Baxi 552 back boiler problem

[NormanH]

Hi Please be gentle newbie!! I have inherited a problem with the above back boiler/fire from my son!!!. The pilot keeps dropping out but after 36 hours?. I have changed the thermocouple (twice). I have checked and replaced the pilot restrictor ( although the old one seemed fine) I have increased the pilot pressure on the main gas valve. All the tests I have done seem to come back fine eg blow out pilot. gas closes off after about 20-25 secs. Hold in main gas valve and ignite pilot, release after 5 secs pilot stays on. Run boiler turn of and on from stat on boiler pilot stays on! run from heating controller on and off pilot fine. in other words cannot get the pilot to go out!!! argh!!. only thing left is the gas valve. if this needs to be changed will get it done but don`t want to spend £60+fitting if this is not the problem. Also just as a further question this boiler seems to be "cycling" very quickly. on 30 secs of 15 secs. We have the same setup at home but it doesn`t cycle anything like that here. and the system works fine. any suggestions would be more than welcome to save my sanity!!!!. thanks again

 

[mickyg]

get an RGI out to look at it. You don't wanna be messing about with gas components if you don't know what your looking for. If the pilot is clean and the correct shape and size, and the burner pressure is set correctly, and the burner is clean and the appliance is not spilling, and the thermocouple is correctly fitted and new then yes you probably need a new gas valve.

 

[namsag]

Was it correct pilot injector. Also pilot tube from valve to injector can get muck in it.
Not by any chance a drip onto the pilot from heat exchanger

 

[NormanH]

Used to be in engineering so a bit of mechanical/ electrical knowledge, but I hear what you are saying! would a "faulty" gas valve account for the very fast cycling times

 

[NormanH]

Yes removed and replaced the pilot feed pipe clear as a bell. (it is and old back boiler setup) and the same as I have at my home

 

[NormanH]

can only assume the original injector was correct. (ex council house) must admit the new injector seems to have a "better flame" will give it a couple of days and if no "phone call" sorted!!