No heating following gas re-instatement - VCW GB 242 E

[Katade]

Our street has recently had our gas mains changed from lead piping to plastic. Due to this change we had had to have our gas supply switched off for a few days. Now it is back on the Central Heating on our Valiant VCW GB 242 E will not come on. The hot water is OK (in fact it is ultra hot), but there is not heating.

Any ideas?

Please help as my wife and I are getting a bit cold now.

Thanks in advance.

 

[corgiman]

probably need a CORGI type to purge the boiler

 

[Agile]

He says its working on DHW so its not in need of purging.

It can only be something really simple like setting the timeclock or the room thermostat or the boiler selector switch.

Tony

 

[Katade]

I think I have found the problem.

I took the panel of the front of the boiler and found that there was a switch (about 2inchs long, black in colour, has a spring attached to the right of it and a little red tag on the leftof it) that was in the up position i.e. the spring was at full stretched. I moved the switch back down with my finger and ha-presto the CH came back on. I sprayed a bit of WD40 on the spring to free it up a little bit. I then watched the switch for a good while and it appears that it moves up and down from time to time. I don't know anything about boilers, but the switch appears to be an overheat switch or valve that the boiler actuates from time to time. It seems that it was not returning to the off position which was stopping the CH from coming. Is this correct?

 

[kevplumb]

its the servo valve & switch
and it will stick again
the pin underneath probably needs cleaning and greasing

 

[meldrew's_mate]

its the servo valve & switch
and it will stick again
the pin underneath probably needs cleaning and greasing

Then expect the water section gland (stuffing box) to leak !!

 

[Agile]

You have now reminded me of this problem which I am dealing with for one of our clients.

You are not solving the problem by moving that. You are making the boiler think there is a demand for hot water which results in heating the radiators.

The real problem is that the system flow switch is operating on DHW but not on CH.

If DP is around he can probably explain it better but there is a restrictor on earlier models which is better removed as it can over restrict.

Tony

 

[chrishutt]

there is a restrictor on earlier models

That'll be the tiny little restrictor in the end of one of the hydraulic tubes connecting to the diverter valve - a banjo connection I think. It's only a few millimeters in size and looks like a bit like a simple check valve.

If you can locate it and identify it with confidence, you can just rip it out, leaving the waterway clearer. I've been told this is OK to do by Vaillant technical, and I've done it successfully once.

 

[ricardo111]

IF YOU MOVE THE BLACK PLASTIC CAM WITH YOUR FINGER AND IT FIRES FOR CH, THEN THE HYDRAULIC TUBES, BANJO,DIVERTER VALVE AND SERVO ARE ALL O.K
IF YOU HAVE TO MOVE THE CAM WITH YOUR FINGER TO RELEASE IT FROM THE RED TAG (MICROSWITCH) TO MAKE THE CH WORK, BUT THERE ARE NO TAPS RUNNING THEN TRY TURNING OFF YOUR WATER MAINS. I SUSPECT THERE IS A COLD MAINS FLOW THROUGH THE BOILER SO IT `THINKS` YOU ARE RUNNING THE TAP (EVIDENCED BY YOU SAYING YOU HAVE TO PULL THE CAM OFF THE MICRSWITCH) AND THEREFORE IT CANNOT GO TO HEATING MODE WHILST THERE IS A DEMAND FOR HOT WATER. IF THERE ARE NO TAPS RUNNING, THERE MUST BE A HOT TAP PIPE LEAKING SOMEWHERE CREATING THE DEMAND FOR HOT WATER. SO, BY TURNING OFF THE COLD MAINS COMING IN TO THE BUILDING, YOU WILL STOP THE LEAK, THE BOILER THINKS YOU HAVE STOPPED RUNNING THE TAP, AND SHOULD (SHOULD) GO TO HEATING MODE. JUST A THOUGHT. THEN ALL YOU HAVE TO DO IS STOP THE LEAK.

MOD

turn your caps lock
off

 

[Katade]

Thank you all for the replies.

The CH has now been on for a good 24hrs without ay problems. I can't see any evidence of leaking either on a tap or pipes. I have been using the HW fine whilst the CH is on and all OK. I am a bit dubious ripping bits out of the boiler, so I will contact my local Corgi man get him to sort it for me. At least I roughly know what it is and can point him the right direction. Whilst he is here I think I'll get him to service the bolier and gas fire as well.

Thanks again for all your help.