Which mixer shower valve to use with a Combi boiler


Postby raypeggy » Mon May 17, 2010 1:33 pm

Hi folks
I intend to fit a shower cubicle in my bathroom and use a mixer shower valve.
I have a Baxi Combi 130HE condensing boiler and the max. DHW temp. setting is 55c .
All the thermostatic mixer valves I have considered appear to require a min. DHW operating temp. of 60c.
Would I be better to use a pressure balanced mixer valve with this boiler

Some info. I have read seems to suggest that I should have a fully modulating boiler to be able to utilise a pressure balanced valve.

Some advice would be greatly appreciated.

Thanks in advance----Ray
Last edited by raypeggy on Wed May 19, 2010 7:47 pm, edited 1 time in total.
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Postby plumbbob » Tue May 18, 2010 7:15 pm

I doubt if the 5 degree difference in water temperature wll make any difference to the efficiency of a shower. The thermostat will compensate for the lower supply.

Choose a shower that has dual controls for both temperature and flow and not just a single lever action.
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Postby raypeggy » Wed May 19, 2010 8:46 pm

Thanks for the advice.
I assumed that when the manufactures say "min. DHW temp. 60c requiered for operation" That at my boilers max. DHW of 55c the inlet for hot water would not open and I would just get cold water or no water at all.
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Postby plumbbob » Thu May 20, 2010 11:24 am

raypeggy wrote:I assumed that when the manufactures say "min. DHW temp. 60c requiered for operation"


I can't say I have ever noticed that requirement in any instructions I have read. In actual fact, current regulation limits DHW water temperature to a maximum of 60 degrees which makes that point a bit odd.

raypeggy wrote: That at my boilers max. DHW of 55c the inlet for hot water would not open and I would just get cold water or no water at all.


The thermostatic mixer, providing that supplies are balanced properly, will control the shower anywhere between 100% hot and 100% cold. Where variance will occur will be with respect to the flow rate which is directly linked to the incoming mains water pressure and the capacity of the boiler to heat it.
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