Boiler firing sequence / Not quite there! Any help welcome

[patboyd]

Hello. I found this website by google and would like some help working something out please.

I have a POTTERTON FLAMINGO II RS40 boiler.

I am trying to work out how it operates - and after reading the manual and some books from my library, still am not 100% sure. Call me sad if you want but I am interested and want to learn!

It has a thermocouple, spark electrode, piezoelectric ignition, pilot jet, main burner, solenoid valve, multifunctional control gas valve and a thermostat.

As far as I know or believe I have learned/to be correct, - when the pilot flame is alight, the thermocouple operates a solenoid valve (which is in the multifunctional gas valve i believe) which allows gas to flow into the main burner.

It has a PERMANENT pilot flame, and if the pilot for some reason goes out, then the thermocouple is not heated and de-energises the solenoid preventing "gassing" of the main burner.

BUT, my question is, when the main burner is satisfied, how does it shut off the supply of gas to it, as the pilot is still alight and will be energising the thermocouple which will in turn energise the solenoid, still allowing gas through to the main burner!

I have been trying to work this out and I have probably missed something very simple, but would like some info/help from any experts who know what I am missing!!

i believe my boiler has the older type, THERMOELECTRIC fail-safe / supervision device (with the pilot flame, thermocouple, solenoid operation)

Thanks to anyone who can put my mind at rest and help me learn further.

Sorry for sounding embarrassing or sad by the way!

 

[gas4you]

The main gas valve is operated by a seperate solenoid to the pilot. This main valve solenoid is turned on and off electrically via the supply to the boiler from the controls and the boiler stat.

The pilot has nothing to do with any electrical supply to the boiler. It is kept alight by its action on the thermocouple producing a very small DC milli amp current/voltage

 

[spacethegas]

if you follow your boiler wiring diagram the answer will become evident.

 

[patboyd]

Thank you for your response.

So basically, the boiler thermostat operates the main solenoid, allowing gas to the burner?

A lot of GAS sections in plumbing books say that the pilot flame's heat on the thermocuple, allows a small current to energise a solenoid which then opens and allows flow of gas to the main burner.

I am guessing this is not the case then now ...

 

[gas4you]

Yes, be it the boiler stat being satisfied or as it is wired in series, the power going off from the programmer/timer.

I think you are reading it wrong. The small current enegises the pilot solenoid and holds this open, hence why you have to hold the valve solenoid button down for approx 10 seconds until it heats up.

 

[patboyd]

Ok. Thanks again for all your excellent help.

I am interested in learning about boilers and have learned that there are lots of different types/workings, ie/ some do not have a pilot flame, some have no thermostat and use thermistors instead, modern boilers have a fan and an air pressure switch, etc!

It seems very complicated, especially at first!!

I believe also as my boiler is pretty old now, that it doesn't have a PCB (although there are obviously electrical wiring connections).

 

[patboyd]

Sorry, one last point: if the programmer/boiler stat opens/energises the solenoid to the burner, then how does the fail safe device work. ie/ it may open still if/when the pilot goes out which would not be safe ...

 

[spacethegas]

you are correct.

 

[gas4you]

The pilot solenoid has to be energised to allow the main burner to open, even if a volatge is applied to it.

Forgot to mention that bit

 

[namsag]

It is very complicated most of us has to qualify as rocket scientists first before embarking on this trade although some took the easier route of working on telle ariels

 

[spacethegas]

two solenoids.

the one connected to the tc has no other electrical connections as has been explained.

 

[patboyd]

Ok, i get it now (i think)!


so this is how it works!!!!! ...

pilot is permanently lit (from the push button which was pressed when the boiler was first installed).

this heats the thermocouple which then holds the solenoid open and keeps allowing gas to flow to the pilot burner

then when the boiler stat/programmer call for heat, as long as the pilot solenoid is activated, gas will flow to the main burner, through the gas valve (as the main solenoid is now open)

when the stat/programmer is satisfied, the main burner solenoid is de-activated, shutting off the supply of gas through the gas valve and to the main burner.

on top of this, IF the pilot light goes out due to a blockage in the pilot jet, etc, then the pilot solenoid also stops the main burner from being open.

also if the thermocuple is faulty this stops gas going to both the pilot burner and of course also the main burner!


have i got it right now ...

 

[spacethegas]

Untitled

• spacethegas
• 26 Jul 2008
• 2

 

[patboyd]

finally!!!


now.... last question i promise!!

As stated, the pilot solenoid has to be enrgised to allow the main burner to open - how does it do this/how are they connected...

Thanks to all who have responded to my post. I am grateful to all of you.

All the best

Pat.

 

[spacethegas]

it is all housed within a multifunctional gas control.

years ago they were separate.