GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Help with Mini split location and size

G D | Posted in General Questions on
Hello GBA community,
 
I’m trying to decide where to locate the mini split head in our 600 sq. ft. condo. I’m leaning toward Mitsubishi single zone either FH09NA or FH12NA. From what I read, the FH models have 2 vanes that can deliver air to 2 different locations. The airflow angles are 100° – 80° – 60° – 40°.  I would like to avoid installing a drain pump and thinking to use one of the existing drain pipes instead (from the old HAVC unit or the washing machine). Attached is the a floor plan with 3 possible locations. 
 
More details:
Climate Zone 5
Solid brick structure, row house with 2 exterior walls (SE and NW)
Htg/Clg 10500BTU/9500BTU @  outside db 13F/88F
Top floor unit, roof R-38
NW exposure doesn’t get much sun due to the narrow tree-lined street. I expect the cooling load to be lower than Manual J’s.
 
Questions:
 
1. Would FH 09NA be enough to cover the entire area?
2. What is the best location for a single head unit (see floor plan 1, 2 and 3)?
3. Would 2 heads FH 06NA connected to a single outdoor unit make more sense? 
 
Thank you
 
Gabriela
 
 

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.

Replies

  1. G D | | #1

    Any advice or suggestions will be much appreciated.
    Thank you

  2. MAheatpumpguy81 | | #2

    Hi Gabriela,

    I'm just a homeowner with some experience with Mitsubishi units, but I'll give you my two cents.

    I'd go with a single FH09NA in location 3. You don't wanna oversize and it is best to go with single 1:1 units rather than multizone units. Do you have any other source of heating as backup (although you probably won't need it, given your specs). It is looking like your home is a single floor... is that correct?

    Also, it may be worth doing something to increase air circulation between your bedroom and the main living space such as an exhaust vent that pulls air from the living space (like the Panasonic Whisper series) and undercut your bedroom door to give 1-2" of opening from the bottom of the threshold as the air return. Alternatively, you could have a little resistance heater in there, but that wouldn't help with cooling of course. Either way, I think your load is low enough that air circulation should help a decent amount with comfort in the bedroom and the main area managed by the mini split. Maybe you could do something with that interior bedroom window between it and the kitchen too.

    It'll be good to get others to chime in too to build a good consensus on this.

  3. Trevor Lambert | | #3

    1. Would FH 09NA be enough to cover the entire area?
    Maybe by the BTU, but based on the layout you're going to need supplemental heat in at least two rooms (three if you go with a single head instead of two). If the place was super insulated and airtight, it might be different, but based on your numbers it's not.

    2. What is the best location for a single head unit (see floor plan 1, 2 and 3)?
    3 looks the best, though not a lot of difference between that and 2. 1 is the worst, as more cool air will drift down the stairs before mixing in the living area.

    3. Would 2 heads FH 06NA connected to a single outdoor unit make more sense?
    I would say yes, but the cost difference is quite significant. It might even cost more than two single head minisplits.

    What is the heating/cooling you have now?

  4. G D | | #4

    Thank you for your feedback.

    MAheatpumpguy, it's a single floor with interior staircase.

    Trevor, we just bought the place and didn't move in yet so we don't know how it will perform. We had an inefficient ducted 24KBTU heat pump, the duct was leaking air into the ceiling, the register in the bathroom was blocked ...I could go on and on. Long story short,  we decided to remove the old system and go ductless. We met few Mitsubishi Diamond contractors in the Boston area, they all took pictures of the old system and sent us offers without performing Manual J calculations. Their estimates range between 14K and 30K, minimum 24K BTU, minimum 2 heads. Thanks to this website I started asking questions and ended up paying for an independent consultant to perform a proper Manual J. It looks like the load is way lower especially for cooling. We realize that if we go with one single head we would need to create a better airflow. So we're thinking to install a window between the kitchen and the bedroom that can also bring more light into the kitchen/living area. The pocket doors will mainly stay open and the transom window above the office door will help with airflow.
    Am I going in the right direction here?

    Thanks

    1. Jeff Wasilko | | #5

      If you need a referral for a good MA Mitsu contractor, we had a great project with Boucher Energy Systems. http://boucherenergy.com/

      They did a manual J (based on info we provided) and were the most accurate. We had other contractors do a Manual J on site and they were way off reality.

      We went from 6.5T of cooling to a 4T heat pump. Our cooling loads are well under 4T but that gives us the heating capacity we need.

      NETR also has a good reputation and only does split installs (no ducted). They may be worth a call depending on where you are.

