Hello,

I have an old mechanical central heating control unit made by SMC. It
has stopped working, the dial no longer goes round, so I cannot set the
timer and also I cannot switch between hot water and central heating,
as whichever setting I have the switch on I get both hot water and
central heating.

I am signed up to the British Gas homecare service, and have called
their engineer out, however he just told me that because it is over 7
years old I am not covered.

Knowing how much heating engineers etc cost, I am hoping to replace
this unit myself with a modern, digital type timer/control unit.

Could anyone advise on whether this would be a sensible thing for me to
attempt - I have done work on electrics before and have a sound
understanding of them, however I kwno next to nothing about central
heating systems and I have read that the wiring is different on the old
mechanical control units to the new digital ones.

Also, would I be within the law/building regs to do this job myself, or
do i have to get a qualified person in?

I can post photos of the old unit and wiring if this helps at all....

Any help or advice would be really useful pleaseeeeeeeeeeeeeee