[Bldg-sim] ASHRAE 90.1 Baseline building question

[Sheila]

Hi Bill,

Yes, in eQuest, only one system can be directly assigned to any given
zone.  However, it is possible to link 2 systems when one system is
dedicated to supplying another system with OA.  The trick is to make
sure that the DOAS is the FIRST system listed in the project component
tree; i.e. the DOAS has to be manually moved to (or created in) the
first position directly in the .inp file, not while eQuest is open.   In
order to satisfy the eQuest system requirement that at least one
conditioned zone must be attached to each system, a conditioned dummy
space/zone (with dimensions of 1x1x1) can be created to attach to the
DOAS which has no exterior or interior surfaces or internal loads of any
kind.  Once the DOAS is in the first position with the dummy zone
attached, on the OA tab of the rooftop unit, select the DOAS as the "OA
from System" in the pull-down menu for that data entry box.  The DOAS
then can model the heat recovery as designed as long as the system type
selected can model heat recovery.

The above procedure links two systems together so that OA can be
provided to a single zone from a separate system.

Good luck!

Sheila Sagerer
Energy Engineer, EIT, LEED AP
Energy Opportunities, Inc, a 7group company
Phone: 717-880-9069
www.sevengroup.com

Hi Sheila,

I hope other people chime in on this. I have not received guidance from
others on how this requirement should be interpreted so I only replied
with what makes sense to me.

The problem in eQUEST is not with the system type. The problem is that
you have one DOAS supplying multiple fan systems. A thermal zone can
only have one system assigned to it. You can't assign both a DOAS and a
rooftop unit to a zone. You can select a system type that allows heat
recovery, but the heat recovery that you model is only for the capacity
and control of the single rooftop unit. So, whenever I have a DOAS
supplying multiple air handlers, I model each air handler as having its
own heat recovery unit. I think the biggest problem with modeling it
this way is that you can't put the system in ventilation-only mode. The
heat recovery can only operate when the air handler fans are running.

Bill

-----Original Message-----
From: Sheila [mailto:sheila at energyopportunities.com]
Sent: Thursday, September 23, 2010 9:10 AM
To: Bishop, Bill
Subject: RE: [Bldg-sim] ASHRAE 90.1 Baseline building question

Good morning,

I have to agree with Chris' interpretation of Section 6.3.6.1.  An ERV
which is acting as a dedicated outside air system to provide OA to other
systems generally has both a supply fan and an exhaust fan.  Therefore,
it is considered a "fan system" and Section 6.3.6.1 would apply.  In
addition, Section 11.4.3(k) stipulates that each unit (including DOAS)
must be mapped on a one-to-one basis in order to determine the
corresponding Budget system type.  As such, if the Proposed building has
a DOAS, so must the Budget building.  In the Budget building, if the
DOAS has at least 5,000 cfm and 70% or greater OA, then the Budget DOAS
must model the 50% effective heat recovery.

In regards to eQuest:  What system type has been selected in eQuest to
model the DOAS/ERV?  We regularly encounter this set-up and model the
heat recovery on a DOAS all the time.  The inability to model the heat
recovery is most likely due to the system type selected.

Regards,

Sheila Sagerer
Energy Engineer, EIT, LEED AP
Energy Opportunities, Inc, a 7group company
Phone: 717-880-9069
www.sevengroup.com


-----Original Message-----
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Bishop,
Bill
Sent: Thursday, September 23, 2010 8:22 AM
To: Chris Jones
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] ASHRAE 90.1 Baseline building question

Chris,

I assume you're doing an ECB model using 90.1-1999 to meet a local
requirement.

I interpret 90.1-1999, Section 6.3.6.1 differently. (For those without
it handy, the wording is, "Individual fan systems that have both a
design supply air capacity of 5000 cfm or greater and have a minimum
outside air supply of 70% or greater of the design supply air quantity
shall have an energy recovery system with at least 50% recovery
effectiveness.") The criterion to evaluate is for individual fan
systems. The ERV is not the fan system, the four rooftop units are the
fan systems. So, you only need to model heat recovery if one or more of
the rooftop units has 5000 cfm or greater of supply air and at least 70%
OA. You're saying the rooftop units have less than 50% OA (and I would
think they're much lower than that), so the baseline systems do not need
energy recovery.

I'm curious, how would you prorate the heat recovery effectiveness? I
frequently model air handlers as having their own ERV when they actually
receive OA from a common ERV.

Regards,
Bill

William Bishop, PE, 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 Please strive to live sustainably.
        
-----Original Message-----
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Chris Jones
Sent: Wednesday, September 22, 2010 7:25 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] ASHRAE 90.1 Baseline building question

The project has 4 rooftop units, and one ERV that provides OA to the 
four roof top units.  Except the ERV only provides 50% of the minimum 
OA for each of the four rooftop systems.  DOE2.2 and DOE2.1e do not 
seem to handle heat recovery in a make-up air system using the 
OA-FROM-SYSTEM command.  The way I typically handle this arrangement 
is to prorate the heat recovery effectiveness and the ERV fan power 
to each of the 4 roof top systems.  The 4 rooftop systems have 
typical OA % for an office building - less than 50%.  My 
interpretation of 90.1-1999 Section 6.3.6.1 is that the ERV has more 
than 5000 cfm and more than 70% OA (the ERV is 100% OA), therefore 
the Budget building ERV requires heat recovery at 50%.  To model 
this, the Budget building will have prorated heat recovery at the 4 
roof top units - again because one can't properly model a make-up air 
system with heat recovery using equest (DOE2.2) or DOE2.1e.

Does this make sense?

And thanks for all the help provided by this group!




Chris Jones
14 Oneida Avenue
Toronto, ON M5J 2E3.
Tel.  416-203-7465
Fax. 416-946-1005


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