and the same in the evening. I set it back to 16 overnight.

Now I'm wondering if the new furnace was a waste of money. With such a significant reduction in heat loss, the old furnace would have probably cycled about the same as the new one with a slightly larger fuel consumption. Before the energy upgrades the old furnace would cycle twice per hour under the same conditions. I suppose the bottom line is that furnace replacement payback is going to me much longer when combined with major energy upgrades.

[zzyzzx]

Sounds to me that maybe your furnce is oversized. I mean why a 72K furnace with a heat loss so low?

[beenthere]

You should have done the energy upgrades first, and then the load calc to get the right size furnace.

Look at it this way, you also upgraded the reliability of your heating system also.

[dan sw fl]

Originally posted by martik
Now I'm wondering if the new furnace was a waste of money. With such a significant reduction in heat loss,

I suppose the bottom line is that furnace replacement payback is going to me much longer when combined with major energy upgrades.

OPEN the Doors
so you can use that New furnace !

[cem-bsee]

do you even need a furn?
put a 500watt elec heater into the bath for mornings --
bake biscuts ea morning

[martik]

Contractor did not want to put in a smaller furnace, there are the odd -15 days here and the next owner may want to maintain a higher temp.

If it only runs twice a day, 4 months a year it will probably last 50 years.

[mayguy]

At 5c degree (42f) is not very cold, but it still sounds oversized! I bet some rooms will be cold while the others are warm when it gets cold out.

-15c, (5f) is not that cold, We get -20f (-29c) and my 60k furnace keeps up quite well.

[beenthere]

Originally posted by martik
Contractor did not want to put in a smaller furnace, there are the odd -15 days here and the next owner may want to maintain a higher temp.

If it only runs twice a day, 4 months a year it will probably last 50 years.


In othee words, th contractor didn't trust your load calc, and doesn't do them himself.


A 50,000 90% would still have given you 30% more heat then your load calc said you need.

[dan sw fl]

Originally posted by cem-bsee
do you even need a furn?

put a 500watt elec heater into the bath for mornings --
bake biscuts ea morning


CEM,

Right, that's what I do !
Well, ONLY on select mornings, few and far between.