Air Conditioner 'Cut Out' (Final Answer?) :)

ENIGMACODE

ENIGMACODE

New member
Hello? :)

In regard to my last thread here:
http://www.homerecording.com/bbs/showthread.php?t=125501

I really do appreciate all of your comments ....

I was just looking for perhaps one final blessing in regard to my approach that I outlined in my last thread to the problem of adapting a conventional non-ducted air conditioner in a small all-purpose rehearsal room ....

In the past I gathered up all of your valuable contributions, and took heed as I implemented some of your points and precautions in regard to construction.

To recap:
The room is simply an all-purpose rehearsal room built within the basement of a tiny row home...
The room is floated over concrete with FREE standing walls - NO direct contact with the existing structure.. Drywall will be 2 layers of 1/2" on the cieling, and 5/8" on the walls - I'm going to follow Rod Gervais's tips in regard to overlapping, and caulking etc.. All and all the construction is generally acoustically 'sound'

What I'm asking:
Because of budget and space limitations, I CANNOT justify the expense of a ducted system ....
Sooooo - Since I'll have to CUT through 2 outside walls in the rear for a conventional wall unit, I will take EVERY precaution to design #2 SEALING Gasketed Doors, that will be CLOSED when the AC unit is NOT operating... AND YES I CAN LIVE WITH THIS .... :)

Sooooo with ALL of this said, am I still on track?
Will this 'Cut Out' have a tendency to 'NEGATE' all of my OTHER efforts to design an acoustically tight room???? OR will the project STILL be worth the effort (given all of my precautions?)

Best Regards
Michael Fraticelli
rocknroll@ucwphilly.rr.com
 
(Nor sure whether to reply to this thread of the other one.

The efficiency of your air handling will be far more compromised by the lack of an exhaust route than by adding some ducting to the input.

You will need air conditioning in this room more than the rest of the house. The room will be very well insulated and contain heat producing equipment and people.

If when practicing folks feel forced to prop the door open and run the air conditioner just to get some air flow then you REALLY have no isolation.

What is a solution like the attached diagram going to really cost you? A few batts of rock wool. You can even make some plugs for the vents for when you do not want to run the ventillation. But you will want to run the ventillation.
 

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ANY penetration in a wall, be it as small as an outlet box, or as large as a window unit A/C is going to comprimise isolation. All you can do is try to minimize that by sealing the perimeter.

Innovations posted a good alternative, but most all window unit A/C's have the controls on the front pannel. I'm not sure how you'd get to those in his diagram.

You could cut out for the A/C as planned, then build a HEAVY HARDWOOD frame to fit exactly around the A/C perimeter, and seal it all up with acoustic caulk.
 
To: Michael Jones & Innovations - 'AC Cut Out'

"Innovations posted a good alternative, but most all window unit A/C's have the controls on the front pannel. I'm not sure how you'd get to those in his diagram."

Not to mention that:
'conventional thru the wall AC units' were NOT designed to have it's air pumped thru any obstructions like 'home-made' duct work etc... I fear that this will greatly impede the unit's capacity to cool as it was designed for and even create condensation WITHIN the wall cavity .... possibly even SHORTEN the life span of the unit ...

"All you can do is try to minimize that by sealing the perimeter."
YES- The perimeter of the 'CUT OUT' (Both inside and outside)
PRECISELY MY INTENT ALL ALONG!

I do appreciate this diagram - but for a hobby rehearsal room, I don't think it's gonna work well with a 'conventional thru the wall air conditioner' "It may greatly impede the unit's capacity to cool as it was designed for and even create condensation WITHIN the wall cavity .... possibly even SHORTEN the life span of the unit"

http://home.ucwphilly.rr.com/livesound/stuff/ac-drawing-2.jpg

Best Regards
Michael Fraticelli
rocknroll@ucwphilly.rr.com
 
ENIGMACODE said:
"All you can do is try to minimize that by sealing the perimeter."
YES- The perimeter of the 'CUT OUT' (Both inside and outside)
PRECISELY MY INTENT ALL ALONG!
Click to expand...

Yep!
Keep us posted and let us know how it works out for you.
(Construction photos are always appreciated!) ;)
 
To Michael Jones

:o Hey Michael :o

I think this is the final blessing that I was looking for...

Although I thoroughly appreciate 'Innovations' idea of creating a 'home-made' ducted system out of a 'conventional thru the wall air conditioner', I assume from your last response that you may possibly agree with me in regard to my comment: ''conventional thru the wall AC units' were NOT designed to have it's air pumped thru any obstructions like 'home-made' duct work etc... I fear that this will greatly impede the unit's capacity to cool as it was designed for and even create condensation WITHIN the wall cavity .... possibly even SHORTEN the life span of the unit''

So then I will persevere and trust that my 'OTHER' efforts to constuct this room as accoustically tight as possible will NOT be for nothing....

"Am I prepared to turn the unit OFF after the room cools? Sure why not?
Will I occasionally leave the unit running on those real hot days with those homemade trap doors open? Sure why not? (As long as sound doesn't get out of control) *And in the dead of winter there may be little reason to open those hatch doors except to get a little air, then CLOSE em up again ...

