[Equest-users] Fwd: system and zone airflow issue

[Carol Gardner]

Ooops. Didn't hit reply all.

---------- Forwarded message ----------
From: Carol Gardner <cmg750 at gmail.com>
Date: Tue, Nov 16, 2010 at 9:45 AM
Subject: Re: [Equest-users] system and zone airflow issue
To: Brian Fountain <bfountain at greensim.com>


Hi Brian,

I don't have time to research this thoroughly but in general for modeling I
would stick to specifying the airflow at the system level. It is important
to remember that eQUEST is an energy analysis tool, not a mechanical design
tool. If you were doing design I, and your client, would expect to see the
VAV box cfms down on the drawings. For energy analysis, I think it's
overkill and, as you have found out, you can run up against weird things.
The other reason? It adds to the time you are using to do the energy model
without getting you anything more (anyone disagree?). I did find one item
out of the manuals that may shed light on what to look at if you want to
understand what you ran up against. I'll paste it below. Let me know if you
figure it out.

Best,

Carol

1.    SUPPLY FLOW
is the calculated or user-specified supply flow for each zone.  Only if you
have specified a value for the ASSIGNED-FLOW keyword in the ZONE command
will the value here correspond to your input. The ZONE keywords
AIR-CHANGES/HR and FLOW/AREA will be accepted by SYSTEMS only if they are
consistent with the user-supplied HEATING-CAPACITY and COOLING-CAPACITY and
are equivalent to a flow larger than that of the exhaust from or the
ventilation to the zone. The ALTITUDE FACTOR will be applied.


On Tue, Nov 16, 2010 at 8:18 AM, Brian Fountain <bfountain at greensim.com>wrote:

>  I recall that there was an issue with entering both system and zone level
> airflow values in eQUEST but a search through the archive did not retrieve
> what I was looking for.  Perhaps someone can jog my memory.  In a review of
> a model where both system and zone level airflows were entered for a VAV
> system, and where zone level values total up *less than *the system value
> entered, we find that deleting the system level airflow increased the
> overall fan energy.  I find this hard to explain.
>
>
>
>
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-- 
Carol Gardner PE



-- 
Carol Gardner PE
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