Central heating timer problems

[mart20]

Evening, i have recently moved into a house where the central heating external timer control does not work.
The timer is a Switchmaster sm300 and the boiler is a Baxi Combi-boiler Instant HE.
I have brought a new timer thinking that it was faulty and did a straight swap, but it still does not work.

The timer has connection N, L, 1, 2, 3, 4.
The boiler terminals are L, N, E, 1, 2.

Connections 1 & 2 in the boiler are connected together with a linking cable.
Connections N & 2 in the timer are connected by a link.
Connections L & 4 in the timer are connected by a link.

The wiring is as follows:
Mains power into N & L of timer.
Cable from boiler to cable as follows: L (timer) to L (boiler), 2 (timer) to N (boiler).

Any help on this would be appreciated.
Thanks

 

[bengasman]

You got the wrong timer for the boiler, you could make it work, but there is little point if you can swap it for the correct one.
Get the timer for this specific boiler, or better, get a good programmable roomstat as it seems you don't have a roomstat connected.

 

[mart20]

Thanks, i have brought a new Switchmaster as that was the original timer and i rang the company and they said it was okay with the boiler? Can i still use it?

I have found a thermostat in the living room cupboard, the cable comes from the thermostat and terminates by the boiler but has been disconnected from the timer.

Can i make this timer work, at least until i can get the correct timer. (I am going away and wish to leave the boiler on timer).

Thanks

 

[bengasman]

Stick the timer back in the box and leave the boiler on without a timer, it is the middle of summer, the house won't freeze.

 

[mart20]

I know the house wont freeze, but i would like to get this sorted sooner rather than later, so when i do need the timer it is ready to go.

 

[londonboy]

You can use any single channel timer with a combi.
What is the model number of the new Switchmaster you have bought and I'll look through the manual.

Andy

 

[mart20]

Thanks for your help londonboy, it is a Switchmaster SM300 24 HR Timeswitch.

 

[namsag]

Just buy the baxi mechanical clock ,fits in front panel costs 21 quid and takes 2 mins to fit

 

[londonboy]

As said above it might be easier for you to buy the plug in Baxi timer.

(in timer)

N = two blues (from mains supply + to boiler)
L = two browns (from mains supply + to boiler)
1 = to terminal 2 inside boiler
2 = spare terminal
3 = spare terminal
4 = to terminal 1 inside boiler

Also consider installing a roomstat.

Hope this helps, Andy

 

[mart20]

Thanks where can i get this from and has the part got a specific name / model number etc...
Cheers

 

[londonboy]

http://www.cheapboilers.com/timer/baxi/combi-24hr-mechanical.htm

Namsag is that the correct model for the Instant? (I rarely use these)

 

[mart20]

Thanks Andy, this is very helpful. One last thing just to clarify, do i leave the links in the timer N to 2, L to 4 or remove them.

Once again thank you very much.

 

[londonboy]

You must remove them.
Rewire the whole lot as I suggested (its easier to start again).

Obviously ensure you have earths at every point.

 

[namsag]

LB No image but by brief description and price it sounds right as they only do 2 one mewchanical one digital at a stupid price

 

[DP]

If you look at the timer, you should have N and L terminals- these run the timer
Terminal 1 will be marked as C
Terminal 4 marked as ON.

Terminal s L and N connect to terminal L and N on timer
Terminals 1 and 2 connect to terminals c and ON on timer.


Having said above, I would put the switchmaster in the bin and go out and buy a Danfoss TP 5000