[EnergyPlus_Support] Control temperatures for WaterHeater:Stratified? [6 Attachments]

["robertogrilloait@xxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx>]

Hello everybody,

I am simulating a water/water heat pump with a stratified tank (10 nodes) and am having questions regarding the control of this 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.

What about the temperature used for cut-out? Is it the highest temperature (node 1)? It does not seem to be so.

With a constant set point, the heat pump switches on and off such that the low node temperature stays around the cut-in temperature, which may seem logical as the highest tank temperature remains above the cut-out temperature.

In the example with moving set point, the heat pump keeps switching on and off (see movingSetPointResults.PNG), even when all node temperatures are below the cut-out temperature, in which case the heat pump should stay on after switching on.

I would be very grateful for a more detailed description of the control scheme for WaterHeater:Stratified, respectively for an explanation of these results.

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Posted by: robertogrilloait@xxxxxxxxx

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