worcester 28i junior, dhw wont work

[dean.]

hi Worcester 28i junior dhw wont work, the ch works fine then when i turn hot tap it turns over to dhw mode it locks out. I was thinking the flow switch, does anyone know the way of checking this.

 

[stani]

remove 3 pin plug test between 2 outside wires you should get
around 5 volt dc, reconnect plug test between green and black you should get between 1.5 to 3.5 volts if you do flow switch ok, try thermistor then PCB

 

[cdodds2004]

hold the eco buttom in so it lights up and try again then please post outcome! sometimes the pre-heat sensor go faulty! and the 28juniors use a flow turbine! these can be removed and checked by a competent engineer! what flashing sequence are you getting?

 

[dean.]

if the boiler changes from ch over to dhw mode during heating does this mean the flow switch is working?

 

[cdodds2004]

only if your turning the tap on, but yea that indicates that its sensing the flow!

 

[dean.]

thanks for that info, ill check again tomorrow. i cant remember the lock out flash seq. ill cleaned flow sensor today and put back but nothing happened.

 

[cdodds2004]

sounds like flow sensor is ok tbh, quickly turn off the pre-heat if that solves it then i would say pre heat sensor! if this doesnt do anything same as above try thermistor then board! but ill be honest i have only ever changed one board on these!

 

[dean.]

ok will do thanks, ill post back how i get on.

 

[gasmarc]

i had one of these this week could not get a spark , I tried everything had pump and fan running but ended up checking everything and changed board that sorted the problem out around £123

 

[dean.]

was it working fine in ch mode, this one is, then when i open hot tap, boiler senses flow changes over to dhw mode but wont fire.

 

[gasmarc]

no I had nothing working bar fan, pump , if the CH is working that proves everything is ok so fault has to be sensor, turbine or board I have had this before but not that common, someone mentioned pre heat which i dont know about.good luck

 

[stani]

have been out to 28i this week no hot water but had heating, heating was on all the time hence rads were warm, but when it tried to go to hot water and then to full rate it would'nt work, finally changed DHW thermistor, still nothing about to change board nd thought would gas rate first, finally dug out cupboard with meter to find....................... ecv was practically closed, custard had jammed so many things in it finally pushed ecv lever more amd more to closed position, opened fully everything working correctly.

 

[gasmarc]

thats a result other wise it could have been expensive

 

[sammathias]

What was the fault with this dean??