Combi - DHW pressure

[boydell]

Not being a plumber can some kind soul explain the mysteries of the diverter valve and DHW pressure to me please?

I have often wondered why the flow from the hot tap reduces as the water temperature increases, and as a result all us Combi (non condensing type) owners become adept at making fine tap adjustments to maintain a steady output.

Does the flow reduce due to the expansion of the rubber O-ring in the flow restrictor with increased heat just like it does with a bog standard tap washer? Or is there more to it than that?

kind regards,

boydell.

 

[Billy Bob Bob]

basicly you are turning the tap down to get hot water but a slow flow by the sounds of it you have a 24kw or 80,000 btu boiler,and water can only slowly flow trough the plate heat exchanger or colirifier because of the boilers ability to heat water in short the combi needs chance to heat the water because of its low output this is only slightly better with a condensing combi because some brands like a performa band b have a third heat exchanger called a recuperater ,which can increase boiler output by 1-2 kw,really if you want good water flow from a combi you should have a minimum output of 30kw,then you will find it goes the other way..to hot,in regards to diverter valves,they dont make any difference to water flow they do exactly what they are called they divert water to a plate heat exchanger or colirifier mixing ch water indirectly around cold water result hot water out of tap

 

[Puddle]

it maybe your tap closing slightly not the boiler flow changing,you may be able to just replace washer type tap head for a disc type ,which will keep flow steady or a better quality washer type head

 

[boydell]

Thanks for the replies lads... I am not sure if I am any wiser or not!... thanks all the same.

kind regards,
boydell.