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Multi-zone minisplit installation time

user-7167677 | Posted in Mechanicals on

I’m hoping to get some feedback on an install time estimate I recently received from an HVAC contractor. Here’s the background:

We are building a 3,300 sqft 2 1/2 story house in Southern NH (Climate Zone 5A) that will be well insulated, simple shaped, & tight. There will also be a 1,100 sqft attached guest house/future in-law suite that we may or may not finish now, but are planning our HVAC around. I ran all the head load calculations myself and have ready through endless submittal sheets for Mitsubishi & Fujitsu and proposed the full design myself. Having met with the contractor, he agrees the load calculations are good & the system will work well for the house.

The system:
1st Floor (open concept) – PLA-A12EA7 ceiling cassette
2nd & 3rd Floor – PEAD-A12AA7 ducted with short runs to bedrooms
Guest house/in-law suite – PLA-A12EA7 ceiling cassette
Outdoor condenser – MXZ-3c36NAHZ

There’s nothing particularly complicated about the install and I will be handling all the ductwork myself. Given that it’s all open construction and centrally located with short (<25′) lines, I expected it to be just under 1 day of work for 2 installers. The estimate for labor came to 120 hours. Profit, overhead, & materials are spelled out separately, so the labor estimate should be purely labor. I’ll be meeting with him in a week or two to talk through the labor breakdown, but I’m hoping to get a sense here if I’m completely off my rocker and the 120 is completely normal or if this is worth digging into more with the contractor.

I will also note, that he has been completely professional through the whole process, immediately suggested a manual J (before knowing I had done this already), and his cost breakdown is done in a way that seems both transparent and fair to me. If the number wasn’t so dramatically different than what I was expecting, I would feel no compulsion to dig into it any further.

Does anyone have thoughts around what might be contributing to 120 hours worth of work that excludes system design, load calculations, & ductwork?

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Replies

  1. Expert Member
    Dana Dorsett | | #1

    120 hours for three zones would be a full 4o hour person-week per zone.

    If you're the one doing the ductwork and custom framing to accommodate mini-duct cassette and ceiling cassettes it seems excessive. If they are on the hook for the custom framing (none of it fits between standard joist framing) there is quite a bit more involved.

    The PLA ceiling cassettes are really designed to be suspended from the structural ceiling in a suspended ceiling for the finish ceiling, rather than jammed into framing, which you'd have to do in most residential applications. (I've only seen one cassette of that type installed where it just slipped right in- right into the already framed out location formerly occupied by a whole-house fan, with minimal modifications needed for mounting.)

    It might be cheaper (and definitely less labor) if you can use MLZ-KP12s instead of PLA-A12s, since the MLZ-KPxx are specifically designed for installation between 16" o.c. joists:

    https://nonul.mylinkdrive.com/files/MLZ-KP12NA_For_MXZ_MULTI-ZONE_SYSTEMS_Submittal-en.pdf

    http://meus1.mylinkdrive.com/files/MXZ_SERIES_MULTI-ZONE_INDOOR_OUTDOOR_COMBINATION_TABLE-en.pdf

    If the PEAD-A12AA7 can be hung below the ceiling joists and you do the build-out of soffits (and access hatches) around it that could peel something off it too.

  2. Expert Member
    Akos | | #2

    Mike,

    It took me about 4 day to install a dual zone (one wall mount and one ducted unit) into an existing house. This included working with a finished interior and running all the ductwork to 4 bedrooms. I'm not a pro, but installing these is not that hard especially into a new build.

  3. DavidfromPNW | | #3

    you should fire them immediately and find a reputable company. I've had two four head mini split systems installed, both consisted of two ceiling cassettes and two wall mounts. Both units were installed in a day. The first was installed in a day by one person, the second installed in a day by two people.

    Not sure were 120 hours comes from. Sounds like someone sees and opportunity to high gross you.

  4. user-7167677 | | #4

    Thanks for the feedback. I’m definitely going to hear him out, but I’m glad to know that I’m not the only that estimate sounds high too (I originally emailed him back thinking he had accidentally added a zero onto the end of the labor estimate).

    Dana, you’re right that the numbers pan out to be a very long time per person (by a factor of about 10 in my mind). I had opted for the PLA because it’s performance is better than the SLZ units and it can work in 360*, which better suits our floor plan than the MLZ. Our floor joists will be 24” OC and I designed the location to allow for a spacing consideration where we were already going to need another beam to support an upper floor wall, so creating a 36” wide box wouldn’t be too difficult. The HVAC contractor wouldn’t have to deal with any of that. Same with the PEAD: I already have the location sorted out and it will be hanging from the ceiling in the laundry room, so again, an install that should be quite easy.

    That said, I am currently rethinking some of this after reading through some previous postings by you (and others) about the poor turn-down ratios in the MVX units. I’ve spent days reading through all the techical manuals I could find and all the literature, as well as talking with Mitsubishi technical support, and the conclusion I’m reaching is that the units are able to vary their output once the outside unit’s threshold is reached, but that the minimum is still REALLY high for a high performance home. The alternatives I’ve found are less than ideal, so I’m still chugging through scenarios and documentation. I appreciate the feedback here and in all the other forums you comment on. You’re perspectives have spurred many interesting forays into the world of heat loads and HVAC systems over the past few months.

    Akos, that’s good to know that you did a dual zone with the finished work in 4 days by yourself. That puts things in perspective a lot.

  5. Expert Member
    Dana Dorsett | | #5

    It's unusual for quotes to be broken down that way, since it invites nit-picking and haggling over line items. I usually see it as a fixed number, take it or leave it, but with room for some haggling over changes from the original proposal.

    Was there a reason for going with the bigger/wider/deeper PLA series rather than SLZ ceiling cassettes of comparable capacity?

    http://meus1.mylinkdrive.com/files/SLZ-KA12NA_For_MXZ_MULTI-ZONE_SYSTEMS_Submittal.pdf

    vs.

    http://meus1.mylinkdrive.com/files/PLA-A12EA7_For_Multi-Zone_System_Product_Data_Sheet-en.pdf

    1. user-7167677 | | #6

      The two things that pushed me towards the PLA series over the SLZs were:
      1. Efficiency: HSPF = 13 vs 9.6, SEER = 27 vs 15.4
      2. I-See sensor: the ability of the PLAs to scan the room and direct airflow & adjust temperatures as needed. I first saw this as a superfluous upgrade, but the more I've thought about, the ability for the mini-split to scan the room with an IR sensor and take temperature readings seems incredibly useful.

      The quote was broken out more transparently than any I've received from other companies. I thought about posting it here, but wasn't sure of the ethics/professional courtesy involved in something like that?

      David, thanks for the sentiment. This company is the most reputable company around. We have a very high end energy efficient home builder in the area and this is the company they use. The quote for the materials is all on level (and cheaper than others have quoted), as has been all my other interactions with them. I'll post back here after meeting with him if there are any insights into the hour quote that would potentially be useful to others.

      Thanks everyone!

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