Boiler not responding to roomstat

[Bunglebonce]

Hi all need some help before I hang myself

This is a long one but I'll try and cut it down!

Had new boiler fitted (Worcester/Bosch 14/19cbi) about 4 years ago.

First night of use came home to find house blazing hot and the roomstat none responsive.

Rang fitter who came out and did something and all was well for about 6 months until it developed an intermittent lockout fault.
So rang W/B under the warranty and the engineer came out and said it had been wired wrong - needed direct wiring of the pump to the boiler not via wiring center, but changed circuit board anyway.

All worked ok so I left it alone, however lockout problem has returned so I thought I'd have a look at the wiring to see if I could rectify it.

Having used the installation manual and the booklet that came with the heating control pack I have now wired it as far as I can see - correctly.

The pump is now directly wired to the boiler, and the boiler has a permanent N and L and a switched L that runs from the boiler to terminal 7 as per the heating pack manual.

All other connections are as per the heating pack manual with the exception of the pump connections to terminals 7, 2 and 3, as the pump is now direct to the boiler.

However, as when I originally had it commissioned, when the boiler fires up, if you turn the roomstat to remove the demand, it clicks, but the heating continues to 'heat'. The only way it cam be stopped is to manually turn it off at the timer.

I've attached links to the two diagrams and any help with this one would be greatly appreciated before I go nuts

http://s8.photobucket.com/albums/a6/Whirlingdurbisher/?action=view&current=BoilerWiringDiag.jpg

http://i8.photobucket.com/albums/a6/Whirlingdurbisher/HeatingControlDiag.jpg

Oh and the room stat worked fine before

Thanks

Geoff

 

[EliteHeat]

When the roomstat clicks off, check the voltage to the white wire on your motorised valve (assuming you have a 3PV), if not 230V then your valve is busted, if 230V present then your roomstat is broken.

Obviously (I think) you need a multimeter and to take all suitable precautions before doing any of this.

 

[Bunglebonce]

Thanks for the help there Elite and I'll keep that in mind if needs be, but I think I've found the fault - Me!

When I flicked the roomstat to 'no demand' last night and the boiler stayed lit, I overlooked one minor detail.

The hot water was on too and was calling for heat!

Tried it this morning without the water on and the boiler burner shut down, the fan ran for about a minute and the pump ran for about 5 before everything shut off.

This is the first time the pump over-run has worked since I've had the damn thing fitted so it looks like I got it right after all.

Just goes to show that when you get tired and frustrated, you sometimes overlook the most obvious things.

Jury is still out on whether this has cured my intermittent lockout problem but time will tell and at least the wirings now good


Cheers

 

[EliteHeat]