Hi

 

I bought a new unfinished  house in SW France some 7 years ago. My English plumber installed a solar panel to heat the hot water and a ground sourced heat pump to heat the house. All has worked well. After a recent installation of photo voltaic panels, and the increase in the price of electricity, I started to see there were ways to improve the systems. I found that the solar panel for heating the hot water was never fully finished as it never controlled the backup immersion heater

Sorry I never finished.

I have rectified the solar water heater problem and am now looking at the heat pump.

I want to control the on period of the pump. In the instructions it is possible to set only one time period and I want two. In the circuit diagram of the controller it shows two connections labelled "Ext", and says this can be connected to an external timer or thermostat. My question is, can I just connect a timer to these terminals? I assume that for the pump to run they must be shorted? 

Put a resistor across the terminals and see if the pump fires up?

Their ASHP has the same connection, you remove the link.  Replace it with a timer or thermostat with zero volt open close connection.  Closed the hp is on open circuit pump is off.

 

Do not use a powered connection 

Thanks, so I've just ordered a timer.