[Equest-users] FW: [Bldg-sim] Discomfort hrs

[Steven Gates]

Good advice was given below.  To further clarify:

 

A packaged single-zone system can have more than one conditioned zone, but
only one of those zones can be designated as the "control zone". The control
zone determines the operation of the HVAC system, both airflow and/or
heating/cooling supply temperature. Any conditioned zones in that system
that are not the control zone (a "subzone" in this discussion) simply get
the air and temperature as determined by the control zone. As a result, a
subzone may not necessarily be comfortable if it has a load profile
significantly different from the control zone (for example, a north facing
zone on the same system as a south-facing zone).

 

Ignoring subzone reheat for a moment, a subzone does not need
heating/cooling thermostat schedules. If you specify one, it will simply be
used to count hours as underheated/undercooled in the SS-F, BEPS, and BEPU
reports. In these reports, a zone is underheated/undercooled if it is more
than 1F beyond the thermostat throttling range. For example, if the
heating/cooling setpoints are 70/75, the throttling range is 0.5F
(throttling range is centered about the setpoint), then the heating/cooling
trigger temperatures for these reports are 68.75F and 76.25F (half the
throttling range plus 1F).

 

If you don't want the subzone underheating/undercooling to be counted in
these reports, don't specify thermostat schedules for the subzones. 

 

Alternatively, if you want to know if subzones are severely out of range,
specify the thermostat schedules for these zones with a higher cooling
setpoint and/or lower heating setpoint than the control zone. Or, use the
same thermostat schedules as the control zone, but specify a larger
throttling range in the subzones. For example, a subzone throttling range of
6F would result in trigger temperatures of 66F and 79F in the above example.

 

Note that if a subzone has a reheat coil, then it is necessary to specify a
heating thermostat schedule in the subzone to control the coil.

 

Steve Gates

eQUEST development team

 

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Carol
Gardner
Sent: Wednesday, April 07, 2010 8:50 AM
To: Bishop, Bill
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] FW: [Bldg-sim] Discomfort hrs

 

What Bill says is true, you are to only have one system per HVAC zone. I
have never taken that to mean, however, that you might not have multiple
spaces/rooms on one zone nor have I received that feedback from the
developers. True, eQUEST insists on providing a zone name for each specified
space, but you can gather the spaces/zones in each HVAC zone and cause them
to be served by one PSZ or other system. Then you have to determine what
your control zone is. After you have done that you go into your zone
spreadsheet and put your heating temp schedules and cooling temp schedules
in your control zone, which is where your thermostat is, and say they are
undefined in the other zones. This should take care of the discomfort hours
provided you carefully selected your control zone. This should not cause the
other spaces to have inadequate heating or cooling since the control zone,
as I understand it, has the highest loads of all the spaces and if it's
satisfied the other spaces are satisfied.

That is my understanding, anyway, and I will accept any/all feedback.
Especially from a BEMP!!

Carol

On Wed, Apr 7, 2010 at 6:39 AM, Bishop, Bill <wbishop at pathfinder-ea.com>
wrote:

Sambhav,

 

Are you modeling the baseline according to Appendix G? If so, and you are
using PSZ, you should have one system per zone. If you are already modeling
one system per zone you should not be getting high unmet hours if you let
eQUEST do the autosizing.

 

If you are trying to model a PSZ with multiple zones assigned to it, you can
do a few things to reduce the unmet hours. As Carol and Rob suggest, you can
remove the heating and cooling schedules to unconditioned zones. You should
not do this for conditioned zones (zones that you want to keep within a
certain temperature range) because you will be letting the temperatures
float. Your unmet hours will go away but the virtual people in those zones
will be calling their virtual landlords complaining about being too hot or
too cold.

 

To reduce unmet hours when multiple zones are assigned to a PSZ, try the
following:

1.)     change the control zone (try assigning to the zone with most unmet
hours first)

2.)     increase/decrease people/lighting/misc loads in the trouble zones
(and copy the values to the proposed model to keep them identical)

3.)     change some interior walls to "air walls" (and copy into the
proposed model)

4.)     increase the supply air flow rate to individual zones, especially if
they are undercooled

 

Regards,

Bill

 

William Bishop, EIT, BEMP, LEEDR 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 Please strive to live sustainably.

  _____  

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Carol Gardner
Sent: Wednesday, April 07, 2010 2:32 AM
To: Rob Hudson
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Discomfort hrs

 

Yes. Only put the heating temp schedules and cooling temp schedules in the
zone you have selected as the Control Zone. If you use the Spreadsheet
option you will be able to do this easily. Use the drop down menu and select
Undefined for all other zones. 

Carol

On Tue, Apr 6, 2010 at 9:18 AM, Rob Hudson <rdh4176 at gmail.com> wrote:

If there are more than one zone assigned to the PZS, then remove the
thermostats to the extra zones.  This happened to me when i attached an
unconditioned plenum space to a PZS space.

 

On Tue, Apr 6, 2010 at 10:52 AM, Vikram Sami <vssami at yahoo.com> wrote:


Have you tried cycling your fans? If you'r doing this for ASHRAE compliance
you need to do this anyway. 

--- On Tue, 4/6/10, sambhav tiwari <tiwari.sambhav at gmail.com> wrote:


From: sambhav tiwari <tiwari.sambhav at gmail.com>
Subject: [Bldg-sim] Discomfort hrs
To: bldg-sim at lists.onebuilding.org
Date: Tuesday, April 6, 2010, 2:33 AM

 

Hi All,
          In one of project my basline building was having packaged syngle
zone system but after running i am getting lot of unmet hours for PSZ system
for each zone almost 450 hrs for basline.

Can any suggest some solution.

Thanks
Sambhav.

 

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