Mini-split unit on roof

I would like to place a mini-split unit on a flat roof. Planned to mount it on the parapet wall but an architect said since it was a small unit (~120 lbs), the DOB would be fine if its placed directly on the roof on top of a ‘concrete board’. The roof joists are wood. What is a concrete board and are there any drawback to placing it on the roof like this?

krobertson

in General Discussion 6 years and 9 months ago

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Guest User | 6 years and 8 months ago

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Hi Joe @HomeAirInc, per ashton13’s recommendation I have been trying to get a quote or a site visit from you guys but you have been very slow to respond to my emails. Hope Sam comes down off that ladder soon to reply : )

lindsaydwyer

in General Discussion 6 years and 8 months ago

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Ashton, once again, thank you for the compliments.

If there is any questions regarding mini-splits, installations, or HVAC related topics, please feel free to email us at INFO@homeairinc.com, with “Brownstoner,” in the subject line, and we will respond quickly – sometimes emailing or calling Sam directly is a little complicated, as he maybe in the middle of an installation or service call, and on a ladder.

I will be more then happy to answer any questions I can or get you pointed in the right direction.

-Joe
Office Manager
Home Air Inc.

smadargolan | 6 years and 8 months ago

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Sorry for the delay – was out of town for a few days. We have two of the M-series wall-mounted units on one floor (https://innovations.mitsubishi-les.com/en/m-series/msz-ef) and one in-ceiling unit on the other (https://innovations.mitsubishi-les.com/en/m-serie/sez-kd). The ducts for the ceiling unit don’t have to go far – we were able to locate it right in the middle of the floor plan above a new bathroom, and from there it branches into three adjacent rooms. The longest run is maybe 10-12 feet. We are extremely happy with all of it – we wish we could have done ceiling units on both floors, but we have low ceilings and exposed joists, so that was a no-go. They are all silent (the in-ceiling – literally) or nearly, and do a great job. The outdoor units are super quiet as well – we put them in the front on the ground bc we didn’t want to have to see them in the back yard (frame house – Sam said if we wall mounted them there would be vibration, and roof mounted, obv per this thread, is complicated, plus they would have had to pipe through our rental unit, and the runs may have been too long, etc) and I was concerned that they’d be noisy, but they barely make any sound at all. I have to underscore my recommendation for Sam at Home Air – we were getting an error code on the remote panel for the ceiling unit, so I emailed him last night at about 9pm. He called me back within a half hour and talked me through a few things to check (power cycling the breaker reset the system and got it going again). Had that not fixed it, he would have come by tonight to check it out in person.

jimhillra | 6 years and 8 months ago

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> @booisgolden
> Hey Jim
Hey. The steel beams should be big enough to carry the weight of the condenser on their own, without the help of the wood beams. The “mini beams” sound like they were put there to distribute the weight of the condenser over several joists, or just to lift the unit off of the roof. Both are good ideas, but neither is acceptable if you have wood joists holding up those steel beams.

m_holmes925

in General Discussion 6 years and 8 months ago

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Hi ashton13,

Great to hear the minisplit worked out for you.
If you don’t mind me asking, what exact line of products from Mitsubishi did you use? We are doing our renovation and had ‘SEZ’ units spec’d initially, but where told to go with ‘city multy’ as our planned duct runs are presumably too long for SEZ to handle. However, we suspect the ‘city multi’ might be much more expensive. We would be very grateful for any info on this.

m_holmes925

in General Discussion 6 years and 8 months ago

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Hi ashton13,

Great to hear the minisplit worked out for you.
If you don’t mind me asking, what exact line of products from Mitsubishi did you use? We are doing our renovation and had ‘SEZ’ units spec’d initially, but where told to go with ‘city multy’ as our planned duct runs are presumably too long for SEZ to handle. However, we suspect the ‘city multi’ might be much more expensive. We would be very grateful for any info on this.

smadargolan | 6 years and 8 months ago

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We put in a system with two outdoor units, one in-ceiling unit ducted to three rooms on one floor, and two wall units on another floor (low ceilings and exposed joists, so that was pretty much out only option) and it was about 15K. Now, this was part of a near-gut renovation, so the walls were open, and that price did not include plastering etc.

I recommend reaching out to Sam Chiu at Home Air (347) 880-4256 sc@homeairinc.com for a quote – our installation was tricky, and he was really helpful in figuring out solutions.

