Glow Worm boiler control board SYMSI7.0

[Dennis Hicks]

I'm trying to change the control board in my boiler (because I periodically get a fault code).

The controller is a SYMSI7.0 but I notice on the web that there are slightly different part numbers e.g.
0310144400015 <- my original board
0310144400R18
0310144400S20

Eyeballing these boards the only difference appears to be the number of relays fitted and the position on the board of those relays.

Are these boards interchangeable? What is the difference between them?

Thanks.

 

[ianmcd]

Which Glow worm Boiler ?

 

[Dennis Hicks]

Glow Worm Xtramax HE

 

[Dennis Hicks]

Looking at the board with two relays on it looks like one relay drives the domestic hot water pump and the other the central heating pump which makes sense. However, other models of SYMSI7.0 can have three or four relays so what would these additional relays be driving?