[Equest-users] Models for energy audits

[Steven Savich]

Ian,

 

Equest thermal inputs use the convention of Mbtu = million btus, while
common usage in the US is still generally Roman numerals with btus:  mbtu =
thousand btus, mmbtu = million btus.  You should be entering 2.603 Mbtu for
the boiler capacity in equest.

 

However, I'd recommend looking at load hours not met in the BEPS report
before and after entering that value.  If the usage is going up when you
enter the 2603 Mbtu value, that may mean something else is going on.  Do
teachers and staff report problems maintaining temperature in the winter, or
does the boiler spend a lot of time in winter running?  Is it possible the
existing boiler is undersized, or is there something else going on?

 

For the elementary gas consumption, it looks like you have a pilotless
domestic water heater set up in the model.  Are you sure that there's no
pilot on the domestic water heater or the boiler?  Do they completely shut
the boiler off during the summer?  

How is the domestic hot water recirc pump controlled?  If it does not have a
timeclock or temperature control to shut it off when there's no system
demand, it may be causing the domestic water heater to cycle more frequently
during the summer when there's no load, especially if the HW & HWR piping is
not adequately insulated.  If this is the case, you can do a side
calculation to estimate the HW & HWR piping UA and enter that in the
domestic water loop as a SUPPLY-UA to get a closer match in your baseline.

 

Thanks,

Steven

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Ian Hadden
Sent: Wednesday, September 11, 2013 6:22 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Models for energy audits

 

I've been working on a couple models for an energy audit project and am
coming up a bit stumped for issues with both buildings. I'd appreciate any
insight folks can provide.

 

Attached are 2 zip files with the .pd2 and .inp files for each project as
well as the utility analysis spreadsheets for each project.  Year 1 in the
spreadsheet is the output from the energy model for comparison to the actual
utility bills (2.5 years of bills).  Here are my primary issues for each
project.

 

Carterville Intermediate

-          The winter electric use is greater than the modeled values while
the summer is much higher.  The shape of the curve is about right but the
values are off.  I think the winter electric is low because I'm not sure
we're seeing fan energy associated with heating.  The system is DX coil unit
vents (condensers on the roof) with hot water coils for spaces and HW
radiators in the halls.  Gym is heating only.  I think the cooling electric
is high because I think the teachers turn off the units because of noise and
they open windows.  The District reports they open corridor entry doors for
airflow and teachers are supposed to keep classroom doors closed. Do I have
the HVAC system configured correctly for the installed system?  What can we
do to adjust operation of the UVs in cooling?

-          I haven't entered a value for the size of the boiler.  eQuest has
input in MBH and my photos show the label at 2603 MBH but that increases gas
use by a factor of 100.  Am I mixing up units here?

-          I haven't figured out how to do anything for exhaust fans.

 

Carterville TriC Elementary

-          The peak summer electric demand is higher than actual but the kWH
curve is a good fit to actual but just needs more hours. The HVAC system is
ground source heat pumps per space with 6-7 ERVs (wheel only no mechanical
cooling/heating) feeding OA to the return air inlet. There is one ERV for a
4 room addition that also has an electric heater in addition to the wheel.
There is no supplemental boiler for the condenser loop. We haven't been able
to learn any data on the actual geology of the site but by plans we have the
correct number of wells in our grid. I think the high demand means we need a
larger well field to keep condenser water temps down and compressor load
down but I may be missing something. It might also be tied to increase OA
load.  I've tried but am just not comfortable with my efforts to set up the
ERVs in the system to temper the OA before the GSHPs.

-          When I go into Detailed edit it appears that my heat pumps all
become equipped with VFD supply fans. This concerns me that I've really
screwed up something in the HVAC system set up. 

-          Gas consumption is driving me nuts.  The shape of the curve is a
great match but their summer consumption is 4 times the modeled value. The
only gas loads I have in the building are the DHW and the kitchen and
they've told me the kitchen is closed during the summer.  I'm a little
concerned by the up/down nature of the model curve.  With DWH and kitchen
only the loads should be pretty smooth shouldn't they?

-          The majority of the classroom wings have pitched metal roofs.
I've walked through my selections with Mark and Cliff but I'm not sure we
have accurately modeled the thermal performance of the roof for most of the
building.

 

 

 

Ian T. Hadden, PE, LEED AP BD+C

Project Executive

Energy/Sustainability Services Manager

Fanning Howey

C: (919) 239-0190

email:  <mailto:ihadden at fhai.com> ihadden at fhai.com

P Please consider the environment before printing this e-mail



 

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