A/C dilemma...New mini-split? Dedicated ducted system?

4036 Views 13 Replies 7 Participants Last post by mhutchins, Jan 26, 2019

petew

Discussion Starter · Jun 17, 2012

The weather is hot (that happens every year about this time). My existing mini-split is not cutting it. Is can't keep the room cool and it's too noisy to use.

Does anyone make a mini-split unit that is quiet? Would a dedicated ducted system be better? I know the answer to the second question.

Here's a partial floor plan of my theater:

The existing mini split is located on the west (left) wall above the desk. The outdoor unit is straight north to the left of the window well.

I've considered putting a horizontal air handler above a dropped ceiling in the hall leading into the theater. Then I'd run ducts in the soffits that line the perimeter of the room. The area above the desk and projector is also framed down to the same level as the soffits so I can easily fit in duct work. The return air opening would be at the far end of the hall (not shown on the sketch). I'd also put a return air in the equipment area to pull cool room air in.

Here's a view of the equipment rack - the hallway is on the right.

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rabident

· #2 · Jun 17, 2012

I asked over on HVAC talk forum and the lowest noise mini split someone suggested for my size room was:

Quote:
Originally Posted by Crazy4thenucks

LG's new mini split, model; LS120HYV, 17dB on the indoor unit on low speed, and 28 SEER....is that quiet enough?

I was considering putting the mini-split in an adjacent room, then using a dead vent to exchange theater with the cooled room air.

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Roger Dressler

· #3 · Jun 18, 2012

Quote:
Originally Posted by rabident /t/1416163/a-c-dilemma-new-mini-split-dedicated-ducted-system#post_22141852

I was considering putting the mini-split in an adjacent room, then using a dead vent to exchange theater with the cooled room air.

That's similar to what I did. I used the SEZ series unit located in the attic space, above the bathroom adjacent to the theater. Then ran ducts in/out of the room. Works great and very quiet.

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petew

Discussion Starter · #4 · Jun 18, 2012

Do you think a unit like the SEZ series would be quiet enough to install in the hallway leading to the theater? It would be inside the theater space unless I decide to install a double door arrangement.

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Roger Dressler

· #5 · Jun 18, 2012

The unit has motors so it creates some vibration. Whether it is enough to conduct through the framing to be audible in the theater is not easy to say. Care would need to be exercised in mounting and supply/return and vent design. But it ought to be easy to make it quieter than one hanging on the wall inside the room. It uses the same outside compressor unit, BTW.

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Elill

· #6 · Jun 18, 2012

FYI - the bulkhead units fans aren't that powerful....I have just installed mine (no ducting yet) and I am hoping its powerful enough to push through a dead vent....not sure its going to be.

Our Daikin models are (have those installed in the bedrooms with longist duct runs)

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Roger Dressler

· #7 · Jun 18, 2012

^^ Yes, the flow velocity is not like a normal forced air AC system. I run my Mr. Slim (Mitsubishi) on medium speed (1 click below max) and it is enough to keep the room cool even with several people plus the PJ and amps/proc all inside the room.

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rabident

· #8 · Jun 19, 2012

One of the nice things about mini-splits is you have the option of a unit that can vary the "capacity" of the outside unit. Normal residential forced air systems are pretty dumb. The outside unit produce a certain level of btu extraction and the indoor coils will freeze up if enough air isn't passed over them. They can't, for example, run the indoor fan at a steady 25% and the compressor at 25%. The compressor is always running 100%. You can buy multiple compressors, or temporarily run the indoor fans at lower speed as coils head towards freeze up, but what would seem like basic intelligence is currently only available in commercial units and mini split systems.

I did a short stint as an expat in HK. There were mini-splits everywhere. Many have a sleep mode that will run the unit as quiet as possible. That would be good for HT. The only downsides I see is no provision for fresh air intake and if located in room I wonder about potential for rattles from the high SPL / very low frequency. Normally low frequency @ high SPL sound is many orders of magnitude more objectionable than any rattles it causes. HT is a rare case where we want to hear that sound, and would be bothered by a relatively miniscule vibration sound.

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Elill

· #9 · Jun 19, 2012

Anyone know anything about using in line fans to boost HVAC supplies (not just fresh air)?

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petew

Discussion Starter · #10 · Jun 19, 2012

I've got a neighbor that works for an HVAC supplier. I think they sell Fujitsu mini splits. I'll pick his brain and get a good installer recommendation from him. I'll report back...

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Bongani

· #11 · Feb 9, 2015

I would love to revive this thread if anyone is out there (or should I start a new one?). I am having go the Mini Split route for my HT as all my Regular Forced Air HVAC blowers and ducts are in the attic (Atlanta) not in the basement! I ran the Manual J numbers and have sized my mini splits for the entire basement and HT (and in doing so discovered I could not have tapped off the existing HVAC even if I had access to the main duct runs).

QUESTION
- those who have gone with mini splits in their HT...please give feedback on the thread or PM.
I'd love to learn from you what worked
- head unit in room or ducted mini split?
- manufacturer recommendation (Im keen on Mitsubishi)
- How did you solve fresh air issue? Did you supply separate air vent/s or did your head unit have a fresh air connection?
- Are the minis as quiet in a HT as you expected?

Any and all info will be most useful.

Thank you

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Bongani

· #12 · Jan 20, 2019

Bongani said:
I would love to revive this thread if anyone is out there (or should I start a new one?). I am having go the Mini Split route for my HT as all my Regular Forced Air HVAC blowers and ducts are in the attic (Atlanta) not in the basement! I ran the Manual J numbers and have sized my mini splits for the entire basement and HT (and in doing so discovered I could not have tapped off the existing HVAC even if I had access to the main duct runs).

QUESTION
- those who have gone with mini splits in their HT...please give feedback on the thread or PM.
I'd love to learn from you what worked
- head unit in room or ducted mini split?
- manufacturer recommendation (Im keen on Mitsubishi)
- How did you solve fresh air issue? Did you supply separate air vent/s or did your head unit have a fresh air connection?
- Are the minis as quiet in a HT as you expected?

Any and all info will be most useful.

Thank you

2019! Happy New Year!!

A whole lot of life happened between February 2015 (when I posed this question to the Community) and now!

I am reengaging my research as the basement is about to get started...

There are 4 additional years of potential people and builds that have gone the mini-split route...I welcome feedback on the above post's questions!

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BIGmouthinDC

· #13 · Jan 20, 2019

Ducted mini-splits with proper ducting are the quietest I never heard. You couldn't tell when it turned on and off, you need a separate room to house the air handler.

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mhutchins

· #14 · Jan 26, 2019

BIGmouthinDC said:
Ducted mini-splits with proper ducting are the quietest I never heard. You couldn't tell when it turned on and off, you need a separate room to house the air handler.

@BIGmouthinDC , do you recall the models used for the ducted systems?

Were they the compact ducted units like the SEZ Series like Roger mentioned above or did they use a more conventional air handler such as the SVZ Series?

Do you think the openings through the "bunker" for the ducting compromised the sound isolation vs. a more traditional mini-split? Do you think the loss of sound isolation could have been mitigated in any way?

Thanks in advance
Mike

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