Oil boiler intermittent lockout

[Jakg]

Have an HRM Wallstar 20/25 (2003 I think) oil boiler.

Seems to be locking out every day at the moment, only notice when the hot waters gone cold.

Boiler was serviced last month.

I had a plumber friend look at it who suggested solenoid coil and then the ignition transformer, but replaced both and no joy. He also suggested intermittent faults like this are very hard to pin down because it works right up until it doesn't.

I've swapped the control box because the replacement offers a lockout flashcode display but the same problem.

The flashcode says (I think!) "Internal fuse defect" / "control box defect" - unfortunately, that doesn't really narrow things down!

Any suggestions?

 

[Johntheo5]

Is there a new photo electric cell in the replacement box?.

 

[Jakg]

Is there a new photo electric cell in the replacement box?.

Do you mean the control box?

If so I think not - it’s a Satronic DKO 970

 

[Johntheo5]

Strange how its happening after a service, a bit of info below.

Honeywell Satronic DKO 970 Mod. 05for one - or two-stage oil burners up to 30 kg/h, diesel and gas burners, heat generators, gas boilers
Flame detection:
- Photoresistor MZ 770 S
- Infrared-flicker detector IRD 1010.1
- UV flame sensor UVD 970
Control units with oil burner DKO 970 mod.05 for oil burners with capacity up to 30 kg /h. They are approved and certified in accordance with European standards and regulations.
Programming sequence based on a microprocessor ensures extremely stable timings independent of voltage variations,ambient temperature and /or cycles.
Built-in information system not only provides continuous monitoring of the actual status (very useful especially to monitor the launch phase) but also informs about the cause of possible blockage. The reason for the block is stored so that it can be accessed even after power failure.
The control unit is designed for maximum safety in case of fluctuations of the supply voltage. If the voltage is falling below an acceptable level, operation is interrupted and the control unit automatically prevents the launching. Thus, the security system will not be under threat when the voltage drop of the network. This low voltage protection works not only during startup but also during operation.

 

[Hairymelon]

I would check the ignition electrodes for cracking , check the leads aren’t bunched up and obscuring the photocell from the light of the flame. See if air bubbles are being drawn into the burner hose ( if transparent hose fitted ). If it locks out every morning check the non return valve either built in the fire valve , or situated below it.also try new new photo cell

 

[Jakg]

Think I've managed to fix this.

After taking the burner off, the bolt holding the electrodes down was loose and they were moving around.

Tightened with the correct gap set and it's not had any issues for a week.

 

[Harry Bloomfield]

Seems to be locking out every day at the moment, only notice when the hot waters gone cold.

Usually due to a flame detection failure.

 

[oilhead]

Over time, the main problem with these is the non return valve incorporated in the fire valve between the oil supply and the flexi. Any air leaks will allow the oil to drain back to the tank and the oil pump is unable to replenish it in the normal sequence timings. In the past, I have installed a stand alone non return valve before the fire valve and this fixes the problem.