I am an installer, who has been asked to repair a friends boiler.
Initially, primary flow pin on diverter wasn't lifting & APS wasn't making, so changed diaphragm & APS, followed by complete diverter valve, only to discover that despite the pump rotor spinning (and heat being dissipated), the pin started to lift only when I changed the pump head.
Next day I get a call that boiler only fires up intermittently. Turns out PCB is faulty and fan was sometimes only coming on intermittently.
Then I discover that H/W performance is poor. Gas rate indicated about 16.5 KW on H/W. Burner pressure goes up to 11Mb then rapidly drops to 2Mb and then cycles between 2- 6Mb.
Resistance on top 2 pins of gas valve show 1.59 & botton 2 pins 2.89 - so assume that is OK.
Changed primary thermistor to no avail, but if I run hot water with thermistor out of pocket, it delivers full gas rate & plenty H/W so can I assume that gas valve is definitely OK ??
I have assumed that primary side is overheating, so have descaled plate exchanger (without any improvement !) & now added X400, which has been in for about a week - but its still the same apparently.
Can anyone give me some useful suggestions, and am I right about assuming a blockage somewhere ??
Sorry for long winded post but too much info is better than not enough !
Initially, primary flow pin on diverter wasn't lifting & APS wasn't making, so changed diaphragm & APS, followed by complete diverter valve, only to discover that despite the pump rotor spinning (and heat being dissipated), the pin started to lift only when I changed the pump head.
Next day I get a call that boiler only fires up intermittently. Turns out PCB is faulty and fan was sometimes only coming on intermittently.
Then I discover that H/W performance is poor. Gas rate indicated about 16.5 KW on H/W. Burner pressure goes up to 11Mb then rapidly drops to 2Mb and then cycles between 2- 6Mb.
Resistance on top 2 pins of gas valve show 1.59 & botton 2 pins 2.89 - so assume that is OK.
Changed primary thermistor to no avail, but if I run hot water with thermistor out of pocket, it delivers full gas rate & plenty H/W so can I assume that gas valve is definitely OK ??
I have assumed that primary side is overheating, so have descaled plate exchanger (without any improvement !) & now added X400, which has been in for about a week - but its still the same apparently.
Can anyone give me some useful suggestions, and am I right about assuming a blockage somewhere ??
Sorry for long winded post but too much info is better than not enough !
