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

 

[Last Plumber]

Have you checked burner pressure on high rate ?
Those readings are a bit out and it may be over gassed on full rate.
It's fairly rare but I've seen it once or twice where a bit of flame lift breaks continuity through flame and it stops rectifying !

 

[sammathias]

Sorry inlet pressure at max rate is 19mbar. All them readings are within limits of m.i. boiler will work fine full bore hot tap on. However if heating is on then you turn tap on it locks out after 20 seconds unless the hot tap is cranked down on isolation valve...then it runs fine! Also does the same in service mode. He said its been doing that basically within a couple of month of having it installed.

 

[kb76]

Strange one that...Warranty job for WB?

 

[sammathias]

Out of warranty. hes just put up with it cranked down practically since its been installed :smile5: looks like ill have to give technical a call, was hoping someone had come across same problem on here. nice one anyway guys.

 

[ambrosia]

their tech help is quite good, by that i mean they answer the phone

but youre going to have to come back and tell us what they said, cant leave this a mystery

 

[cdodds2004]

has it had the electrodes changed on it ever?i would probably start with a full strip down of the burner and change the electrodes and possibly leads. double check the polarity aswell out of daftness

 

[bewsh]

You can't have both running at the same time, its one or the other. Is diverter actuator moving ok?

I've had one on the new I ERP boilers where the diverter motor had failed and for some reason it would go through the motions of startingf a demand, fan would run etc... but didn't go to ignition. New diverter motor and worked a treat. It was a bit of a head scratcher that one.

 

[Dogby]

Try removing diverter motor and manually flicking it over between demands , just wonder if the motor isn't reacting as it should creating an issue to cause the lock out.

 

[sammathias]

Can have them both running at same time as long as the flowrate on hot tap is cranked down on an isolation valve. If its on full bore it will lock out after 20 seconds or so, even in service mode or normal operation. Havent been back yet but will investigate diverter properly. Seemed to be doing its job mind.

 

[kb76]

You might want to check that, like all combis to my knowledge are hot water priority, as soon as the flow turbine is activated the diverter will move over to hot water regardless off flow rate restriction. If it's dumbing heat down the flow then you have an issue other than in service mode. From previous post I thought it was happening when changing over from heating to hw