Are these shower mixers any good with a combi boiler and do they give the pressure thats claimed. Also what benefit does the thermostatic mixers give you apart from the temperature control.
Basically I'm trying to decide between the CDX h2o £79a nd something like the MIRA 415EV at £236
Thanks Simon
My mother now has a Mira 415 and a cheap 99 quid shower. She prefers the latter because it has separate temperature and flow controls. The Mira has a single dial that was not able to control flow rate and "forgot" the temperature last used as you have to spin the dial to turn it off, losing your setting.
They're off an unvented cylinder rather than a combi, though.
Christian.
Hi,
If you are after something relatively inexpensive (Triton Aire for £66 all in) have a look here:
cheers, Pete.
They're not what you want with a combi: basically they use the pressure of the mains cold water to boost the flow of hot water from a gravity fed system to give a reasonable pressure and flow to the shower, but a combi gives mains pressure[1] hot water anyway so all you need for that is a mixer (preferably thermostatic).
[1] usually: you may exceptionally have a combi whose cold water inlet is fed from a tank in the roof, giving low pressure.You want more benefit? :-)
As Christian says, if you have a 2-knob thermostatic mixer you not only get a shower that stays the same temperature even when someone uses other hot or cold taps in the house, but you can also start it up and have it come out at a the same temperature it was last set at without fiddling about. Just don't share it with someone who likes cold showers :-)
I've fitted the Sol shower valve from BES (£100 inc VAT) to a system with a Combi and it does what it says on the tin. There's also a 2-knob thermostatic mixer including shower hose, head and rail etc (all a bit plastickey) from Screwfix for about £70.
-- John Stumbles
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In article , John Stumbles writes
They don't work like that, they do not respond fast enough. You still get a big temperature change though it corrects itself within about 10 seconds. Enough for a nasty surprise.
There should be two mechanisms for temperature control. The thermostatic control will gradually fix any temperature variation. There should also be a pressure balancing valve, which is much faster. When a tap downstairs is turned on, the valve senses the pressure change and chokes off the opposite supply. This happens very quickly, about 0.25 seconds on mine. It is quick enough so that it doesn't scaled/freeze you, although you can tell it has happened.
I suppose with a combi, there might be other effects, as the temperature of the hot water may drop if someone opens a hot tap. However, I'd expect it to be gradual enough for the thermostatic side of the valve to operate.
Perhaps your valve doesn't have a pressure balancing section, or it has become disabled?
Christian.
In article , Christian McArdle writes
No, it doesn't have anything like that, I had it in bits recently and it just has a bimetallic curly coil to adjust the temperature (cheap Gainsborough thing).
When I replace the shower (cos even the thermostatic bit does not work properly) I will look out for that feature as well. What model of shower are you referring to?
I think you would be hard pressed to find one without a pressure balancing section. All the ones I've ever looked at had this feature.
Christian.
In article , Christian McArdle writes
Well I have found one! Serves me right for buying something cheap, I should know better.
The one I fitted didn't do that. I tested it by running it at a comfortable temperature with my elbow under it and turning on the basin hot tap: the flow reduced quite promtly but there wasn't a long surge of cold while it settled. This was with the Sol valve from BES, which seems to me to be a nicely made bit of kit. The HW source was a combi (Ravenheat RSF84).
ISTR I checked the Screwfix £70 job when I fitted that and found it to be quite stable. That was with gravity HW (with a good head - the bathroom was on the 1st floor of a 3 storey house) with mains cold.
-- John Stumbles
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