Page 1 of 3 123 LastLast
Results 1 to 13 of 27
  1. #1

    Hmm Which Heat Pump should I use??

    Hello,

    I am considering replacing my HVAC system with a heat pump/oil furnace combo system. I already have an oil furnace that uses, on average, around 700 gallons of oil per year to heat (at a locked-in price of $4.09 per gallonfor this year) and a central AC system that was put in around 4 years ago by the previous owner ( I don't know what the SEER rating is for this unit; the furnace is an 11 year old Rheem). I hear that Heat pumps are more energy efficient and my HVAC guy suggested the combo unit of a heat pump operating until a set temp of around 30 degrees and then the furnace kicks in. This seems ideal to me but, he has reccomended two different types. Both are Ruud units but one is a single stage 13 SEER R-410A unit. The other is a 16 SEER TWO STAGE HEAT PUMP ADDS. My house is a 2250 sq. feet bi-level. Most of our living is on the 2nd level. I live in PA. The electrical rate caps are set to expire in about 2 years so my electric will go up, eventually. Currently we spend about $130 per month for electric give or take $25 considering the season.
    So, what are your thoughts? Is the 2 stage a better option? I think either will pay for itself in time. Just what is the better option based on my situation? Thanks for all of you who respond!
    Last edited by volpone1a; 08-01-2008 at 12:28 PM.

  2. #2
    Join Date
    Jun 2008
    Posts
    80
    Without knowing your KWH cost, I think your HVAC guy is right that an HP will save you down to around 30 degrees, especially with per gallon cost like that. Its hard to estimate how much of a savings, so see below.

    Since you didn't mention tonnage, how did the tech size these HPs?

    I suggest you verify the btus of those units to be certain you're comparing apples to apples. If you check a number of posts here you'll find that sometimes the units aren't always the same BTU output.

    Check out this heating cost comparison calc. It may help you mix and match different types of HPs with your oil furnace as backup versus just your oil. Its not perfect, but you can personalize the numbers for your application to give you a ballpark. I'm no expert so I stress the ballpark part. This spreadsheet requires you to estimate usage of your system, so play around with best and worst case scenarios.

    You can estimate a 14 SEER or 15 to see where your sweet spot is in long term payback.

  3. #3
    dac122,
    Thanks for your reply. My electric rate is, on average, 2.70 cents per KwH. I tried to use your calculator but I could not figure it all out. Maybe I didn't enter the right info. I didn't see my possible system on there, either. Some of the anual energy costs for thos e systems were at over $27,000.00 !! What was I doing wrong?

  4. #4
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,741
    I don't know of any place in PA that pay 2.70 a KWH.

    Most areas average $0.105 a KWH delivered.

    Since your oil furnace isn't a VS blower, I would recomend just getting the single stage heat pump.

    Our electric will go up in 2010, but oil isn't going to be any cheaper then it is now either.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  5. #5
    beenthere,

    According to my bill, cost per KwH is around $0.270, on average. I agree, that oil won't get any cheaper and I think that a HP would be more economical. From what I have been able to discern, doesn't a 2 stage use less electricity by only pulling full electric load when the demand for either heat or AC is greatest? (like on a 70 degree day only one compressor or coil will run and on unusually hot or cold days both will run as opposed to a single stage running all of the time to maintain set temp.?) I admit, that I am a novice at all this but I would like to make the best decision I can. Thanks for all your help! I live in New Cumberland, near Harrisburg, by the way.

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,741
    Ok.
    Take your electric bill. Divide your KWs used by the cost. And that will give you an idea of how much you pay including all delivery and taxes.

    Rheem uses Scroll unloading compressors. So you will have only one compressor.
    Your indoor coil, unless custom ordered(unlikely) won't be a split coil.
    So when running in first stage, the entire indoor coil is used. So since the blower can't slow down much, the coil will not be very cold, and won't remove much moisture, so you will end up with a high humidity. Which could make you have to set the stat lower to feel as comfortable.
    In heat, when its in first stage, the air will feel cool coming out the registers even when its 50° outside. Which can make you feel cold, so you end up turning the heat up higher.

    You will be better off with the highest efficiency single stage heat pump you can get.
    Then a 2 stage unit with a standard blower.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  7. #7
    Join Date
    Jun 2008
    Posts
    80
    Quote Originally Posted by volpone1a View Post
    dac122,
    Thanks for your reply. My electric rate is, on average, 2.70 cents per KwH. I tried to use your calculator but I could not figure it all out. Maybe I didn't enter the right info. I didn't see my possible system on there, either. Some of the annual energy costs for those systems were at over $27,000.00 !! What was I doing wrong?
    Okay, so you're definitely doing something wrong. It took me a while to reconfigure this spreadsheet to my tastes, but then I do this type of stuff all day long.

