[Equest-users] Water side economizer
Nicholas Caton
ncaton at catonenergy.com
Sat Nov 7 17:43:36 PST 2015
Hi John,
I haven’t opened/picked apart your model, but some time ago I provided the
following outline to this mailing list for a procedure to consider:
*Hi Nikola, good to hear from you!*
*An approach I like to start with (sometimes this is a rough approximation,
other times it is very accurate & appropriate), is:*
*1. **Establish an outside temperature at and below which the
waterside economizer is designed to handle the building’s cooling loads (or
largely so)*
*2. **Create a “free cooling” chiller with an EIR a hair above zero
(something like 0.0000001), attach it to the CHW loop(s) servicing your
coils, alongside the regular chiller(s)*
*3. **Create a pair of equipment control sequences: “Free” and
“Normal”*
*a. **For the “Free” control sequence, assign the “free cooling
chiller” in the first row to handle loads first. You may optionally also
assign the actual chillers and associated capacity ranges for each.*
*b. **For the “Normal” control sequence, specify your normal chiller
sequence of operations*
*4. **Then create a Load Management of type OA-TEMP. *
*a. **Set the outside air temperature below which free cooling is
active under management sequence 1, and assign the free cooling control
sequence defined in the previous step.*
*b. **Set management sequence 2 to a maximum OSA temp of 999, and
assign the normal control sequence from the previous step*
*Integrating WSE into eQuest is one of those things I always plan on
spending extra time on – the devil is in the details! I don’t believe
waterside economizer systems are something you can make a simple rote
procedure around, as actual waterside economizer system
operations/limitations are varied and nuanced. Consider this a simple
outline to convey the approach concept & get you started. I would
particularly advise paying close attention to your pumping and heat
rejection energies from this point forward.*
*Hope that helps get you started - Happy new year!*
*~Nick*
I have simulated a number of different WSE arrangements since posting
that, but still follow the same general outline/strategy. The sequencing
part in particular is where the meat of the puzzle lies, project to
project. You should be able (and I advise) to describe for yourself in
writing exactly how the chiller(s) and free cooling operation should
sequence with each other. Then go and translate that into a meaningful set
of equipment control sequence inputs. I have found actually entering the
“capacity” of free cooling at the chiller makes complicated sequencing a
bit more manageable as an extra tip, but it may come down to just how your
brain processes the problem what approach is easiest.
Best of luck!
~Nick
*NICK CATON, P.E.*
*Owner*
*Caton Energy Consulting*
306 N Ferrel
Olathe, KS 66061
office: 785.410.3317
www.catonenergy.com
*From:* Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] *On
Behalf Of *John Aulbach
*Sent:* Thursday, November 05, 2015 11:21 AM
*To:* Bishop, Bill; Julien Marrec
*Cc:* Equest-users
*Subject:* Re: [Equest-users] Water side economizer
Gentlemen:
Here is the model. Pick away. I just don't think it makes sense in SoCal vs
an air side.
Please keep the client close to your vest. This building is on the site of
the old Gene Autry studios.
On Thursday, November 5, 2015 8:39 AM, "Bishop, Bill" <
bbishop at pathfinder-ea.com> wrote:
John,
The energy savings for air handler water-side economizers (WSE) will
largely depend on the pumping energy, as you note. These are different than
the water-side economizers that are cooling towers for serving chilled
water systems, allowing chiller(s) to turn off.
The default coil head is pretty high (20’) so override the default if
appropriate to your design.
The DOE2.2 help menu description for WSE is in this section: Volume 2:
Dictionary > HVAC Components > SYSTEM > Cooling Equipment
Part of the description mentions operation to supplement (not entirely
replace) the cooling coil and/or air-side economizer:
The water-side economizer coil is assumed to be downstream of the mixed air
plenum, and upstream of the cooling coil. As such, the cooling coil may
supplement the operation of the water-side economizer. The air handler may
also have a conventional outdoor-air economizer, in which case the
outdoor-air economizer will operate first to meet the supply-air setpoint,
then the water-side economizer will supplement the outdoor-air economizer,
and the cooling coil will pick up the remaining load, if any.
Regards,
Bill
*William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers &
Architects LLP*
*Senior Energy Engineer*
134 South Fitzhugh Street Rochester, NY 14608
*T: (585) 698-1956* F: (585) 325-6005
bbishop at pathfinder-ea.com <wbishop at pathfinder-ea.com>
www.pathfinder-ea.com
[image: http://png-5.findicons.com/files/icons/977/rrze/720/globe.png]Carbon
Fee and Dividend - simple, effective, and market-based.
*From:* Equest-users [mailto:equest-users-bounces at lists.onebuilding.org
<equest-users-bounces at lists.onebuilding.org>] *On Behalf Of *Julien Marrec
*Sent:* Thursday, November 05, 2015 11:17 AM
*To:* John Aulbach <jra_sac at yahoo.com>
*Cc:* Equest-users <equest-users at lists.onebuilding.org>
*Subject:* Re: [Equest-users] Water side economizer
John,
Never did a waterside economizer for RTUs, but a couple of points I think I
remember:
The waterside economizer in eQuest is all or nothing: if it can satisfy the
entire load, then it's on, otherwise it's off. Are you autosizing or
hardsizing it?
It also poses the questions of how you reset the condenser water loop
temperature, and how you reset the rooftop supply air temperature during
low load condition.
What are your current settings?
Julien
--
Julien Marrec, EBCP, BPI MFBA
Energy&Sustainability Engineer
T: +33 6 95 14 42 13
LinkedIn (en) : www.linkedin.com/in/julienmarrec
LinkedIn (fr) : www.linkedin.com/in/julienmarrec/fr
2015-11-05 15:11 GMT+01:00 John Aulbach <jra_sac at yahoo.com>:
Hello all and HALP !!
I have an office building in Los Angeles that is looking to go LEED Core
and Shell. It has some exterior and back of the house lighting, so the
savings there make sense. But the building has 6 DX 30-50 ton Trane rooftop
package units, two on the 1st floor and one for each of the other 4 floors.
These are WATER COOLED units.
These units have a central outside air stream, and have WATER SIDE
ECONOMIZERS.
My Base model has an air side economizer (still water cooled condensers).
The proposed model removes the air side and replaces it with the water side.
The units themselves are EER 14+, whereas the Base units are 10.8 EER.
Results show a SLIGHT savings in Space Cooling, which I attribute to the
EER improvement MINUS the air side economizer removal (Jan and Dec space
cooling load INCREASES in the Proposed Case).
But the pumping energy skyrockets about 50% (remember, no chilled water).
I am unsure if I am running the water side correctly. There is only the one
line of data at ever SYSTEM level.
Help??
John R. Aulbach
Aging engineer (by the minute)
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