Load Reset Control - EMS?

asked 2016-11-02 11:39:15 -0600

updated 2017-05-17 12:19:31 -0600

I have a central plant loading scheme which uses a Load Reset to control the supply water temperature. The control logic is thus,"...the chilled water temperature is reset upwards to maintain at least one control valve serving an AHU is open greater than 90% open."

I haven't found a single "SetpointManager:XXX" object in Energy Plus which has this ability. Is this correct? Does this lend itself to use of the Energy Management System object(s) to achieve this control? Is there another Group of Objects that I missed? If it is EMS, are there examples anyone can point to/reference? Thanks in advance.

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So this is a constant flow, variable temperature plant loop? If so, this user voice request I opened 1 year ago should be of interest, linked to this UH question.

Anyway in this case, EMS would indeed be the way to go.

Julien Marrec gravatar image Julien Marrec  ( 2016-11-02 17:28:32 -0600 )edit

If it is variable flow, I'd guess SetpointManager:ReturnTemperature:ChilledWater could come fairly close to replicating the desired behavior after some trial and error to find a return setpoint that met the logic, depends how many different chilled water loads you have. Otherwise EMS, no examples.

Archmage gravatar image Archmage  ( 2016-11-02 17:59:08 -0600 )edit

It is a variable flow chilled water system. The actual control logic is that the CHW Temp reset occurs after the CHW pumps have been a minimum speed for 15 minutes. Thus, the intent is to unload the chiller when the pumps are at minimum speed; with the control point being the most open control valve at the coils. I've seen this logic in other instances where the goal is to keep at least 1 control valve open, resetting the supply temperature until this is true, and then reversing towards 'normal' once more values open, thus demand is increasing.

dradair gravatar image dradair  ( 2016-11-02 18:19:20 -0600 )edit

(continued) It is essentially a 'load reset' option type option. Load/demand decreases, the Chiller/supply can unload as well.

Its similar to supply air temperature reset, where the fan is at minimum speed and the DAT can then increase. Yes?

@Archmage ...that is a thought on using the return CHW temp.....may have to see...otherwise - off to EMS we go...

dradair gravatar image dradair  ( 2016-11-02 18:23:32 -0600 )edit