heatslave lockout

in need of help with this one please. Worcester heatslave on a sealed system.It's had a number of issues recently including loss of pressure and intermittent lockouts.Fitted new PV,PRV,AAV and a capacitor.Pressure loss has greatly reduced but still goes down gradually,have checked all rad valves and inside boiler.Burner works ok when i'm there but locks out regularly for the owners, except when i was just leaving today. There was a loud thud (diverter valve) and the burner locked out. On reset worked perfectly. Any suggestions for pressure loss ? Could the thud from the diverter valve ,which i will change, cause a lockout ,possibly by shaking a poor connection in a relay or elsewhere ?ANY useful suggestions greatly appreciated, STIX.

outinthestix said:

in need of help with this one please. Worcester heatslave on a sealed system.It's had a number of issues recently including loss of pressure and intermittent lockouts.Fitted new PV,PRV,AAV and a capacitor.Pressure loss has greatly reduced but still goes down gradually,have checked all rad valves and inside boiler.Burner works ok when i'm there but locks out regularly for the owners, except when i was just leaving today. There was a loud thud (diverter valve) and the burner locked out. On reset worked perfectly. Any suggestions for pressure loss ? Could the thud from the diverter valve ,which i will change, cause a lockout ,possibly by shaking a poor connection in a relay or elsewhere ?ANY useful suggestions greatly appreciated, STIX.

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if i where you i would go round and bleed all valves, if this as been done and their is still pressure loss turn the flow and return valves off and repressurise and see what happens,keep the boiler turned off, if it drops try the expansion valve, if you get water coming out of the valve the diapharme as split.

I think he means expansion vessel not valve.
What Capacitor have you changed - uneless you mean the expansion vessel?

The capacitor i have changed was the motor capacitor as it was below its rated value .However this has not cured the lockout's. I have also tried changing the transformer and solenoid but these did not work either so changed them back.Motor bearings are fine and the control box was changed by some other technician several months ago.Gas analysis is good although the CO2 is only 10.3 and i seem to remember oilman saying it should be higher on an inter so if you are reading this oilman please put me right on this one. As far as the burner goes there only remains control box,base and pec to try.
The pressure loss is so far a mystery. The expansion vessel is good and holding charge.The new prv is not letting by and the aav is good.Had the baffles out and no sign of internal leakage even when i pressurised the system up to 2.5 bar.Bled all rads .There are no pipes underground and no sign of leakage anywhere exept some green stuff on 1 trv but even this is dry when the system is pressurised cold.
Any other thoughts please.

change the oil pump. only takes 15 mins, and it might cure it? nothing to lose.

wilhelm said:

change the oil pump. only takes 15 mins, and it might cure it? nothing to lose.

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15 MINUTES?!?!?!?!? yeah, right. you really are a card such a one with the wit. SOMETHING will go wrong and the 15 minutes will soon be 30.

I don't know how old your heatslave is but have come across a few were the check valve behind the fuel nozzle isn't functioning correctly. To get at it remove nozzle, screw in a 6mm bolt (i think it's 6...could be 5) pull, and it will pop out. While your at it change the coil armature (the thing the coil slides on).

check valve part no 87161566580
pump armature 87161427780

thanks fella's, I'll give everything you said a try.STIX.