Re-Use XE78 furnace?

[Hotrocks]

I've just stumbled onto this board a few days ago, and really got into the efficiency discussion with COP and therms cost for HP and Furnaces. Thanks for all the great info.

In the spring, I tore down a rotten chimney, and with it, the flues for my fireplace and my furnace. FP was ng non-vented so no problem. A neighbor had a similar furnace but had it horizontally vented with a power ventilator, so I decided to not rebuild about 16 feet of chimney and use the power ventilator or get a new efficient HP system. Since money is tight now, I've decided to put off the purchase of a new efficient HP system till next year and use the tax credit. My current system for the 1st floor is a Trane 2 Ton compressor ('94) XE1000 (SEER 10?) with a XE78 (78% efficient?) furnace.

I bought a Tjernlund power ventilator($), and will be hooking it up shortly. Since NG is cheap right now, and I live in Raleigh NC where winters aren't too bad, I wanted to know I could insert my old furnace inline with a new High efficiency Heat Pump system I plan to get next year? I don't want to have to use the heatstrips, but don't think it would pay to get a really efficient furnace. Elect rates here are approx .10/kw and .98 to 1.04 for therm of NG.

Also, I was wondering if the power ventilator decreases the efficiency of the furnace alot verses just a draft flue?

Hotrocks

[beenthere]

Removed Tjern price. No prices in post. Please read site rules, thank you.

Fuel cost are allowed.

[yourairman]

I've just stumbled onto this board a few days ago, and really got into the efficiency discussion with COP and therms cost for HP and Furnaces. Thanks for all the great info.

In the spring, I tore down a rotten chimney, and with it, the flues for my fireplace and my furnace. FP was ng non-vented so no problem. A neighbor had a similar furnace but had it horizontally vented with a power ventilator, so I decided to not rebuild about 16 feet of chimney and use the power ventilator or get a new efficient HP system. Since money is tight now, I've decided to put off the purchase of a new efficient HP system till next year and use the tax credit. My current system for the 1st floor is a Trane 2 Ton compressor ('94) XE1000 (SEER 10?) with a XE78 (78% efficient?) furnace.

I bought a Tjernlund power ventilator($), and will be hooking it up shortly. Since NG is cheap right now, and I live in Raleigh NC where winters aren't too bad, I wanted to know I could insert my old furnace inline with a new High efficiency Heat Pump system I plan to get next year? I don't want to have to use the heatstrips, but don't think it would pay to get a really efficient furnace. Elect rates here are approx .10/kw and .98 to 1.04 for therm of NG.

Also, I was wondering if the power ventilator decreases the efficiency of the furnace alot verses just a draft flue?

Hotrocks

The combustion blower/induced draft motor actually increases efficiency in the furnace. There are a couple of things to keep in mind with regards to replacing your furnace.
1. It will only heat your house when the temperature is below freezing(or whatever the changeover temp is set at)
2. You will not be able to achieve high efficiency with the new heat pump without a variable speed blower. Nothing over a 14-15 seer and most likely not over 14.
3. There are no heat strips with the type of system you are referring to, at least with what is existing.
4. 10 seer and 78% efficient is correct

[Hotrocks]

The combustion blower/induced draft motor actually increases efficiency in the furnace. There are a couple of things to keep in mind with regards to replacing your furnace.
1. It will only heat your house when the temperature is below freezing(or whatever the changeover temp is set at)
2. You will not be able to achieve high efficiency with the new heat pump without a variable speed blower. Nothing over a 14-15 seer and most likely not over 14.
3. There are no heat strips with the type of system you are referring to, at least with what is existing.
4. 10 seer and 78% efficient is correct

That's interesting that the draft motor will increase the efficiency. good to know.

1. Agreed, that's why I'm thinking about keeping it. Although, I have since read more threads here, and I'm debating a new dual fuel because we don't know how Cap and Trade will affect KW/NG prices. I really like the idea behind being able to change the crossover from HP to Furnace at will, geek software engineer that i am....
2. I think the 30% tax credits are for 15 SEER and above, so that's probably what I'd be looking at.
3. Agreed for existing. I was referring to utilizing the old furnace so the new HP system I'm deciding to purchase wouldn't need to use heat strips.

Thanks for the quick response yourairman.

Hotrocks

[egads]

I'm HO & not a pro. What you need to understand is a your old furnace would act as the air handler for a new heat pump. The blower and electronics that control it would not be well matched to a heat pump that meets the tax credit criteria. You would probably need a new furnace as well.

[catmanacman]

that furnace is about 16 years old i would replace at the same time, have seen many motors crap out at that age get a complete new matched system with a 10 year parts and labor warranty

[Gunnery Sergeant Hartman]

That old furnace more than likely will not match with a heat pump to give a true 15 SEER/12.5EER/8.5HSPF.
Just because the glossy ad says 15 SEER doesn't mean anything. The ARHI match is what the government is interested in.

[jjou812]

most power venters are not plug-and-play. they have a throttle that needs to be adjusted correctly or they will draw too much air through the heat exchanger. be safe and have a pro set it up.

[Hotrocks]

That old furnace more than likely will not match with a heat pump to give a true 15 SEER/12.5EER/8.5HSPF.
Just because the glossy ad says 15 SEER doesn't mean anything. The ARHI match is what the government is interested in.

I was thinking of just getting a whole new efficient HP system, and just having my old furnace ducted in-line instead of using the inefficient heat strips that would come with the new system. Wasn't thinking about blower of the old furnace is probably needed for it to function.. Doh... Thats what I get for just "thinking".

I've already settled on getting a new dual fuel system. Best of both worlds, and can be adjusted for the best efficiency with the uncertainty of elec/ng rates in the future.

Thanks to all the responded.

Hotrocks