[Equest-users] Water side economizer

Thu Nov 5 08:39:13 PST 2015

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.

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The DOE2.2 help menu description for WSE is in this section: Volume 2: Dictionary<mk:@MSITStore:C:\Users\bbishop\Documents\eQUEST%203-64%20Data\Help\DOE-2.chm::/Docs/volume2dictionary.htm> > HVAC Components<mk:@MSITStore:C:\Users\bbishop\Documents\eQUEST%203-64%20Data\Help\DOE-2.chm::/Docs/hvaccomponents.htm> > SYSTEM<mk:@MSITStore:C:\Users\bbishop\Documents\eQUEST%203-64%20Data\Help\DOE-2.chm::/Docs/system1.htm> > Cooling Equipment<mk:@MSITStore:C:\Users\bbishop\Documents\eQUEST%203-64%20Data\Help\DOE-2.chm::/Docs/coolingequipment.htm>
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

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From: Equest-users [mailto: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
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LinkedIn (en) : www.linkedin.com/in/julienmarrec<http://www.linkedin.com/in/julienmarrec>
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2015-11-05 15:11 GMT+01:00 John Aulbach <jra_sac at yahoo.com<mailto: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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