In my last place I had a Mira Magna shower that I fitted myself. It had a "
digital mixer" which blended hot water from the cylinder and cold water fro
m a tank in the loft and pumped it to the shower head. It was great and I m
In my new place I have an Ideal Logic+ Combi 24 boiler and a puny electric
shower that I hate and of course now the weather is colder it's even worse.
I'd like another Mira shower that'll be fed from the combi boiler and I wo
nder if someone could point me to which Mira models I should be looking at.
I don't think I need one with a pump, just one that blends cold from the m
ains and hot from the combi.
Would it help if I was to measure how much hot water a minute my boiler can
On Sun, 26 Nov 2017 11:20:31 -0800, Murmansk wrote:
That kind of mixer is pretty standard these days - a lot of houses have
Standard way of fitting is hot from the combi and cold from the mains.
Pumping is not good because you would end up sucking on the mains, and
anyway a combi can't get heat into flowing water that fast. Much better
than an electric shower but not a patch on a good shower pump. I am
assuming that you have enough mains flow to run the combi flat out, which
The manual for the combi should tell you how many litres a minute it can
heat. As you say, you probably need to measure the total flow through the
mains because you will be sharing that between the hot and cold sides of
the mixer. The shower details should say how many litres a minute it is
I still miss our power shower from stored water (mind you, it was a damned
big pump) but I traded space for water storage for reduced shower power.
Oh, and the boiler went into the airing cupboard in place of the hot water
Can't help with specific models, but (assuming that your shower is over
the bath) you have the choice of a bath mixer with shower or a dedicated
Hope this is some help.
AMD FX-6300 in GA-990X-Gaming SLI-CF running Windows 7 Pro x64
24kW will give you from around 10 lpm in cold weather to just under 14
lpm with warmer incoming water. Note that is with the hot water at
shower temperature - you won' need to mix much cold with that.
Most showers are rated by minimum water pressure they will handle -
since you are using mains pressure, any thermostatic mixer should work.
The specs for the shower itself should give you an expected flow rate
for the pressure.
Some advocate pressure balanced showers for combis.
You will need to choose the shower head with some care, since you won't
have the boiler power to supply a "thirsty" one (so avoid massive soaker
heads and body jets etc)
"digital mixer" which blended hot water from the >cylinder and cold water f
rom a tank in the loft and pumped it to the shower head. It was great and I
shower that I hate and of course now the >weather is colder it's even wors
e. I'd like another Mira shower that'll be fed from the combi boiler and I
wonder if >someone could point me to which Mira models I should be looking
at. I don't think I need one with a pump, just one that >blends cold from t
he mains and hot from the combi.
What you are looking for are called digital showers. Mira make two mixer ve
rsions one to suit a single head and one for dual head showers. As far as I
can remember Mira produce three ranges the only differences are the type o
f shower heads and remote controls the mixer unit is the same for each rang
I don't think you're ever going to relive that with a combi.
Or just measure using suitably sized bowl etc.
In my limited experience of 3, I find combis are quite blunt tools, and
a basic mixer tap with shower outlet is good enough for a half decent
shower. Even then, not a great deal of mixing goes on, with just a
little cold needed in the summer.
I've found the basic kit supplied shower heads fine. I did get a Mira
'eco' shower head, and didn't find much difference.
In the words of Scotty: "Yea kannae change the laws of physics!" ;-)
(you may get some variations in the numbers depending on if the boiler
power is being quotes as its input or output power - most these days
tend to quote the output)
Yup a plain (non thermostatic) mixer will also work (we managed to run a
Mira 88 of a 35kW combi fine for years), although it does depend a bit
on the plumbing and where the other take offs are in the system.
You can get cases where the temperature will fluctuate (typically down
rather than up) if something else can place extra demand on the hot water)
(note also that some combis include flow regulators to limit the supply
rate of of DHW to keep it at the set temperature. Many however will
treat the set temperature more as a top limit rather than a target)
Yup many bog standard heads are designed to give a reasonable shower on
most systems, and will only need about 7 or 8 lpm.
If the combi can only deliver 10 - 15 lpm of water at the right
temperature, then all a shower that needs more to work properly will
achieve is either lots of coolish water, or warm enough water but with
Even a 24kW combi will give a good firm shower (verging on the painful!)
if you have decent mains pressure, and an appropriate shower head.
I found previously that the 35kW combi we had in the last place could do
one very good shower, or two concurrent not bad showers)
Thanks for the helpful replies
I've measured how much hot water my bath tap can produce and it's about 10 litres per minute.
I'm thinking of this model
I rang Mira who weren't interested in how much hot water I can produce but said it needs to be a minimum of 0.5 bar of pressure.
Is there some way I can estimate the pressure as I've no idea what 0.5 bar might "look like"! I'm in a ground floor flat and the cold water doesn't exactly explode out of the kitchen tap but is it likely to be more than 0.5 bar?
There is a requirement on the water supplier to provide mains water at a
minimum of 1 bar. So chances are you have more than that.
A quick "rule of thumb" test (quite possibly literally!) is to turn the
basin tap on gently, and then see if you can stop the flow of water out
of the tap by sticking your thumb over the end. Half a bar you could
stop easily. 1 would be harder, and chances are 2 or more you would not
be able to stop easily by hand.
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