Ferroli Optima 701 - APS Venturi

[Pablo719]

Just wondered if anyone could describe where the venturi is that operates the APS? The boiler takes a little while to fire up following demand for hot water and I understand that it may be due to a blocked/dirty venturi (somewhere around the flue?).

Any ideas would be much appreciated.

Thanks

[gucciman]

the venturi is a small conical shaped piece of plastic that site inside the neck of the fan assembley where it connects into the flue. they can become blocked and it could also be the impulse tubes that connect the fan to the air pressure switch.
one word of warning, to get at the fan you have to re-move the combustion chamber cover which is sealed to prevent any possibility of fumes leaking into your house so you may want to call in a corgi engineer rather than do it yourself.
if the problem was due to a blocked venturi or impulse tubes i would have expected it to be the same when calling for heat as well as water. this is also true if it was the air pressure switch itself sticking.
this type of problem is usually caused by a sticking diverter valve but most ferrolis don't have diverter valves so thats probably not the fault.
could possibly be the thermister on the hot water side at fault.
try putting your question on the main home and garden page rather than the diy section as you will get more answers then, theres a guy on here called gasman who is more experienced than me and he gives good answers on this type of problem.

[Pablo719]

Thanks for that Gucciman. May well call out an engineer, but I have a little bit of engineering experience (of the DIY kind!) so may give it a try myself first.

[gasman]

Hi Pablo7, The venturi test point is located behind the combustion chamber cover at the top left of the boiler It is a small tube that sticks up from the top of the heat exchanger lid left of the flue outlet. Also check the Air pressure control damper is not stuck or need adjusting this is located to the top right hand side just below the fan. Try cleaning the posative and negative spigots of the Air pressure switch while you're at it , located below the combustion chamber to the right of the gas valve. Then finally check that the flowmeter is not faulty and the filter is not clogged up. This should be a T shaped fitting with a wire coming out of it, an arrow pointing right and a nut on the bottom of it. It will be attatched to the incoming cold water pipe inside the boiler at the bottom before it bends up and goes into the combustion chamber. If evething checks out OK then the waiting time is operating and it will require a new Circuit board. Hope this Helps. By the way I should point out that it is illegal for a non CORGI registered engineer to remove the combustion chamber cover....!!!!

[Pablo719]

Thanks very much Gasman. Great help. Will let you know how I/an engineer (as obviously I wouldn't break the law!) gets on.