Alpha 24cbx lockout

[Kerr Gas 1]

Working on an alpha 24cbx today which would get to temp then lockout from overheat, I've tested over heat stat and replaceD, all seemed fine then locked out again after couple hrs, anyone had this problem. Previous experience would suggest sludge or faulty pump. Could the thermistor affect this . Took a resistance today when boiler had cooled down but the reading seemed ok. Any advice?

 

[coley]

heater exchanger blocked try put some cleaner in the system for a couple of days and give a good flush out
Pump not circulating does it turn freely
air in the heat exchanger I think there is a vent at the top left hand side
check flow and return temps does it short cycle

 

[Alpha man]

Yellow (b) light flashing fast?

What colour are the NTC sensor's?

 

[Kerr Gas 1]

hi alpha man,

we spoke a while back about a 24 cbx locking out on overheat (solid red A) since then i have flushed system replaced pump and replaced overheat stst, i didnt hear back from the customer for weeks then i got a call today so its doing the exact same. any advice thanks

 

[Alpha man]

A) red light on continusly? B) yellow doing what?

If its just the red light on, could be, gas related, incoming /working pressure, gas valve or molded black plug and lead or electrodes!!

If the red light flashes, could be either APS or PCB.

 

[Kerr Gas 1]

its a red flashing light, i will check all tomorrow but i thought it was an overheat lockout, heating and hot water works for a couple hrs the locks out but as i said before iv flushed the system, changed the pump and the overheat stat. running out of ideas

 

[Millsy 82]

Its not something daft like all rads fitted with TRV's and set fairly low so shutting down causing boiler to lockout.

Caught me out a couple of times

 

[diamondgas]

A cupl of hours intermittent fault would take me towards ignition rather than overheat ... *shrug* If it's o/heat then its strange that it takes so long to occur? Soz not much help

 

[Alpha man]

APS or PCB.