Valliant vuw 282 boiler

Indicates low water flow. possibly bad electrical connection to flow detector in dhw pipe or seized dector in pipe or blocked up heat exchanger. certainly a blockage somewhere in the pipes

Hi Mustafa, you are going to need a Gas Engineer to fix this one. It could either be the Hot water sensor or the flow switch that activates the water to come on. Good Luck.

Had this happen to me before, if you have hot water from the boiler going in and out of the boiler mate and the temps are not rising within the hot water means more than likely you may need to remove exchanger and clean sediment off element, basically sediment creates a blanket over the heat source causing poor thermal conductivity. Things to check before removing heat exchanger

- outlet temp of boiler water to aquamate -inlet temp of boiler water to aqua mate= 20-30'F if low then bad thermal transfer or poor water movement
-make sure sensor is reading properly
- get boiler temp higher to speed up thermal gain in water heater

It could be dyslexia, but I think you want to know what may be wrong with your boiler in this case!
This is a VERY old design. The diaphragm is on the water section, this operates a switch to turn ON the pump, and a further device causes the diverter valve to divert boiler water from CH duty to HW duty.
From your description it appears that the boiler is shutting down on internal boiler water temperature (too high), your 'briefly too hot' HW symptom may be caused either by the boiler side of the secondary heat exchanger being blocked/caked in sludge, OR the DHW side of it being scaled. Either way a new or replacement (descaled) secondary heat exchanger MAY inprove things. It's not easy on these old clunk-pots, and EVERY disturbed seal will subsequently leak, so get a good supply of o-rings and fibre seals before you start ("you" being the competant fitter you employ)

most likely the diverter valve.. when hot tap turned on the movement of the water through the valve operates a diaphragm which pushes a pin/button//switch to tell the boiler to fire up

Your boiler is overdue for a service.

Combi boilers are unlike regular boilers in that they have quite a few moving parts, it's vital that these are serviced annually if you want the boiler to remain reliable and to avoid expensive failures.

In your case, the diverter valve has most likely failed. Normally, when the heating is on this senses when there's a demand for hot water and temporarily diverts the primary hot water circuit to feed the domestic hot water heat exchanger. When the demand for hot water ceases the primary hot water circuit is diverted back to the central heating heat exchanger. The valve has a number of moving parts including a rubber diaphragm which can wear out and split and moving shafts which can seize.

When the valve fails it can leak and also can divert hot water to the central heating heat exchanger when hot water is used. The reason that only the highest radiators in the system are affected is probably because the failed valve does not necessarily cause the central heating pump to activate and circulate the hot water throughout the system (it does on some boilers though). If hot water is introduced into a cold heating system it will rise via convection to the highest points in the system like an old fashioned gravity circulation system which was unpumped.

Call a heating engineer out as soon as possible; I'm not going to advise how to do the repair yourself as gas appliances MUST be serviced by qualified persons only for reasons of safety. If you're lucky then the valve simply needs cleaning up and a few new diaphragms plus other minor seals and rings. If it's gone too far then the valve and possibly the manifold it's attached to will need to be replaced.

In the UK the part alone typically costs between £100 to £200 depending on whether it's just the valve or the manifold as well. The diaphragm kit typically costs up to around £15 and is routinely fitted when the boiler is annually serviced, and a new valve will already have new diaphragms fitted. For a routine service expect to pay for up to two hours labour (many can be done in one hour), but if the valve/manifold have failed it will be longer as one failure often causes other parts to need further inspection/repair.

I hope that I've helped you today, if so please return the favour by rating my answer.

there are two main faults with combi boilers not giving hot water. one is a faulty flow sensor, the other is the most common which is a blocked heat exchanger caused by debris and scale in the system. this needs to be flushed out or may require a new heat exchanger depending on the age and condition of the boiler some plumbers may suggest a new boiler.

if the boiler fires when the tap is opened then the diverter valve is working ok it must be a blocked plate heat exchanger which is the stainless steel rectangular block inside the boiler connected to the pump and the mains cold water.
it will be blocked on the central heating part probably with black scale. it is possible to clean out but sometimes it is better to just change the plate. but remember to flush the system as well or the same thing will happen.

baxi boiler relief valve blows off when heat is turned on when hot water is working it is fine