S plan CH and HW problem

[toaster0nfire]

Hi

I have S plan system: two port Myson MPE 222 at the hot water cylinder, the other Myson 222 under stairs. Have a TH471 control unit and Firebird oil burner outside.

Problem is as follows

Can have either water or CH on - but not both at same time.

Had the motorised valves replaced (again Myson MPE 222) but this has not made any difference.

Also water gets scalding hot and if left on for more than 30-40 mins when I turn it off then CH will not kick in until I've drained a lot of the HW away.

any help much appreciated!!!

 

[toaster0nfire]

I should add i've had the cylinder stat replaced as well (its a Horstmann)

 

[flameport]

Has this system ever worked properly?
Likely to be a wiring / electrical problem.

 

[DP]

To be asking this question either you are not familair with the system or you are here for a laugh,

Switch HW on at the programmer- does the HW motorised valve open? Does the boiler fire? Switch HW off at the programmer.

Now do same for CH. Does CH motorised valve open? Does the boiler fire?

If not, find out why not