worcester 28 cdi rsf,no hot water?

I had the same problem. If your heating is already on then when you turn on the tap you will get instant hot water because the heat exchanger is already heating the water for your heating. It will go luke warm or even cold as you run the tap because cold water is passing through the heat exchanger and getting heated like it should but, is getting diverted to the heating system. Your problem is the diverter valve. The diverter valve has a diaphram in it which moves every time you turn on the tap. If the diaphram develops a tiny split or hole in it then less hot water is diverted to your tap. This will get worse as the split or hole gets bigger. You will have to replace the diverter valve. Hope this helps.

Norm.
August 2010

the heating is fine,when the heat setting is on 2 i open the tap abt 75% the water gets hot then goes luke warm,i then reduced the flow to abt 30% and the temp stayed the same,i then open the tap to abt 70% again and the temp goes really hot then goes luke warm again. i tried changing the dial setting when running the water to max (1min/4max)and the water went skin stripping hot then reacted accordingly when the flow was changed,move dial back to 2 and it acts up.it always ran ok and hot enough on heat setting 1 before, i cant understand it,and cant work it out.

steve
December 2008

Could be either. 1st, legally, all work should be done by Corgi reg repairer. personally I have found some of them do dangerous work.
Not Boiler specific, BUT
1st check your dial water temp setting, on opening a tap, can you hear the boiler start up. Is heating OK. Does changing your water temp at the boiler have any effect, No effect more likely thermostat. But. Does the water temp increase if running slower, If no change in temp with change in rate etc, should get a slight increase with lower rate, initially, then back to normal, would tend to say thermostat, internal in boiler could be ok, Cheaper option to Pcb. try it 1st. But, it could still be the control pcb, 1st have a look at it, you may find a damaged component,BUT if it not marked as to the value. Replace the control, do not guess the value. too dangerous. Be careful. Only replace as is.

Sheepdog
December 2008