3 way diverter valve

[Kawakiman]

Hi, my Honeywell 3 way mid position diverter valve needs changing.
It has an isolation valve (tap) on the input side and another one on the radiator side so I can shut those off, but the one that enters the cylinder does not have a valve to allow me to isolate it from the cylinder.
I am planning on shutting off the mains water supply, going into the loft and drain the water header tank and then undo the 3 x 28mm connections to remove the diverter valve. I know there will be some water still in the header pipers and coil in the cylinder but have I missed anything else I should do? I plan to isolate the wiring on the diverter and replace the wires likle for like. Should I drain off at least one low lever radiator also?

Any help would be greatly appreciated

 

[oldbuffer]

From the sound of it you have an open vented system. I.e. the water supply to the hot water cylinder coil and to the radiators is from a small tank (feed and expansion, F&E) in the loft.

If this is correct, then to avoid getting wet I would advise you to:

a. Shut off the supply to the F&E and turn off electrical power to the system.
b. If the F&E tank has a lot of sludge in it, empty the tank and clean it. (If you don't, all that sludge will wash down into your central heating system)
c. Drain down the CH and DHW circuits (manually set the three way valve to mid-position) to a level just below the three way valve. If these are in a first floor airing cupboard, drain until the water from the highest bleed point on a ground floor radiator stops.
d. Replace the valve, wiring the new one in exactly as the old.
e. Re-fill the system.
f. Provided there are no leaks, drain down again to base of F&E plus a couple of buckets full. Add inhibitor, refill.

On the other hand, if you're lucky, the cover of your valve will have a small metal dimple sticking up from it. If it has, turn off all power, remove the cover (small screw at one end, loosen then pull off), remove the actuator head (two screws into brass base which sits on the pipe-work). Then see if the valve opens / closes easily (there is only about 20 degrees of movement of the spindle between DHW and CH ports). If the valve works OK, replace just the actuator head. (I'd buy the whole valve, then if the valve does turn out to be faulty you've got the mechanical part ready, and the price difference between actuator only and whole valve is small). Again rewire as previous valve. No need to drain any water.

There is a third possibility (and quite likely), which is that the small electric motor which powers the valve has broken. These can be replaced and only cost £10-£15 but its a bit fiddly, particularly if access is poor. They are called Synchron motors and you can get them from the likes of Screwfix. No complex rewiring (two leads, no polarity to worry about), no need to drain.

Good luck

 

[Kawakiman]

From the sound of it you have an open vented system. I.e. the water supply to the hot water cylinder coil and to the radiators is from a small tank (feed and expansion, F&E) in the loft.

If this is correct, then to avoid getting wet I would advise you to:

a. Shut off the supply to the F&E and turn off electrical power to the system.
b. If the F&E tank has a lot of sludge in it, empty the tank and clean it. (If you don't, all that sludge will wash down into your central heating system)
c. Drain down the CH and DHW circuits (manually set the three way valve to mid-position) to a level just below the three way valve. If these are in a first floor airing cupboard, drain until the water from the highest bleed point on a ground floor radiator stops.
d. Replace the valve, wiring the new one in exactly as the old.
e. Re-fill the system.
f. Provided there are no leaks, drain down again to base of F&E plus a couple of buckets full. Add inhibitor, refill.

On the other hand, if you're lucky, the cover of your valve will have a small metal dimple sticking up from it. If it has, turn off all power, remove the cover (small screw at one end, loosen then pull off), remove the actuator head (two screws into brass base which sits on the pipe-work). Then see if the valve opens / closes easily (there is only about 20 degrees of movement of the spindle between DHW and CH ports). If the valve works OK, replace just the actuator head. (I'd buy the whole valve, then if the valve does turn out to be faulty you've got the mechanical part ready, and the price difference between actuator only and whole valve is small). Again rewire as previous valve. No need to drain any water.

There is a third possibility (and quite likely), which is that the small electric motor which powers the valve has broken. These can be replaced and only cost £10-£15 but its a bit fiddly, particularly if access is poor. They are called Synchron motors and you can get them from the likes of Screwfix. No complex rewiring (two leads, no polarity to worry about), no need to drain.

Good luck

Hi, many thanks for your quick reply. Yes it is an open vented system as you suggest, and I will check the tank for sludge. The Valve fitted is the old Honeywell type where the 4 screws go straight through the gearbox into the valve body so if I undo them I will get wet. The manual slider is floping around loose so of no use. The new one has 2 captive screws so will be easier to replace next time! I will drain the system as you suggest and refill with fresh water and Fernox.

 

[Kawakiman]

Just re read your suggestion the motor was the likely cause and sure enough it was hot and stuck. Swapped it for the one off the new valve and the hot water is now back. Nice one and thanks for your response it saved me a lot of hard work changing a valve when all I needed was the motor. You are a star!