Subject: Re: Strange HVAC design

From: [email-masked] (Richard Byrd)
Date: 20 Oct 1995 04:40:00 GMT

In <[email-masked]> [email-masked] (TMETHOD) writes:

>
>In article <[email-masked]>, [email-masked]
>(Richard Byrd) writes:
>
>>
>>Today I did an investigation at a multi-story story luxury
condominium
>>building (in Beverly Hills of course).  A resident on the top floor
is
>>intermittently getting odors from the floor below.
>>
>>Each condo has two A/C's in closets, with electric heat.  The closet
is
>>used as a return plenum.  In each closet there is a vent, going to a
>>shaft up to the roof.  I would assume that these are intended as
>>outside air intakes; on the blueprints they are labelled as exhausts
>>(no, I did not mis-read the prints).  With the A/C off, they do
>>function as exhausts; with the A/C on, air is pulled from the
"exhaust"
>>vents.  Obvious conclusion: When downstairs neighbor is cooking with
>>their A/C turned off, and upstairs neighbor has A/C on, they pull the
>>odor right in through the outside air / exhaust /
>>what-the-heck-is-it-anyway vent.
>>
>>Questions for all you oh-so-wise HVAC people: What is the purpose of
>>this vent?  Is there some code requirement involved?
>>
>>
>
>The question is whether the shaft was intended for fresh air or
exhaust.
>If it was intended for fresh air, then a motorized damper (open with
>either A/C) would be needed in each apartment to prevent reverse flow
>(into the shaft).
>
>If the shaft were meant for exhaust, then the closets should not be
used
>for a return plenum and the returns need to be ducted. Do the prints
show
>the closets being used as return plenums? It wouldn't be too
surprizing to
>find that someone saved a few bucks by not installing return ducts.
>
>Hope this helps.
>
>Gary
>

Thanks Gary.  The construction matches the prints; return plenum and
all.  They say the shafts are exhausts.

Wouldn't it be optimum to turn the shafts into outside air intakes by
putting a fan at the top of the shaft? Should prevent backflow whether
the A/C's are running or not, correct (if fan is sized right)?

Rich

---

From: [email-masked] (TMETHOD)
Date: 19 Oct 1995 18:51:19 -0400

(Richard Byrd) writes:

>
>Today I did an investigation at a multi-story story luxury condominium
>building (in Beverly Hills of course).  A resident on the top floor is
>Each condo has two A/C's in closets, with electric heat.  The closet is
>function as exhausts; with the A/C on, air is pulled from the "exhaust"

The question is whether the shaft was intended for fresh air or exhaust.
If it was intended for fresh air, then a motorized damper (open with
either A/C) would be needed in each apartment to prevent reverse flow
(into the shaft).

If the shaft were meant for exhaust, then the closets should not be used
for a return plenum and the returns need to be ducted. Do the prints show
the closets being used as return plenums? It wouldn't be too surprizing to
find that someone saved a few bucks by not installing return ducts.

Hope this helps.

Gary

================================================
Everything should be made as simple as possible, but not simpler.
     -Albert Einstein-

Gary R. Lloyd CMS
TECH Method Training
Trouble Shooting Books/Software
Tel 313-671-0188  Fax 313-676-9262

---

From: [email-masked] (TMETHOD)
Date: 22 Oct 1995 20:11:45 -0400

In article <[email-masked]>, [email-masked]

>all.  They say the shafts are exhausts.

Are there other exhausts for the building? Are bathrooms, kitchens (or
other exhausts) dumping into the shafts?

>the A/C's are running or not, correct (if fan is sized right)?

The (squirrel cage type) fan would have to be large enough to provide a
slightly positive static pressure with all A/C systems running (hot
weather). This might create a cold draft problem with all A/C systems off
(cold weather). Maybe with static pressure controls...

Gary

Gary R. Lloyd CMS
TECH Method Training
HVACR Trouble Shooting Books/Software
Tel 313-671-0188  Fax 313-676-9262