BIASI Combi boiler - no hot water but CH ok

[Ste1974]

Hello

I have a BIASI combi boiler Model:245. Yr of manf:2002.

The CH works OK, but there is no hot water to the taps. However if i turn the shower & the bathroom HW taps on, the boiler does light.

From other posts i've read on this site (not specific to this boiler) it sounds like the diverter valve???

Firstly, is this assumption correct?

Secondly, can anyone tell me approximately how much a new diverter valve would be? And is it a swine to fit?

My first child is due anytime now, so a quick reply would be very much appreciated.

Thanks in advance.

Ste

 

[wiggikins]

Sounds like diaphragm to me, investigate that possibility before going down the road of a whole new valve. Get a local engineer to properly diagnose for you,could work out cheaper in the long run!

Keith.

 

[mehran]

i have never heard of that model number, you sure it is not a "S" or something with"M" at the start?

only biasi boiler with numbers like that is biasi savlo gaia 424, but i have never seen one.

 

[Ste1974]

wiggikins

Thanks for your reply.
I have since dowloaded the service manual for the boiler and caried out a few checks according to the manual.

The DHW switch gives the correct voltages (measured with a multimeter) wheather in CH or DHW mode. Therefore i can assume switch is ok?

I then removed the DHW switch and checked the operation of the shaft that operates the switch, i.e. the shaft moved into the open position only when I turned on both the shower and sink HW taps.

So I guess this agress with your diagnosis of the diaphragm being faulty / split?

Looking at the exploded view of the diverter valve shown in the 'spares manual' (which i have also downloaded) it lists two diaphrgms. One being the larger 'CH pressure switch membrane' and the smaller "DHW pressure switch membrane'

It seems sensible to me that the membrane i should look to get replaced is the smaller DHW membrane, do you agree? (It does not mention anything about the DHW membrane in the service manual)

Thanks for your help
Ste

 

[Ste1974]

i have never heard of that model number, you sure it is not a "S" or something with"M" at the start?

only biasi boiler with numbers like that is biasi savlo gaia 424, but i have never seen one.

Yes, your right it is an 'S' as in the model number is '24S'

 

[wiggikins]

Biasi Riva 24s is the model,Yes small diaphragm.

 

[mehran]

the large one is for your dhw and works when your hot is use, the small one is your pump proofing and works to show/proof the pump is working.

 

[Ste1974]

Thanks for all your replies.

I replaced the DHW membrane (the larger one) and the boiler works fine.

Keep up the good work
cheers
Ste