[Equest-users] Heating mode stuck at minimum flow rate

[Paul Diglio]

Rosie:

I tweaked your project.  Please see attached files.

I set the Warehouse Unit minimum flow for heating to .4 and the maximum flow for 
heating at 1.0
I enabled the zone heat as Furnace, cleared your maximum discharge air 
temperature for heating and entered 20 degrees as the reheat delta T in the 
air-side tab.

By the way, the infiltration in the warehouse is very high, as much as 126,120 
CFM.  Is this correct?

Anyway, you now have only 17 unmet heating hours for the warehouse and none for 
the two office areas.

Regards,

Paul Diglio







________________________________
From: Roselin Osser <Rosie at buildingscience.com>
To: Paul Diglio <paul.diglio at sbcglobal.net>; equest-users at lists.onebuilding.org
Cc: Brian Fountain <bfountain at greensim.com>; "Bishop, Bill" 
<wbishop at pathfinder-ea.com>
Sent: Mon, January 17, 2011 11:52:17 AM
Subject: RE: [Equest-users] Heating mode stuck at minimum flow rate


Hi everyone,
 
At this point I think the problem has to do with the fact that I have zone 
reheat specified as “not installed;” I only have furnace heating at the air 
handling unit.  When I add in zone reheat, increased flow in heating mode is 
enabled.  My system is serving a single zone so there isn’t actually any reheat, 
but maybe putting in furnace heating with furnace reheat is a workaround.
 
I’ve attached my .inp and .pd2 files in case anyone wants to take a look; this 
is the version without zone reheat.
I have a reverse-action thermostat and have tried adjusting the throttling range 
to 4 or 6 but these don’t affect the minimum flow in heating mode.  I was using 
the Memphis, TN TMY3 file.
 
Thanks for your ideas and suggestions,
Rosie
From:Paul Diglio [mailto:paul.diglio at sbcglobal.net] 
Sent: Monday, January 17, 2011 6:30 AM
To: Roselin Osser; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Heating mode stuck at minimum flow rate
 
Rosie:

What is your thermostat throttling range?

Try 4 degrees and see what happens.

Paul Diglio
 

________________________________

From:Roselin Osser <Rosie at buildingscience.com>
To: equest-users at lists.onebuilding.org
Sent: Sun, January 16, 2011 9:24:30 PM
Subject: [Equest-users] Heating mode stuck at minimum flow rate
Hi folks,
 
I’m modeling a packaged VAV system (PVAVS) serving only one zone.  The maximum 
airflow the unit can provide is 450,000 cfm, which I have entered in as an 
airflow parameter.  The problem is that whenever the system goes into heating 
mode, the total cfm goes to minimum airflow (observed from hourly output), even 
when more heating is needed, so I end up with a lot of underheated hours.  The 
minimum airflow is calculated from the 10% outdoor air ratio I have entered.  I 
have tried adjusting the HMAX-FLOW-RATIO field to allow the heating airflow to 
go above the minimum if necessary, but the field seems to have no effect.  I 
have a reverse action thermostat in the zone.  Anyone else run into this?  There 
must be some other parameter I’m  using that is preventing the field from 
working.  Any advice would be appreciated, as I have tried a lot of input 
variations and none of them allowed the heating minimum flow to increase when 
more heat is needed.  I’m using eQuest 3.64.
 
Thanks for your help!
 
Rosie
 
 
Roselin Osser, BEMP, LEED AP
Building Science Corporation
30 Forest Street
Somerville, MA  02143
978-589-5100 x 5284
fax:  978-589-5103
 
Building Science Corporation
Somerville MA  |  Waterloo ON
www.buildingscience.com
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