KESTON CELCIUS 25 (NAT GAS)

[oldflame]

Can anyone assist? I've been called out to a Keston Celcius 25. Apparently it's been playing up for quite a while.

The boiler ignites and three of the four green LEDs light up OK. As soon as the fourth LED lights up the boiler cuts out. This happens on heat only, on water only and when calling for both.

I've taken the case off and called for heating. Don't know why, but I placed my hand over the air intake pipe that is attached to the fan (this is inside the boiler and not associated with the air intake from outside the property) thus restricting the negative affect. With the intake restricted the boiler then remains in operation.

Any offers?

 

[htgeng]

deleted

 

[Keston]

Simple really,

All your doing is restricting the air getting into the combustion chamber (the fan draws the air from within the boiler casing) therefor altering the combustion.

Go back with a flue/gas analyzer.

located on the fan pcb in the corner closest to you is a small red jumper (connection CN12) pull that off and turn the knob on and off until the 3rd green light is showing on the bottom row, make sure the knob is now in the stand by position.

Put the jumper back on and fire up the boiler. (should be going flat out, high fire) with your analyzer you want a reading of 8.6 C02 the test point is located above the flue spigot. to adjust high fire, located on the front of the gas valve (as you look at it) is 2 test points with a small screw located to the left of them (should have white paint on top) turn this a quarter of a turn clockwise to decrease (anti-clockwise will increase) until you have 8.6 C02.

Once again take off the jumper this time making it so the second green light is on (follow the instructions above) the boiler should now be in low fire. you want a C02 reading of 8.2. the adjustment for this is the main governor on the gas valve (star shaped cap on top i believe, also i think it says do not adjust ignore this warning) as with high rate turn it a quarter of a turn clock to increase (anti-clockwise to decrease) until you have 8.2 C02

Once both have been set take the jumper off again and make it so no lights are on, on the bottom row. this brings the boiler back to normal operation.

voila!

p.s.
If you have problems getting the boiler to stay on while setting up high rate pull off the clear plastic tube on the gas valve set up high rate then put the tube back on and readjust

P.P.S
This took forever to type!!!