Queries

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Hi all,

I am an eQuest newbie and had 2 small queries which hopefully would be
answered.

01. What's the logic behind eQuest giving positive (+ve) Cooling Loads &
(-ve) negative Heating Loads. (I made an Admittance Method Algorithm & it
gives me the opposite values, eQuest i.e. negative cooling loads & +ve
heating loads, have checked all sign convention...can't figure out why? My
algorithm simulates for Delhi's (India) climate predominantly, cooling
loads.

02. I have asked this before...is there any library for data of alternating
solar gain factors, especially for Delhi, India. (As far as i believe
it does'nt take into account the alternating solar gain factor...)

hope these get resolved soon, thanks in advance.

Regards,
Piyush

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Dear All,

What would you choose as the minimum efficiency for baseline modelling for the DX cooling (923 kW) of System Type 5 from Appendix G (Packaged rooftop VAV with reheat)? I am looking at a model previously done by someone else and the COP has been chose as 2.96, which could mean that they have used Table 6.8.1A - Condensing units, air cooled. But I am not sure if this should be correct.

Thanks,

?mer Moltay, LEED AP

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Piyush,

I can help with 01., but I do not understand the concept of alternating
solar gain factor that you are referring too, or maybe I just don't
understand the question exactly.

For 01. I have always known the symbols of heating energy to be referenced
as (+) for cooling and (-) for heating although I can't give you the exact
reference this nomenclature comes from. In terms of the positive for
cooling energy it is a description for heat energy being present in the
conditioned space(s)/building in terms of heat energy being gained (or
generated.) Where the negative symbol is used to represent heating energy
this is describing that heat energy from the space/zone is being
lost via....whatever the mechanism (i.e. ext. wall or window conduction
losses, to exhaust air heat energy loss from the building, to infiltration
effects, etc.)

As long as you can keep your symbols managed with in your own simulation
work don't let this little quirk stop you from reporting your numbers in
your preferred format. It is good that you are asking these types of detail
questions so that you can ensure your own foundation of understanding for
the tools you use. This is what makes a good energy simulator. Keep
asking questions, this list is a HUGE benefit from my experience.

pasha

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Joined: 2011-09-30
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Omer,

I would use 6.8.1D. Just because you are looking at a COP value doesn't
mean that it wasn't originally an EER or SEER value, you might want to back
out the EER value from your equivalent COP and see if you can reference it
from the 6.8.1D table for Packaged equipment performance.

pasha

2010/5/4 ?mer Moltay

Pasha Korber-Gonzalez's picture
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Omer:

For system type 5 you should be using sub-category "single package" with the appropriate heating section type from Table 6.8.1A. Table 6.8.1D applies to system types 1 and 2, small packaged terminal units.

Hope this helps. Have a great day!

Cam S. Fitzgerald, PE, LEED AP

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It make think of the sign convention used in Thermodynamics. You have the System and its Surroundings. Let's say that the System is the building.

In Thermo, heat received by the system from its surroundings (cooling load) is "positive". The heat lost by the system to its surroundings (heating load) is "negative".

It is the inverse for work.

_____________
Demba NDIAYE

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Hi,
thank you all...again the alternating solar gain factor is thorn in my
flesh...i was actually looking for hourly data for New Delhi for eight
orientations (N,S,E,W,NW,NE,SW,SE)...
just in case anybody is familiar with the Admittance Procedure here is the
formula

Qs(swing)-Swing in Fluctuating gains for Transparent surfaces.
A-Area of the glazing
I-Intensity
S-Solar Gain Factor

Formula
*Qs(swing)=A X I(swing) X S(swing)*
where, I(swing)=Intensity(at time t) - Average Intensity
& S(swing)=S(at time t)-Average S

here is what Nick had suggested...but having tried that i didnt quite get
the right results...maybe i am doing some thing wrong.....I would get S=.86
for all sunshine hours(mult factor=1) & S=0 for the night(& early morning)
hours when there is no sunshine (mult factor=0) but here is a gist of the
previous brainstorming session..

