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wet_dog_soup

Replacing 26YR Old HVAC - need Guidance!

Wet_dog_soup
9 years ago

Hi all,
I have a 65 yr old beach duplex near Wilmington, NC in need of a HVAC replacement for the upstairs unit. The 2nd story's 1988 Trane 2.5 ton 8 seer a/c & gas pack is getting long in the tooth (recharged 5 yrs ago and needs another, plus flakes of rust are coming off of the heat exchanger in the attic). Figured it might be time to take advantage of the better efficiencies before it dies and leaves me in a pinch (or does me in from CO!) The downstairs 1.5 ton unit is still purring along.

Thanks to reading your HVAC forums for the past month, I had a good idea of what I wanted before getting quotes from 3 respected contractors.

House:
a) 1008 sf w/ wood plank siding with no insulation in walls and minimal in ceiling
b) most of the dbl pane, dbl hung windows installed in '88 were replaced last year with mid+ grade vinyl windows last year
c) roof shingles were replaced 2 yrs ago with metal roof w/ ridge vent (now much cooler in attic - gable vent fans hardly came on this summer)
d) Manual J calc just over 30k btu

Liked Heat Pumps with their savings over LP gas, but since gas lines and venting is already in place and going straight HP would require new electrical to handle heat strip load, made sense to focus on hybrid systems. So narrowed it down to 3 ton 2 stage HPs with 80% var spd furnaces.
All prices are after manufacturer and utility co rebates.

Trane: 15.75 seer
XL18i 4TWX8036
TUD2B060
coil?
xl824 t-stat
$7845

Am Std: 16 seer
4A6H7036B1000A heat pump (xl18i w/o plastic top & 12yr warranty- same as Trane xr17?)
ADD2B060A9V3VA furnace (pretty much same as Trane?)
4TXCB032BC3 coil
ACONT824AS52DA (xl824)
$6650

Carrier: 16 seer Infinity components
25HNB636C003 Coastal Series HP
58CVA070-12 furnace
CNPHP4221ALA Cased coil
t-stat TP-PHP01 (you all like to rec the Infinity stat with Infinity components - maybe ask if he'll throw that in to seal the deal)
$6425

2 of the 3 contractors said existing ductwork looked fine and wouldn't rec changing it out ($1800 - $1900)

Thanks!
Don

Comments (25)

  • energy_rater_la
    9 years ago

    I must be reading this wrong.
    1.5 tons downstairs
    2.5 tons going to 3 ton for upstairs?

    on a 1,008 sq ft house?

    American Standard is heat pump?

    sounds off to me.
    can you please clarify?

    best of luck.

  • Wet_dog_soup
    Original Author
    9 years ago

    Sorry,
    When I reread it, that did come across a bit confusing.

    The house is duplex with separate upstairs and downstairs apartments. The new hvac system is for the 1008 sf upstairs apt.

    The 1.5 ton downstairs unit conditions approx 950 sf.

    The American Std HP # looks to be their Gold 17 series which I'm thinking is the same as the Trane xr17.

    Don

  • energy_rater_la
    9 years ago

    a bit clearer, but still twice the size hvac system
    for 58 sq ft more?

    there is no way you'd need 3 tons on 1008
    sq ft. the 2.5 is even oversized.
    ideally the same size for both floors.

    when a/c is so oversized you have short cycling.
    this doesn't allow the system to run long enough
    to remove humidity. high indoor relative humidity
    (RH) is a sticky cool. lowering the RH is the goal
    in hot humid climates. adding more tons isn't the
    way to go at all.

    before you make the final decision, learn a bit
    more about what you need, rather than just
    what the hvac co wants to sell you.

    two ton (at most) with variable speed air handler unit.

    mastic seal ductwork, and make sure that it is
    sized for the system.

    don't get caught up in the bigger is better stuff.
    bigger means higher up front cost,
    higher operating costs
    and shorter life of unit.
    all things you'll be paying for long
    after hvac co has gone on to oversize the
    next house.

    the method to sizing a system isn't rule of
    thumb. the method is manual J. this sizes the
    specific size for the specific house...not just
    a stand across the street & hold up fingers
    sizing.

    best of luck.

    and yes, American standard is Trane's sister
    company.

  • Wet_dog_soup
    Original Author
    9 years ago

    Thanks ER La, I'm right there with you!

    The 2.5 ton unit was struggling in the heat of summer (it is 26yrs old), so I was hoping that a new unit with new windows and cooler attic temps might be able to be downsized from the current 2.5t to 2 ton. (too bad these mfgs don't make a 2.5t 2-stage HP)

    Yesterday afternoon I went back to the two contractors that did Manual J's. Not wanting to really "contest" their calculations, I asked if we could downsize to a 2 ton unit if I added blown insulation over the old thin rockwool insulation in the attic.

    And I like your suggestion of new mastic on the joints if we are to reuse the existing ducts.

