As the hot water on an S-plan system was far too hot, I worked through the following logic.
The immersion heater was definitely off.
There had been no recent work on the system.
The cylinder thermostat was set correctly and the Myson 2 port 28mm zone valve (Neon and motor) responded to manually turning the setting dial.
The actuator head was removed and was seen responding, with the motor turning the slot.
The now exposed valve stem on the body was free to move.
(At this point I suspected the brass valve internals to be worn & letting by; hence my earlier thread about obtaining replacements)
The shoes and arm in the internals of the brass valve were examined and OK, not stuck or broken.
Replaced everything but water continued to become too hot.
Turned hot water off at programmer and left system to run on heating only. Used up hot tank water and the contents became & remained cool.
Was that a sensible investigation pathway so far?
I reasoned that the only culprit must be the Potterton PTT100 thermostat. A replacement was not available but I got a Drayton HT53which is similar, although the Potterton had its wire connections soldered directly into the micro-switch and unmarked.(One live feed-redwire- from timer, one to zone valve motor-black sleeved red, - & one –grey-made safe unused. All via the wiring centre.)
The new one has 3 terminals. marked as C common ( which I have connected to live feed,) 1 Call for Heat & 2 Satisfied .
There is a sticker saying “On temperature rise C1 break, C2 make.”
Using a multimeter, with the thermostat setting at minimum (positive off according to instructions) the No1 terminal is live.
I am scratching my head to understand from those instructions which terminal to connect with the black wire that goes to the zone valve. Could somebody interpret it, please?
Thanks for reading
The immersion heater was definitely off.
There had been no recent work on the system.
The cylinder thermostat was set correctly and the Myson 2 port 28mm zone valve (Neon and motor) responded to manually turning the setting dial.
The actuator head was removed and was seen responding, with the motor turning the slot.
The now exposed valve stem on the body was free to move.
(At this point I suspected the brass valve internals to be worn & letting by; hence my earlier thread about obtaining replacements)
The shoes and arm in the internals of the brass valve were examined and OK, not stuck or broken.
Replaced everything but water continued to become too hot.
Turned hot water off at programmer and left system to run on heating only. Used up hot tank water and the contents became & remained cool.
Was that a sensible investigation pathway so far?
I reasoned that the only culprit must be the Potterton PTT100 thermostat. A replacement was not available but I got a Drayton HT53which is similar, although the Potterton had its wire connections soldered directly into the micro-switch and unmarked.(One live feed-redwire- from timer, one to zone valve motor-black sleeved red, - & one –grey-made safe unused. All via the wiring centre.)
The new one has 3 terminals. marked as C common ( which I have connected to live feed,) 1 Call for Heat & 2 Satisfied .
There is a sticker saying “On temperature rise C1 break, C2 make.”
Using a multimeter, with the thermostat setting at minimum (positive off according to instructions) the No1 terminal is live.
I am scratching my head to understand from those instructions which terminal to connect with the black wire that goes to the zone valve. Could somebody interpret it, please?
Thanks for reading