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PostPosted: Sat Nov 28, 2009 8:03 pm 
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Hi all,
I've been looking for a single AC/ventilation solution for a new studio I am building in my backyard. It's 12'x16' with 8ft walls and peaked ceiling. It's got a 4" thick concrete foundation with 18" deep footings w/rebar. The framing is 2x4 @ 16" O.C. The ceiling beams are 2x8's.

My idea came after seeing a diagram in Rod's book (page 130). I was very interested in buying one of those split-ductless systems until I found out that they didn't actually provide any fresh air to re-oxygenate the room. I'm specifically talking about Mitsubishi's Mr Slim split ductless system (the 9500 btu model). From what I've read, it seems they do have two air lines: one that takes the air out of the room (Return Air) and then another line that brings the newly cooled air back into the room (Supply Air). But it's a closed system. What if I customized one of the lines and opened it up to some fresh air.

So my idea is... what if I splice in a "fresh air" vent/pipe into the Return Air line on the outside of the building but before it reaches the condenser unit to be cooled and sent back inside the building.

It would be just like Rod's diagram on page 130, only it would be ductless and wouldn't have the "mechanical room".

My main concern is would the system actually suck enough fresh air from the newly spliced "Fresh Air Supply" vent/pipe? Would the vacuum of the airflow system be enough to bring in fresh air from outside? I'm thinking of this like a siphon; the system would still suck the warm air out of the room and blow in cool air but the open vent (in between the outside wall and the condenser unit) would allow fresh air to be "siphoned" into the system to be cooled and then blown into the room.

What do you guys think? If this would work then I'd just need to find a de-humidifying solution and I'll be set.

As I'm writing this I get the feeling it is too easy of an idea to work.

Thanks for any advice on this,
-Doyle


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PostPosted: Sun Nov 29, 2009 12:20 am 
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Unfortunately the line sets you are talking about are not air supply and return but carry r-410a refrigerant. Both lines are pressurized and you could not add air to them. There are a few units that have an air intake but the tend to be the ceiling units like this one http://www.ajmadison.com/cgi-bin/ajmadison/18XHS72.html

What I did was use mini split systems plus an ERV (or you could use a HRV) with duct lines running to each room. also be aware that there is a 30% tax credit on some mini split units (see my post half way down viewtopic.php?f=2&t=1929&start=120 )

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PostPosted: Tue Dec 01, 2009 8:24 am 
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Jester,
Ahhhh.... that makes sense. Thanks for links on the ERV idea. I love all the photos you posted. Very helpful.

For anyone else interested in a Mr Slim idea... I got this reply from Mitsubishi. I thought fact that it has a dehumidifier built-in was interesting. The way I'm looking at this, I need 3 elements out of a HVAC system 1) conditioned air (cooling/heating), 2) fresh air (so I don't suffocate), and 3) de-humidifier (so I don't have water condensing on the walls). This Mr Slim seems to take care of 2 out of 3.

From:
"Tienken, John" <>
...
No, that model does not bring in outside air. Actually, none of our wall mounted units have outside air capability.
All of our units do dehumidification while in cooling. Our units also have a "Dry Mode" which is a dehumidify-only mode.

John Tienken
Mitsubishi Electric USA, Inc
HVAC Advanced Products Division

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Last edited by realdoyle on Mon Dec 07, 2009 10:37 am, edited 1 time in total.

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PostPosted: Tue Dec 01, 2009 9:40 am 
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Location: Sweden
I am also looking for a cooling fresh air solution. Is it really that much more expensive with a central unit? I mean if I gonna use split systems I will need at least 3 units, for control room, live room and so on. Wouldn't a central unit be more efficient?
Also are there good split units that you can put inside the walls or ceiling and then build a muffler around them, so that they are silent?


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PostPosted: Tue Dec 01, 2009 11:10 am 
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If you need several mini splits you might be better with a central system. I would have gone with a central system but I didn't have room for the air handler and the ducting.

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PostPosted: Tue Dec 01, 2009 1:19 pm 
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realdoyle wrote:
From:
"Tienken, John" <jtienken AT hvacDOTmeaDOTcom>



Remind me not to give you my email address :)

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PostPosted: Tue Dec 01, 2009 8:38 pm 
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Location: Sweden
A central system seems more appealing, but I have gotten some offers from companies in Sweden which are down right scary amount of money (15000 EUR for the unit only exl. VAT and installation). Does anyone know a good system, that doesn't brake the bank? My studio will be 140m2, average 5m height divided into several rooms.

