Dear all,

We are trying to simulate a water to water heat pump with vertical boreholes heat. Therefore, we integrate a text file with heat requirements, and with that we want to measure how many boreholes we need.
Because of high heat power, we chose a two stages water to water heat pump (Type 1221). According to the heat power, we determine the different flow rates and the number of used stages of the heat pump (0 m3/h if it's not working, 21.5 m3/h if we need only one stage, 43 m3/h if we need two). To obtain that, we have in parallel two pumps, they are working with fixed flow rate, one starts whenever we need heat and the second one starts only when it's necessary to have a higher heat power.
So, we have three different flow rate set-points for the heat pump. However, every time a problem appears when we try to simulate this scenario :

Error message :
The file C:\Trnsys17\Tess Models\SampleCatalogData\Water-to-waterHeatPump\Normalized2-stage\WWHP_2ndStageHeating-Normalized.dat was called 636 times (7% of the time) with a fourth independent variable value above the range supplied in the data file. Data is interpolated within the data file range but is not extrapolated beyond the range. Performance of the equipment modeled by this UNIT may be incorrect.

The problem seems to appear when the value of the flow rate changes. What can we do to solve the problem?
With the email, we add our trnsys file if you need it.

Thanks for your help.
Best regards,

Morgane LE BRAS
BET ETB

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