[Equest-users] Economizers

[Greg Collins]

Keep in mind what kind of system you are using when adding an econo cycle.  If your system has a single-stage compressor and you do not lock it out, it will be cycling on and off if the OA requires just a little bit of cooling to meet your mixed air setpoint and will not work well.  If you have a multi-stage DX cooling or chilled water, it will work much better. 

Greg Collins
GLUMAC | (949) 833-8190

-----Original Message-----
From: Dave Bastow [mailto:dbastow at mcclure-engineering.com] 
Sent: Tuesday, March 29, 2011 8:26 AM
To: 'Dane Heimerman'; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Economizers

Dane,

The following settings have worked the best for me. 

Under Air-Side Economizer Cycle
Outside Air Control: Set to OA Temperature
Dry Bulb High Limit:  Set at 70 degrees
Lockout Compressor:  Set at No
Maximum OA Fraction: Set at 1.0 ratio
On all other entry items enter nothing.

On the Dry Bulb High Limit, you can experiment runs with temperatures up or
down from 70 degrees to see what gives you the best return or savings.

Normally, if you say yes under lockout the compressor then the refrigeration
compressor will run a lot more, as the economizer will only be used when it
can meet all of the load and the compressor will be on the rest of the time.
While if you say no then the refrigeration compressor will just help with
trim on that little bit that the economizer air doesn't quite meet the load.

This is what seems to have functioned the best for me for modeling purposes.
On a medical clinic with high internal heat gains you should have
significant savings if the air-side economizer and the minimum OSA settings
are set up correctly.


David A. Bastow 
McClure Engineering, Inc.  

   

-----Original Message-----
From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Dane
Heimerman
Sent: Tuesday, March 29, 2011 8:19 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Economizers

Hi Everyone,
I just wanted to know if anyone has seen significant savings from air-side
economizers. Most of our buildings are in Pennsylvania, I'm guessing
location is the biggest factor. I'm trying to figure out if I'm setting them
up right. I've tried them in a couple projects, and they always show about a
5-6% cooling energy savings. I use the 'OA Enthalpy' 
control method, with a high limit of 30 Btu. I have 'lockout compressor' 
turned off. The building is a 4000 sq. ft. medical clinic. I'm not sure if
other building types typically save more energy than others.

Let me know your thoughts.

Thanks,

--
Dane Heimerman
HVAC Engineer
Michael L. Norris&  Associates, Inc.
270 Walker Dr, Suite 201B
State College, PA 16801
p:814.867.3823
f:814.867.4823
daneh at mlnai.com


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