    Don

    This post was edited by Wet_dog_soup on Thu, Sep 25, 14 at 10:02

  • tigerdunes
    9 years ago

    Find out the cost to upgrade electric service for a 7 KW heat strip on a separate circuit.

    Gid rid of propane altogether. Now is the time.

    Average winter lows for Wilmington are above freezing.

    IMO

  • tigerdunes
    9 years ago

    For Energy rater...

    The cooling load Upstairs for a beach condo located in Wilmington most always will be higher than a similar sized downstairs area. I do not want to be borderline in cooling. Possibly a 2 ton but I would want to see facts supporting this.

    Man Js are a great tool but good common sense is just as important especially for Southern coastal locations.

    IMO

  • Wet_dog_soup
    Original Author
    9 years ago

    Tiger,

    do you rec deleting the propane because it's not cost effective (+ equip cost, +complexity, and reliability of components) for those few weeks when heat strips would kick in (below 35 deg?). Or is it more the Pain in the A factor and safety?

    I ask because I would still need to have the LP tank & lines for cooking.

  • tigerdunes
    9 years ago

    I don't like propane period where there is a good alternative both in cost of fuel, tanks, and especially a reasonably mild winter location like yours.

    There would have to be a very strong reason not to get rid of propane altogether. I have not seen it yet.

    IMO

  • weedmeister
    9 years ago

    In general, propane and electric heat strips are going to cost about the same to operate.

    My guess had been you had such a large system upstairs because you had a large heat load coming from the attic. Seems to be true. You could do a lot to reduce you AC needs by re-insulating the attic. It would be more cost effective over time.

    It would also be worth knowing your electric rates (complete) and your cost of propane.

    I have a 2.5 ton single stage HP with a variable speed blower (DC area). This does an excellent job removing humidity since the blower runs at low speed for several minutes when starting up. I personally believe that 2-stage units are not necessary for humidity removal and that a variable speed blower can do a lot of the job by itself.

  • tigerdunes
    9 years ago

    Not meaning to disagree with Weed and his post above but I will have to.

    I don't know the fuel rates but I made what I believe to be some reasonable assumptions.

    Electric rate $.10/kwh at 2.60 COP which I believe to be quite conservative.
    Propane fuel $3.00/gal at 80% eff, pay attn here, OP was quoted the 60 K XV80 furnace.

    Results are as follows.


    Cost per 100,000 btu of useable heat
    Electric baseboard: $2.64
    Heat pump: $1.13
    Propane: $4.10

    I'll let the results speak for themselves and will be glad to update if I know the exact rates plus any costs related to propane tank. Keep in mind, the furnace and heat strips would be rarely used because of the relatively mild winters.

    IMO

  • Wet_dog_soup
    Original Author
    9 years ago

    You were close on energy rates, but it's even a wider discrepancy.

    Duke Power: $.94/kwh (although they've asked for a rate hike)
    LP: $4.30 / gal

    So the HP is far cheaper to operate than the gas furnace. But how do you factor in the expense and frequency of the heat strips coming on during the winter?

  • Wet_dog_soup
    Original Author
    9 years ago

    Whoops!
    Did I miss that "electric baseboard" is actually heat strips?

    In which case electric heat strips are still only 1/2 the cost of LP?@#!

    D

    This post was edited by Wet_dog_soup on Thu, Sep 25, 14 at 15:20

  • tigerdunes
    9 years ago

    New comparisons numbers...

    Cost per 100,000 btu of useable heat

    Electric baseboard: $2.48
    Heat pump: $1.06
    Propane: $5.87

    Note that straight electric resistance heat(strip heat) is less than 1/2 cost of propane.

    And you can't really factor the frequency of need for backup heat r supplemental strip heat because that is all weather dependent. You know that that electric will be cheaper than propane significantly.

    The decision here is really a no brainer. Find out the cost to upgrade your electric service to handle a 7-10 KW heat strip.

    IMO

  • Wet_dog_soup
    Original Author
    9 years ago

    Holy cow!

    Thanks for laying it out so simply.

    This is turning into a real no brainer when you add in my electric service has spare capacity (and room in the panel).

  • tigerdunes
    9 years ago

    Now to get the size of system correct. I would not go with 3 ton, go either 2 or 2 1/2 ton. Add the TAM7 var speed air handler and correct stat and you are there.

    IMO

  • Wet_dog_soup
    Original Author
    9 years ago

    I'll go back and ask for revised quotes based on a straight HP system.

    From what I've read on this forum, you really like the var spd air handlers for comfort and efficiency.

    What about the HPs being single or 2 - stage?
    I appreciate Weedmeister's input that a lot of humidity can be addressed by the VS blower. I don't mind a little extra $ for comfort & efficiency, but I wouldn't want it to be at the cost of reliability.

