worcester bosch combi ignition problems

[valandian]

Hi,
we have got a worcester bosch 24i combi about 3 years old, for about the past 12 months it has been a bit tempramental sometimes there is no hot water when the tap is turned on, we can turn the tap off and then on again, a few times maybe before we get H/W. occasionally we have to pull the power plug out and then back in again before it will work.
taking the front off to observe what happens :- the ignition spark lights the pilot light, a small row of jets light but then go out before the main jets kick in!
my partner upped the pressure the other day to near bar 3! and since then it has been constantly trickling from the overflow pipe
one other thing is we have to keep upping the pressure about once every couple of months. is this normal?
can anyone help me with this please or at least give me some possible causes so I don't get ripped off
thanks alot!

 

[COG]

Just to get things clear the 24i has no pilot it will ignite all the burners at a minimum level around 0.50 mili bar then the ignition will stop when the flame sensor at the rear of the burner detects the flame it will burn for a max of 7 seconds if the flame censor does not detect the flame then stop . is this what is happening ? if the flame does not reach the rear of the burner within 7 seconds then it will go out . you will have to have the gas valve re set if this is the case (it wont need replacing they just drift out )

 

[valandian]

Hi thanks for the reply
If I can be more specific thanks to your help this is what is happening :-
I turn on the tap and run to look at the boiler
there is an ignition spark which lights one jet and then all the burner jets not long after but it keeps sparking for a while, I notice a probe, which I asume is the detector being heated by the flame. the flames are at a low level and in normal operation these jets then burst into life! but instead they are just fading out!
I hope that clarifies things a bit better
thanks again

 

[COG]

Does the ignition continue to spark untill the flames go out or does it stop some time befire the flames go out ?

 

[valandian]

it stops sometime before they go out!

 

[galacey]

This sounds like the same problem I'm having with my 24i which has become progressively worse. It started from new with the central heating sometimes not coming on in the morning. Now it never comes on. When it is on, it will switch itself off. Turning on a hot tap sometimes lights the boiler but it will go off after a few minutes. Sometimes it comes back on again.
Quite often, turning on a hot tap does nothing and I have to switch off the power to the boiler and then back on again.
Looking through the little window, I observe the same results as valandian, ignition sparks, one flame, then a row of flames, then it goes out. If I turn on a hot tap before the flames go out,it will burst into life.
Any idea on what is needed to repair this and how much it will cost?

Best Wishes
Gary Lacey

 

[bradleybear]

needs a good clean out. The burner is probably slightly blocked, and is failing to cross light in time to the ignition probe, needs a proper service by a corgi engineer, if that fails, change the probes, investigate gas pressures etc.

 

[jtw]

just a quick comment - i had a 24i junior installed a few weeks back, and although the c/h isn't hooked up yet, the hot water is patchy. you turn the tap on at a reasonable rate and it will run hot for a bit, then randomly go cold, turn the flow up a bit and maybe it goes hot again. The guy who installed it is coming round Friday so I'll ask him what's up. I was wondering if there is a way of setting the minimum flow rate needed for ignition, but there's nothing in the manual.

 

[COG]

JTW when you say the ch isnot hooked up yet ? i hope you have at least one rad on full of water or you have damaged your boiler

 

[jtw]

no, all rads have been taken off for decorating purposes. the boiler is on summer mode, i.e. hot water only. why will it be damaged?

 

[DP]

Because the boiler does not come to a complete stop at the end of HW demand. Pump can run on at the end of CH or HW demand. With no heat load connected to the boiler, pump will be stressed.

 

[COG]

Your boiler if it is a 24i has only one heat exchanger with a double matrix ,in other words two coils above the main flame one full of domestic water circulated by mains pressure when you run a hot tap and thje other coil full of heating water circulated by the pump on demand . If you run the boiler on hot water with no water in the ch system then you are putting 24KW on to a heating coil full of nothing but air,potentialy dangerious.I would guess that your boiler is a 24 cdi or you must have some pressure in the heating circuit as your boiler should have gone bang by now if not your lucky

 

[jidhanga]

Hi,
I have similar problem with Worcester Jr 24i. I recently moved into this property and the boiler is purchased by earlier owner in 8/2004. My boiler HW worked fine for 2 months since i moved but from yesterday it is very temperamental for the HW. HW comes if I start heating, which was not necessary earlier. Also, sometime when I switch it off from Power the HW comes. It's not reliable.
The pressure gauge shows black arm < 0.5 and red arm < 1. I called Worcester and the lady on the other line told me that the pressure is low and has to be topped up. She gave me some instructions which I couldn't understand. I don't know how to open the boiler. She said use a white key, which I don't know since earlier owner didn't left any. She told to me to use white key to open silver hose pipe, I coldn't see any silver pipe from bottom on the boiler.
Also, the boiler dripps sometime. I don't know how to raise the pressure to get HW... need urgent help.. please help asap...