room stat operates even when programmer is off

[castellpenbryn]

Hi Stem,

Thank you for your previous information. My boiler an Ideal Classic FF260 is located in my kitchen. The hot water cyclinder is upstairs in the bathroom, with the main pump, junction box and a combination of two, two port valves and the main wiring junction box for the heating system. My bolier has been firing even though the room stat is off.

So I replaced it with an up to date one on recommendation by a plumber. This did not elimate the problem- i set the new Room Stat to zero, switched on the timer to constant and within seconds the boiler fired up as did the pump etc upstairs. Further to this I disconnected the new stat kept the wires seperated, switched on the power and within seconds the boiler kicked in.

Back in Aug 2012 i replaced one of the two port valves because i had the hotwater on its programme and every time the hotwater came on the heating did as well. Again spoke to a plumber and this was recommended and it sorted the problem.

So in short any idea why the boiler would run whilst the Stat is on zero. The manufacture Ideal have said it is down to the Boiler being "TOLD" to switch.

The timer is working fine switch it off and the boiler shuts off.

 

[denso13]

Faulty motorised valve - stuck microswitch perhaps. If it used to work properly it doesn't sound like a wiring issue.

 

[stem]

Welcome to the forum, but for future reference you should start your own new thread not "hijack" someone elses.

With your system having two, 2 port motorised valves (Known as "S Plan") the boiler is switched on by micro switches inside each of the valves. The motorised valves are in turn opened by the room thermostat (heating) or cylinder thermostat (hot water) When the thermostat switches the power off, the valve is pulled closed by a spring, and releases the microswitch which turns the boiler off.

It is possible for one of the microswitches to stick in the on position, but to check this you will need to have and be able to use a multimeter safely. If you can it's not difficult to check. Each motorised valve will have an orange and grey wire in its connecting lead. These are the wires connected to the microswitch. With the power off, Disconnect them from the wiring centre and measure the resistance across them. It should show an open circuit, if it doesn't then the microswitch is still in the on position.

If you aren't able to do this, then you will need to get someone competent to test the rest of the system.

Pah beaten by denso13. At least we said the same thing, only as usual perhaps I used too many words

 

[stem]

As an after thought. That doesn't explain why it goes off when the timer goes off, unless the live to the microswitch is taken from the switched side of the timeswitch.

Do you just have one timeswitch for both heating & hot water? or can you set their times separately?

 

[doitall]

Got wired wrong all over it.

It would be a good idea to start another thread and post some details about the programmer make/model and what valves you changed.