Worcester 28i junior lock out problem.

[sammathias]

Alright guys, another problem which i havent actually been to investigate but the blokes a plumber i know so ran through it over the phone....
Basically if he turns heating on, heats up fine no worrys. however if he then turns ho****er tap full bore at same time boiler will lock out after 20 seconds or so...however if he cranks the isolation valve down on the hot tap and runs both heating and hot water boiler doesnt lock out?????
If he just runs hot tap full bore and no heating boiler copes with the demand. anyone ever come across this?

 

[AllyBongo]

FGA it, maybe not been serviced in a while

 

[sammathias]

FGA it yesterday.

readings: 3.2% o2
98ppm
10.1 co2%
0.0010 ratio
flue temp was 76 degrees
inlet pressure 19mbar
and gas rate was 2.96m/h

so readings all good. i had to reset it a few times tho until i turnt an isolation valve down on the hot tap (after test)... would it be overheating? thought at first it was a diverter vaslve problem but thats doing its job. i'm more of a installer/servicer...when it comes to breakdowns im newish to the game

 

[gassafe]

Is this the little old jnr or later condensing one?

 

[sammathias]

sorry its the greenstar condensing boiler g.c 47-311-87. any help much appreciated.

 

[kb76]

If heating ok and locking out on hot water I'd be looking at a blocked plate

 

[gassafe]

If heating ok and locking out on hot water I'd be looking at a blocked plate

But the boiler runs fine on hot water only...

 

[kb76]

Does it lock out in service mode?

 

[gmartine]

Partial blockage of condensate trap and outlet? Worth checking and cleaning out anyway.

 

[gassafe]

You should be able to feel / hear if it's overheating with case off ... is the hex all rippled, could be sludged up...

Worth checking the condense trap as said, plus sump onto condensate & the electrodes are a common fault & normally first to wear on these.... but yours is a percuilier fault