Do I have your blessing? :)

Best Regards
Michael Fraticelli
rocknroll@ucwphilly.rr.com
 
Last edited:
ENIGMACODE said:
"Innovations posted a good alternative, but most all window unit A/C's have the controls on the front pannel. I'm not sure how you'd get to those in his diagram."

Not to mention that:
'conventional thru the wall AC units' were NOT designed to have it's air pumped thru any obstructions like 'home-made' duct work etc... I fear that this will greatly impede the unit's capacity to cool as it was designed for and even create condensation WITHIN the wall cavity .... possibly even SHORTEN the life span of the unit ...

I do appreciate this diagram - but for a hobby rehearsal room, I don't think it's gonna work well with a 'conventional thru the wall air conditioner' "It may greatly impede the unit's capacity to cool as it was designed for and even create condensation WITHIN the wall cavity .... possibly even SHORTEN the life span of the unit"

http://home.ucwphilly.rr.com/livesound/stuff/ac-drawing-2.jpg
Click to expand...
As for the front panel controls I was planning on just setting them and controling the unit with a switched outlet.

Maybe my approach is being influenced by my climate. Maybe you can sit in a completely airtight highly insulated room with a lot of electrical gear rebreathing your own air for an extended time and not feel hot, clammy and lightheaded from reduced oxygen. There is a reason why the building code requires ventilation of a minimum number of air changes per hour in all windowless spaces, even in Philadelphia.

As far as the warnings against attaching your own ductwork to the AC unit...The reason that the manufacturers give that warning is that some fool would make a homemade boot and try to force all the air into a four inch diameter piece of flexible dryer vent twenty feet long. That adds a lot of friction and backpressure. The baffled plenum that I illustrated has no constriction and gentle changes in direction. It would add miniscule backpressure. ON THE OTHER HAND your plan to have the AC blow into a completely airtight room with no exhaust route would add HUGE quantites of backpressure and strain on the unit. By giving no route for the air to escape you might as well just be duct taping the vents closed for all the air movement you will get

(And the diagrams that I drew were meant to be down the middle of the plenum, you would use a couple of more pieces of rigid insulation at the studs to enclose the sides)

As for adding condensation inside the wall...all of the condensation occurs inside the unit, where the air is the coldest and likely to fall below dew point. Once it is outside the unit it has already warmed slightly and will be above dew point.

Sealing up around the perimiter of the AC is not going to buy you much because the AC unit itself is a hollow metal box with a few pumps and coils inside.

In addition the AC unit itself is a huge source of noise, particularly low frequency vibrations. By mounting the box OUTSIDE of your OUTER wall rather than in the MIDDLE of your wall you have more routes for that sound to dissipate away from your space rather than be caught IN your space..

And one other thing I seemed to notice...your diagram talked about wanting to 'completely fill' the space between the walls...bad idea. Air is the middle part of a mass-air-mass barrier for a reason.
 
Here's a slightly different approach, I asked Rod Gervais about it a while back and he thought it would work fine -

http://www.johnlsayers.com/phpBB2/viewtopic.php?t=644

You would need a mass-air-mass wall for the inner wall, then the small room acts as a "chiller" room (wouldn't need to be very large) - the AC would cool the chiller room, then you duct cool air into the studio through baffled double-wall ducting, and return it to the chiller room the same way. You would need access to the chiller room though, to set the controls - also, several of the newer window units are electronic controls and default to OFF when powered down, so you'd need to get a more basic model that still has manual control knobs... Steve
 
To Innovations - Thanx for all your conributions

I do appreciate all these comments.....

Ya know it's just so frustrating - it appears the more information one provides, the more complex and confusing the whole damn thing turns out...

What folks don't pick up from these posts (always missing from lack of actual conversation), is 'REALITY' relative to a particular dilemma.....

You mentioned:
"ON THE OTHER HAND your plan to have the AC blow into a completely airtight room with no exhaust route would add HUGE quantities of backpressure and strain on the unit."

I don't know what you're talking about here???

I NEVER intended to mount this 'thru the wall unit' OTHER than what it was intended for.... Exhaust will come THROUGH the unit as it was intended - just like it would be in a window ..... In fact they are made for thru the wall or thru the window ....

I currently have an 18,000 BTU unit thru my rear dining room wall - I installed it years ago and it works great - what am I missing here?????

And your comment:
"By mounting the box OUTSIDE of your OUTER wall rather than in the MIDDLE of your wall you have more routes for that sound to dissipate away from your space rather than be caught IN your space.."

At first glance this sounds like a good thing???? What am I missing here?????

And I was wondering why you didn't answer my questions on the graphic??
http://home.ucwphilly.rr.com/livesound/stuff/ac-drawing-2.jpg

Ok Ok - I get it - I will NOT fill that void completely and allow air space - but didn't you see that I was asking you about that very topic in the graphic?

