[Equest-users] Water Side Economizers

[Brian Fountain]

My understanding (feel free to correct, those who know):

- the water side economizer chiller is the newer, more correct way of 
modelling the system you describe -- where a plate frame heat exchanger 
is in parallel with the chiller with chilled water on 1 side and 
condenser water on the other.  This is what I use.

- the air-side, water-side economizer tab adds a new cooling coil 
connected to the condenser loop to precool your incoming air as well as 
pre-cooling the condenser water before it goes to the chiller.  Similar 
but this adds fan energy (static across the new chiller) and pumping 
energy and isn't really how a water-side economizer system that I am 
familiar with is implemented (at least around here).

- in DOE-2.1e, you used to be able to set your cooling tower control to 
"strainer cycle" which would also give you a water-side economizer but I 
believe this was lost in going to DOE-2.2, with real loops etc.  Adding 
the water-side economizer chiller, restored this function.

One more note -- I understand that you do not need a load management or 
equipment control to operate a water-side economizer chiller ... and 
further if you add them, they will be ignored anyway.  If there is 
sufficient cooling based on the outdoor air temperature for the 
water-side economizer chiller to carry the full cooling load, then it 
will operate (for that 1 hour timestep).  Otherwise, it will not operate 
and the chillers will carry the full cooling load.  There is no partial 
operating mode.

Cheers,

Brian



On 6/6/2011 1:09 PM, Patrick Keeney wrote:
> Hi All,
> What is the difference between a "water side economizer chiller" and a 
> "water side ecomizer," which you find under the air-side HVAC cooling 
> subtab?  What does each do for their respective systems?
> I am trying to model a water-side economizer that runs in series with 
> the other chiller, so I am pretty sure that I want the "water-side 
> economizer chiller."  I just want to be sure because there is a 
> substantial difference between the two in energy savings (water-side 
> ecomizer chiller is more efficient).
> Thanks,
> Patrick
> -- 
> Patrick J Keeney
> MArch-MSSD Candidate
> 410-299-5627
>
>
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