    Trane xr15 vs xr17
    Amer Std Silver15 vs Gold17
    Carrier - looks like I'd need to stick with the Infinity16 to get the "coastal" version

  • energy_rater_la
    9 years ago

    I have 15 SEER Heat pump with vs ahu.
    propane for stove & water heater.
    best move I made was getting away from
    propane for heat.

    variable speed air handler unit keeps RH
    between 52-55%.
    I only hooked up half of my heat strips & only
    once has vs ahu gone into high speed. both times
    last winter...when we had 3 weeks of freezing temps.

    this is where I was heading with you op...but
    tiger dunes did it very well!

    just like you want to mastic seal ducts, air seal the
    ceiling/attic floor before insulating. air will still
    move from attic into conditioned space through
    the insulation. this will de-rate the insulation value
    & not let insulation perform at its R-value.

    caulk is a great air sealer.
    buy clear caulk with a long life.

    btw...lot of difference between 26 year old
    unit's efficiency & the ones you are choosing
    between.

    best of luck.

  • tigerdunes
    9 years ago

    Is this living area rental, vacation, or year round property?

    While you have not mentioned your budget or use of property, I think two stage equipment for a small zone is a waste of money. I would be looking at XR15 or XR16 single stage Tranes.

    Same available from sister company Am Standard. I would have to look up models if interested.

    I think Trane/AS hold up better in a coastal environment.

    IMO

  • Wet_dog_soup
    Original Author
    9 years ago

    I live in the upstairs unit that's getting the new HP and rent out the downstairs (downstairs a/c still functions fine;)

    I was leaning 2-stage thinking it would be better for humidity control. Since this was for my unit, I didn't mind paying a little more for comfort and efficiency.

    If you suggest ditching it, I'm good with that.

    p.s. The contractor quoting Trane was almost 20% high, so I was just going back to the Amer Std and Carrier contractors

  • tigerdunes
    9 years ago

    I would add insulation to your attic if needed.

    Keep in mind that 2 stage only comes in full ton sizes. A 3 ton for your upstairs unit would be ridiculous.

    So for Am Std HPs, I would recommend the single stage Heritage 15 in either 2 ton or 2 1/2 ton. If 2 stage then 2 ton Heritage 17. See below.

    5021088 Active Systems AMERICAN STANDARD HERITAGE 15 AMERICAN STANDARD, INC. 4A6H5024G1 *AM7A0A24H21 725 23600 13.00 15.50 21600 9.00 13000 1 HRCU-A-CB 189 441 Yes

    5021984 Active Systems AMERICAN STANDARD HERITAGE 15 AMERICAN STANDARD, INC. 4A6H5030G1 *AM7A0B30H21 950 31600 12.50 15.00 30000 9.00 18900 1 HRCU-A-CB Yes 261 662 Yes

    5771531 Active Systems AMERICAN STANDARD PLATINUM XM AMERICAN STANDARD, INC. 4A6H7024A1 *AM7A0B30H21 940 735 25800 13.00 17.00 25000 8.50 15200 1 HRCU-A-CB Yes 188 584 Yes

    IMO

  • Wet_dog_soup
    Original Author
    9 years ago

    1) Would I be cooling deficient going with the 2 ton units since my Man J came in at just above 30k? (although I am going to blow additional insulation in the attic)

    2) The 13 eer/17 seer of the Gold17/(Trane XR17?) is enticing and it does give 25.8k btus - but is it more problematic with it's 2-stage compressor?

    3) gold XV (Trane XL824?) t-stat?

    4) Am I reading the Carrier website correctly that the "coastal" version is only available in the Infin 16 or the Comfort 13 (lower ratings than I'd prefer)?

    Sorry for so many questions, but this has been a great (and frustrating) learning experience!

  • udarrell
    9 years ago

    Here in SW WI even when there was a high priced shortage; which they are adding storage to guard against; on January 31, 2014; unit price per gallon was $2.319.

    A little less than 100,000-Btu per gallon @91,500-Btu. but I use it in a 95% furnace & like it over fuel oil that I used to have.

    Here, some times Propane is around $1.75 a gallon; hopefully this heating season it will not go above $2.00 a gallon.

    Electric rates are .1046-KWH, or just under 10.5 cents a KWH.

    I'll let you do the figuring...

  • tigerdunes
    9 years ago

    Not certain what the point is for previous post.

    Yes, propane prices vary based on region. Generally they track fuel oil prices.

    And second, Wisconsin and Wilmington, NC are two entirely different areas of the country both location and climate.

    There is no economic justification for propane use either for main or backup heating use for this homeowner.

    IMO

    This post was edited by tigerdunes on Mon, Sep 29, 14 at 5:07

  • tigerdunes
    9 years ago

    Your biggest challenge is getting sized correctly.

    Get that attic insulation taken care of.

    I think both Trane and AmStd are better choices for coastal locations. I also prefer same over Carrier/Bryant because of heat pump electronic demand defrost feature.

    You have the big picture along with my advice. Don't think I can add anymore. You are beginning to over think everything possibly because of TMI.

    Good Luck.

    IMO

  • Wet_dog_soup
    Original Author
    9 years ago

    "TMI"

    Spot on!

    I'll get it done ;)

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