Question about Water Heaters
As stated above, the heating works fine but since yesterday when i turn a hot tap on the boiler makes an odd noise and cuts out so I have no hot water from the boiler at all. Thanks in advance..
Odd noise like popping or singeing fire....clicking noises.....sounds like you have a water leak putting out the pilot.......or your thermo coupling is bad....or the noise is the tank full of calcium buildup and that will make noises when the burner is on
Posted on Jan 20, 2013
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Posted on Jan 02, 2017
is this a baxi 105? chances are you diaphragm has gone on your diverter valve. Or your diverter valve.
Do you will initially get a liitle hot water if your heating is on?
Posted on Dec 30, 2008
the problem was solved on my system by replacing thermostatic valve on shower and putting non return valves on hot and cold feed to shower . the problem was caused by cold water getting into the hot water line through the shower hope this helps
Posted on Dec 30, 2008
SOURCE: Combi Boiler gives CH but not HW
Combi boilers have many moving parts compared to conventional models so must be serviced annually to prevent breakdowns.
Your boiler most likely has one of four problems:-
1. When the receiver for the wireless thermostat was fitted, other wiring was loosened and has come adrift. It's a possibility, but in my experience unlikely as the wiring involved isn't anything to do with HW supply..
2. During receiver fitting the pcb suffered a static electricity surge. Possible, but unlikely as this sort of damage is usually immediately evident. However, boiler pcb's are notorious for sudden failures anyway and can happen anytime. Combi pcb's are more prone to fail as they usually have up to four solenoids fitted and these do eventually fail due to mechanical wear.
3. When you your combi is in CH mode it heats the primary water circuit and directs the flow through the CH heat exchanger. When you open a hot tap (US=faucet) you're opening a supply of cold water initially as there is no stored hot water like in a conventional system. As the water starts to flow through the combi's diverter valve there's a pressure drop which activates a rubber diaphragm with mechanical connections to other parts. The diaphragm is one part which is routinely replaced annually as it will eventually fatigue and fail with the symptoms which you describe. In addition, the mechanical parts connected to the diaphragm pass through various seals in order to activate at least one micro switch. If the seals fail then the moving parts eventually corrode and seize up. Regular servicing prevents this. Combi seizures are a very common complaint in hard water areas.
4. One of the micro switches activated by the diverter valve has failed. Possible, but not likely. The purpose of the switches is usually to fire up the boiler to provide HW when the CH is not currently running, but as you haven't said which Vaillant you have I can't be definitive on this.
One major problem with combi boilers is that multiple failures can and certainly do occur almost at once. Unmaintained units may appear to be correctly functioning but in reality a number of worn parts can be close to failing. When one part fails, the others can't cope with the stress and fail as well.
In most civilised countries including the UK it's a criminal offence to attempt most repairs yourself unless you're qualified to work on gas appliances, so you need to find a decent heating engineer to service your boiler (ask your new neighbours). In the UK you can expect to pay around £120-£150 annually for a routine boiler service. If the circuit board has failed then it can easily add over £100. If parts inside the diverter valve/manifold have seized then you can be looking at an additional £80-£150. Note that diaphragm failures on their own do not merit diverter/manifold replacement and that if you have a new diverter fitted then a new diaphragm will already be present inside.
Dishonest heating engineers always diagnose a failed pcb as they know that you have no way of knowing whether it's true. If you can live with the problem for a few days then failed pcb's are usually a straightforward repair and there are plenty of companies who will send you a guaranteed exchange unit for much less than the cost of a new one. As long as you are not opening the main boiler casing which houses the combustion chamber and gas valve assemblies then some territories allow non gas qualified replacement, but others insist that the work is done by a qualified electrician: this is not the case in the UK as long as the pcb is not connected directly to mains electricity (no modern domestic ones are).
Posted on Oct 13, 2009
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