[BLDG-SIM] RE: Process Loads and LEED

[Brandon Nichols]

Thanks for getting this going Varkie, it has been a great topic...
 
 
Having just modeled a heat recovery system for a large 100% outside air
system with runaround waterside heat recovery, I can answer a couple of
your questions (staying far away from LEED interpretations):
 
1) To turn off the airside economizer in eQuest, set the 'Minimum OA
Control Method' to 'Fraction of Design Flow' (OA-CONTROL = FIXED).
 
2a) The 'waterside economizer' terminology is a bit ambiguous, in my
understanding it's referring only to 'free cooling' available by running
cold condenser water through chillers that are off.  Something like 15
to 20% of a chiller's rated capacity may be utilized in cold months
without running the compressor given the right ambient conditions.  
 
2b) If its a runaround waterside economizer you want, with recovery
coils constantly in the outdoor and exhaust air streams, then use the
airside economizer and set up the parametric run along the lines of the
following example:
 
$ adjust the supply and returns statics of the main unit to 
$ account for the increased pressure drop
SUPPLY-STATIC    = 6.00
RETURN-STATIC    = 3.00
ERV-RECOVER-TYPE = SENSIBLE-HX
$ specify OA and EXH flows if only a portion of the exhaust is recovered
ERV-OA-FLOW      = 46960
ERV-EXH-FLOW     = 28590
$ potentially the effectiveness can increase to 0.75 if a two-pass coil
used
ERV-SENSIBLE-EFF = 0.53
ERV-RUN-CTRL     = OA-EXHAUST-DT
ERV-RECOVER-MODE = OA-HEAT/COOL
$ some may argue this control method, FLOAT gives maximum heat recovery
ERV-TEMP-CTRL    = FLOAT
ERV-CAP-CTRL     = MODULATE-HX
$ input the runaround pump power consumption here, it will be switched
$ on only when the ERV is activated
ERV-HX-KW        = 4.5
ERV-FANS         = HVAC-SUPPLY/RETURN
ERV-MOTOR-CLASS  = HI-EFF
$ set the ERV statics to zero, since it is NOT a separate unit 
$ in series with the main unit
ERV-OA-STATIC    = 0
ERV-EXH-STATIC   = 0
ERV-FROST-CTRL   = USE-CAP-CTRL
 
 
 
Hope that helps, corrections and improvements will be posted here:
 
http://elcca-exchange.blogspot.com/2007/02/equest-heat-recovery.html
 
 
Regards
 
Brandon


  _____  

From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of Varkie
Thomas
Sent: Tuesday, March 06, 2007 3:59 PM
To: BLDG-SIM at gard.com
Cc: BLDG-SIM at gard.com
Subject: [BLDG-SIM] RE: Process Loads and LEED



Thanks for all the responses.  It does not solve my problem where the
proposed process load in this "office" building that I am looking at is
more than 60% of the total annual energy use.  Here is a suggested
solution.  The proposed process load should be entered in the baseline
and proposed models since it affects the heating and cooling loads and
the difference in efficiencies of the baseline and proposed systems
serving the loads. However, when determining the percent energy savings
for LEED certification, the common process load should be removed from
both sides.

I apologize for bothering BLDG-SIM subscribers with more questions
because of my ignorance.

A high process load offsets the heating load in the perimeter zones and
you can get a building in a cold climate with no heating.  If the
perimeter zone is reduced to 1 foot with no process loads, people or
lighting, then the computer program will not account for the benefit of
day-lighting on the lighting system unless the program can ignore this
perimeter zone and apply day-lighting to the adjacent zone if it is
separated by an "AIR-WALL" (DOE2.1E).  

The building that I am looking at has ceiling PIU boxes designed to
serve a less than 1 foot perimeter zone and UFAD PIU boxes serving the
interior zone.  Both sets of PIU boxes are served by the same system.
In this building, the glass height is 12 feet and the ceiling height,
beyond the 1 foot perimeter zone, is 10 feet.  Since the zone depth
entered into the program is 15 feet and has a 10 foot ceiling, eQUEST
flags it down as an error but not DOE2.1E.  Perhaps VisualDOE will not
call this an error.

