Riello oil burner problem

[Tamasheen]

Hi, First time in here so go easy on me!! My problem is with a riello40 G5 oil burner type 444T50. I've serviced this boiler for several years and in the past have fitted new nozels, cured the locking out by changing the capasitor, changed a leaking air jack etc. My problem now is that every now and again the boiler fan runs but is not lit and dosent lockout, Am I correct in assuming that the oil solenoid will not have opened and that the spark will not have happened?? or it would surely have lockedout.
I have fitted a new control box and the problem is the same. I checked continuity and get 1 ohm between black and blue wires of solenoid coil, although between blue and brown is a high resistance, ( I thought this was the hold on coil and nothing to do with the running of it). Why is there 3 wires to a solenoid when 2 would do ??(you can see I'm an old electrician), Also how do you test voltage from lv tapping on motor??, (cant get at terminals when control box is in place.
This boiler can run for 2 or 3 days at a time before this problem occurs, when found with only the fan running it just needs switched off and back on again to make it run for the next 2 or so days
I think the next thing for me to change is the coil, mainly because it only costs about £9 Any help would be much appreciated.

Kind Regards. Tam O'Chanter

 

[cjb1971]

Try your photocell,next time fan runs but it wont ignite,disconnect it,if its at fault burner will ignite then go out after a few seconds.

 

[WDIK]

ok, this is not going to lockout?
but the fan is running?
is there a fan/air proving switch?

 

[Tamasheen]

Hi, Fan will run, no lockout and no flame.
I thought photocel only came into play once oil valve opened??
The photocel has NOT been changed, it was swopped fron old to new control box.
Sorry dont know whayt a fan air proving switch is.

 

[Tamasheen]

ok, this is not going to lockout?
but the fan is running?
is there a fan/air

Hi, Fan will run, no lockout and no flame.
I thought photocel only came into play once oil valve opened??
The photocel has NOT been changed, it was swopped fron old to new control box.
Sorry dont know what a fan air proving switch is. dont think theres one.]

 

[Kingsway]

are you getting normal oil pressure at the oil pump

 

[WDIK]

Hmm doesnt make a lot of sense, it doesnt use an a proving switch so thats not the reason.
basically the box runs through a sequence from fan start, ign, oil open, flame proved, yes run, no lockout.
in this case it appears to have stopped on air.
why did you change the box?
was it a like for like swap?
was there any wiring mods you had to do?
is the wiring to the base ok?
is the new box ok?

 

[Tamasheen]

Av Been fur a few haulfs the nicht already ( its friday nicht) so youl huv tae excuse ma spellin. Oil pressure?? A huvnae a clue whit it is. The bieler runs fine fur days oan end then Al find it just wi the fan runnin. A wid think that its no gettin tae the countdown tae lockout, so ile isnae gettin in and the spark isnae happinin or it wid lockout, or am a wrang here??
jeest tae keep ye up tae date it ran O'night nae probs and,in the mornin, A fitted a new coil oan the solenoid although the resistance readins were the same as the old wan. mibbie the temp is making it fail though?? and everythin wull be ok now (Aye that i'lbe right)
Next thing tae chinz eftir this,, An no share,, Photocell but A didnae think it wid be comin intae play at this stage, Whit dae you think??
If the controler had instigated the count down to firin, then it wid lockout, no ???.

 

[WDIK]

anyone know the battery size for a babel fish?
mine appears to require changing

 

[Tamasheen]

Sorry wdik , A wis too busy havin anither dram thata missed you replyin tae me. The new control box was fitted jeest because A had wan, A hav tae say am no share its a guid wan bit it is new and its causin all the same things as the auld wan, so mibbie there baith gubbed the same wiy.
Trere was nae wiring changes made.
It is stickin at the fan purgin stage withoot gaun oau tae the next wan, which a assume is lettin the ile in an then the spark??
Sumbody suggested chinging the photocell, whit dae you think??

 

[WDIK]

nothing to do with the photo cell

 

[Tamasheen]

nothing to do with the photo cell

Thanks for that, it's whit A thoucht.
A think Am gettin close tae the prob. If it runs for a day or two then the oil pres and noz and photocell an whitever are all ok.
A take it the control box is the thing that moves it through the sequence?? So with the fan runnin what stars this sequence?? OR in this case what dosent start this sequence. Am A gettin close here??

 

[WDIK]

periodic loose connection?

 

[Tamasheen]

OK. I'll have a closer look. I did try giving it a few knocks when it was fannin away, without any luck
I take it when the solenoid coil gets a supply or signal, that starts the sequence, so no point in lookin at O rings or mechanical part of valve?? I was thinkin that even if solenoid coil was faulty ( before i changed it) the biler would surely have gawn tae lockoot at end of sequence.
I have tae say that it is a very intermitant fault the every time I change anything I think it's cured, until next time.

 

[Tamasheen]

Apologies for the ramblings last night, Im quite embarassed, a lot of it I dont understand myself.
I'll look at boiler again today, should have said, it heats my neighbours swimming pool so actually has to be checked to see what it's doing.

Many thanks. T OcH.