Mira shower recommendation needed

[Murmansk]

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 iss it.

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 produce?

Thanks

[David]

That kind of mixer is pretty standard these days - a lot of houses have combis.

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 isn't hard.

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 designed for.

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 tank.

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 shower mixer.

Hope this is some help.

Cheers

Dave R

[DerbyBorn]

Have had a Mira 415 since the house was built in 1988. Works well with my combi (and previous one)

[John Rumm]

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)

[Tricky Dicky]

"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 miss it.

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 e.

Richard

[RJH]

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.

[Huge]

I have one of each and they're brilliant. As is Mira's support when they go wrong!

[DerbyBorn]

That is critical - a good shower can be rouned by a large shower head.

[Murmansk]

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?

[John Rumm]

Digital showers are fine, but your basic thermostatic mixer shower should work nicely as well (and are half the price)

[John Rumm]

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.

[Huge]

I would say that's bass-ackwards. Tiny shower heads are rubbish. Most showers in the UK are rubbish, too. Weedy little dribbles of luke-warm water.

[John Rumm]

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.

[Murmansk]

I've tried to stop the flow of cold water from the tap and it is quite a challenge!

My friend's flat two floors above me has decent enough water pressure and she has a pressurised cylinder so I reckon it'll all be OK

Thanks everyone

[dennis]

Mine does about 24l a minute so not much use for a combi.

The little hand held head would probably be OK.

[dennis]

Weak thumbs? I can stop mine and it has enough pressure to break some hozelock fittings. About 6-8 bars at a guess.

The hot water PRV gives 3.5 bar and it never drops below that.

[DerbyBorn]

Huge wrote in news: [e-mail]:

No point in exceeding the capacity of the combi boiler and ending up with a shower that is too cool - or isn't flowing enough water.

[Huge]

Boiler's too small, then. I'd rather not bother than have a shower like being wee'd on by an incontinent hamster, like most British showers.

[John Rumm]

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 no oomph.

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)

[Huge]

... it's too small.