Bosch 30 CDi Fan constantly running

[pootle18]

Hello I have a Worcester Bosch with a issue. When the unit is on but there is no demand on the system the fan constantly runs. All rads are fully off and no water ran for 1 hour + the fan still runs. I am told it should goto stand-by after 4 mins. Anyone came across this, I was thinking air pressure switch?? Cheers.

 

[EPH]

Ring technical they're excellent over the phone. Sounds high limit stat or PCB at a guess.

 

[Barry98]

whar makes you think it would be a pressure switch?????????????????????

 

[stevetheplumber]

unlikly to be preasure switch as this doesnt come in to play till the fan is running

 

[pootle18]

whar makes you think it would be a pressure switch?????????????????????

If the switch is faulty it will keep the fan on, yes/no

 

[pootle18]

The fan is running, constantly.

 

[EPH]

Are you a GSR engineer?

 

[Barry98]

Are you a GSR engineer?

lmao .

 

[diamondgas]

Any lights on the front pootle18?

Good advice regards ringing worcester BTW .... Does it effect the working of the boiler, still geting plenty water and heating? Sounds like fan over-run is kaput!

 

[pootle18]

I am, I am a install engineer, Faults on combi's are not my strong point. but yes i am registered.

 

[diamondgas]

pootle18, bye the way ... is it a greenstar CDi were talking about here or the older conventional CDi?

 

[pootle18]

Any lights on the front pootle18?

Good advice regards ringing worcester BTW .... Does it effect the working of the boiler, still geting plenty water and heating? Sounds like fan over-run is kaput!

No it does not effect the working, plenty hot water, plenty heat and there is no symbols on the display. Im going to ring them tomorrow, Regards.

 

[diamondgas]

No it does not effect the working, plenty hot water, plenty heat and there is no symbols on the display. Im going to ring them tomorrow, Regards.

Have you been to the job? reason I ask is coz the greenstar came as a 30CDi and doesn't have an APS ... The older CDi was 24,28 or35CDi and had an APS. New CDi has a pre-heat mode so could just have a leaking tap somewhere kicking the boiler in now and again! Loads of possibles pootle18

 

[Barry98]

air flux sensor switch

 

[diamondgas]

:rofl:

air flux sensor switch

:rofl: I'd just have to bow down to your superior intelect:lightbulb: my friend .. never thought of that :banghead:

 

[pootle18]

air flux sensor switch

Regards BOD

 

[RoryD]

u sure it's the fan? If it is, can only imagine there is a voltage less than 240v being delivered. If it was 240v, the boiler would go thru sequence. Sooo, It should be the PCB ??

 

[pootle18]

u sure it's the fan? If it is, can only imagine there is a voltage less than 240v being delivered. If it was 240v, the boiler would go thru sequence. Sooo, It should be the PCB ??

Attended the job today, Turns out its not the fan thats making the noise( low frequency hum), it seems to be coming from the diverter valve housing, This is a friend of a friends boiler so didn't have to long a look(wants a freebie). Its strange that if you take it off timer it runs for 2-3 mins then shuts down to "stand-by" as it should but if you put it back on timer with no load on the system it will hum all day according to the customer. Its a 30 cdi greenstar.

 

[jam1979]

maybe it needs a new head unless its a diaphram type might just want cleaning out

 

[Kev the gas]

Is the digital timer integral?

The hot water side of the timer controls the pre heat on/offperiods. Are you turning off the hot water side to stop the hum??

 

[pootle18]

Is the digital timer integral?

The hot water side of the timer controls the pre heat on/offperiods. Are you turning off the hot water side to stop the hum??

Yes the timer is integral, To stop the hum switch the "heating" side of the timer to "off", 2-3 mins later it clicks off and goes quiet.

The hot water is always at off, the customer never pre heats water.

If the timer on the heating side is set to "timed" it comes on at the required time but if there is no radiators turned on in the house (I checked) the combi will constantly hum, It never goes quiet. I understand if there is no demand it should goto "standby" waiting for a rad to be turned up.

 

[RoryD]

Attended the job today, Turns out its not the fan thats making the noise( low frequency hum), it seems to be coming from the diverter valve housing, This is a friend of a friends boiler so didn't have to long a look(wants a freebie). Its strange that if you take it off timer it runs for 2-3 mins then shuts down to "stand-by" as it should but if you put it back on timer with no load on the system it will hum all day according to the customer. Its a 30 cdi greenstar.

Right, so this must be the new type? ensure there's no voltage being delivered to the flow sensor, must be receiving a voltage or perhaps it's shorted? part number 87161157540 or GC H02529