  5. MAheatpumpguy81 | | #6

    Putting a 6k head in the bedroom is way too large for that space. Best to use a little space heater after improving air circ w/ the main space. I'm eyeing an Envi 500W wall mount unit myself right now for a similar application. You're on the top floor so you will get "free" heat from your downstairs neighbors. I wonder if the Manual J even considers this... your heat load may be even lower than the stated 10.5kBTU.hr. The trick will be to see if you can cool your bedroom in the middle of summer without an AC unit in there (or you could always just stick a tiny window unit in).

    Those quotes are too high, IMO. I'd keep shopping around. I got 2x multi-zone systems with 6 heads for $28k (along with the Kumo Station and full WiFi controls), which I think is still too high. You don't need to buy Mitsubishi either. There's a guy here who's had a great experience with a 12k BTU Gree that is rated to perform well in subzero temps.

    Also, make sure to get all your rebates... we have a ton here in MA. Don't forget the Alternative Energy Credits (AEC) from the Mass DOER.

    1. Jeff Wasilko | | #7

      MAheatpumpguy81 what was your experience with the AECs? I applied for our project. I understand the batch for our install date closed 2/15, but nothing has happened with our application. How long did it take them to get to yours?

      1. MAheatpumpguy81 | | #8

        Hi Jeff. I haven't done it yet. I actually just discovered the existence of them last week through poking around on the internet. My installer never mentioned them. I'm still on the fence about what to do because I can rip out my oil boiler to bump my payout up another $1400, but I dunno if I'm prepared to rip out my backup heat system yet.

        1. Jeff Wasilko | | #9

          Ahh. In that case I'll post here if my application ever moves.

          My contractor didn't want to deal with the AECs so I did it on my own.

          1. G D | | #10

            Hi, Just wanted to share some info about the APS Renewable Thermal program - thanks MAheatpumpguy81 for mentioning it. I spoke with CLEAResult, one of the aggregators, and it looks like homeowners can apply directly but the complete application needs to be submitted before the deadline for the quarter. For instance, for equipments installed in Q 1 you would need to apply by May. Small units such as Mitsubishi mini split (I mentioned FH09 or FH12) qualify for approximately 90 credits with incentive payment $7-$10/credit.
            Here is the link to the program https://www.mass.gov/guides/aps-renewable-thermal-statement-of-qualification-application#-application-instructions-

            Hope that helps

            Thanks

            Gabriela

  6. MAheatpumpguy81 | | #11

    Hi Gabriela,

    I wrote the Mass DOER following the info you just posted. Thankfully, I can still get my rebate even though my system was installed a year ago. Here are my questions and their response to them:

    QUESTIONS

    I recently found out about the existence of AECs for ASHPs. I have a whole house ASHP system (57.2k BTU/hr) currently supplying 100% of my home's heating and cooling needs (3500 sqft home). This system was installed by XXXXX in March 2019. My system displaced my 50 year old oil boiler for heating and an old central air system for cooling. I have two main questions:

    Is there a deadline for filing for these AECs? I ask because I understand that my AECs are worth more if I rip out my oil boiler, but I'm not sure I'm prepared to do that quite yet. Along those lines, what does removing the old fossil fuel system entail, regarding this rebate? Does it simply meant removing the oil boiler, or does the fuel tank and/or baseboards also need to be completely removed to qualify?

    Would you please recommend an aggregator for my area? I live in XXXX MA and am serviced by Eversource East. Also, is there a way to do this myself without an aggregator? If you, would you please provide a link to the application?

    RESPONSE

    We do have quarterly deadlines to apply for AECs, but if you miss the deadline, you won’t be disqualified, you would just receive your AECs a few months later. Removing your boiler will result in roughly a 30% higher incentive, since we apply a factor of 2 to ASHP systems that keep their non-renewable system, but a factor of 3 t those who have it removed. As long as you have the fuel tank removed, then you can keep the baseboards. I wouldn’t recommend working without an aggregator. We typically see across all our programs, those who chose to work without one tend to end up with a lower sale price for their AECs, resulting in a lower total incentive. We can’t provide a recommendation of who to work with, but we do provide a list of aggregators who work specifically in this program, see link below. I hope this was helpful and feel free to let me know if you have any other questions.

    1. G D | | #12

      Good to know - thanks for following up on this. CLEAResult has also suggested working with an aggregator due to the complexity of the application. Just keep in mind that the aggregator will charge a fee to do the work. Good luck and please keep us posted.

      Gabriela

Log in or create an account to post an answer.

Community

Recent Questions and Replies

  • |
  • |
  • |
  • |