How would you turn off the Airside Economizer in a DOE2 based program.
With TRACE700 you can say Yes or No.  Climate zone 3A does not require
and airside economizer for the baseline for a large office building.
Setting the "Drybulb High Limit" and the "Economizer Low Limit" in
eQUEST to their maximum values of 80F seems to do the trick.  I cannot
find the Waterside Economizer in eQUEST although the keywords and
commands for modeling this, exists in both DOE2.1E and DOE2.2.

How is the Zone-Fan-Ratio (ZFR) determined for Fan Powered Terminal
Boxes?  In eQUEST the default for Series FPB is 1.0 and for Parallel it
is 0.5.  How was this determined.  The definition in the DOE2.2 manual
is:  ZFR * Primary CFM = FPB Supply CFM.  

In the case of the project I am looking at (a UFAD system with Parallel
FPBs) the Primary Air Temp is 48F (for dehumidification), the FPB Supply
Air Temp = 65F and Recirculation Air Temp is 78F.  What is the ZFR?
Would an increase in ZFR reduce the energy use.  The Simulation
Guidebook by Energy Design Resources suggests putting 25% of the people
and 33% of lights and equipment in the ceiling plenum.  This produced
very little in energy savings.  

Is this an acceptable solution:


Summer Cooling Indoor Temp:  From 0' to 7' at 75 F.  From 7' to 10' at
85 F   Average Temp = 78 F.  (0.7*75) + (0.3*85) = 78


Winter Heating Indoor Temp:  From 0' to 7' at 72 F.  From 7' to 10' at
62 F   Average Temp = 69 F.  (0.7*72) + (0.3*62) = 69

(As with the theoretical method of moving internal loads to the plenum,
the fact that hot air collects at the top should be not an issue since
we are looking at heating only the mass of air from 0' to 7' to 72 F).

How would you account for the energy savings using ECM motors.  One
suggestion is to reduce the energy use of the fans in PIU boxes by 25%.
The default KW/CFM in eQUEST is 0.00033 (0.33 kw for a 1000 cfm box).
Reducing this by 25%  produced almost no energy savings using eQUEST.

According to the Code of  Federal Regulations (10CFR435/436) occupancy
based lighting sensors can be modeled by reducing the lighting
schedule/profile fraction by 30%.  Is this acceptable to LEED?  I am
assuming that occupancy based ventilation can be modeled by creating a
MIN-AIR-SCH (DOE2.1E) that is equal to the design OA fraction (from a
trial run) multiplied by the occupancy schedule fraction.

The energy program developers should provide guidelines for modeling
energy conservation measures using their programs.  Code and LEED
authorities should test them and approve them.

 

----- Original Message ----- 
From: Mike Tillou <miket at etcgrp.com> 
Date: Tuesday, March 6, 2007 4:21 pm 
Subject: RE: [BLDG-SIM] Process Loads and LEED 
To: thomasv at iit.edu, BLDG-SIM at gard.com 



I went back and looked at the public review version of LEED 2.2 dated
December 2004 on the cover and October 19 in the footer.  Here is how
the original credit was proposed:
"Must be compared against a baseline building that both complies with
Appendix G to Standard 90.1-2004 (without amendments) and that has a
process energy consumption that is a minimum of 25% of the total energy
consumption for the baseline building."

In the final version of the the LEED 2.2 dated October 2005 that same
verbiage had been changed to 

"Must be compared against a baseline building that complies with
Appendix G to Standard 90.1-2004 (without amendments). The default
process energy cost is 25% of the total energy"

 I think the intent is that the default process energy cost used in the
calculation of LEED credits for V2.2 is a max of 25%.  If your building
has 60% process energy you would only have to count that portion of
process energy that equals 25% of the total energy.  This would level
the playing field for all buildings regardless of how much process
energy is used.  If a building uses less than 25% then you have to
justify the legitimacy of that claim.  

I think someone should submit a CIR asking whether this is the correct
interpretation of the Credit.

Respectfully,

Mike

Michael Tillou, PE 
ETC Group - Energy Engineering for a Sustainable Future 
Ph:413-458-9870 



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