Hi Piyush,

Apologies, I wasn?t sure whether you meant SHGF.

I did some googling to check my vocabulary and found this reference:
http://www.levolux.com/L_PDF_Files/Lev.
Comp Analysis Table.pdf

It looks like: Solar Gain Factor (S Factor) = Shading Coefficient (SC) *
0.87

I can add that: Shading Coefficient (SC) = (Center of Glass SHGF) / 0.87

So to answer your first question, while this is the first time I?ve
personally run into S Factors, it would appear they?re analogous to a
center-of-glass SHGF, but can vary based on external shading devices
(including trees, curtains and shades) per the above. I?m copying
eQuest-users to share the following procedure and to allow others to correct
any misunderstandings we may have regarding what S Factor really means ? I
hope you don?t mind!

So per your second inquiry to determine the hourly S Factors, and because I
was curious, here?s a procedure:

- Set up your windows and all variable shading items.

- Create an hourly report/block for the window(s) in question
selecting the items shown in the screengrab below ? SC and ?Value by
which?? SC multiplier for those of you in the archives.

- Run the simulation and open the hourly results up in excel (hit
the ?hourly results? button in the sim viewer).

- Multiply those values across to get your hourly effective SC, and
again by 0.87 to get an hourly S Factor.

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Cam,

I'm curious to where you found the reference for a "single package"
sub-category and how it is pointing to table A to be used for performance
factors of packaged equipment as opposed to table D which is specific to
packaged a/c units.

I looked back through 90.1 and can't find any notes or guidance to follow
your recommendation to point me to table 6.8.1A. Can you please provide
more specific reference to where you are getting this info from Appendix
G? This could be a significant thing for the rest of us to learn and for
me to correct if I have missed the info you are refering to.

Thanks for your help on this.

pasha

Pasha Korber-Gonzalez's picture
Joined: 2011-09-30
Reputation: 400

Pasha,
Appendix G section G3.1.2.1 indicates: "All HVAC equipment in the baseline building design shall be modeled at the minimum efficiency levels, both part load and full load, in accordance with Section 6.4."

Section 6.4 includes Tables 6.8.1A through 6.8.1G.

Mark Zoeteman, FTC&H

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This happened to me before, but I do not remember how to recreate the.INP file.?I have the complete (I think) .PD2 files, so I think this should be able to recreate the .INP file. There IS still an .INP file, but has virtually nothing in it.

Any suggestions?

John R. Aulbach, PE, CEM

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Frequently I see 2 ,inp files, one with data one with no data.
Carol

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Do you have any .inp files from parametric runs from before the crash? Each time this has happened to me I've been able to rename one of the parametric .inp's and use it to open the model again.

Matt Dubrovich, P.E.
LEED AP.

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Pasha:

The description for system 5 in Table G3.1.1B describes the system type as "packaged rooftop variable air volume with reheat" which is the type of equipment covered in Table 6.8.1A Electronically Operated Unitary Air Conditioners and Condensing Units. The "single package" sub-category can be found in the fourth column from the left in this table which also contains information for split systems. Table 6.8.1D covers very small capacity terminal air conditioners which are defined in Section 3.2 as "a factory selected wall sleeve and separate uncased combination of heating and cooling components, assemblies, or sections. It may include heating capability by hot water, steam, or electricity and is intended for mounting through the wall to serve a single room or zone."

More information can be found about these system types in the ASHRAE Systems & Equipment Handbook.

Cam Fitzgerald

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You indeed have to use Table 6.8.1A. The units in Table D are for the terminal units (they are normally un-ducted, in direct contact with the space they serve).

