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Heating & Air Conditioning
sunfeather

Estimates for ductless A/C all over the place on size and cost.

sunfeather
6 år sedan

I've tried to compare all of our estimates and it is very confusing. We have open floor plan in living/kitchen/dining. We've had recommendations that vary regarding BTUs:

1 (30K) Mitsubhishi or Daikon

2 (15K) one in LR and one in Kitchen (Mitsubishi)

2 (18K) one in LR and one in Kitchen - Mitsubishi)

1(24K) in LR and 1(12K) in kitchen - Carrier

We have also gotten various information about the noise from the condensate pumps.

Some recommend one compressor unit and others recommend two. I'm very confused.

Kommentarer (5)

  • socalgal_gw Zone USDA 10b Sunset 24
    6 år sedan

    We had one mini condensate pump just beneath a wall unit that went on every few minutes and was very noisy/annoying - it was removed and it turned out the condensate from that unit could drain by gravity. We have another condensate pump under the house for 2 other units. It is much larger capacity and only goes off about once an hour. I can hear it but it isn’t bad.

    sunfeather thanked socalgal_gw Zone USDA 10b Sunset 24
  • sunfeather
    Författare
    6 år sedan

    Socal - what brand did you have installed?

  • socalgal_gw Zone USDA 10b Sunset 24
    6 år sedan

    Mitsubishi. We love it. Installed in the bedrooms of a 1932 house that didn’t have room in attic or crawl space for ductwork. Installed by a Mitsubishi Diamond contractor. We got two quotes that were very, very close in price so we went with the company that was willing to work with us on the location of the outdoor unit.

    sunfeather thanked socalgal_gw Zone USDA 10b Sunset 24
  • PRO
    Cool Flat Roofing MA
    6 år sedan

    What is your square footage??? MOST LIKELY you won't need anything more than 6K btu for kitchen and 9K btu for Living room!!!

    I researched this for very long time, and almost bought into "mitsubishi" hype. Also, many HVAC guys were saying I need 18K BTU for a 600 s.f. split level loft. (for me, 9k unit was MORE than enough!)

    After talking with "Green Energy" guys, and doing my own heat loss calculation, I realized that most HVAC guys either don't know what they are doing OR want to get more money from you and cover their butts.

    1) 99% of HVAC contractors oversize your system ... just in case you have a super cold/hot day, where your load is not enough

    2) Bigger systems yield more $$ for installers.

    In my case I went with 9K BTU (instead of 18K) Fujitsu RLS3HY (HY for high heat model)

    My heat pump was installed in late Dec 2017, and was immediately put to the test with 2 weeks of 10F temperatures. It performed marvelously, heating 600 s.f. without breaking a sweat! My model will actually perform at 100% heating capacity down to -5F (same size Mitsubishi will be at 63% capacity at same temp).


    https://www.youtube.com/watch?v=KqWDNPyiwm0



    As for cooling - Fujitsu has highest in industry 33 SEER (same size 9K Mitu is 30.5 SEER)


    My advice:

    Go with 2 separate systems at opposite ends of your house. Your open floor plan will allow hot / cold air to move around.

    Lower capacity systems have MUCH higher efficiency that Dual Zone / Multi Zone units (single compressor). For example, a 9K BTU single zone will have 30 SEER, and 18K will be 20.5 SEER (data for high end MITSUBISHI) ... Cost wise, you will pay almost the same for two 9K units!

    Also - DO NOT OVERSIZE. Do heat loss calculation and be aggressive. Heat pumps are VERY efficient.

  • ionized_gw
    6 år sedan

    Advantages of two systems over one include redundancy in case of breakdowns and easy running with a backup generator at partial capacity. In addition, with two units of identical size you throttle back to half the capacity compared to one when running one since some "cool" will spillover into the less used area. You can drop back to about 30% of overall capacity with a typical compressor. If you are driving two indoor units of 12,000 BTU with one outdoor of 30,000 BTW and demand drops back to 6000 BTU, you only get down to 10K with the single outdoor unit and that results in cycling. With two systems, (12K) you can throttle back to 4000 BTU with one system in your sleeping area with no cycling and better comfort, efficiency and humidity control.

    One disadvantage of two completely separate systems is mechanical complexity. You have twice the parts to fail. Another might be placing the systems. Many people don't have very much outdoors to work with.

    The rule about avoiding oversizing at all costs might need to take a break with variable speed heat pumps. In some cases a little oversize might be better. At full output, they are less efficient than at partial output, Depending on lifestyle, you might spend less money on fuel with an oversize system. It is difficult to calculate what is best. Better controls allowing for more efficient, slower recovery from set backs are overdue. Boiler manufacturers did it years ago and heat pump manufacturers should get on the ball.

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