Vaillant 418 open vent - switching CH on after power cut

[Elektra99]

I think this problem has been there since first install, the service engineer, yesterday, said the boiler wasnt working correctly and I needed to get vaillant out to fix it. It is 12 months old and under warranty. I have no faith in the orginal installers competence - long story.

If mains power to the boiler is cut and restored the HW side works as it should but the CH wont come on. The only way to fix it is to cut the power and as soon as the radiator sign appears in the display presss the adjacent button to select it then increase press the temperature up button one or two degrees.

Additionally if the boiler is shut down on the room controller for say a week whilst one is on holiday - there is a good chance that it will throw an F28 fault when it tries to power on. Doing 3 or 4 resests with the central heating time active usually powers gets it working, Resets with the HW active doesnt seem to fix it , more likley to lead to an F29 fault.

The big question is - Is this how Vaillant 418 boilers work or is there an fault with it

 

[Mottie]

I used to have exactly the same problem with my system with the same boiler as you after a weeks holiday. Nothing to do with the boiler, turned out to be a lazy motorised valve. Powering off then on would clear it. I changed the motorised valve head on the heating circuit valve and I’ve had a couple of holidays since with no problem.

Odd problem with heating/boiler. One-off or something on the way out?

Odd problem, as above. Just got home from a weeks break. We have a sealed 'S' plan central heating system and unvented hot water. Vaillant ecotec boiler, Honeywell digital room stat, controller and motorised valves. When I went away I turned the hot water off at the controller and left the...

www.diynot.com

 

[Elektra99]

interesting thought, but not convinced that is the problem. getting the CH to come on at system power up has, from my perspective been a challenge since day on. The solution adopted was to take out the 3 way motorised valve and replace it with a V4044C 2 way divertor valve, engergised to HW. So the valve has been swapped out already. My suspicion is the controls or valves havent been wired in correctly.

 

[Mottie]

interesting thought, but not convinced that is the problem….. My suspicion is the controls or valves havent been wired in correctly.

What controls are you using - Vaillant programmer or anything else? One problem I had with mine from the very first day was that the installer forgot to remove the 24v link on the boiler control panel. That ONLY remains if using Vaillant controls as they are 24v. Anything else and you have to remove that link. Boiler was running when it shouldn’t, wouldn’t switch off etc etc. I removed mine myself after speaking to Vaillant and while waiting for the installer to return. They told me many Vaillant approved 'installers' forget to remove it.

 

[Elektra99]

VRC 700f/4 with VR 66/2.

The other interesting issue is, which may or may not be relevant. is that the display on the front panel doesnt show the radiator symbol in the bottom right panel, except at initial power on. It appears highter up on the LHS when heating is live. The parasol doesnt appear when the heating is switched to off and the system diagram is set to 1 but the wiring diagram booklet suggests it should be 2.

 

[Elektra99]

finally found out what the problem was - the maximum outside temperature setting in the installer menu was set to 10C , as it was above 10C outside the CH wouldnt stay on. Changing the setting back to the default 21 fixed the problem