PDA

View Full Version : Power service for gas furnace vs air handler


mrhatlanta
10-16-2006, 02:23 PM
I've been receiving quotes for 2 new split HVAC systems to replace my existing single system. My house is finished on 3 levels and a basement furnace heats the whole house, with a single condensor unit outside. I'm planning to replace the basement furnace with a new duel-fuel variable speed model (Trane XV-80 or American Standard equivalent) coupled with an XR-13 heat pump. Additionally, I plan to install a new furnace/air handler in the attic for the upstairs bedrooms coupled with an XR-13 A/C condensor or heat pump.

One contractor recommends a traditional gas furnace and A/C condensor in the attic, while the other recommends an all-electric air handler and heat pump. I've never had a heat pump before, but my research has indicated the duel-fuel system is a good investment for long term efficiency. I'm a bit concerned about an all-electric air handler, however. The prices for either system are comparable. Any advice on this decision would be appreciated.

Another concern is with the load that will be placed on my existing electrical panel. For my 5 bedroom (3 used), 3 1/2 bath house (approx 3200 sf), I have 150-amp service. I have an electric double oven, range and dryer drawing 240-volts. My panel is currently full (no available breaker slots), but I've been advised I can "double up" some slots for the new breakers required for the 2nd condensor/heat pump and 2nd furnace/air handler. If I also have to add 240v heat strips for the air handler to the load, I'm concerned about overloading the panel. For instance, what happens when we're cooking a Holiday dinner in 2 ovens, with the dryer running, and the heat strips kick in? The contractor recommending the air handler doesn't seem to think there will be a problem, but I would like some input from the experts.
t527ed
10-16-2006, 02:54 PM
would probably have to upgrade elec service for heat strips. i would go with furnace.
BaldLoonie
10-16-2006, 03:15 PM
Where are you? What are your electric & gas rates like?
mrhatlanta
10-16-2006, 03:18 PM
I'm in Atlanta. I'll have to check on the electic and gas rates and respond later.
BaldLoonie
10-16-2006, 07:38 PM
Guess I should have analyzed your user name better :)

You won't need much backup heat upstairs in the winter, with your climate and heat rising from downstairs, the heat pump will do almost all the work. Still 150 amp main is probably too light and as it is, probably borderline for what you have in the house.
BaldLoonie
10-16-2006, 07:39 PM
Guess I should have analyzed your user name better :)

You won't need much backup heat upstairs in the winter, with your climate and heat rising from downstairs, the heat pump will do almost all the work. Still 150 amp main is probably too light and as it is, probably borderline for what you have in the house.

Still could consider upgrading the panel and going with electric upstairs. Even the smallest gas furnace may be bigger than you need. And if you factor the cost of running gas upstairs and adding a flue plus the added cost of a gas furnace over electric strips, may not be a whole lot different. And you get a new panel out of the deal.
mrhatlanta
10-16-2006, 10:46 PM
Here are my current utility rates:
-Gas = $0.98/therm (variable rate)
-Electricity = $0.10/kwh

I've been quoted a similar cost for a gas furnace installation in the attic (AS Freedom 80 AUD060C936K) as an all-electric air handler in the attic (Trane 2TSC3F24A). Both systems will work with a 2.0 ton A/C or heat pump. Given the choice between the two and the utility rates above, what do you recommend?

Again, the Trane contractor does not plan to add an electrical subpanel, so I'm a bit concerned about the air handler. Which would cost less to operate, the gas furnace or electric air handler?
peytonc2682
10-16-2006, 11:02 PM
are you sure about that your gas rate? That seems really low. Electric is about right.
swagging tool
10-16-2006, 11:05 PM
Seeing that the airhandler is a 2 ton unit I would asume that the installer quoted you on installing a 5 kw or maybe even a 3 kw heat strip since the unit is going upstairs where you really dont need alot of suplmentry heat. Thus your added ampreage would only be 30 amp circuit at the most drawing much less than the 30 amp rateing even with the heat strip on. So we're talking an addition of 20 amp outdoor and 20 amp indoor breakers most likely with the actuall load once again being much less than the rated load thus with a full load on the airhandler and outdoor unit with the heat strips engaged at 3 kw of strip you would only be pulling aprox (this is just an educated guess i did not look it up) 10 amps more then the furnace on dual fuel set up. If your installer uses the 5 kw strip it will be slightly higher but still nothing drastic. But once again as stated go with the installer you feel will do the best instalation with price being sugestive but not the total objective to your purchase.
mrhatlanta
10-17-2006, 09:01 AM
Thanks for the input.

Bald Loonie - what do you mean by the statement "Even the smallest gas furnace may be bigger than you need"? My attic furnace quote is for a 3 ton, 60,000 BTU furnace, which will heat 4 bedrooms and 2 1/2 baths (approx 1100 sf).
drsmith012
10-17-2006, 10:58 AM
You need an electrician to evaluate your service. 150 amp is a little low for a house. However, I have never seen a true 150 amp meter base or service. They have always been 200 amp wiring into a 150 panel. When I worked for an electrician the best explanation he could come up with was that the builder was able to save a few bucks on the 150 panel over the 200. There is a chance you have 200 amp wiring. In that case all you will need is a new panel. And at worst new wire to the meter base.

I don't like double breakers. You are better off with a sub panel.