Worcester Bosch 24i Junior problem

[mcfcantc]

Morning everyone,
I was wondering if anyone could give me some advice before i call someone out.
I have the above model boiler installed in my terrace, always worked fine with no issues that I can recall. we have just been away for 2 weeks, wasnt on before we went due to weather. When we got back just over a week ago i turned the boiler on and it fired up as normal, then after 10mins I started getting the fast flashing light, the rads started going cooler and the boiler (whilst still whirring away) wasnt lit.
I've tried it a few times since and its done exactly the same sequence.
The hot water is fine, showers, baths, washing up not a problem.
Last night I bled every rad and tried again. This time the boiler stayed on for a good hour (a lot longer than previously) but then returned the flashing light, boiler off etc same as before.
Sorry for the lengthy post but i was just wondering if anyone had any ideas or similar experiences of things i could maybe try before calling someone out.
Thanks in advance.

 

[Loofah]

Low pressure?

 

[mcfcantc]

topped it up a couple of times and when on it seems to be getting upto pressure fine.

 

[Loofah]

crud in the pump? This is about the limit of my knowledge so I'll let the 'sperts provide some better advice!

 

[Agile]

Without further info I am not able to make any guesses.

I would want to know flow and return temperatures just before it turns off.

Although not common on that model a temp sensor might be faulty when hot.

Tony

 

[mcfcantc]

being a bit of a novice, and obv not wanting to mess with a boiler too much, how would i check what you mentioned Tony?
Also what further info could i get if any?
Thanks for your replies.

 

[Agile]

You use a contact type temperature meter on the boiler flow and return pipes!

Tony

 

[DP]

OP, why not use your hands to see if heat is getting to the closest radiator to the boiler.

Do same under the boiler but be VERY cautious as pipe may get VERY hot.

When the boiler fires for central heating, look at the pressure guage- is it stable or jumping about when burner goes out. Is there any noise coming from the boiler just before the flame goes out.

 

[mcfcantc]

the rad nearest the boiler is getting hot as are all the other rads, yet to check the pipe under the boiler.
The pressure gauge is stable, am i right in thinking that on this model the gauge rises once the boiler is turned on until it reaches the correct pressure?

 

[DP]

The pressure has to be right when you run the boiler. Low pressure should e avoided.

 

[mcfcantc]

Yes i understand that. The pressure is right when the boiler is running, i meant is it right for it to be at zero when the boiler is OFF on this particular model?
Thanks

 

[kidgreen61]

Your pressure gauge should read 1-1.5 bar when cold.

Depending on how many rads you have etc, this may rise a little as the system warms up.

The pressure gauge should not bounce around when hot water is drawn off.

I think you need a pro to look at it.

 

[mcfcantc]

Ahh right, we might be getting to the bottom of it here.
Its always read zero, until the boiler is fired up, then whilst the heating is working it reaches the correct pressure.

 

[mcfcantc]

update, topped the boiler up to between 1 and 1.5 bar last night, all fired up and worked fine, however the pressure went above 2.5, more like 3.5 which i know is too high. Any ideas??

 

[Terry7556]

At the top of the posting list page are the FAQ s and stickys
Read the central heating/boiler one on expansion vessels and recharging them
Se e if it applies here
The coper pipe that goes through the wall to outside ( should be like a hook, pointing back at. The wall) has this been dripping?