l need to replace 2 two port zone values as the c/h/hw control switch is not working and a plumber said this was the problem. ... The two port values are on the same pipe seperated by about 8" and in between them is a tee that l presume goes to the cylinder(not sure without looking).
If you have just two 2-port valves, one controls the central heating, the other controls the hot water circuit. The tee pipe will go to the boiler.
Are you comfortable working with electrics?
The first think to check is where the problem lies. It could be in either the timer, a thermostat or one of the valves. The valve could be sticking or the motor/actuator faulty.
Turn power off
There is a lever in a slot on the side of the valve. It should be at the Auto end of the slot. Slide the lever to the other end. You should feel some resistance as you are opening the valve against a spring. If the lever is floppy, the valve is stuck open. You can usually cure this by removing the actuator and putting a small amount of WD 40 or similar on the valve shaft. If the valve still sticks, you will have to replace the complete valve.
If not sticking, we can now carry out electrical tests.
The valves have a four wires, brown, blue, orange and grey.
Disconnect both brown wires (make a note of where they are connected).
Connect one brown wire to the Live input of the junction box.
Turn power on.
One of the valves should operate (you should hear the motor) and the boiler light.
If it operates, but does not light, the valve switch is faulty. You may be able to repair this, otherwise it's a new actuator or valve.
If it does not operate, the motor is faulty. You can buy new motors at most DIY sheds or a plumbers merchant.
Turn power off.
Disconnect the brown and connect the other brown to the Live input
Turn power on.
Check the second valve.
If both valves work OK, the fault is either in a thermostat or the timeswitch.
The brown wires are normally connected to the Switched Live side of the appropriate thermostat. We can check both timer and thermostat by connecting the brown to the other side of the thermostat. As the two wires to a thermostat will be in the same cable it is easy to identify the other wire.
Connect HW valve brown wire to HW stat live terminal.
Turn power on
Turn HW on at timer. The boiler should light. Check the options on the timer (timed, constant etc) to make sure they work.
Turn power off
Disconnect HW valve brown wire from HW stat live
If this test fails, the HW side of the timer is faulty.
Connect CH valve brown wire to the CH stat live terminal
Turn power on
Turn CH on at timer. The boiler should light. Check the options on the timer (timed, constant etc) to make sure they work.
Turn power off and disconnect brown wire.
If this test fails the CH side of the timer is faulty.
If both tests pass, then you have faulty thermostats.
Connect the HW brown wire to its original teminal.
Turn power on
Set HW ON and turn HW thermostat up
Boiler should light.
If it does not the HW thermostat is faulty
Turn HW and Power OFF
Connect CH brown wire to its original terminal
Turn power on
Set CH to on and turn CH thermostat up
Boiler should light.
If it does not the CH thermostat is faulty
how much are two port values
Do a Google!
Any plumbers merchant,
screwfix, DIY shed, online. Take your pick
l think these are honeywell.
Good make.