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Community and Q&A

Total HVAC Replacement System

Mike Kolder | Posted in Mechanicals on

Hello folks..  I hope your all doing well during these uncertain times..

My 3 ton A/C compressor went to ground in my 1700 sq’ split foyer home in Iowa City 5A.  It has a finished basement, but the attic is a accessible truss system. The furnace, carrier infinity 58MVP080, and york 3 ton split system were installed in 99.  The capacity is fine and I wouldn’t dare reduce it any further (4 ton down to 3 ton and 100k 80% down to 80K 96%).  Considering the natural gas furnace has performed flawlessly except for a main ECM blower module failure which I repaired with a $4 thermistor, I’m tempted to only replace the condenser and A-coil depending on how severe the burn out is.  But Ive also considered a total replacement, since the system is 22 years old.

Ive been out of the furnace replacement business for 26 years and haven’t kept up with the latest and greatest.     What options do I have, or what would you do considering I plan on selling it within 5 years?


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  1. Paul Wiedefeld | | #1

    Heat pump is an easy recommendation, with or without a furnace included. Key feature is multi stages - could be 2 stages or hundreds. I’d be shocked if your heat loss needs the full 80k x 96%. You could likely use the heat pump for almost all of your heating.

    1. Mike Kolder | | #2

      Thanks Paul..

      But I'm skeptical.. Because the two people I know who installed one in my area weren't happy..

      My infinity puts out 75K and when it's -47 degrees during the polar vortex, I need it!! I don't dare go lower because I set it colder to 55 when I go to work and it runs a long time to catch up.

      1. Paul Wiedefeld | | #3

        Easy, keep a furnace/electric strips for the polar vortex days, heat pump for the other 99.5% of days. No real need for a setback energy-wise, just personal preference. The staging helps with comfort.

        1. Mike Kolder | | #4

          Thanks for bringing the heat pump option up.

          So your suggesting the heat pump at 18 cents per kWh might be cheaper to heat with than NG, or less emissions?

          1. Paul Wiedefeld | | #5

            Possibly cheaper to heat with vs. NG, but that depends on the marginal cost of gas, electricity, and the outdoor temp. Every utility seems to structure their rates differently.
            Definitely less emissions, but that will also depend on outdoor temp.
            If your electricity rate is really $.18/kwh, solar would save you a bundle.

          2. Expert Member
            Zephyr7 | | #6

            Heat pumps move heat rather than making it directly (just like an air conditioner, but in reverse), so you have a "coefficient of performance". All that means in practice is that you get more BTUs out than the equivalent BTUs of electrical energy you put in. It's not magic -- it's just scavenging the "extra" from the outside air. That's where heat pumps can save money, and they CAN be cheaper than natural gas heating to run at times.

            Regarding emissions, that's more complex. Much of the new generation that has come online in the last decade or two has been new natural gas fueled generation, not any kind of renewables as some would like you to think. What that means is that going "all electric" often means you're actually using natural gas indirectly, through a power plant miles away. To really know if your new sytem has a benefit in terms of lower overall emissions, you have to know your local generation mix, system losses, and a bunch of other stuff. It's not accurate to just think "all electric" means "no emissions".

            BTW, you should check with your utility co to see if they have any other rates that might save you some money. I'm on a "time of day" rate, by choice, which saves me around $20-30 per month on average. This works because I use more power when I'm at home nights and weekends, and the time of day rate is cheaper at those times and more expensive (compared to the regular flat rate) during the day when I'm at work. There are usually also "space conditioning" rates that might save you some money on electricity used to run heating or cooling systems. You want to get your utility's "rate book" (which should be publicly available) to see what they offer.


  2. Mike Kolder | | #7

    I "get" how a reversing valve turns my inside coil into a condenser.. But what Ive always had a hard time figuring out is what my kWh rate is.. I use mid america energy and I'm in the east zone in Iowa City.

    Guess I'll have to call them..

    1. Patrick OSullivan | | #8

      > But what Ive always had a hard time figuring out is what my kWh rate is

      It should be clearly spelled out on your bill. Make sure to add the distribution and generation numbers together (each may be called something else). Sometimes utilities give you a 'price to compare' (for the purposes of engaging a 3rd party energy 'provider') but that isn't the full price you pay, which is actually what you care about when doing energy source calculations.

  3. Paul_Iowa | | #9

    I live up in Decorah and heat about 2000 square feet with a 3 head, 3 ton ductless multizone fujitsu cold climate ASHP. 2/3 of the house is 1850s solid masonry and the other 1/3 an addition I added two years ago. It worked surprisingly well during the cold snap this past February. We ended up using the forced air gas furnace for about three days, mostly to heat the unfinished basement that was getting dangerously close to freezing.

    I have a 9.5kw solar array and went into winter with about 4500kwh of electricity banked. That lasted till February 10th, at which point we bought from the utility (Alliant) through the end of the heating season. In all we spent about $180 in electricity for the heating season. If I had to guess, I think it used about $900 in electricity for the entire heating season.

    I know MidAmerica's power mix is way better than Alliant's (which is potentially the world's most retrograde, pathetic monopoly in existence), which comes mainly from coal/gas supplied by Dairy Land Power.

    ASHPs work in this climate, so capacity per se shouldn't be your biggest concern. Best of luck!

  4. Jon R | | #10

    > only replace the condenser and A-coil depending ... the system is 22 years old.

    When switching to R410A, better to replace the lineset too.

    With my numbers, a heat pump is less expensive to run only when it's above about 45F outside.

  5. Mike Kolder | | #11

    >With my numbers, a heat pump is less expensive to run only when it's above about 45F outside.

    Thanks Jon.. There are 5 months each winter below average of 45, yet only 3 months between average 68 and 45. Must be why heat pumps are more popular the further south your located.

    Me paying less than 12 cents kWh and even less in the winter means it would take me over twenty years to break even on solar panels. The solar panel calculator I used said I payed more than twice as much. And after watching Michael Moore's "Planet of the humans" which was removed/censored from youtube/google since it doesn't fit the ceo Sundar Pichai's narrative, I question if solar equipment really does require more oil to produce than it saves.. Its hard for me to believe anything anymore.

    I'll need to buy new AC equipment in a refrigerant transition period.. Turns out R410A is just as bad as R22 regarding global warming potential, so the EPA will start phasing 410A out in 2023 probably when the patent expires. Its to early to tell which refrigerant (R32?) will replace 410A. What a shyt show and thanks Mr dupont! Rant over.

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