"In addition the AC unit itself is a huge source of noise, particularly low frequency vibrations"

YES YES - I understand BUT this unit will NOT be functioning continuously....
As I mentioned before - I AM PREPARED TO OPEN AND CLOSE A HOMEMADE HATCH EACH TIME THE UNIT GETS POWERED UP ..... what's the big deal???

My friend has a similar studio in his basement - and after a session, and during breaks, he allows some outside air flow through doors etc...
It works just fine ....

As I've mentioned over and over - these row homes are OLD, and tight to work in .....

This all-purpose rehearsal room project is a hold over for me for the next 3 1/2 years - at which time I will retire to a small SINGLE home and build a BETTER studio with all the amenities...

Split Systems? I'm VERY familiar with them - As I've said - NO Money - and No Room outside for the condenser...

I hope that you can still address some of these questions - as I may consider your ducted approach inside the wall - and I do realize that we're not talking about a lot of money here - but I'd have to rely on a double pole 220 volt switch to throw the unit directly into cool mode without having access to the front controls...

Building codes?

I've been a Licensed Electrical Inspector for the City of Philadelphia for thirty years - (as my profile indicates) I work with BOCA certified Building Inspectors all the time .. :)

Perhaps I'll hear from you again? :)

Best Regards
Michael Fraticelli
rocknroll@ucwphilly.rr.com
 
Forget Everything I Said!

I just realized that there is a MUCH better alternative for you!

http://www.shopping.com/xPC-Sunpent..._Manual_Control~SRID-0c1dd6083e958bbe4110b724

Rather than having huge back-to-back doors through the wall you need only one 5 inch diameter hole! and since it has a 5 foot flexible hose the holes between the walls can be offset by that amount! Rather than having big complex doors a 5 inch circular plug, like a big cork, could plug the hole on each end.

I feel foolish for not thinking of this sooner.
 
Michael,

Sorry it took me so long to get to this - but I have been trying to work out in my mind the actual effect here...........

It will be important that this hatch of your be as good as it can be - when I say this picture this as a sound isolation door - same construction - same gasketing.

If your wall was an STC 65 and 16' x 9' in size - and you cut a 3' x 2' hole through it - (This is averaged STC - it really is frequency dependant - but we don't need to deal with it at that depth) and then this hole ends up with an STC of 25 - then your wall will wind up with an STC of around 38.79.

Get the picture?

We all need fresh air - and the portable unit doesn't handle that - so do it like you're describing - but make certain that your hatch gets the job done.

Rod
 
Rod Gervais said:
We all need fresh air - and the portable unit doesn't handle that - so do it like you're describing - but make certain that your hatch gets the job done.

Rod
Click to expand...
The portable unit does exhaust air, so as long as there is a route for fresh air to get in you will have ventillation. So you could add a 5 inch passive intake elsewhere, (and snake the duct so that the holes in the two walls did not have to be opposite each other).

So you would end up with two much smaller openings offset from each other rather than a huge hole straight through the wall! When you are putting holes in a wall having them not be opposite each other makes a big difference.
 
Innovations Force of Nature is the 'Winner'

Hey Hey :D

After Innovations posted this option last nite on the board, I researched it
further - it appears the 12,000 BTU unit will do the trick:
http://www.priceground.com/su12btupoair.html

I read some of the reviews and the unit sounds pretty good!
A bit noisy when the fan is on High, but as I've said ALL
ALONG, this is a 'hobby rehearsal room', and after the room
cools down, the unit can be turned off.. :)

This option will NOT require me to cut such a Hugh
gapping hole in all my good handy work...
This option eliminates the necessity for spending soooo
much money for a split system that is PROHIBITIVE
for such a small project, in such a small basement, and
in such a small row home ..

In Philadelphia, I'll need it about 30% out of the year.
During the winter, when the unit is not needed, out the
door it will roll on it's castors for storage during the winter! :)

'Innovations', and others have CORRECTLY stated repeatedly:
A large opening 2' X 4' cut directly THROUGH both walls for
a conventional thru the wall AC Unit, is gonna be a tough
cookie to seal properly! IF AT ALL! :(

So ya see, 'perseverance', 'valuable contributions by others', and
plain ole' research pays off again!

In the meantime, I'd like to ask Rod Gervais to take another look
at my newer design (inspired by him), to help reduce the
transmittal of sound from NEW structures to the existing structure:
http://home.ucwphilly.rr.com/livesound/stuff/combo-gas-2.jpg
(note that the only material that touches both surfaces is 'rubber' -
there are NO screws piercing into the NEW structure)
Rod - whaddaya think? :)

Thanx again 'Inovations Force of Nature', and 'Rod Gervais'
Best Regards
Michael Fraticelli
rocknroll@ucwphilly.rr.com
 
Almost as important as the two holes being smaller, the ability to snake the duct through the space so that the two openings do not have to be straight through will help a lot.

I am guessing in your climate there will be a lot of time where you can do fine with just a little ventillation. You might consider after running the exhaust and intake ducts through the wall you might consider putting some small low speed fans on the outside for ventillation alone. You could even put them on a dimmer switch to dial down the speed and noise as needed.
 
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