As I understand it central systems are so much more expensive because of the amount of air they have to move. I have calculated that if I am going to cool the rooms I would need something in the order of 3000m3/h of air circulating with 8-12 degrees under temperature.
My fresh air need for a big session is about 400m3/h, so it is a big difference. But I guess that I would have to have the 3000m3/h of circulation inside the rooms (using split systems) anyway if I am going to get the cooling that I want?

Have I understood this correctly, or can someone explain it to me?


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PostPosted: Tue Dec 01, 2009 8:53 pm 
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Quote:
I thought fact that it has a dehumidifier built-in was interesting


Every AC dehumidifies the air. When water (water is in its steam form in the air) temperature drops it condensates, thats why you have to drain all AC units, unless they have a system where they let the water drip down on something hot and re-enter the air (frost free fridges uses this system by letting the water drip down onto the hot compressor).

This all depends on your climate, but in Sweden where it is cold a large part of the year, to dry air is a big problem. It makes instruments go out of tune, it makes singers trouts soar, and can even crack pianos! So at least for me, large use of AC means that I also will be using a humidifier to restore the natural humidity in the air. But if your sessions consists of a big band, then the moisture of the musicians will probably be more than enough to humidify the air...


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PostPosted: Thu Dec 03, 2009 8:01 pm 
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xSpace wrote:
realdoyle wrote:
From:
"Tienken, John" <jtienken AT hvacDOTmeaDOTcom>



Remind me not to give you my email address :)



Oooops. :oops:

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PostPosted: Sat Jan 09, 2010 6:47 pm 
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The temperature is your most dangerous enemy in making your studio comfortable. Use dehumidifier to protect your expensive sound equipments, tapes, CD, etc from harmful corrosion and contamination effects of moisture. It also eliminates bad odors coming from molds and mildew.

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Last edited by freak.zanjay on Sun Jan 17, 2010 6:50 pm, edited 3 times in total.

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PostPosted: Sat Jan 09, 2010 10:59 pm 
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Quote:
I'm going to suck enough air back up through a pipe. And I think it would just be the cost of fans to draw in the enough air to keep the house cool. Therefore, there will also be a “fresh-air” vent from the outside. Basement Dehumidifier
I doubt that would work for a serious studio. The pipe will probably act as a resonator and will not silence the airflow anyway, plus a simple vent or pipe without a proper silencer will destroy your isolation. You'd need a rather large pipe, and the fans would have to be synchronized. And most home dehumidifiers that I've seen are very noisy. I wouldn't want one of those in my studio!

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PostPosted: Tue Feb 02, 2010 8:11 am 
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I have another idea I'd like to run passed the community here.

After consulting with others on this forum who are also doing a single structure, one-room studio like mine, I realized that my fresh-air solution may be hampered by the lack of space in the walls for duct. My studs are only 2x4 and I'm concerned that this will not allow enough airspace within the duct once the duct liner is installed. I can't extend the duct out on the inside because I will be using RSIC-1 clips with hat channel.

My idea is to build the duct enclosures on the outside of the building. See sketch-up.

The external duct enclosures would need to be designed to withstand the elements but is the idea a good solution for my fresh air situation?

Thank you for your help.
-Doyle


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PostPosted: Tue Feb 02, 2010 8:19 am 
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My friend has just done this in his studio.
But only put silencers on the intake! So there is some noise coming in.
But the fans are quite.

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PostPosted: Tue Feb 02, 2010 9:51 am 
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Ahhh... I see. I'd have to essentially "soundproof" the external duct enclosures on the outside so they wouldn't leak sound into my studio. :(

Any other ideas?

Ooooh wait, I just had an epiphany... :idea:
my ceiling studs are 2x8's!!! Could I go back to my previous idea (running the insulated ducts behind the drywall, between the studs) but just do it all in the ceiling and not in the walls? Having 2x8 ceiling rafters should allow me the room to run appropriate sized fresh-air-in and stale-air-out ducts behind the ceiling drywall.

The only immediate draw back to that idea is that the roof might get hot and heat up the fresh air that is coming in and battle with the a/c unit.

Thoughts?

-Doyle


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Last edited by realdoyle on Tue Feb 02, 2010 10:58 am, edited 1 time in total.

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PostPosted: Tue Feb 02, 2010 10:51 am 
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I'd vote for the outside cover up job. You have more flexibility as far building your baffles. Best chance for noise control, in and out.


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