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

[Roselin Osser]

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
 <http://www.buildingscience.com/> www.buildingscience.com

 

 

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