Poor hot water with Biasi combi boiler

[David937]

Hello,

My Uncle is a having a problem with his boiler (Biasi standard efficiency boiler, 7 years old). He is complaining that the hot water takes too long to get hot.

I said it could be:

a) Scaled plate HE.
b) A faulty sensor somewhere?

After talking to a heating engineer he reckons that the system needs flushing out and the HE be cleaned (he did not state which one). Why would the system need flushing if the radiators heat up fine and the water seems clear?

What do you think is the most likely problem?

 

[twgas]

maybe the diverter is slow to move and/or not shutting heating off completely.

 

[Agile]

This will be a 24S. The way the diverter valve operates it cannot operate the DHW demand switch until the manifold section has switched,

The boiler should be pretty well stabilised after about one minute.

The secondary heat exchanger may well be rather blocked nd that would be evidenced by the temperature indicated on the boiler exceeding 65° C.

Its also possible that he expects more heat than 24 kW can provide. That boiler can only heat up about 6-7 litres per minute to be too hot to keep your hands under.

He has probably never had it serviced properly either. The gas settings might be out of adjustment.

Tony

 

[David937]

I don't know if it's been serviced.

Can I check the diverter valve by seeing if the CH pipe gets hot when you draw of hot water?

The boiler has no temperature indication lights so I wouldn't be able to check the plate HE.

 

[Agile]

I don't know if it's been serviced.

Can I check the diverter valve by seeing if the CH pipe gets hot when you draw of hot water?

If the boiler fires up for DHW then the diverter valve will not be leaking into the CH.

Couldn't you ask your Uncle if its been serviced? And if not then why not?

The boiler has no temperature indication lights so I wouldn't be able to check the plate HE.

Why would you want any temperature lights when it has a full analogue temperature gauge? You can read the temperature at the point the needle reaches on the analogue scale

Tony

 

[David937]

I forgot about the temperature gauge.

I think this problem may well be his fault; he always gets a cowboy to service the boiler and then complains that he didn't replace the case properly.

You pay peanuts you get monkeys.

As for the divertor valve I thought it might not be diverting quick enough for DHW so I could check in the way described.

 

[Agile]

You check the diverter valve by having the CH off and turning up the DHW flow rate slowly until the boiler fires up.

It should switch on at about 2 litres/minute and certainly before 3 li/min.

Tony