[Equest-users] Thermal Blocks

[Jeff Ross-Bain]

Here is the comment - it could be that I drew a blank - the comments so far
have helped to clear up the issue. I initially interpreted the comment to
imply a separate shell for each thermal block. 

 

According to the SV-A report, the Baseline Case was not modeled with a
separate PSZ-AC serving each thermal block as requested.

 

However, I do appreciate the comments regarding thermal blocks and they have
been very helpful.

 

Thanks for the response,

 

Jeffrey G Ross-Bain, PE, LEED AP, BEMP

404-228-2893 office 

404-408-2577 mobile
www.rbgb.com

  _____  

From: Bishop, Bill [mailto:wbishop at pathfinder-ea.com] 
Sent: Wednesday, May 04, 2011 11:18 AM
To: Paul Diglio; Jeff Ross-Bain; equest-users
Subject: RE: [Equest-users] Thermal Blocks

 

I'm also curious to hear Jeff's LEED reviewer interpretation of thermal
blocks. I'll add some general comments.

 

I believe it is incorrect use of terminology to talk about "multiple zones
per thermal block" in eQUEST.

 

The words space and zone both have specific meanings in eQUEST. For each
space, there is a single corresponding zone.

Multiple zones can be applied to a single system. (Unfortunately, multiple
systems cannot be applied to a single zone, but that is another thread.)

The term thermal block does not have a precise meaning in eQUEST, but I
would not describe the group of zones assigned to a single system as a
thermal block.

 

If you wanted to try to model the exact intent of a proposed design, you
would model each thermally-unique area as its own space/zone. A
generalization is that a zone is an area served by a single thermostat.

To simplify a model, similar zones can be combined into thermal blocks per
the guidelines in ASHRAE Standard 90.1.

Modelers have to make judgments calls on if/how to combine zones into
thermal blocks.

 

In eQUEST, the decision to combine zones into thermal blocks really should
be done at the wizard input level, when the zones are defined. You combine
multiple zones per the design intent into a single zone definition for
simulation purposes.

You don't have multiple zones in a thermal block. Each thermal block is
defined/modeled as a single eQUEST zone.

You could still assign multiple thermal blocks/zones to a single system, but
I would be wary of over-simplifying a proposed design.

 

Regards,

Bill

 

Signature in jpg form

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Paul Diglio
Sent: Wednesday, May 04, 2011 9:21 AM
To: Jeff Ross-Bain; equest-users
Subject: Re: [Equest-users] Thermal Blocks

 

Jeff:

ASHRAE 90.1 allow spaces of similar thermal characteristics to be combined
in thermal blocks.  I do not include what you call support spaces because
the load and occupancy is much different than, say a classroom.  I would
define the corridor as a separate zone within the thermal block but served
by the same HVAC system.  This allows you to have a different set-point,
airflow, occupancy and schedules for the corridor.

You do not have to define a separate shell for each block, you can define
the block by custom zones in the wizard.

I divide up a thermal block into as many reasonable zones as possible.  This
allows me to find out which area of the thermal block is causing any unmet
heating or cooling hours.  It also allows me to change the HVAC system
control zone to that zone which is the hardest to satisfy in the summer and
winter.  These zones can be served by a single HVAC system.

For a proposed model that needs to conform to an actual design, defining
multiple zones per thermal block allows you to balance the airflow to zones
that have unmet hours without increasing the overall airflow of the HVAC
system.  I define the zonal airflow in the Zone tab.  I reduce the airflow
to the zones without any unmet hours and increase the airflow to those zones
that have unmet hours.  I do not define the total fan CFM in the Airside
Systems tab.

What were the comments from the LEED reviewer?

Paul Diglio

 

 

  _____  

From: Jeff Ross-Bain <jeff at rbgb.com>
To: equest-users <equest-users at lists.onebuilding.org>
Sent: Wed, May 4, 2011 9:05:15 AM
Subject: [Equest-users] Thermal Blocks

Hi All,

 

Are there any additional discussions out there regarding thermal blocks
besides what is in ASHRAE Standard 90.1 and the User's Guide? I have
received comments back from a LEED reviewer that seems to reflect an
interpretation of that concept which I have not seen before.

 

In a nutshell, does each thermal block require a separate shell with
individual HVAC system? I understand the concept of having individual
thermal blocks or combining these if they are similar space use categories.
I am assuming then that the similar space use categories (say a college
classroom building) can also include support spaces such as corridors,
storage spaces, faculty offices, etc. 

 

So if several thermal blocks are combined into one, can they not be served
by a single, similar type of HVAC system?

 

I hope that I have made myself clear and many thanks for your thoughts and
comments.

 

Regards,

 

Jeffrey G Ross-Bain, PE, LEED AP, BEMP

404-228-2893 office 

404-408-2577 mobile
www.rbgb.com

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