[TRNSYS-users] (no subject)

Jeff Thornton thornton at tess-inc.com
Sat May 12 08:50:36 PDT 2018


Although you didn’t tell us quite enough information about the layout and control of your system to be sure - especially as it pertains to the collector - I can provide the answer if we assume that the heat pump sends all the flow to the tank if it’s cold and the building is warm, all the flow to the building if it’s cold and the tank is hot, and half to each if the tank and building are cold.

In that case, use an equation block that has two inputs - let’s call them Tank_Cold and House_Cold.  These two inputs should be connected to the output control signals from the aquastat watching the tank and the thermostat watching the house.

The control signal for the diverter to the tank is then:

TankFraction = MAX(0,(Tank_Cold-0.5*House_Cold))

and then 

HouseFraction = 1 - TankFraction

You’ll also likely need the pump and heat pump control signals:


However in practice, heat pumps are rarely directly connected to the building in a 1-to-1 configuration as their capacity doesn’t match up typically to the heating device.  For example if you use radiators, the capacity of the radiator varies with the temperature and a heat pump may shut down on high temperature before the radiator gets up to temperature and delivers the load.  Best practice seems to be to have the heat pump charge the tank (top to bottom flow) and the house draw from the tank (bottom to top flow). This also works really well if you have collectors feeding the top of the tank with hot water.  You may also have to use a tempering valve to not overfeed the building supply temperature.


Sent from my iPhone

> On May 12, 2018, at 4:09 AM, berkane ahlem via TRNSYS-users <trnsys-users at lists.onebuilding.org> wrote:
> Hello sirs,
> I simulate a solar collector separate from GSHP for heating a building and DHW and i have some problems about the relation expresses the control function :
> 1) if water storage tank , collector and the building are cold simultaneusly  the type 647 will send half  flow of the GSHP  through house and half to tank
> How can i express them in calculator of trnsys 
> Thank you
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