And FWIW – we did Mitsubishi, and the in-ceiling unit is literally completely silent. My wife had mixed feelings about jumping into this expense vs just doing window units, and she thanks me every day for insisting. The wall units are quiet too, but not silent, and since we had no choice, we’ve gotten over seeing them. Also, the heating function works pretty well (there have been some recent threads on the matter; we just have the regular system, not the hyper heat) – better than we’d expected.

greenworks | 6 years and 8 months ago

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Hey Jim Hill, steering this back to original topic if you’re still around –

so, when you say mounted to something noncombustible, does that mean as long as the beams roof joists are also reinforced with steel?

Once this topic popped up, I looked at a ton of photos of roof installs and found many with the condensing unit on the roof resting on mini beams (technical term) that were only a little bigger than the condensing unit.

When I see that type of install, does that mean the joists below were also reinforced or should have been? Otherwise, if there’s a fire, that type of mounting only insures that something heavier will fall on top of the firefighter, yes? Hope this makes sense.

adam_dahill | 6 years and 8 months ago

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Make sure to come back to this thread when you complete the job to compare costs. There are a lot hidden costs with A/C installation. Steel Dunnage, Plaster work, skim coating, painting etc.. the costs vary depending on how “hidden” you want the units to be

Guest User | 6 years and 8 months ago

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Thanks EJR and booisgolden. That range is to be expected and much more manageble. I had combed previous threads but I’ve noticed even in recent months contractor prices have risen. For instance, I contacted a roofer back in March how much it would cost to replace the roof and maybe some of the plywood – it was 12K back then. Just contacted the same guy again and his price jumped to 20K. It’s amazing how much everything in the construction industry increases in a short period of time, while the average typical salary doesn’t.

greenworks | 6 years and 8 months ago

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There’s a few threads recent threads where people discuss cost in depth if you search for mini split, even within the last year. That’s where I got my ballpark numbers.

EJR | 6 years and 8 months ago

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I have 2 condensers plus 4 air handlers (1×3 and 1×2). Each of those installs was about $14k all said and done, so I imagine something in the $25-30k range would be correct. The cost will be higher if you are doing anything substantial to the roof to support the units. One of my units is on a concrete pad in my backyard, the other is on the parapet on my roof.

Guest User | 6 years and 9 months ago

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We need 6 air handlers and 2 condensing units. I realize 14K is low – maybe the GC didn’t include the equipment. Yes we are doing ducted mini splits in the ceiling with floor grilles because we don’t like seeing the boxes on the walls. What is a more reasonable price including equipment?

adam_dahill | 6 years and 9 months ago

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14k is insanely low. Maybe for one or two air handlers mounted on the rear wall. It depends on how many air handlers and compressors you need. Are you doing a ducted mini split hidden in ceilings etc?

Guest User | 6 years and 9 months ago

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Has anyone gotten any good quotes on installing mini splits throughout a brownstone? A contractor previously quoted me 14K while an HVAC contractor quoted me 103K. I find it mind boggling to receive such wildly different numbers!

jimhillra | 6 years and 9 months ago

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Either on or mounted to something non-combustible. The roof joists can be reinforced with steel, but the steel alone must be able to support the unit if the wood joists burn. This is all to prevent a big piece of machinery dropping through the roof on top of a firefighter during a fire, so think of it in those terms.

krobertson

in General Discussion 6 years and 9 months ago

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I asked FDNY about the placing the split units directly on the roof and the inspector pretty much said as long as its approved by DOB its fine. But if the unit is over 3 HP, I’ll need to have a Equipment Use Permit. I think he probably meant 3 Tons, not HP — which comes out to 36,000 BTU.

Guest User | 6 years and 9 months ago

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I am also getting a mini split system and met with two roofers last week. One roofer said he would simply reinforce the joists below and put the condensers on top “no problem”. The other roofer said he wants nothing to do with the securing of the mini splits and that our HVAC contractor should take care of that. Does anyone have a photo of steel dunnage spanning between party walls that does not look too hideous? Thoughts?

krobertson

in General Discussion 6 years and 9 months ago

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Is the mounting method usually drawn/specified on filed DOB plans? My draft plan only shows the location and model #. I would hate to place it on the roof and then fail inspection because DOB says it needs to be on the parapet wall.

Key reason I’m considering the direct on roof option is it can be recessed 2-3 feet from the wall to be non-visible from the ground.

@booisgolden good point on FDNY, I’ll try giving them a call and ask.