Alpha CB24

[Petefinny]

Hi guys got a Alpha CB 24 saying there is a problem with the pump or restricted flow, pump seems fine, plate exchangers fine where else would you advise me to check, any one dealt with this problem before?

 

[Plumb Ugly]

Is it an over heat fault being shown?

 

[Petefinny]

No its got a permanent red light and a flashing yellow light which is saying a pump fault or flow restriction.

 

[Plumb Ugly]

Will it reset or just stuck on the fault light? Could check the thermistor values, voltage to the pump and continuity through the over heat stat. If it will reset some pipe clamps on the flow and return should show up an under performing pump and the resistance on the pump is normally 150 to 300 ohms. If everything appears ok then you may have a pcb issue

 

[Alpha man]

NTC sensor, replace both!

 

[Plumb Ugly]

If alpha man thinks so that's good enough for me go with the thermistors:43:

 

[Petefinny]

Yeh it resets i get it all working get the heating on turn the hot tap on and off about 20 times and it never cuts out, i go away then an hour later the women is back on the phone saying it has cut out again, its doin me no favours what so ever.

 

[Petefinny]

NTC Sensor? ive just finished work now been a long day can you clarifiy this to me as my brain has stopped working ha ha.

 

[Plumb Ugly]

NTC or negative temperature coefficent is a thermistor where electical resistance decreases with increasing temperature

 

[Petefinny]

Thanks for that, where would you find that?

 

[Plumb Ugly]

Where would you find it on the boiler? I don't know the exact postion of them on this particular boiler but Alpha man might! They will be located usually on the flow and return pipes from the main heat exchanger

 

[Plumb Ugly]

Check the boiler schematic to be sure!

 

[Petefinny]

Ive looked at the mi's, there is a screw on the primary flow switch which can be adjusted do you reckon thats it?

 

[AMGasServices]

I've attached an image and its number 22 dhw temperature sensor

 

[Petefinny]

Thanks for that, this is why these sites are so important so we can gain experience and knowledge, thankyou

 

[AMGasServices]

There is also another thermistor look at number 5 too

 

[Petefinny]

I've changed both thermistor the dhw one and the primary sensor, when I put my clamps on the flow and retuen to see if the pump is under performin what difference in temperature am I lookin for?

 

[Plumb Ugly]

The MI's are the best place to find that answer but usually a differential of greater than 20c indicates poor circulation

 

[Alpha man]

Is this boiler noisy in use?

 

[Petefinny]

No its finr, dosent make any noise i got a tempertire difference of 24 on the flow and return, it locks out then just kicks back in itself then go's onto lock out again then it kicks back in again, the yerllow and red lights are alternating flashing, pump fault or restricted flow. Really winding me up now, so plumb ugly says with my differenitial in flow and return temperture it could well be an under performing pump.

 

[allwright]

Just wandering Pete if the fault code is primary sensor fault if the A and B are flashing alternately.

 

[Petefinny]

Primary and hot water has been changed, primary flow switch has been changed, still showing fault!

 

[Plumb Ugly]

Sounds like you have a circulation problem did you check the resistance across the pump terminals? More than 300 ohms I'd change the pump