Heat Recovery Chiller and Boiler Work Together

asked 2016-08-15 16:48:06 -0500

lyw0211
429 ●7

updated 2019-11-07 11:29:10 -0500

MatthewSteen

10077 ●18 ●25 https://www.nrel.gov/b...

I am working on a complicated heating hot water system, which supplies hot water by boiler (Outdoor air temperature is lower than 60F) or by heat recovery chiller (Outdoor air temperature is higher than 60F). Although there is some suggestions here, but I don't know how to combine it with a boiler. Does anyone has any experience or suggestions can offer? That will be very helpful! Thank you! Some topic about heat recovery chiller: https://unmethours.com/question/1742/

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Please always tag your questions with the software, thanks.

MatthewSteen ( 2016-08-19 13:47:41 -0500 )edit

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answered 2016-08-19 11:53:03 -0500

jmcneill

1749 ●6 ●16 https://edoenergy.com

The recovered heat from the Chiller:Electric:EIR will be added to the attached heat recovery loop, and is a passive benefit. You can control the heat recovery chiller to only recover heat to meet the loop setpoint. You will need to connect the heat recovery loop to the main heating loop with either a WaterHeater:Mixed or a HeatExchanger:FluidtoFluid. I recommend the WaterHeater:Mixed so you don't have to worry about the approach temperature, if modeling a three-way valve.

Then I would use the PlantEquipmentOperation:OutdoorDryBulb to control whether WaterHeater:Mixed or Boiler:HotWater is staged on. It may be a bit tricky to get this to work properly. I've had to really tune the temperature setpoints of the loops to get this type of system to work properly.

If that control doesn't work than I would recommend using the EMS manager to stage the equipment. Look at the PlantEquipmentOperation:UserDefined object for this capability. The Application Guide for EMS is a good resource to get started with this type of control.

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E+ 8.7 I'm modeling a chilled water system with 4 water cooled chillers, 2 w/ HR capabilities. The set of chillers are sequenced based on ranges of chilled water load, sequencing the 4 machines is simple. My (2) HR chillers, when operating, attempt to heat a closed low temperature water loop serving several VAV boxes w/ HW reheat. HW demand is served by a boiler under conditions when the HR chillers are idled.

James can you describe, in E+ parlance, the relationships of all loops and objects, and which side (demand or supply) they belong to, for your example above? A 1 line schematic ?