[Equest-users] [Bldg-sim] DCV per ASHRAE 62.1 in eQuest

[Victor Yeung]

Dan,

 

eQuest cannot properly model ASHRAE 62.1 outdoor air rates, as it takes
the maximum OA value from OA-FLOW/PER or OA-FLOW/AREA, not the combined
sum as required by ASHRAE 62.1.  However there is a very tedious
workaround to this.  Using your occupancy schedule, you need to
calculate the total OA requirement (area and person) for each hour, and
enter that into your zone OA schedule as a fraction of the design flow
of the RTU (OA cfm / RTU cfm).  Basically, you need to replace all the
-999 values to a desired hourly fraction value. Unoccupied hours should
be set to zero. You need to repeat this for every OA schedule in each
hvac zone that has DCV.  Do not use the 'DCV zone sensors' option, as it
is useless in this case.  Use the default (should be 'Fraction of Design
Flow').  It gets messy if you have more than one occupancy schedule.

 

Regards,

 

VICTOR YEUNG, BASc, LEED(r) AP

EIT - LEED(r)/Sustainable Development

victor at invirosystems.ca <mailto:victor at invirosystems.ca> 

 

 

From: Bishop, Bill [mailto:wbishop at pathfinder-ea.com] 
Sent: May 28, 2010 1:43 PM
To: Dan Coutin
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] [Bldg-sim] DCV per ASHRAE 62.1 in eQuest

 

Dan,

 

[I copied the equest-users instead of bldg-sim.]

 

You need to enter zone-level OA as OA-FLOW/PER and/or OA-FLOW/AREA. The
OA flow/per (person) is what will vary the OA on an hourly basis, based
on your occupancy schedule(s). (Hourly OA = (# of people) * OA-FLOW/PER
* (% occupancy in schedule)). In order to turn OA off during unoccupied
hours, I create a MIN-AIR-SCH, coinciding with the fan schedule, set to
zero when fan is off (or night cycling) and -999 when fan is on. The
hourly OA can be verified by creating a new hourly report for the system
to track total system supply air flow rate and ratio of outside air to
total supply air.

 

Regards,

Bill

 

William Bishop, EIT, BEMP, LEED(r) AP | Pathfinder Engineers &
Architects LLP

Mechanical Engineer

 

134 South Fitzhugh Street
Rochester, NY 14608
T: (585) 325-6004 Ext. 114
F: (585) 325-6005

wbishop at pathfinder-ea..com

www.pathfinder-ea.com

P May is National Bike Month. Bike to Work Day May 21st.

________________________________

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Dan Coutin
Sent: Friday, May 28, 2010 12:02 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] DCV per ASHRAE 62.1 in eQuest

 

Using eQuest 3.63, I am modeling a school building with a high
ventilation requirement. The schedule indicates a minimum OA cfm and
employs DCV that adds OA per occupant in a manner similar to ASHRAE
62.1:2004.

Can someone informed, please suggest 

a) how this may be best input in eQuest, and: 
b) importantly, how it may be verified in the output. 

As in real life the amount of ventilation (used/modeled) has a
considerable energy impact and needs to be particularly accurate.

I see the DCV Zone sensors options, and have read the zone/system
ventilation help, but I find the help descriptions somewhat ambiguous.

In this example the system is constant volume roof top units with heat
recovery. Unoccupied control is cycling fans with no ventilation.

Thanks 
Dan Coutin, Erdman Anthony, Albany, NY. 
coutind at erdmananthony.com 

 

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