Hot Water Tap Goes Colder Than The Cold Tap!

[russunsworth]

we have a problem, when we turn our hot water tap , the temperature goes down instead of up. I can see the temp dropping til its actually colder than the cold tap- this is happens when heating on. I have complain to landlord who sent "repairman" out who when he tries he does something and it works- 1st I was told it needed a part, then when the second people came to fit it they said it didn't- it was " just the way these boilers work" and I should " turn tap on slower" ive tried that... and all I get is clicking from the boiler- and cold water..its frustrating because they are saying we make it up and I think they know what it is but are dodging a repair..the boiler make is a biasi model number m90e.28s

[BRIGHT SPARK]

I recon if you run both taps for 5 mins without boiler operation they will be at the same temp...unless the cold comes from a storage tank.
However it sounds like the boiler fault could be the domestic hot water flow sensor.If this starts to fail then it cant sense a demand for hot water...the fault can be intermittent.

[The Builder]

What error code do you get, Russ. or which diagnostic lights come on?

From the clicking, it sounds as though the electrically operated actuator for the diverter valve is sticking.

The DV simply steers the water either to CH or hot water as required.