Worcester 24i combi boiler loseing water from outside overflow pipe to much water in boiler i thinkwhat position should black finger be set at and how do i let water out of system annie

Hi Steve, I am not a plumber but have done a lot of DIY on my own heating system with Worcester Bosch combi boiler! I believe that you can have the hot water on without the heating system filled, just turn all the settings as for summer use and the thermostat right down so the heating is forced to stay off!

Wiring is wrong.

Change the expansion vessel sounds as if its leaking somewhere

When water is heated it expands. To deal with this all boilers are fitted with a small expansion vessel which is like a reservoir which holds the excess water.

This expansion vessel is like a balloon in a metal pot. When the water goes in the metal pot the baloon squashes a bit to make room for the extra volume of water. When it cools the balloon pushes the water back into the heating system.

What has happened is your expansion vessel no longer works. When the water heats up there is nowhere for it to go so the pressure jumps up to 4 bar. The Worcester boiler lets high pressure water escape (most boiler allow this to go through the safety valve at say 3.5 bar).

When the water cools the pressure drops very low as the volume of water contracts.

The problem is your expansion vessel - normally a little red painted metal cylinder inside the boiler.

3 psi is a little over the average, 2.5 is the optimum setting. If it empties itself, it means that the safety valve is working,which prevents any kind of damage to pipes etc...Make sure the valve is open and close at the right time and top up the system slowly rather than in a hurry. If the system requires regular top up then there must be a small leak somewhere, so it is best if you can fix that too. Remember that there are some solutions that are added to the water circulation and if you are constantly topping up with water then you are losing these solutions that prevents rust build up etc...Hope this helps.

Two types dependent on age
Early - in the mains water inlet pipe there should be a service valve/tap which when turned on will refill [it is close to or part of the fill loop - a metal braided flexible pipe
Later - underneath there is a hole for a plastic tap [supplied with boiler] to be inserted [usually just right of center] Insert and turn 90 degrees then close to it another small knob or 2nd tap which when turned [same action as a basin tap] will refill. If the first tap is not inserted properly water will drip out past its seals
For both Refill to about 1.5 - 2 bar and turn off
For the later as above but also remove the 1st tap

your condensation pipe may be frozen get a hairdryer on it or a hot kettle that should sort it thats the whit pipe on the left usualy plastic

Pressure is ok? at 1 bar or above
I think on this one there should be a reset button [red] on the left hand top of the casing - or lower the control panel [ phillips screw on each side] and the button is on the left of the base plate. Press this and try the heating.or hot tap
P.S. if you're on a prepayment meter check you have gas.

This is lack of water flow through the diverter valve.

First have you got a good flow from any cold tap? If yes then see below

If I remember there is a pipe carrying cold mains crossing the lower front of the boiler with an in line filter usually clogged. Remove clean & replace
check also any filter in rising mains to boiler

another cause is the diverter valve itself - diaphram inside may be punctured/split

replace pressure release valve