Mira Sport vs. other cheaper Easy/Multi-fit Mira and Triton models

[endecotp]

I am replacing this old Mira Sport electric shower, mainly because it is only 7.5 kW but also because it is falling apart:

I found that both Mira and Triton have models that are supposed to be easy to retro-fit as replacements because they have lots of options for water and electricity input connections. That sounds like a good thing. Notably, these are relatively cheap models - around £100. On the other hand, a new Mira Sport is around £250.

Does anyone know whether the Sport models are superior in any important way? This is not my main shower (I have a mixer that runs off the combi); I’m fixing it now because it will be useful to have a working backup later in the summer when I do some other plumbing.


Here’s what’s behind the shower:

Note the small diameter pipe; this only comes through the wall and doesn’t seem to cause any problems. I guess I could connect that to any new shower, right? My main concern would be accidentally breaking the pipe off where it emerges from the plaster…..

I also have some questions about the tiles but I’ll post that in Tiling.

 

[Hugh Jaleak]

Given the Microbore supply, I wouldn't go for anything too spectacular, (although I'd stick with Mira to be fair), as you're not going to get any better performance than that pipe can supply.

 

[endecotp]

Given the Microbore supply, I wouldn't go for anything too spectacular, (although I'd stick with Mira to be fair), as you're not going to get any better performance than that pipe can supply.

My building pressure and flow rate is pretty good, and the 8mm is a short length; with that old shower, flow rate was OK on the cold setting. Shower performance is limited by electrical input and supply water temperature in winter.

I may do a flow rate test now to confirm for you…

 

[Johntheo5]

You can get, I think, up to 10.5kW Mira showers but these (45.6A@230V) will require 10mm2 cabling so yours may require a rewire, I have a 9.0kW Triton T80Z Fastfit using 6.0mm2 cable which supplied a 9.0kW Mira Sport for around 20 years previously to this, the Triton has excellent options on cable & water entry points.
A 9.0kW will give a (9.0/7.5), 20% increase in flowrate and pro rata for any higher powered one.
Any 7.5kW shower will give a flowrate of 4.9LPM at 40C from a present cold mains temp of 18C, a 9.0kW, 5.9LPM), in the debths of winter at say 5C, you (only) will get 3.1LPM & 3.7LPM respectively.

 

[endecotp]

My building pressure and flow rate is pretty good, and the 8mm is a short length; with that old shower, flow rate was OK on the cold setting. Shower performance is limited by electrical input and supply water temperature in winter.

Static pressure = 4.0 bar.
Flow rate = 11.8 l/min.
Dynamic pressure at that flow rate = 3.0 bar.

 

[Johntheo5]

Don't know if you measured that flowrate from the existing shower but you should still be fine, most shower manufacturers give their max flowrates at a minimum dynamic pressure of 1.0bar at the shower. In any case, using a minimum required showering temperature of say 35C and assuming a maximum (summer) mains temp of 20C, a 7.5kW shower required flowrate is 7.2LPM, and a 9.0kW, 8.6LPM, a 10.5kW would require 10.0LPM.