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I have a Viessmann compact heat only boiler used for Central Heating only. Issue: When boiler starts (even from cold) the flame intensity or level stays on minimum on display (see attached picture). I have been advised by Viess Tech support to notch up the CH dial but even on setting 6 the...

All wiring for thermostat to boiler and pump done, I owe it to Rob and Fixitflav for their efforts and for pump setting to Johntheo One last glitch, I cannot get over is flame symbol on display, I have reset it a number of times with no luck, it starts and keeps firing at lower rate. I was...

It should be wired this way as per schematic?

sorry, our posts crossed. So programmer gets N,L from wiring center to turn the heating (boiler) on.

Correct. Just the capacitor connected to 1 and N terminals (G) See attached schematics; a marked and unmarked version. I have attached un marked for corrections (if any)

No zone valve for this heat only set up. You are right, I had a 3 port valve with the package but I have separate HW arrangement for now. Wanted to use programmer as a timer switch only to put heating on at set times of the day. I agree no compromise on safety, will follow safe practices for...

It has N,L and 3 which is call for heat. Things are making sense and clearing up for me! So for Thermostat to work, the link between 1 and L has to be removed. With Therm Stat out of the way, programmer doesn't need to get N,L from boiler? Does a SL or other cables need to go to Thermostat...

The link wire was indeed missing and it did the trick! Thank you @Madrab and @fixitflav Couple of questions : - The control wire from boiler (G) 1 which is SL should go to Thermostat terminal (call for heat); Correct? - I haven't found what the second dial on the left do? Apart from setting...

Room stat is connected via wiring center. Apart from mains power, we haven't taken any connection to or out of the board. I'll try the link wire and report back.

I can confirm this is the case. No No bridging wire between 1 and L on 96(G). That is exactly what it is doing and is not firing up. I'll try the link wire and report back.

I can try connecting Room Stat to SL (1) to see if it works? You reckon that boiler should fire without anything connected to external control ports? L/N/E are going out (F) to wiring center. Nothing going in to the board or boiler PCB. Wiring center fed by Spur. Could be. It does make...

Room stat was never connected to the board. Capacitor is still in place on board. SL should have been taken from port 1 to Thermostat? Yes

Boiler and Pump are connected in a wiring center with their respective N,L and E. I dont have the cable or wire harness to connect the pump directly to the boiler. I have tried to run it without Room Stat connected to the boiler with same result.

Exactly. I am not getting any error or fault code on screen. I have sent Viessmann an email, lets see what they say.

https://www.diynot.com/diy/threads/wiring-a-viessmann.248503/post-1794427 See post 4 on this link.

As per attached trouble shooting steps; the fan starts as soon as boiler is switched on but then it doesn't get to ignition stage and I don't see any error message on display, it just shows water temperature on screen.

Its a wired Drayton Room stat (old dial type). This is how I get into Serv mode.

Yes, Pump is connected to the wiring center, when there is call for heat, I can hear the pump circulating water when boiler fan starts its purge cycle.

I have tried bypassing the Room Stat and tried to connect boiler directly with same result. It doesn't fire up. It only fires up when I reset it and it goes in 'serv' mode. The boiler and pump are connected to the wiring center. Wiring center N,L and E is fed by Spur. The Programmer and Room...

Yes. When the thermostat calls for heat; fan on boiler starts and after a brief period shutdown. The screen shows the water temperature starts from 100deg C and quickly goes down to 30s. It stays there forever. I then have to reset the boiler by turning the CH knob to reset and then counter...