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Control nodes for WaterHeater:Stratified

asked 2018-06-28 07:08:17 -0600

aubr gravatar image

updated 2020-01-20 15:11:25 -0600

Hello, The control of a WaterHeater:Stratified for space heating is giving me trouble: I cannot figure out what heights/nodes are used for cut-in and cut-out, and whether I can modify this according to my needs. More specifically: I am simulating a water/water heat pump with a stratified tank. According to the documentation, the heat pump would be supposed to turn on when the tank temperature is less than the cut-in temperature, and turn off when the tank temperature is more than the cut-out temperature. However, in the case of a stratified storage, it is not specified in the documentation what node temperatures are considered here. According to the results I obtain, it looks like the temperature used for cut-in is the lowest temperature (node 10 in my case), which also corresponds to the height of the source-side outlet and the use-side inlet. As for the temperature used for cut-out, it does not appear from the results what it is. What I would like is to have the highest temperature (linked to use-side outlet and source-side inlet) used for cut-in and the lowest temperature for cut-out. It would be great if someone could tell me if this is possible, and if so how to do it?


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answered 2018-07-11 11:21:24 -0600

Inspection of the source code shows that the use side outlet temperature at the end of the previous system time step is used to control indirect (source side) heating demand for plant loop heat sources serving a WaterHeater:Stratified tank.

For air-source heat pump water heaters, there are fields to specify the height of the control sensor(s).

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Thank you very much for your clarifying answer! Let me draw my conclusions for the case I want to model (water source heat pump with stratified tank, use-side outlet temperature to control cut-in and use-side inlet temperature to control cut-out):

  1. The control model coded in EnergyPlus will not allow me to model the case I want, because use-side outlet temperature is used to control both cut-in (as desired) and cut-out (for which I would like to use another node).
aubr gravatar image aubr  ( 2018-07-11 14:18:15 -0600 )edit

2 - Assuming I use WaterHeater:HeatPump as a workaround (using the air source heat pump to somehow model a water source heat pump), the field "Control Sensor Location In Stratified Tank" would allow me to specify a single node for heating demand control (both cut-in and cut-out), so this would not be satisfactory either. 3 - The only possibility remaining to model a control scheme with separate nodes for cut-in and cut-out is probably to use the Energy Management System (EMS) method, so I will look into that.

aubr gravatar image aubr  ( 2018-07-11 14:19:12 -0600 )edit

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Asked: 2018-06-28 07:08:17 -0600

Seen: 154 times

Last updated: Jul 11 '18