Revert efficiencies to autosize from detailed?

5 posts / 0 new
Last post

HI All-

While there are some posts similar to this issue, I want to ask the group
for clarification for a slightly different application. Please bear with me
for some assistance, I'd sure appreciate it!

I am working on someone else's model that has had comments back from GBCI
for a LEED project. The model came to me in detailed mode. They note that
in the baseline model apparently non-90.1 baseline efficiencies were used.
Looking at the model, it does seem that the modeler manually entered
efficiencies (they are in red) and they do not seem to be correct (even the
GBCI comment notes this). They are less efficient than 90.1. In some of the
similar threads on this topic, someone mentioned that you can revert to
autosizing by right clicking on the heating and cooling capacity and
selecting "restore default". Since the modeler did not manually input
system size, just system efficiency (both cooling and heating hp eff, fan
design kw/cfm and total eff frac seem to be manually entered), my question
is if I restore those efficiency values to default (using right clicking),
will Equest use the proper efficiencies and I'm good to ho? I've done this,
and it seems to work, although I'm not experienced enough to truly verify
this.

When I compare the two models (original base and my reverted base) I do see
where the power demand has dropped (SV-A), and none of the peak loads have
changed (LS-A) but the equipment sizing (SV-A) has increased. This all
seems correct, do others think I am on track here? Using the correct
methodology?

If I can also confirm another question, LEED specific. I understand 90.1 is
the only appropriate base case for LEED even in Washington state, even if
portions of their energy code are more stringent, correct? The requirement
to achieve a 10% reduction is how I think LEED addresses more stringent
state codes so the base doesn't need to be written specific to those
(numerous) state codes. Correct? One comment from the client leads me to
think that complying with WA code might explain the difference in equipment
efficiencies used in the base case, and even though it doesn't add up I want
to confirm my understanding.

Another issue that further confuses this is that the modeler apparently
chose two of the systems to be variable speed (all are system type 4,
constant volume in 90.1) and I'm not sure why. The original modeler is not
available for questioning. Any ideas? The VFD's were applied to an office
space and data/server room packaged heat pumps, but not a large storage
space. Based on what I know right now, it seems those should be modeled
constant volume. If I'm updating the base model, I think it makes sense to
correct this if the base incorrectly models a more efficient system.

Lastly, can anyone tell me how to change the project descriptor at the top
left of the sim reports? It's got some boilerplate name and it sure would
be nice to have the filename show, or at least a single descriptor I can
update in each model run.

Thanks so much-

Laura

Laura Howe, RCE's picture
Offline
Joined: 2011-09-30
Reputation: 0

Laura,

Many questions here, so I will try to respond succinctly to each, but
forgive me if I am a little short on details.

1) eQUEST WILL NOT default to the proper 90.1 baseline efficiency or
fan power for your systems. You need to look up the appropriate EER (or
COP, or whatever) and convert it to the proper EIR (unitless) efficiency
to input in eQUEST. However, to further complicate things, if the 90.1
baseline efficiency includes system fan-power, you need to separate out
that fanpower from the EIR rating and input the fanpower separately. There
has been much discussion of this even in the past week on the forums, so I
recommend doing some searches for "separating fan power" or the like.

2) Yes, use the defined 90.1 Appendix G baseline even if local code
is more stringent. Consider it a nice little bonus of working on projects
with strict energy codes.

3) System 4 (PSZ-HP) should have constant volume fans. You are taking
a penalty if they were made variable speed in the baseline.

4) You can edit the project name by opening the .inp file in a text
editor, and changing the "Title" field. Then save the .inp, reopen in
eQUEST and it should be good to go.

Nathan Miller, PE, LEED AP BD+C

Nathan Miller's picture
Offline
Joined: 2011-09-30
Reputation: 200

short answer: no

longer answer: equest reverts to a default efficiency of the type of
unit selected, in eir/hir not seer/eer or hspf/cop, that is not based on
90.1-2004, 2007, or 2010. the 'easiest' method of determing a 'correct'
efficiency (search archives for different methods of calculating a
'correct' efficiency') is to simply open a dummy project, go to the hvac
systems, change the efficiency (in seer or eer as applies to the minimum
required for your unit type) to the 90.1 required, save the project,
then switch it to detailed mode & look at the hvac unit efficiency in
eir/hir.

out of curiosity, what was the exact comment & what did the modeler use
for what system types?

Patrick J. O'Leary, Jr.'s picture
Joined: 2011-09-30
Reputation: 0

Nathan is quicker on the draw =). Here's my response as assembled prior to his flying finish - I think I get through his bullets 1 + 2, and I've nothing to add to his answers for 3 & 4:

This is not a knock on anyone, but I advise at the outset to take GBCI review commentary with a grain of salt, particularly when it concerns means/methods specific to eQuest or any given software package.

My baseline models normally include manually entered efficiencies and autosizing capacities (cooling, heating, airflow) - I do not see anything wrong in that. I am further personally unaware of any 90.1-baseline approach that relies on utilizing eQuest defaults for cooling/heating/fan efficiencies - to my knowledge there is no direct correlation between what eQuest wizards suggest for default efficiencies and any particular vintage of 90.1. I understand these should all be manually entered, after performing separate baseline fan power and efficiency calculations per 90.1 appendix G. My preference (and I think, the normal) is to use kW/CFM inputs for fans over the motor efficiency option.

If you aren't sure how to verify the effects of overriding manually entered heating/cooling/fan efficiencies, then I hesitate to recommend any course of action before pursuing that understanding first. Otherwise you can only be shooting in the dark.

An informed course of action, in an auditing role, would involve reviewing or better performing the calculations yourself from scratch for Pfan and corresponding cooling/heating efficiencies, then comparing your results against what the modeler assembled and input, thus identifying and correcting any faults directly.

LEED baseline requirements never shift to anything more strict than the appropriate vintage of 90.1. You can choose, at your option, to reference and document compliance with "qualifying energy codes" for EAp2 if I recall the present template language correctly, but nothing mandates doing so over 90.1. If a team should choose to design a building to meet/exceed 90.1-2010 or Title 24, that does not mean a LEED v3 baseline is anything better or more stringent than as prescribed in 90.1-2007.

~Nick
[cid:489575314 at 22072009-0ABB]

NICK CATON, P.E.

Nick-Caton's picture
Offline
Joined: 2011-09-30
Reputation: 605

The modeler used heat pump for heating and cooling. The exact comment is
long (too long for me to type, about 1/3 of a page), but it does talk to
using proper efficiency based on Equest autosizing (which as far as I can
tell autosizing was used, however there may be issues with the internal
loads used, that's another thing to investigate). I'm not sure how the
dummy project example you give will work, without fully building the
facility and loads in a model, autosizing isn't going to really work since
the required efficiency is based on system capacity? I'm thinking I will
work with the apparent system sizing I have now, update the efficiency
based on 90.1, rerun and hope the sizing stays within the same category.
Iterate if necessary.

The comment also brought up the need to break out fan energy from
cooling/heating energy, which I guess I had hoped would be worked out with
reverting to default. In response to Nathan's comments, I will review this
topic in the latest forums (this one and bldg-sim being the only two I use,
any others pertinent?) and hopefully get it straightened out.

On the flip side, a non-mandatory point is that they also seemed to use too
high of an efficiency for cooling. Perhaps that will cancel out the low
heating efficiency in the end..

Thanks so much, anything else is appreciated. I'm sure I'll be back once
I'm fully confused with splitting as Nathan talked about.

Laura Howe, RCE's picture
Offline
Joined: 2011-09-30
Reputation: 0