Electrical loads

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When modeling energy use in a residential high-rise I set up schedules
for misc. loads like refrigerator, microwave, oven washer/dryer etc.. I
actually lumped these all into 1 schedule, approximated their actual
loads and then applied a daily and weekend schedule to approximate their
use.

My schedules showed pretty low percentages since these appliances would
not be used much.

I received comments from the client and another modeler that these loads
are inconsequential and should not be incorporated into the model.

Here is the comment

Plug-ins are typically assumed to be the copiers, medical equipment, etc
and I would think refrigerators, microwaves because how do we really
measure the use of such things in a current comprehensive computer
modeling situation - it's beyond a scope of comparison in a finite way
- that's why MISC should be junked.

Any opinions?

Mike Rabena, P.E., LEED AP

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The last question is specific to LEED EA Credit 1

Mike Rabena, P.E., LEED AP

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There is a requirement of 25% of the total cost should be misc loads for
LEED.

Also, when you look at the breakdown of energy efficient residences, the
plug loads is a big chunk.

-Rohini

Brahme, Rohini            UTRC's picture
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FOR LEED the 25% is not a requirement. It is more of a guideline for
energy modelers to account for energy consumption on their plug loads.
If the 25% of the Process Load is not reached then you should
documentation explaining your assumptions. For example in a hospital you
would typically go over the 25%, this doesn't mean you stop at 25%, you
should account for whatever your plug load is and do not have to submit
extra documentation (unless asked). On the other hand if you had a
school, you would probably fall short of the 25% making you submit extra
documentation with your assumptions. As long as your assumptions are
reasonable the 25% should not be a big issue. In your case you would
have give your schedule and energy intensity of your plug loads and
explain your assumptions based on a reference.

ARTURO HERNANDEZ, LEED AP

Hernandez, Arturo's picture
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I would hardly say that residential internal loads are inconsequential. You
can get average yearly energy use for refrigerators and washing machines
from the energy star website. You'll then have to break it down into power
density and a yearly use schedule. Also check out:

http://www.eia.doe.gov/emeu/recs/recs2001/enduse2001/enduse2001.html

for general appliance yearly energy use. Funny thing is that residential
apartment lighting seems to be the most difficult parameter to nail down.

--
Karen

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Only one opinion - don't take advice from that modeler anymore.

-DSE

Sent from my iPhone

David S Eldridge's picture
Joined: 2011-09-30
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That's true. I should have phrased my reply to include that one needs to
give an explanation for anything less than 25%. Anything more than 25%
does not need extra documentation.

-Rohini

Brahme, Rohini            UTRC's picture
Joined: 2011-09-30
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ASHRAE 90.1-2004 appendix G states that these plug and other loads shall
be included in both baseline and proposed design. If you have more
efficient HVAC system for your proposed design, it will actually help
you. A microwave or oven maybe not be, but refrigerator will run
continuously and add heat into space. This makes HVAC system to run
more.

Kosuke Kato, LEED AP

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