IMI Powermax 135 switches off

[adey]

I have just moved house and am experiencing problems with the boiler (IMI Powermax 135). It has a digital programmer (horstmann I believe) which seems to keep 'resetting' itself. It will turn the HW and CH to the off position and the time will reset to 12:00. This can happen 3 or 4 times a day, but sometimes will run for several days before resetting itself.

Does anyone have any answers or clues as to where the fault is likely to reside, before I have to resort to trawling through the Yellow pages and taking pot luck on finding a honest plumber.

rgds
Adey

 

[boilerbeasty]

Well it sounds like the timer - which if its a simple electronic device you may not need a plumber's particular skills to change it. Timers are just electronic switches telling the boiler 'on' or 'off'.
Some Horstmann timers have backup batteries in for periods when the mains is off. Some have a battery 'off' switch to prevent it using it - which if its flat or defective could cause problems.

What model of timer is it ? This might be hidden, so you could look on the web for a similar picture/feature e.g. here

 

[adey]

I have looked on partsareana.com and it shows two parts for the timer/programmer. Mine looks like the one in the diagram (a small black square box). So it is either a 'Timer - Switchmaster 101510' or 'Programmer - Horstmann 526I'.
I can't find either of these anywhere on the net to differentiate between the two.
Whats the difference between a 'timer' and a 'programmer'? The unit I have can be set for two time periods per day, with the option of constant or timed for HW, and constant, once, or twice for CH.

 

[boilerbeasty]

From this compatibility chart:
http://www.tlc-direct.co.uk/Technical/DataSheets/Horstmann/Horstmann.htm
Looks like the Channel Plus 21 or 27 would be compatible with "simple rewiring". You may as well go for the 27 for 7 day programming.
The wiring diagrams are here:
http://www.tlc-direct.co.uk/Technical/DataSheets/Horstmann/H21.htm
Compare these to you boiler documentation, and rewire if appropriate.

Make a diagram of the wire colours and where they go before you start ! And turn off the mains.