"John Rumm" wrote in message
...
IMM wrote:
The Mira 415 is the one to go for. Dedicated to mains pressure systems.
It
is not thermostatic and has an integral pressure balancing valve. The
combi
provides the constant temperature, so no need for a thermostat cartridge
in
Why do you say the combi provides a constant temperature? Even
modulating combis with a maximum water temp thermostats will vary
temperature in inverse proportion to requested flow rate (the max temp
rising up to the cap set by the stat at low flow rates)
So if you have the boiler stat set to limit at 60 degrees and draw off 8
l/min then the temp will be 60 deg. If the dishwasher then decides to
take the total hot water flow rate to 15 l/min the temperature will have
to fall. How does the pressure balance cope with that?
(I can see how it would work well on a unvented HW cylinder for example,
because the HW flow rate would not affect the temperature of the water)
Here is a cut & paste from Plumbworld on a stand alone pressure equalising
valve:
"
- Automatically equalises hot and cold water pressure by dynamically
adjusting the higher water pressure to balance with the lower
- Can turn a manual shower into a shower that doesn't suffer temperature
fluctuations
- Provides - stable water temperature
- Pressure range 3psi to 150psi
- Eliminates risk of scalding
- Cost effective and easy to install
- Cast brass body, Premium nickel finish
- 15mm compression connections
- Can be used on low and "mains" pressure hot water systems
- Ideal for - Rest Homes, Hostels, Hotels, Private Homes, Sports Clubs,
Hospitals
- Can turn a manual shower into a shower that doesn't suffer temperature
fluctuations
"
http://www.plumbworld.co.uk/344-0000
BES sell what looks to be the same valve (made in NZ) at the same price.
A poor performing thermostatic valve or a standard mixer can really perform
after fitting one of these on the supply. The Mira 415 has one built-in.
It may be cost effective to buy a standard non-thermostatic mixer and one of
these @ £35 plus VAT, if space is available. Then it is a matter of only
replacing the valve if it goes wrong rather than a whole expensive mixer.