_____________
Demba NDIAYE

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John,

If you edited your project in detailed mode, you will not be able to
recreate the inputs with pd2 file alone. If your main 'MyProject.inp' file
is corrupted, I'd check in the project folder to see if you have other
usable inp files such as 'MyProject -Baseline Design.inp' or ''My Project -
1.inp' (created by Parametric Run tool). You can pick the workable inp file
for the run that is most similar to your main project (contains fewer
parametric changes), save it as 'MyProject.inp', open the project in eQUEST
main interface, and update the inputs that were different in the surrogate
inp file. For example if you used inp file for the parametric run that
changed building azimuth (App G baseline rotations), you would change the
azimuth back to reflect the actual orientation.

Good luck,

Maria

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So what's the difference (other than minimum efficiency) between a 230,000 Btu/h single package air conditioner in Table 6.8.1A and a 230,000 Btu/h single package vertical air conditioner in Table 6.8.1D?

I guess the SPVAC is installed on an outside wall (per the definition in Section 3.2), but I don't see where units in Table 6.8.1A are necessarily rooftop units per the Table G3.1.1B requirement.

William Bishop, EIT, BEMP, LEED? AP

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Hi all,

Second Law of Thermodynamics, heat flows from hot body to cold body, thus a
pos/neg sign convention necessary: cooling load positive, heating load
negative.

Regards,
Carol

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90.1P ECB Subcommittee can you provide us with some definition? Mike R?
Jason? Help!

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I agree with Bill, he stated better than I could when he said, "I don?t see
where units in Table 6.8.1A are necessarily rooftop units per the Table
G3.1.1B requirement."

pasha

Pasha Korber-Gonzalez's picture
Joined: 2011-09-30
Reputation: 400

Yes, as Carol said you will typically see two .inp files for your base
project--one will be yourproject.inp & one will be yourproject-Baseline
design.inp.

The latter one I have always experienced it to be empty (0 kB), but the
first one is the one you are looking for. Maybe just double check you are
opening the first file for your project.

If it's a bigger problem than that, send your zipped files to look at.

pasha

Pasha Korber-Gonzalez's picture
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Bill & Pasha:

Not to belabor the point, but I suggest (again) you look in the ASHRAE HVAC Systems and Equipment Handbook. In the 2004 edition Chapter 45 provides detailed descriptions of Unitary Air Conditioners and Heat Pumps and Chapter 46 covers Room Air Conditioners and Packaged Terminal Air Conditioners. If you do not have this reference, I strongly suggest you acquire it since understanding the various system types is crucial to the correct application of ASHRAE 90.1.

Cam S. Fitzgerald, PE, LEED AP

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Has anyone had good luck with modeling steam boilers? It seems odd that the only loops that can be created are HW loops. There's no such thing as a steam loop in eQuest.

Thanks,

KATIE L. M. TUTTLE EI, LEED(r) AP

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The test procedure differentiates the equipment. If it is
rated using ARI 390 then it is a SPVAC while different ARI
test procedures are used for Table 6.8.1A equipment. I have
always believed that System 5 "packaged rooftop VAV with
reheat" from Table G3.1.1B is referencing Table 6.8.1A
single packaged equipment.

Jason

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Hi Katie,

Zero experience designing/modeling steam boiler systems, but I see an
option to create a steam boiler in both the detailed and wizard modes.

Creating a dummy forced draft steam boiler in wizards makes a boiler/HW
loop with starting setpoints of 230F/180F, and a help file says the
larger of the two will be used - 230F looks something like a steam
temperature to me, so it appears to be a steam loop in function, if not
in name... I see a default pump is added from the wizards - not sure
whether one can remove that without causing errors, or even if you
should... My rudimentary understanding of steam distribution is that
there is no explicit pump/fan for circulation - the steam boiler
provides the pressure?

I'd be very interested for someone with more experience to chime in on
this!

NICK CATON, E.I.T.

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Unfortunately you need some water flow in the loop. If all heating is by
steam add a dummy zone with some small HW heating load.

Mike

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