Worcester 28i SRF hot water cutting off (1)

[aquafix plumbing]

was asked to take a look at my mates worcester 28i. When calling for hot water the boiler fires up fine and the water gets hot. After approx 30secs of running hot water the boiler shuts down. With the hot tap still running( water gone cold) the boiler then fires up after about 5sec and continues to do this over and over again for the same time intervals. In central heating mode there are no problems. I Serviced the boiler to the manuals instructions and all ok. I took an uneducated guess and changed the hot water thermistor but this didn't solve it. Then i noticed the boiler stays lit when calling for hot water if the inner casing is off but soon as i tighten the last screw of the casing creating a seal the boiler shuts down. I suspect the fan but wouldn't want to be wrong again due to the cost. Any advice off some experienced gas engineers would be much appriciated
I am a gas engineer

 

[aquafix plumbing]

I am guessing is the fan speed!

 

[Deleted member 267285]

I am a gas engineer

Better asking in the combustion chamber part of the site. Also is it the 28i or Greenstar junior?

 

[aquafix plumbing]

Where is that please!

 

[aquafix plumbing]

was asked to take a look at my mates worcester 28i. When calling for hot water the boiler fires up fine and the water gets hot. After approx 30secs of running hot water the boiler shuts down. With the hot tap still running( water gone cold) the boiler then fires up after about 5sec and continues to do this over and over again for the same time intervals. In central heating mode there are no problems. I Serviced the boiler to the manuals instructions and all ok. I took an uneducated guess and changed the hot water thermistor but this didn't solve it. Then i noticed the boiler stays lit when calling for hot water if the inner casing is off but soon as i tighten the last screw of the casing creating a seal the boiler shuts down. I suspect the fan but wouldn't want to be wrong again due to the cost. Any advice off some experienced gas engineers would be much appriciated
I am a gas engineer

 

[Deleted member 267285]

Where is that please!

https://www.diynot.com/diy/forums/combustion-chamber/

You need to register with gas safety details or prove qualifications

 

[denso13]

Gas Fitters Only Forum, The Combustion Chamber

After numerous requests we have setup a new forum section that only registered gas fitters can access to discuss issues that aren't suitable for unqualified eyes to read! The new section is free to use but to ensure only qualified gas fitters access the forum, members will be pre-approved. So...

www.diynot.com

 

[ianmcd]

Do you mean 28i RSF ?

 

[aquafix plumbing]

Yes.its RSF the old one please

 

[aquafix plumbing]

was asked to take a look at my mates worcester 28i. When calling for hot water the boiler fires up fine and the water gets hot. After approx 30secs of running hot water the boiler shuts down. With the hot tap still running( water gone cold) the boiler then fires up after about 5sec and continues to do this over and over again for the same time intervals. In central heating mode there are no problems. I Serviced the boiler to the manuals instructions and all ok. I took an uneducated guess and changed the hot water thermistor but this didn't solve it. Then i noticed the boiler stays lit when calling for hot water if the inner casing is off but soon as i tighten the last screw of the casing creating a seal the boiler shuts down. I suspect the fan but wouldn't want to be wrong again due to the cost. Any advice off some experienced gas engineers would be much appriciated
I am a gas engineer

 

[denso13]

Gas Fitters Only Forum, The Combustion Chamber

After numerous requests we have setup a new forum section that only registered gas fitters can access to discuss issues that aren't suitable for unqualified eyes to read! The new section is free to use but to ensure only qualified gas fitters access the forum, members will be pre-approved. So...

www.diynot.com