SOLVED - Drayton Digistat+ RF and SCR Receiver Problem - SOLVED

XrayDave

XrayDave

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The red 'Receive/Alarm' light on the SCR flashes periodically for around 5 seconds every five minutes or so (which means that the Digistat and SCR are communicating) and the green light is 'on'. This means that we should be getting heat.

However, the zone valve doesn't actuate, the boiler doesn't fire and the radiators remain cold.

If I then turn the digistat DOWN to below ambient (e.g. to 10C) then back up to 24C, the valve will actuate, the bolier fires and we have heat.

Is this simple to fix?

Is there a procedure for 'resetting' the SCR (WR1) unit (e.g. power off/power on).

Does the Digistat need re-pairing with the SCR unit? (seems unlikely as when you turn the stat down to 10C and then back up to 24C, the green light goes off and then back on again.

From what I've managed to find on-line it suggests that there is a problem with the SCR unit (either not sending the signal to the boiler or some other issue). Is the SCR easy to replace (I've know that Toolstation (98517) and Screwfix (73146) have these for between £80 - 110). I'm competent at electrics (just not Part P qualified) so is this something that I could replace myself or do I have to call out our heating engineer?

Thanks in advance,

Dave
 

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Thanks Ian

That looks simple enough.

As long as I turn the 240V mains supply off it should be okay.

I've sourced a suitable capacitor from ebay and should have it delivered in a couple of day's time.

XRD
 
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Those holes in the PCB should be cleared of solder with a de soldering sucker before putting the leads of the new capacitor through them.

upload_2021-11-16_17-29-59.png


There is every chance that the plated-through connection from the under side of PCB to top side will have been damaged or destroyed.

Without the plated-through connection the reliability of the joint cannot be guaranteed.

Plate through destroyed.jpg


When the plated-through connection is intact the dark blue solder is connected to the top side of the PCB
When the plated-through connection is not intact the only connection is through the light blue solder on the top side of the PCB.
 
Thanks Bernard.

Aware of this but thanks anyway.

I have a solder sucker (I really need to get out more and meet people).

Dave
 
The replacement capacitor arrived this morning.

Turned mains supply off (& verified), removed WR1 (SCR) unit from the wall managed to prise the clips holding it together apart (without breaking any) de-soldered the old cap and re-soldered the new.

Re clipped everything back together, put WR1 back on the wall and set programmer and thermostat to call for heat.

Minor problem - WR1 (SCR) had a solid red light (indicating it wasn't receiving data from the thermostat), so removed batteries from Digitstat, counted to 30, put batteries back in and yay, we have heat.

Adjusted programmer & thermostat so that there was no heat demend, changed programmer time to come on in 5 minutes, turned Digistat up to 23C and waited.

At appropriate time, valve opened with a click and boiler fired up.

One Happy Bunny (especially since a new Digistat+ RF / SCR would be somewhere in the region of £80-110 and this cost me the grand total of £4.45 plus around 10 mins of time).

A special 'Thank You' to @ianmcd. That video you provided the link for was spot-on.

Dave
 
Thanks Dave always good to get feedback, far too many come on ask for advice, get it and dont have the decency to let us know how they got on, happy to have been of help
 
I totally agree with the above post Ian.

It costs nothing to say thank you or to tell others how the situation developed (hopefully solved), but means a lot to folks that have spent time and taken the trouble to offer help and suggestions.

I always try to recognise folks that have been truly helpful in solving any problems I may have. Any help or suggestions by others are gratefully received.

It is a shame that I don't have enough knowledge (certrainly of Central Heating syetsms) to 'pay it back' (although in post #8 this thread, I explained what happened in my particular case so that it may possibly help others facing the same).

Take care, and thanks once again.

Dave
 
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