Air Side Economizer savings

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I have been trying to model an existing building for which one of the
parametric run being Air Side economizer savings. Every time (for
different buildings) I do this run I come across negative savings. The
building is located in New York. The system is a multi zone system. I
hear that many people have across this situation. My cooling savings is
also minimal. Am I doing something wrong?

Please advice.

Thanks

Anusha

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Which keywords did you adjust in your parametric component?

Joe Fleming
E.I., LEED AP BD+C, BEMP

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Outdoor Air Vent &Economizer - OA Control - OA
temperature

This is the parameter I changed. And then I also inputted DBT High Limit
(65F) and DBT low limit (45F).

Thanks

Anusha Sabesan

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Ok. Add Econo-Lockout and set it to yes. Then, when you are in the Parametric Run Definitions dialogue box, click on grid view and compare to the Baseline items.
For an accurate savings comparison, check to make sure Baseline has "NO" compressor lockout and your run says "YES". Also check to make sure the baseline OA control is set to "FIXED". (And you can compare other inputs to make sure you are comparing the two systems the way you want).
Can you email the grid view?

Joe Fleming
E.I., LEED AP BD+C, BEMP

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Joe,

So this worked for a multi zone building that I had. Thanks

I tried the same one for another building which has packaged Multizone,
Packaged VAV systems.

In addition to AIR Side economizer savings I am also going Night
setback, Fixing VAV's ,SA temp reset and finally the air side economizer
savings.

This is my Grid view. I really appreciate your help.

Amber,

I am getting negative heat savings. I am looking for a very conservative
number and that is why I chose 65 and 45. Thanks

Anusha Sabesan

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Assuming that the comparison is being made between the "SA Temp..." run and the "Air Side..." run;

* try setting the economizer dry bulb limit down to 55 degrees. Probably not helping at that high entering temp. More cooling will be required when all of that 65 degree air comes in, especially when it is humid outside.

* Change the compressor lockout to "NO", you want to maintain a constant leaving air temperature and mix the air streams to 55.

* Try lowering the lower limit below 45 or doing away with it altogether. You are missing out on the free cooling you will get when the air is 30 degrees outside. Since you are always supplying 55 degree air, 30 degree entering air will be mixed to 55 and less cooling will be needed for the interior zones.

Let me know how it goes

Joe Fleming
E.I., LEED AP BD+C, BEMP

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Hi All,

I was hoping for a comment on a suitable approach for modeling a university
classroom building that has laboratory exhaust fume hoods. Of the three
floors, the lab hoods are only about a third of one floor but do have a
significant airflow discharge (with make-up). The building is about 50,000
sf.

I plan to develop a schedule for the fume hood fans and apply airflow to the
fans and have these be the same for the baseline and proposed cases. Do I
simply apply it to the standard exhaust inputs or is there a "lab hood" area
in eQUEST I cannot find? Any advice on how to capture and schedule this
exhaust would be helpful if this approach is not suitable.

Thanks for all of your help!

Jeffrey G Ross-Bain, PE, LEED, BEMP

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Anusha,

Are you having this problem with the Packaged multizone or the packaged
VAV? If you are having the problem with the packaged multi-zone that is
b/c you have a dual duct system and while you are cooling off the SAT,
you are also lowering the heating temp (which then has to be heated).
This is expected for Packaged multizone (or dual duct systems where each
zone air is mixed).

In regards to economizer setting you should try and see the cooling
savings you get when the economizer is set to 70F and even up to 73F.
The air is likely not too humid when the OSA temp is this mild. This
will reduce your cooling because it reduces the delta T seen at the
coil. You will want the compressor to be able to run when the
economizer is on b/c you may be bringing in 70F air (which is better
than 76F return air temp) and this temp will need to be reduced to 55F
(or whatever your setpoint).

Make sure you have cooling deck supply reset, so you can reduce the
heating when most of your building will need heating.

Amber

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Jeff,
The newer versions of eQUEST have the ability to track exhaust on a zone-by-zone basis (I think this was added specifically for fumehoods). You would use the track exhaust flow option (where it modulates the supply to ramp up from minimum to match exhaust flows). You can assign power numbers to the exhaust fan.

Vikram Sami, LEED AP

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