I have a biasi 24s combi boiler. The central heating works fine, but at present the DHW temp is too low even though DHW stat is turned to full !, i have confirmed the DHW flow switch is fine as the boiler continually runs once a tap has flow. The boiler when supplying DHW never goes off on the stat as it never reaches this point. I can only think it could be the stat or the hot water probe, most probably the probe. I will be doing some resistance checks across it tomo. Can anyone shed some more light, i understand could be probe, stat, Control board PCB or maybe even the DHW heat exchanger reducing the efficiency due to limescale etc , do these heat exchangers significantly reduce efficiency, the boiler is only 5 years old ?
ok, will check diverter v/v tomo. Thank you. Gas modulation seems fine on c/h. This diverter v/v if it is passing into c/h flow will i notice the temp rise quite fast or will i need to leave a hot tap flowing for a good ten mins. Once again thanks in advance.
[quote="htg engineer"]Check CH flow, with the system cold, run the hot tap.
If there's heat going down the CH pipes then it's the diverter at fault.
Could also be gas pressures/modulation
ok thanks, will check diverter v/v. If this v/v is passing will i need to run a hot tap for a good ten mins before i notice heat going into the c/h flow. The modulation of gas seems fine on the c/h side of things. Thanks in advance again.
hi, checked the diverter v/v and it is fine, checked the temp probes and the resistance readings are fine as per biasi temp/resistance graphs, cleaned dhw filter all ok. The stat potentiometers appear fine when tested too ??? The DHW gets upto nearly temperature and then the burner ramps down, if i increase the tap flow the boiler ramps up to try and raise the temp, so everything appears normal apart from still not getting to set point temp. Is all i can come up with now is the PCB. Its like eveything works as should but the stat isnt setting as hi as it should/used to.
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