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  1. #1
    Join Date
    Apr 2008
    Posts
    14

    Heat Pump or Air Conditioner in NJ?

    We recently bought a house in Cherry Hill, NJ (just outside of Philly). The house has a 4 year old 80% Gas furnace, and an ancient Air Conditioner that doesn't work anymore. Since the furnace is only 4 years old I'm not planning on replacing it. I got quotes from a few different installers, and none of the mentioned heat pumps, however I asked the last one if it was a good idea. She said it was a good idea and could end up saving us alot of money (of course I then wonder why if it was a good idea she hadn't mentioned it).

    It was only about $300 more for the Heat pump (4TWX4036B1000A vs 4TTX4036B1000A), and although I don't have any way to tell, and have been unable to find enough information to calculate it, it seems likely it would easily be worth the extra $300. However the problem is that there is a $300 rebate on the Air Conditioner, but not on the heat pump. I didn't really understand why, since the NJCleanEnergy website says that it only has to have a HSFP of 8.5, and Trane's website says it has a HSFP of 9. This means that the differance is at least $600, which I'm not sure I'd be able to recover.

    I've tried a few online calculators (including the HVAC OpCost one) and haven't really gotten any satisfactory answers, so does anyone have any better way to calculate it?

  2. #2
    Join Date
    Mar 2006
    Location
    The South
    Posts
    2,189
    jaguar

    with today's expensive fossil fuels, an 80% AFUE gas furnace is a dinosaur for your area/climate.

    What is your electric rate?

    what is your nat gas cost/therm?

    you will only achieve the higher HSPF heating eff with a matched system that includes a var speed blower.

    Here is a fuel comparison calculator that may help you with your decision.

    IMO

    http://www.warmair.com/html/fuel_cost_comparisons.htm

  3. #3
    Join Date
    Jun 2007
    Location
    The Twilight Zone
    Posts
    2,964
    Cost of 1 million btus:

    Natural gas at $1.50 per therm, 80% efficient
    (1,000,000 / 103,000) x 1.50 / .8
    = $18.20

    Electricity at 10 cents per kw-hr, outdoor temp = 35F (COP = 3)
    (1,000,000 / 3413) x .10 / 3
    = $9.77

    With the prices above, the heat pump costs almost half as much to run. Insert your own prices for more accurate info.

    Keeping the 4 year-old 80% gas furnace and pairing it with a new heat pump and coil is a good idea.

    Note that heat pumps produce 95-degree air out of the registers while a gas furnace is more like 120-degree air. Just so you know that the air from a heat pump is not as hot as a gas furnace.

    What is the model# of the indoor coil?

    Good luck.

    PS: I used to work in Cherry Hill back in the '80's (Old Cuthbert Road). I am originally from South Philly.

  4. #4
    Join Date
    Jan 2005
    Location
    Lanoka Harbor N.J.
    Posts
    48
    Try going with the carrier hybrid.2 stage, variable speed,94% furnace & a h/p with the infinity control. It's a great set-up for us here in NJ

  5. #5
    Join Date
    Apr 2008
    Posts
    14
    Thanks guys, I know that the 80% furnace we have isn't so great, but I'm not replacing it, as its only 4 years old, there is no way I'd ever get the money back. So that means all the higher end systems are out since I'm stick with the fixed speed blower.

    Gary, How do you know what the COP will be at different temperatures? And can you change at what temp it transitions between heat pump and furnace?

    Also the air coming out of our registers is only about 95-100 degrees now with just the furnace.

  6. #6
    Join Date
    Jun 2007
    Location
    The Twilight Zone
    Posts
    2,964
    Quote Originally Posted by jaguar36 View Post
    Gary, How do you know what the COP will be at different temperatures? And can you change at what temp it transitions between heat pump and furnace?
    From the Product Specs for my new Goodman heat pump, 3 tons:

    Outside Temp----------COP

    65---------------------4.37
    55---------------------4.04
    45---------------------3.64
    35---------------------3.25
    25---------------------2.82
    15---------------------2.46
    5----------------------2.06

    To automatically transition fom the heat pump to furnace, you need a thermostat capable of doing that (like the Honeywell Vision Pro IAQ) or a "fossil fuel kit" for the furnace.

