Worcester 28 i Junior wont light.

[grill]

Hi guys,

Called out to this one because it runs for a while then kicks off on thermo and when it goes to come in again it doesnt light. You get the warning light flashing once per second which can be a number of probs.

So i stripped it all down, set water pressure correctly, checked all pressures which were fine. Checked i had a spark which was fine (i cleaned the electrodes), turned it off and on again 10 times and everytime it lit.

It lights on low flame at 1.4 mb pressure and then goes up to high flame at about 14 mb. These check out on the manual.

The guy had the thermo set at 19 degrees and it ran fine all day. He turned it down to 15 degrees, went out and came back and it was giving the same problem.

From listening to it over teh phone it goes through teh run sequence until it gets to the ingnition stage and then you can hear a series of quick ticks then it locks out.

Cany get any parts now until wednesday anyway so all ideas welcome!!!

Cheers

G

 

[grill]

P.S. I forgot to run a spellcheck. Sorry!!!!

 

[Livesgas]

Is it overheating requiring a manual reset of the limit stat?

 

[grill]

Nope,

Isnt going to overheat.

G

 

[scatmanjohn]

Is it overheating requiring a manual reset of the limit stat?

Think you are on the wrong boiler fella, no manual o/h on a junior

 

[Gasguru]

I'm assuming with the room thermostat set at 19 the boiler would have remained on more of the time (even though it modulated down) but on 15 it would have cycled off more and greater chance of lockout.

Is the correct flue restictor ring fitted? Have you checked flue draught/APS pressure requirement. If the ring is missing the gas could be "pulled" off the burner ribbon failing to ignite.

Otherwise you could try upping the minimum burner pressure a little as a temporary measure to see if things improve...it wouldn't be the first boiler to have this type of design fault (ie a very low ignition pressure).

 

[Livesgas]

Is it overheating requiring a manual reset of the limit stat?

Think you are on the wrong boiler fella, no manual o/h on a junior

Think your on the wrong boiler pal. The high limit stat on the 24i and 28i Junior range is located on top of the boiler next to the flue. I`m not talking about the HE range. Come back fella when you know your job.

 

[Livesgas]

If the hot water is ok but no heating then it may be the heating thermistor. The opposite applies if hot water and no heating. Also the old non condensing `i` range have a cross flow heat exchanger. This means that the pump is only needed in heating mode. If hot water but no heat ( or the problems appear in heating mode) check the pump.

 

[Gasguru]

The overheat stat on the Junior is auto resetable but the lockout must be cleared the front push button, on the 28i RSF it's on the top left of the combsution chamber.

 

[grill]

ALright guys.

HW was working fine when i was servcing it. Havent had a chance to check and see if it is kicking it in when this fault is happening. If so will change/check the HW thermistor.

Thought about the minimum pressure. Seemed low. What should i bump it up to??

As for the required flue draight/ flue restrictor then i ahvent a clue. How do i check that value.

Is there anything i should be checking. Could i be a sticking gas valve?/ PCB not opening solenoid? Etc Etc!!!!!

G

 

[clf-gas]

Grill clearly knows where the highlimit reset is, the help he is looking for is whats the fault.

Initially I would suspect a faulty high limit, if you let it go to fault and then check continuity on orange wires and stat. There is a way of proving this, sure you know it without posting that in a public forum. Also check for resistance on the multi block to the board, cant remember the pin numbers but the brown wires should read between 60 and 100 Ohms, the violet the same and the blue between 10 and 25 Ohms.

It is possible your looking at a board or valve fault .

 

[scatmanjohn]

Is it overheating requiring a manual reset of the limit stat?

Think you are on the wrong boiler fella, no manual o/h on a junior

Think your on the wrong boiler pal. The high limit stat on the 24i and 28i Junior range is located on top of the boiler next to the flue. I`m not talking about the HE range. Come back fella when you know your job.

I'm back

6 posts in and already talking daft

If what you are saying is true (it isn't by the way)

Whats the little black disc shaped thingy attatched to the heat exchanger (back rhs) just behind the water pressure switch, orange wires if i'm not mistaken

If the hot water is ok but no heating then it may be the heating thermistor

The light flashes 4 times a second if a thermistor is out of range ( that range being 25kohms@ cold to 1kohms @85 deg)

This one is flashing once per second

 

[clf-gas]

Whats the little black disc shaped thingy attatched to the heat exchanger (back rhs) just behind the water pressure switch, orange wires if i'm not mistaken

Please John, Please. I know, can I tell him,,,,,,,,Or go on let me

 

[grill]

Okay guys ill take it step by step.

Will check high limit first and take it from there.

Still have a sneaking suspicion it has something to do with gas valve problem (no gas getting through) but i totally bow down to the knowledge on here.

This question may be where i let myself down but if it was a faulty high limit problem why would it go through the run sequence and try to ignite??

The joys of learning about gas boilers. The more you know teh more you have to know!!!!!

Cheers

G

 

[grill]

Sorry.

That maybe doesnt make any sense. What im trying to say is that it defo locks out when it is trying to ignite.

G