Vaillant combi boiler overheating

[Alex Kennedy]

Hi,

I have been having a problem with my Vaillant combi Boiler. It is a VCW sine 18 T3WF-H. The problem I have been having is that the boiler overheats. I have to open the panel to push the overheat reset button to get it working again. It the heater also does not come on when you turn the hot water tap. I only get Hot Water when I switch the central heating on. I suspect it might be the water pump but as I know nothing about boilers, any help would be greatly accepted.

Many thanks

Al.

 

[kevplumb]

methinks the diverter AIN't

 

[namsag]

Its not the pump. Also they don`t have a divertor valve .They have a flow switch on the left hand side about 14 inches long with about 4 connections on it . And right i middle of boiler at the centre bottom they have a water section .The diaphragm in these wears which stops a pin moving and hitting microswitchs to bring HWon if this pin is moving and connecting it is the flow switch causing no HW

 

[ChrisR]

Waxstat?
That isn't realy a suggestion as much as a question - because I've got a spare one but I don't know WTF it does. Does it open a DV à la puma?
Really must dismantle that T3 I've got in the shed...

 

[Agile]

All the combi versions I have ever seen have a diverter valve!

Its even at the back left with two switches on the top! They seem to drive the preheat satisfied.

Its driven by Chris's wax stat like his Puma but unlike the Puma which short circuits the CH the vaillant one really diverts the system flow from CH to the calorifier at front left.

It does not really need one but just to over engineer the boiler they decided to add a water flow diaphragm unit underneath to switch on the boiler for DHW. Not a simple two pipe one eith!

All quite simple if you waste your time on them.

The diaphragm may even fail less often that the stuffing gland gets stuck. That gland was £1.57 +vat which is a very reasonable price when many diaphragms can be £10 ! On this one its either gland seized or diaphragm holed.

Tony

 

[namsag]

Agile as much as it does the same function as a divertor it is called a flow switch in the parts list , probably because water has to flow past the wax capsule to cause the pin to move

 

[Agile]

Since the function is to divert the system flow to CH or DHW then I would call it a diverter valve regardless of any funny name the makers might choose to call it.

Its a pity they cannot standardise on the same mames for parts with the same function! Its a common time wasting problem when I need a part.

Many of the Itallian makers cause the DHW diaphragm a "membrane" but the best one of all is the AAV on some boiler ( C&M?) which is called a "jolly valve".

Tony

 

[Alex Kennedy]

many thanks guys for your info. I will now contact someone to come and fix it.

I will give him your suggestions as I have not got a clue what the hell you are all talking about.

many thanks