    First, enter in your data up top, house size, heat loss, heating degree days (most likely less than 9000). Check some weather sites to get this number.

    Next enter in your KWH costs in G9 and G10 of 0.27 if figured correctly from beenthere's advice, and then heating oil. Look at the bottom where heating oil is, enter or estimate your efficiency and then play with the house size, heat loss, etc. to get the usage close to your annual gallon usage. You can then play with this number for best or worst case winters.

    The last block, 'Cold Climate Heat Pump with Fuel Oil' you can use for you new system. Change the efficiencies in column D,E. For a 13 SEER maybe put in 160% to 210%. If you have the COP curve on your proposed system you can put in actual numbers. Finally, note the calculations in column F contain a weighted average usage of the two pieces of your system. The optimistic writer of this spreadsheet (who was trying to sell cold climate HPs) thought their HP would run 95% and the backup heat 5%. Change those to what you think - say maybe 70/30, 60/40 or 50/50 HP/Oil. Others might have some idea how much each of those systems will run in your climate.

  8. #8
    beenthere,

    Rheem uses Scroll unloading compressors. So you will have only one compressor.
    Your indoor coil, unless custom ordered(unlikely) won't be a split coil.
    So when running in first stage, the entire indoor coil is used. So since the blower can't slow down much, the coil will not be very cold, and won't remove much moisture, so you will end up with a high humidity. Which could make you have to set the stat lower to feel as comfortable.
    In heat, when its in first stage, the air will feel cool coming out the registers even when its 50 outside. Which can make you feel cold, so you end up turning the heat up higher.


    I apologize for sounding naive but does this refer to the 2 stage unit? How would the single stage unit operate, then?



    What do you think of this particular model (Ruud 13 SEER R-410A, 3 ton cased coil)? It is the single stage one. I have read and heard that Ruud (Rheem) is a reliable brand. It is obviously cheaper than the 2 stage unit I have to decide between. If you don't like it, then what would you reccomend?

  9. #9
    dac122,

    Thanks for your help. It made much more sense the 2nd time around. According to the spreadsheet, I should only spend around $142/month for electric with this system. Even with electric rates going up in 2010 (estimated by about 50% more than now) our monthly electric bill would be approx. $203/month. I consider that acceptable. Much better than the oil prices being what they are and will probably continue to be. BTW, what do you think....should I go witht the single stage HP or the 2 stage? Thaks again!

  10. #10
    Join Date
    Jun 2007
    Location
    The Twilight Zone
    Posts
    2,964
    Quote Originally Posted by beenthere View Post
    Since your oil furnace isn't a VS blower, I would recomend just getting the single stage heat pump.
    This is the answer to the single stage / dual stage compressor question.

    I would also check into a 14 SEER heat pump. Sometimes the 14 SEER provides a higher EER (Energy Efficiency Ratio) and HSPF (Heating Seasonal Performance Factor), even with a non-vs air handler motor.

    If you post the model numbers of both the condenser (outside unit) and matching indoor coil, someone can check the performance and btu numbers for you.

    Good luck.
    Last edited by gary_g; 08-01-2008 at 04:14 PM. Reason: Added 14 SEER comment

  11. #11
    Join Date
    Jun 2008
    Posts
    80
    Quote Originally Posted by volpone1a View Post
    dac122,

    Thanks for your help. It made much more sense the 2nd time around. According to the spreadsheet, I should only spend around $142/month for electric with this system. Even with electric rates going up in 2010 (estimated by about 50% more than now) our monthly electric bill would be approx. $203/month. I consider that acceptable. Much better than the oil prices being what they are and will probably continue to be. BTW, what do you think....should I go witht the single stage HP or the 2 stage? Thaks again!
    Keep in mind you have estimated COP and estimated weighting.

    The COP number you can get by checking perhaps Goodman's website where you can download COP numbers for their different SEER models and tonnage. You can then perhaps average your expected lowest COP and highest. I don't endorse Goodman, its just the only website I know that freely documents their COP numbers.

    To get some idea on weighting your HP and backup run times throughout the season you could try posting another thread. I'd love to see what everyone thinks.

    I would now ask for 14 and 15 SEER quotes.

  12. #12
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,741
    Rheem/Ruud has always been a reliable unit.
    Their heat pumps are made sturdy, easy to service, and give a good temp rise in heat mode.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  13. #13
    dac122, gary_g, and beenthere,

    Thank you all for your help. It has been invaluable. If y ou think of anything else that may be of use, please feel free to reply to this thread. Thanks again!!

Page 1 of 3 123 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event