    Good luck.

  7. #7
    Join Date
    Nov 2006
    Location
    Montana
    Posts
    134
    Quote Originally Posted by jaguar36 View Post
    Thanks guys, I know that the 80% furnace we have isn't so great, but I'm not replacing it, as its only 4 years old, there is no way I'd ever get the money back. So that means all the higher end systems are out since I'm stick with the fixed speed blower.

    Gary, How do you know what the COP will be at different temperatures? And can you change at what temp it transitions between heat pump and furnace?

    Also the air coming out of our registers is only about 95-100 degrees now with just the furnace.
    The COP values comes from the manufacturers data. An outdoor thermostat handles the switch-over to the gas furnace if your indoor thermostat doesn't have the capability to do so. However, a Break-even COP MUST be calculated to determine the switch-over temperature setting or Economic Balance Point. This is the temperature at which the heat pump is no longer cheaper to run then the gas furnace.

    This is a farly involved calculation in which a heat loss calculation is involved. Don't expect every contractor to know how to do it (especially if they don't perform load calculations) and don't accept the contractor just setting the switch-over temp to some arbitrary number based on "experience". Every house is different and all equipment has different COP ratings (even within the same model family). 2 houses that look the same from the outside and located right next to each other may have different switch-over temperatures.

  8. #8
    Join Date
    Mar 2008
    Location
    Jackson, NJ
    Posts
    176
    Quote Originally Posted by gary_g View Post
    Cost of 1 million btus:

    Natural gas at $1.50 per therm, 80% efficient
    (1,000,000 / 103,000) x 1.50 / .8
    = $18.20

    Electricity at 10 cents per kw-hr, outdoor temp = 35F (COP = 3)
    (1,000,000 / 3413) x .10 / 3
    = $9.77
    Gary, is this a standard formula, just substituting your costs and efficiencies? I mean, where do you get the 103,000 and the 3413 from?

    Would Propane have a differant number?

    I'm fascinated by these 'save money' calculations. Mostly because I am fascinated with keeping more of my money.

  9. #9
    Join Date
    Apr 2008
    Posts
    14
    Quote Originally Posted by shodinjido View Post
    This is a farly involved calculation in which a heat loss calculation is involved. Don't expect every contractor to know how to do it (especially if they don't perform load calculations) and don't accept the contractor just setting the switch-over temp to some arbitrary number based on "experience". Every house is different and all equipment has different COP ratings (even within the same model family). 2 houses that look the same from the outside and located right next to each other may have different switch-over temperatures.
    That may be all well and good for the initial setup, but what happens when next year (or even next month) the prices for gas and electricity have changed? I'm not gonna be calling the contractor every few months to come adjust the change over temp, so is that something that I could do myself?

  10. #10
    Join Date
    Feb 2007
    Posts
    999

    Utility costs

    Hi: I'm from your area.

    If you get your electric from PSE&G, your cost per KWH last year ranged from about $ .13 - .17. Gas fro So. Jersey Gas ranged from $1.46 - 1.54 per therm.

    AM

  11. #11
    Join Date
    Apr 2008
    Posts
    14
    Quote Originally Posted by Jopopsy View Post
    I mean, where do you get the 103,000 and the 3413 from?
    Those are just conversion factors, 1kW-hr = 3413 BTUs.

  12. #12
    Join Date
    Jan 2008
    Location
    Wisconsin
    Posts
    1,125
    If the furnace was in the house when you bought it, then you ain't really losing out by putting a new one in. The difference between a 80% and 90+% is a big one. I'd replace the whole system and put in matching components.

  13. #13
    Join Date
    Mar 2008
    Location
    Jackson, NJ
    Posts
    176
    Quote Originally Posted by jaguar36 View Post
    Those are just conversion factors, 1kW-hr = 3413 BTUs.
    Okay, so can somebody tell me what the conversion factor is for Propane?

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