Nowadays, home type water heat pump system normally works without fan coil. This heat pump has summer mode (cooling) and winter mode (heating). In the heat pump control system, there is one thermo sensor connected. This sensor connected to main controller. If outside temperature more than 25-degree, system has signal pulse from the thermo sensor to switch heat pump to summer (cooling) mode. If outside temperature lower than 15-degree, system has signal pulse from the thermo sensor to switch heat pump to winter (summer) mode.  Those modes switch automatically done by heat pump control system. There is no relationship with thermostat.   However, to keep connected thermostats work in the same mode as water heat pump is extremely important and meaningful. Our thermostat system should work reversely in different mode. Winter time we should set higher degree of the room to make the room hotter. Summer time we should set the degree lower to make the room cooler.  Therefore, in the thermostat, there should be CO input contact. This contact is “Normally Open Contact”, dry contact. When the 230/24V signal pulse comes from the heat pump, base unit will switch to summer mode (cooling), and send this 230V/24V signal pulse to connected thermostats. When all thermostats get this 230V/24V signal pulse from wiring cetnre, all room thermostats will switch to the summer mode (cooling). If the room temperature higher than thermostat value, thermostat let the actuator open and let the cool water inside into room pipe system.   If there is no signal from heat pump to CO contact at wired 8 zone wiring centre, thermostats should work in winter mode (heating). At that time, if room temperature colder than thermostat value, digital programmable thermostats should let the valve open and let the hot water inside into room pipe system.     Xiamen E-Top Controls as professional ODM thermostat suppliers, we provide both 8 zones wired wiring centre and digital smart WiFi thermostats.   For detail information, please contact with us from info@etopcontrols.com