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jhschlak

2 HVAC systems for home - ideas?

Jeff
9 years ago

Hello,
We are looking to replace our two 18 yr old Trane forced air HVAC units in our 3800 sq ft home near Cleveland, Ohio. About 2200 sq ft ground floor has a 100,000 btu furnace and 3.5 ton AC and second floor has 80,000 BTU furnace and 2.5 ton AC. We have large trees that provide great shade in summer. I added blown in insulation in attic to make it about R-35. House was built in 1996.

A heat pump intrigues me, but does it make sense in a two HVAC unit household? The upstairs HVAC is only on in the evening to heat/cool and the same in the early morning. The downstairs unit is always on when we're at home. Does it make sense to install a heat pump for the ground floor, and a traditional unit for the second floor? Does the advantages a heat pump provides vanish since the second floor is not always heated/cooled at all times?
Thanks for any advice! I'm sure I missed some critical piece of info. Please let me know if I did.
Jeff

Comments (16)

  • mike_home
    9 years ago

    What fuel do you use with the current furnaces? If is natural gas then adding heat pumps may not save any money. Posting your electric and gas rates will help determine this.

    If you use propane, then the heat pump will likely save money. The rates would confirm this.

    If a heat pump is more economical to operate then it does not matter if the upstairs unit is not used that often.

    I think the current sizes of your furnaces and AC condensers are too big. You should look for a contractor who will perform a load calculation.

  • tigerdunes
    9 years ago

    "I think the current sizes of your furnaces and AC condensers are too big. You should look for a contractor who will perform a load calculation."

    I agree.

    IMO

  • Jeff
    Original Author
    9 years ago

    Thanks for the replies.
    Yes, we are using natural gas.
    Electricity rate:$0.05690 per Kwh
    Natural gas rate: $0.60190 per Ccf
    Is loadcalc.net a reasonably accurate way to estimate BTU's needed?
    If I don't go heat pump route, I would definitely spend the money on an efficient HVAC for ground floor, but should I just get a more basic unit for the 2nd floor?
    Thanks,
    Jeff

  • tigerdunes
    9 years ago

    No HP for first floor, just go high eff 2 stg 95% eff var speed furnace paired with min 15 SEER AC condenser.

    For 2nd floor, 80% two stage var speed furnace paired with either 15 SEER AC or HP condenser.

    I don't believe the rates you posted are all inclusive costs. Please dbl check.

    You will need filter box cabinet and true two stage thermostat for each system. Best matching evap coils, too.

    If reusing lineset, size should be verified to manufacturer spec for new condenser.

    IMO

  • Jeff
    Original Author
    9 years ago

    Looks like my total natural gas rate this past month was $0.77294 per CCF. For electricity the rate of $0.05690 per Kwh is correct + $36.00 per month distribution related charges.
    My existing AC line has a hole, so I'm thinking I probably should switch out the line sets.
    I am leaning toward American Standard Equipment. Opinions?
    Thanks,
    Jeff

  • tigerdunes
    9 years ago

    Load calc is needed for this zone. And AmStd HVAC is high quality.

    IMO

  • Jeff
    Original Author
    9 years ago

    I have to ammend my prior post: ground floor AC unit is 3 ton (not 3.5 ton).
    Thanks,
    Jeff

  • Jeff
    Original Author
    9 years ago

    Got my first quote:
    Ground floor: Gold ZM 95% variable speed furnace 100,000 BTU $2500
    AC: Platinum XM Series 18 SEER 3 ton $3175
    All furnace install quotes include: new thermostat, any needed gas line, metal work, electrical box, electrical whip, labor and taxes. 10 yr parts warranty, lifetime heat exchanger warranty and 1 year labor.
    All AC install quotes include: new thermostat, new copper line set, air conditioner pad, disconnect, electrical whip, labor and taxes. Platinum XM AC series has 12 yr compressor warranty, 10 year parts warrant, 10 year coil warranty and 1 yr labor warranty.

    I have various Gold and silver series AC and furnace quotes from same guy that top out in the 2800 dollar range for gold line for both AC and furnace unit for 2nd floor space.
    What do you think?
    Thanks,
    Jeff

  • tigerdunes
    9 years ago

    The sizing on furnace is absolutely absurd and stupid. If the truth were known, you might could get away with a 60 K.

    And any two stage furnace needs a true two stage thermostat that controls staging not a timer on furnace control board or a thermostat that works off software algorithm.

    TD

  • Jeff
    Original Author
    9 years ago

    This is just the first quote. I have another more knowledgeable (I think) company coming out this afternoon and another on Monday. I will ask them to calculate a manual load.

    Is the Nest thermostat considered a true two stage thermostat? Or would a Honeywell Pro thermostat be a better choice?
    Thanks,
    Jeff

    This post was edited by jhschlak on Fri, Jun 20, 14 at 11:45

  • tigerdunes
    9 years ago

    I would not recommend the Nest. I would recommend HW Prestige VP IAQ.with or without WIFI.

    TD

  • Jeff
    Original Author
    9 years ago

    I bet that thermostat doesn't come cheap!

  • mike_home
    9 years ago

    The second generation Nest thermostat is $250. I don't think the first generation could control 2-stage equipment. If you are going to spend that kind money, then buy one of the several Honeywell thermostats that are appropriate. If you want to save some money you can drop the WiFi feature. It is not necessary in my opinion.

  • Jeff
    Original Author
    9 years ago

    Latest quote:
    2 gold 96.7% 2 stage variable furnaces 80 and 60 btu
    2 silver 16 seer AC units 2.5 ton and 3 ton
    2 aprilaire media filter model 2410
    2 Honeywell touchscreen tstats with wifi
    Run new 8 wire tstat wire two both floors
    Replace existing AC lines
    Using american standard coils for AC units
    Fixing some ductwork that is about to fall
    $12,500
    What do you think?
    Jeff

  • tigerdunes
    9 years ago

    I would not have the Nest thermostat, any model, period. It appears the Nest is built more around the lifestyle of the homeowner over the operational functionality of the HVAC system.

    Read thread below if you haven't already.

    Where will furnaces be located?

    I need to see the model numbers of the AC condensers and evap coils to give you an informed opinion.

    Post back.

    IMO

    Here is a link that might be useful: Nest and Ecobee

  • Jeff
    Original Author
    9 years ago

    Not getting nest. I posted that I'm getting honeywells.