After 35 years of faithful service, the Switchmaster 3-port motorised valve in our CH/DHW system gave up the ghost. The rotor shaft seal had clearly been weeping for some time, judging by rusting of the galvanised plate that the motor/gearbox is mounted on. The final drive shaft of the gearbox had seized. The rotor shaft was also stiff to turn. Time for a replacement valve.
So I unclip the motor/gearbox. I plan on draining down the system and removing the old valve the next day, but in the meantime think that to prepare for that I'll remove the galvanised plate on the valve body to give more spanner-wielding room. Four Phillips screws hold the plate in place. The first three came out easily, but the fourth was stubborn (isn't it always the last screw/bolt that's awkward?). Big mistake! The plate came off ok but, as I discovered, is the only thing apart from O-ring friction that keeps the valve rotor in place. Top-up tank pressure was enough to eject the rotor. Half a gallon or so of water drenched me and the carpet before I could push the rotor back into the valve and re-attach the plate. The water also found its way between floorboards and some stained the ceiling of the room below.
The next day I successfully replaced the valve, refilled and bled the system (no leaks
), reconnected the electrics and switched on. Oh! Circulation pump not working. Out with the multimeter. Pump motor coils check ok. Wiring of pump to controller and thermostats checks ok. Must be a pump fault. Close the isolator valves either side of the pump and remove/dismantle it for inspection. A spring and a short rod fall out. These must have dropped out of the old valve (sited immediately above the pump), when the rotor was ejected and had jammed the pump. Re-assemble/install pump. Switch on. Success!!
All that remains now is to repaint the ceiling .......
Read more: https://www.diynot.com/diy/threads/...isaster-experiences-here.74082/#ixzz4bmCrjAeY
So I unclip the motor/gearbox. I plan on draining down the system and removing the old valve the next day, but in the meantime think that to prepare for that I'll remove the galvanised plate on the valve body to give more spanner-wielding room. Four Phillips screws hold the plate in place. The first three came out easily, but the fourth was stubborn (isn't it always the last screw/bolt that's awkward?). Big mistake! The plate came off ok but, as I discovered, is the only thing apart from O-ring friction that keeps the valve rotor in place. Top-up tank pressure was enough to eject the rotor. Half a gallon or so of water drenched me and the carpet before I could push the rotor back into the valve and re-attach the plate. The water also found its way between floorboards and some stained the ceiling of the room below.
The next day I successfully replaced the valve, refilled and bled the system (no leaks
), reconnected the electrics and switched on. Oh! Circulation pump not working. Out with the multimeter. Pump motor coils check ok. Wiring of pump to controller and thermostats checks ok. Must be a pump fault. Close the isolator valves either side of the pump and remove/dismantle it for inspection. A spring and a short rod fall out. These must have dropped out of the old valve (sited immediately above the pump), when the rotor was ejected and had jammed the pump. Re-assemble/install pump. Switch on. Success!!All that remains now is to repaint the ceiling .......
Read more: https://www.diynot.com/diy/threads/...isaster-experiences-here.74082/#ixzz4bmCrjAeY
