New boiler controller

[tom b]

Hi all, thank you in advance for any guidance you are able to give on the below.

I have an old Potterton Suprima boiler with a pumped CH and gravity fed HW (I believe), when we brought the house there was a switchmaster 300 timer attached to the boiler. This never worked as a timer and we would always just flick it onto constant when we wanted heating and/or a short while before we wanted hot water. In the summer I have always just turned the TRVs on all radiators to 0 so these would not heat up and we would just get got water- not the best but works for us.

The boiler has been very reliable and as such I have no interest in changing this however I did wish to install a 5/2 day, digital programmer to control this better and allow us to come home to a warm house and in the summer, with the TRVs turned off heat water at the beginning of each day.

I'm aware that usually in these situations, a dual channel programmer would be used however as the switchmaster300 is single channel I decided to replace with a single channel. I also, possibly wrongly, believed that as we were gravity fed I cannot have seperate HW anyway. The programmer I brought was a Danoff TS715Si.

I turned the power off and removed the switchmaster300 and backplate as I knew it would not be compatible- This had connections as follows:

N - 1 blue wire attached coming from a power switch
L - 1 brown wire attached coming from a power switch
1 - 1 black&awhile wire from the power switch attached and 1 black &a white wire from the boiler attached
2 - 1 blue wire from the boiler attached
3 - 1 white wire from the boiler attached
4 - 1 brown wire from the boiler attached

There were also 2 links, 1between N&2 and 1 between L&4

After Some research seemed I needed to switch the wires in 1 & 4 over on the new backplate and attach a link between L&1

I did this and powered everything up however when the timer should turn everything on the Boiler does not do anything- I can hear the pump running (the CH pump I guess) but the light on the boiler is not on and it doesn't light.

Could anybody shed any light on the correct wiring in this arrangement?

Thank you again.

 

[stem]

The SM300 didn't use terminals 2 and 3 for anything, so they were just be used as connectors for the wires inserted into them. The TS715 does use terminal 2 (although you won't need it) so do not make any connection to it. If you do, you may cause a short circuit. Just connect the wires that did go to terminal 2 together with a screw terminal connector. [No need for this if my drawing below is correct and the N wire from the boiler is long enough to reach the N terminal of the timeswitch]

There was no real need to swap over the wiring between termianls 1 and 4 they are just a switch. When the time switch is 'on' the two terminals are simply connected together, either way around would be fine.

This is what I would expect to find, it excludes the black & white wire that you say used to go from terminal 1 of the SM 300 that goes to the power switch because this is a puzzle to me. What is it connected to at the power switch?

As you haven't given details of the wiring at the boiler end, I have made assumptions based on where you say they went at the SM300, so please check they do go where I have assumed before making any connections.

I also assume that the pump is controlled by the Suprima. If so, you may have pumped hot water and heating, as when the boiler is 'on' the pump will also be 'on'. Can you confirm how the pump is wired?

 

[tom b]

Hi stem, thank you so much for your incredibly comprehensive and helpful reply, I am very grateful.

I am in work currently but will endeavour to find the information you asked for tonight and post it.

Thank you again.

 

[tom b]

Hi stem,
I have attached pictures of my (rather dusty) siting cupboard which shows the pump at bottom right and the old school valves.

I will have to wait till tomorrow to turn the power off and check the wiring at the boiler end but thought the attached might help you envisage the setup at least.

Thank you and I'll be in touch soon.

 

[stem]

Hi Tom

Sorry for slow reply, I've been on holiday in Cuba where the internet is poor / non existent.

Looking at your photographs, although I can't follow all of the pipes fully, it does look like a fully pumped system, so the pump will probably controlled directly from the boiler. So, if my assumptions for the wiring at the boiler end as shown on my diagram are correct, then you should have everything you need, if not, post back what you do have.

 

[slippyr4]

Suprima requires pump overrun. If it isn't wired off the boiler, it should be.