need some advise about swapping a old seibe sm400 programmer

chopper · Oct 8, 2011

does anyone no what programmer would be a suitable swap, not done much on heating systems really a think its a fully pumped system, back plate has CHon in 1, 2 is spare 3 HWon, 4 is CHOFF BUT THIS IS NOT CONNECTED DONT KNOW WHY AND ADVISE PLEASE

topquark · Oct 8, 2011

It doesn't appear to have an CH off, so I'm guessing just deasserting CH on is sufficient. Otherwise connections appear to be as you've said, I doubt you'll find a direct swap, you'll need to reconfig the connections to a standard backplate (ie N L HWOFF CHOFF HWON HWOFF).

chopper · Oct 8, 2011

do the newe programmers need cables for choff and hw off as they is none

topquark · Oct 8, 2011

It's whether the boiler or the way it's been configured in the wiring centre needs it (to close valves without return springs etc). As the existing system isn't using it then I can't see why you'd need it.

chopper · Oct 8, 2011

okm cheers do u reccomend any

topquark · Oct 8, 2011

Not really, it depends on what you want. You'll prob want 2 CH (HW/CH) then it's a question of 5/2 or 7 day cycle and how many on/off periods you want during a day. Loads to chose from if you're not space limited. I tend to go for 5/2 as it's the way most folk live (cycles different at the w/e).

chopper · Oct 8, 2011

ok are programmers different for differnent systems then they just need a bobby basic 1 5 and 2 be fine with probly just 2 on off periods

topquark · Oct 8, 2011

Programmers are just glorified on/off switches, two channel ones you can think of as being two gang switches. The on/off are just inverses of each other; when HW on is at 230V then HW off is at 0V and vice-versa. So programmers are pretty generic. What sometimes needs to be specific to a particular environment is the actuator for the valves (some are high torque etc).

The ON's are then used in series with the stat (either room for CH or tank for HW (if it has one, most combi's don't unless they have solar as well)).