Combi boiler only provides hot water with slow flow

[ukitr]

I am unhappy with the hot water temperature of my Combi Protherm 80E combi boiler that was installed a few days ago. I've set the hot water temp to about 60C. The control panel displays the water temperature and if I turn the hot tap on any more than a slow flow the hot water temp drops to about 47C.
The specification of the boiler is:
Flow rate @ 35C = 9.6 (L/min)
Output HTG & DHW = 9-23.3 (kw)

How do I test the performance of the boiler- ie fill a bucket

 

[ogoshi]

Call back the heating engineer who installed it.If he cant suss it out he can phone the manufacturer for advice.The manufacturer guarantees the product and the installer guarantees the work.

 

[masona]

Sadly,plumbers are installing Combi boiler regardless of what water pressure as it is less work for them.If you haven't got a good cold water mains pressure then Combi boiler are useless.Combi boiler was design for tower flats as a space saving device as it does not need cylinder + tank and now installing in housing estate.Having said that they are getting better all the time.Agreed with ogoshi,get the heating engineer back in as it could be something simple.You can also check the mains stopcock is not back to front as this will reduce water pressure.

 

[COG]

As said you can only check the flow rate, but its sounds as if you dont have enough gas pressure at the burner.if your waters too slow then the temp will rise relative but if gas pressure too low then not enough power too heat the water.You should have your installer to check the gas pressures its part of the commission that he should have done?.If your not happy then just get potterton out,if they do charge you because its an installation fault then youl have to see your plumber,but they dont usually charge.

 

[ukitr]

Cheers guys for the advice.

The engineer checked everything yesterday and couldn't find any faults. I'll call the boiler company now. Any idea what flow rate (litres/min) at 55C I should expect? The specification quotes 35C but no higher.

Thanks

 

[COG]

35c is the temp rise above the cold inlet at the given flow rate ,ie, 17 deg C inlet (temp of incomeing water today) plus 35c =52degC at the flow rate given,if you slow down the flow you inc the temp rise.