Vallient Combi Boiler


  #1  
Old 10-24-06, 12:18 AM
G
Member
Thread Starter
Join Date: Oct 2006
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
Unhappy Vaillant Combi Boiler

Its come to that time of year when the boiler gets fired up again, I have a VCW BG 242 EH, the hot water works fine as it has been all summer. The problem is that the central heating will not come on, I have checked the thermostat and it seems to be working, I have tried running the hot water and then switching on the heating and then switching off the hot water, this didnít work either, the pump has been checked and is working, the radiators have been bleed, has any one any ideas?
 

Last edited by Gadget_Buster; 10-29-06 at 10:51 AM.
  #2  
Old 10-24-06, 09:29 AM
A
Member
Join Date: Jun 2005
Location: Yorkshire,England.
Posts: 43
Upvotes: 0
Received 0 Upvotes on 0 Posts
Any other external controls like a time clock.
 
  #3  
Old 10-24-06, 11:26 AM
G
Member
Thread Starter
Join Date: Oct 2006
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
Yes there is a timer, which seems to be working fine. I have a reverse current coming back to the boiler when the thermostat and timer are demanding heat. Some one mentioned to me that it may be the thermistor? do you think it may be that??
thanks for your help
 
  #4  
Old 10-24-06, 12:34 PM
A
Member
Join Date: Jun 2005
Location: Yorkshire,England.
Posts: 43
Upvotes: 0
Received 0 Upvotes on 0 Posts
Thermisters on vaillant boilers are the most reliable componants you can get.

These boilers can be fairly complicated and I would recommend getting in someone with experience on the 242 model.

There is a device called a servovalve in the middle to the bottom of the boiler its black in colour and has 3 ( I think )
impuls tubes going into it. If any of these become blocked it will stop the heating from working.

When you put the central heating on do you get any noise from the boiler like the pump running.

Andy
 
  #5  
Old 10-24-06, 12:47 PM
G
Member
Thread Starter
Join Date: Oct 2006
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
Hi Andy
Thanks for your help
The microswitch housed in the middle of the boiler at the front is working, this one has the three tubes you mentioned. It switches on when the tap is run. There are two more microswitches under a clear plastic cover on the right of the boiler, with a sort of piston arrangement. When the piston is pushed in it looks like it will activate the two micro switches. unfortunatley the plastic cover is too close to the housing of the bolier and cannot be removed so i cant see if there is movement in the piston arrangement. It does look a little corroded on the shaft of the piston though. Would i be right in assuming that that piston should be going in if the thermostat demands heat? The unit that has the clear plastic cover is under the water pump attached to the right of a three way junction/housing thingy ( sorry dont know what it is. Im just going in to the loft to try and find my installation manual BRB
 
  #6  
Old 10-24-06, 01:01 PM
A
Member
Join Date: Jun 2005
Location: Yorkshire,England.
Posts: 43
Upvotes: 0
Received 0 Upvotes on 0 Posts
I will try explain how it works.

When there is a demand for hot water a spindle rises from the diaphragm and pushes a cam at the rear of the serovalve this adjusts the flow of water to the diverter valve ( the thing in the glass housing ) via the impulse tubes. this puts the diverter in hot water mode allowing the water to be warmed via the hot water heat exchanger on the far left hand side ( old versions black new silver )

After the demand for hot water the spindle should drop and allow the water to be diverted in a different direction through the impulse tubes but again to the divertervalve but because the pressure is going through a different tube it makes the diverter valve move in a different direction opening it up to the rads.

It is usually the servovalve not seating properly so not diverting the flow correctly that causes the heating not to come on.

To be honest though it could be 20 other things as well.

andy.
 
  #7  
Old 10-28-06, 02:09 AM
G
Member
Thread Starter
Join Date: Oct 2006
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
Angry getting more and more frustrated

Some body told me it may be the thermostat/thermistor/safety switch that has gone. I take it all of these words are the same thing just worded differently? I have located this fitting/sensor, it is on the down pipe from the combustion chamber just before it T's into the main outlet to the radiator's. If I was to remove the two wires from this or alternatively run the two wires with a jumper between them would and the central heating still not work, would this mean that it is not this fitting/sensor that is at fault?

Thanks for any help you can give
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: