Discussion in 'Plumbing and Central Heating' started by tvrjohn, 11 Jan 2010.
and what are the faults with them ?
Having issue with 28cdi Worcester Combi
Its a valve that is triggered to activate HW or Heat.
I guess you have HW and no heating or other way round.
There is a good chance it will fail at one point
The Halstead ace boiler I think is typical.
There is a 'diverter valve' which is movable to the left. When moved it diverts the water from CH circuit to the HW circuit (heat exchanger)
At the end of its travel the valve triggers a microswitch.
You can see a faulty micro switch or a sticky valve and you have problems.
But the main problem is related to the 'diaphram operated switch Assy'.
It's this Assembly that moves the valve. How?
The Diaphram has mains water on both sides of it. When the hot tap is opened the pressure on one side is reduced. This allows the pressure on the opposite side to push the valve across. If this diaphram is split/holed the higher pressure water passes to lower pressure side. The result being the valve does not move or may move slightly, but not sufficient to light boiler.
This I believe accounts for many problems when no HW on a combi
Thank you for the Explanation
I repaired a diaphragm on a Vailant boiler quite an easy job apart from the rusted screws! Had to do both diaphragms.
The Halstead Ace is the best kind of diverter valve.
The most common type as used on Worcesters have a manifold section which has to follow the DHW bit under spring pressure and often gets stuck but you cannot see what its doing.
Mine has gone one further and leaked water out of it and into the plug which is popping the 3A fuse.
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