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HVAC quote - design and price comments

Posted by Greg__R (My Page) on
Wed, Jun 20, 12 at 19:42

My home has a heat loss of 60k btuh and a heat gain of 40k btuh based on the manual J calc & I live in a fairly temperate climate. Electricity is significantly cheaper than gas (per btu) so we're looking at the better heat pump options. Some systems are 4 ton because 3.5 ton are not made and others are 4 ton because the installer says it's needed for the higher efficiency systems. The attached image file is a snip from my spreadsheet showing the various systems (furnace btu is what goes into the house based on AFUE). All installers are NATE cert'd and Angie's list A-rated. Comments r.e. design and price are welcome, thanks!

Greg


Follow-Up Postings:

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RE: HVAC quote - design and price comments

let's see if this shows up any better...


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RE: HVAC quote - design and price comments

One thing to note is that the Carrier dealer only recommended an 80 AFUE gas furnace (V.Speed fan) because it would rarely be used. The other dealers were pushing the 95+ AFUE furnaces.


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RE: HVAC quote - design and price comments

What is location?

What size system are you replacing?

Just to be clear, you have nat gas service to your home already?

What size living area is your home?

What is your nat gas and electric rate?

Post back.

IMO


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RE: HVAC quote - design and price comments

location: Portland, OR
Size: No existing A/C, replacing 80 AFUE furnace (90 or 92k btu on the plate, I can't remember exactly... we're ~80kbtu effective)
gas already exists @ the install location
electric: $0.15 kwh (with HP it may push into the next pricing tier of $0.30 kwh)
gas: Currently $0.45 / therm; 10yr high is $0.85/therm


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RE: HVAC quote - design and price comments

Umm... Your electricity is significantly more expensive than NG so a heat pump looks like a horrible idea (and I rarely say that).


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RE: HVAC quote - design and price comments

My apologies... I looked @ the listed rates online and not at my bill. I called my wife at home and here are our current rates:

gas - $1.08 per therm. Our peak usage last winter was 250 therm over a 30 day period.
electric - 0.1035 kwh (we are currently using ~1300 kwh each month)


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RE: HVAC quote - design and price comments

Annual gas usage with 80 AFUE furnace is 1650 therm. We have 2 gas fired water heaters, one of which is rarely turned up (it drives a radiant heat system in our in-law suite).


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RE: HVAC quote - design and price comments

I did my own analysis using daily temperatures for the past few years to determine the required daily BTU for a given day. In general, it would be extremely rare for the gas furnace to turn on if I gave priority to the heat pump (~$20 to run the gas furnace for the least efficient option). If I factor in initial equipment cost, the Carrier Greenspeed becomes the least expensive option by the end of year 3.

Does anyone have any comments r.e. pricing and/or quality? Thanks!


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RE: HVAC quote - design and price comments

With your climate and the Greenspeed, you might not need a furnace at all. I mean, how often does Portland get to 17F?

However, the Trane XL15 system is $2000+ cheaper, probably more so if you went with an %80 furnace. Could you compute how long it would take for the Greenspeed system's savings to make up the difference?


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RE: HVAC quote - design and price comments

weedmeister,
I calculated that the Greenspeed would save me ~$750/yr in utilities versus ~$200-$250 for the other options (HSPF=9). IMO, this is primarily due to the Greenspeed's larger heating capacity at low temperatures. I assumed a linear relationship between delta-T and heat loss in the home to reach this conclusion. So, it would take ~4 years to make up the cost differential. Also, the Carrier 16 fared better than the Trane XL15 and is similar in cost.


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RE: HVAC quote - design and price comments

If going Greenspeed which I really think is overkill. I would go all electric w/heat strip backup.

Otherwise, go conventional high eff HP with 80% eff two stg VS furnace.

Your location/climate has a mild winter heating season climate.

IMO


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