I have a Worcester 28cdi which isnt supplying hot water but my heating works. Weirdly, I can get hot water to my taps when the heating is on (the water demand indicator light remains off however) but when I turn the heating off, I just get cold water. Any thoughts would be appreciated

PAUL T Oxford, May 2010

Hi, sorry to bring up an old thread.
Ive had a similar problem, heating works but to hot water, water can be luke warm in the tap if the heating is on.

Its got gradually worse over time since i had a leak in what looks like a flow switch at the front of the boiler (black plastic inline part with i think 2 wires coming out of it) i tightened the nuts on either side which stopped the leak, since this time the hot water hasnt worked properly.
I am happy to tackle the job myself, i am a motor technician.
Any ideas?
Wrcester 28 CDi

Rhid, December 2012

I had a bath last night and no problem. Only this morning I wanted a wash before going to work and low and behold, there was NO WATER coming from the hot tap. It wasn't even running cold - just NOTHING coming from the tap!!
Cold water no problem - so no freezing supply water issues here.
There aere no indications coming from the 28CDi to say there is a fault and no indication that the hot water red light is on.
This is strange. Anybody shed some light on this for me?

Mark, Kettering, England, November 2010

I wish I was so sure. I also had CH but hot water was running warm and cold but never hot. The burner kept cutting out even when the tap was still on.

I read similar advice to that above and have just spent a day changing the membrane in the diverter (the old one was perished) and a couple of other parts (PSV and AAV to fix a pressure drop).

Now the hot water is tepid at best, never warm and the burner continues to cut out intermittently.

When I run hot taps the CH flow out of the boiler gets red hot but the HW out remains tepid.

The pressure gauge is also climbing slightly (from 1.6 to 1.7 bar)

Any chance this is the water to water heat exchanger?

tayga, September 2010

wehre can you get the gio service kits from ????

RICHI LIVERPOOL, June 2010

Paul - DHW DIAPHRAGM is your problem guaranteed. With the amount of work involved or should i say the potential leaks you can get from isolation valves or o'rings when disturbed. Job can take 70 mins if your lucky - unlucky can be 3 hours. either get a private heating engineer to do it, if useing a service kit will probably charge around 150. If Brtish gas do it 12 month guarantee £165 all inclusive of leaks so no hidden labour charges if and when it goes tits up

paul, May 2010

Hi, this is Worcester, Bosch Group.

Our technical support team can help with enquiries, please call 0844 892 3366.

We look forward to helping you

Worcester, Bosch Group, May 2010

needs new service kit in diverter manifold/also check flowswitch where plastic contact make

pat cronin, May 2010

bottom center of the boiler is a diverter valve.when you operate a tap a differential in pressure operates a micro switch.the differential in pressure is above and below a diaphram, does not happen if the diaphram is split or streched takes about 90mins to do can be tricky, cost for giovanni service kit about £20.00p

john, May 2010

Your 3 way valve is u/s either cruded up or the operating diaphram holed. Attached to this diaphram is a brass push rod which inturn activates the micro switch for the domestic water on light. I would hazard a guess your fault is in this area.

Guytawe, May 2010