Can I have an electric shower and toilet on same feed from CWS tank?

[Ch_152]

8cm is only 3 inches, also I don't know why the tank bottom is allways quoted, practically speaking, its from the water level in the CWS cistern that should determine the minimum requirement so that might meet your requirements?.

A few other points, the T80SR (SR stands for silent running) is called the T90SR in this neck of the woods, I have a T80 which is a mains supplied shower so ensure that you are looking for a integrally pumped shower.
6MM2 cable will supply a 9.0kw shower so assuming a "average" showering temperature requirement of 40C, a 9.0kw shower will supply a flowrate of 3.8LPM from cold water supply of 6C in the very debths of winter, a more realistic cold mains of 10C will give result in a flowrate of 4.3LMM at 40C and at 15C will result in 5.2LPM.

A well known shower installer (> 1000 showers/annum) a contributor to our Boards.ie website has a very very low opinion of the pumped Mira Quiet (called, I think here), he said that after 3 attempts to re engineer a simple item like a water elbow that they still fail and start leaking and very frequently the pump/motor fails, he said he has rarely if ever had to replace the pump/motor in the Triton T90SR.

Yeah, unfortunately the shower and the CWS are on the same floor, and the bottom of the CWS is about 30cm below the top of the existing electric shower. Mira don't have a particularly good diagram to scale off, but it appears the inlet is slightly higher on the existing than the Triton - so potentially the unit would end up being even higher. I'm going to see if I have room to shift the CWS up a bit. Good point on it being the level of water within the cistern though, hmmm...

On the flow rates, I found the image below which aligns with your calculations. I am hoping that (aside from the pump) I should at least also get some benefit from the cold water tank (which is located in the spare room cupboard) being a little warmer than the incoming mains - especially during winter.

 

[Ch_152]

While we're here. The existing electric shower is a Mira Sport Max 9.0 kW.

When run on the "High" setting (9.0kW) even with the temperature turned fully down, it is far too hot to stand under (and I do like a generally warm shower, ~38-40 degrees). But the flow is adequate (~4 to 5 or so l/m). I can only get away with this in the winter, presumably because the incoming mains is a few degrees cooler.

In the warmer months I have to run on the "eco" setting, (4.5 Kw) and the temperature dial turned up to, say, 1 o'clock to get a reasonable temperature. The flow is around 2.5 to 3 l/m. Which is rubbish.

I guess that makes sense, but want to check I'm not going to run into a similar issue if I was to change to the Triton?

 

[Johntheo5]

While we're here. The existing electric shower is a Mira Sport Max 9.0 kW.

When run on the "High" setting (9.0kW) even with the temperature turned fully down, it is far too hot to stand under (and I do like a generally warm shower, ~38-40 degrees). But the flow is adequate (~4 to 5 or so l/m). I can only get away with this in the winter, presumably because the incoming mains is a few degrees cooler.

In the warmer months I have to run on the "eco" setting, (4.5 Kw) and the temperature dial turned up to, say, 1 o'clock to get a reasonable temperature. The flow is around 2.5 to 3 l/m. Which is rubbish.

I guess that makes sense, but want to check I'm not going to run into a similar issue if I was to change to the Triton?

Well, one of three reasons for that, either a dynamic mains pressure of ~0.5bar at the shower, a faulty flow stabilization valve or a dirty inlet filter.

I had a 9.0kw Mira Sport for nearly 18 years, gave excellent service and during a 2 day mains (water) outage I installed a bypass to allow usage of water from the CWS cistern for house hold H&C usage and discovered to my amazement that the Mira flowed 3.9LPM from the storage tank (head ~ 4M), I was able to use it no problem on its economy setting and on another shorter mains loss duration one winter, I was able to run on the two elements!, I tried the Triton when I installed it two years ago but there was hardly a dribble from it from the the CWS cistern, however no cause for complaint as these are mains supplied showers.
The Mira flowed 8.9LPM at a measured dynamic head of 2.1bar at the shower, the Triton flowed 7.9LPM when I installed it, at a dynamic pressure of 2.3bar.
Both triton and Mira infer that you should get ~ 8.0LPM at a dynamic head of 1.0bar, not true,

I installed a (pumped T90SR) for a friend of mine with no easy access to the CWS so I installed a drop tight PRV fed from the mains set to ~ 0.5 bar and its fine for the past 3 years or so but remember this invalidates the warranty, I think the PRV was a Caleffi? but there is now no easy access to it to check its model.

 

[Ch_152]

Well, one of three reasons for that, either a dynamic mains pressure of ~0.5bar at the shower, a faulty flow stabilization valve or a dirty inlet filter.

I had a 9.0kw Mira Sport for nearly 18 years, gave excellent service and during a 2 day mains (water) outage I installed a bypass to allow usage of water from the CWS cistern for house hold H&C usage and discovered to my amazement that the Mira flowed 3.9LPM from the storage tank (head ~ 4M), I was able to use it no problem on its economy setting and on another shorter mains loss duration one winter, I was able to run on the two elements!, I tried the Triton when I installed it two years ago but there was hardly a dribble from it from the the CWS cistern, however no cause for complaint as these are mains supplied showers.
The Mira flowed 8.9LPM at a measured dynamic head of 2.1bar at the shower, the Triton flowed 7.9LPM when I installed it, at a dynamic pressure of 2.3bar.
Both triton and Mira infer that you should get ~ 8.0LPM at a dynamic head of 1.0bar, not true,

I installed a (pumped T90SR) for a friend of mine with no easy access to the CWS so I installed a drop tight PRV fed from the mains set to ~ 0.5 bar and its fine for the past 3 years or so but remember this invalidates the warranty, I think the PRV was a Caleffi? but there is now no easy access to it to check its model.

That's very interesting, thanks.

My flat is split between the 2nd and 3rd floors of the building. I know that the mains pressure is ~0.7 to 1.0 bar (static) at the 2nd floor, so it could well be that it's around 0.5 at the shower on the 3rd floor...

 

[Johntheo5]

From the T80SR MIs.
Minimum inlet pressure 0.08 metres 0.78kPaMaximum inlet pressure 10 metres 100kPa (1 bar)

 

[Ch_152]

From the T80SR MIs.
Minimum inlet pressure 0.08 metres 0.78kPaMaximum inlet pressure 10 metres 100kPa (1 bar)

My existing electric shower (Mira Sport Max) runs from the mains.

I won't exceed the max inlet pressure for the T80SR from the CWS. But I do need to raise the tank to meet the minimum head/pressure.

 

[Johntheo5]

Yes, I appreciate that but the T80SR can have a maximum inlet head/pressure of 1.0bar and if you did opt to feed it from the mains like I did for my friend then no need to raise the tank and if you are confident that the mains pressure will allways be < 1.0bar then no need for a PRV but would probably be prudent to install one, of course with the caveat of no warranty and if its no big deal to raise the tank then thats the proper way to do it.

 

[Ch_152]

Yes, I appreciate that but the T80SR can have a maximum inlet head/pressure of 1.0bar and if you did opt to feed it from the mains like I did for my friend then no need to raise the tank and if you are confident that the mains pressure will allways be < 1.0bar then no need for a PRV but would probably be prudent to install one, of course with the caveat of no warranty and if its no big deal to raise the tank then thats the proper way to do it.

Oh I see what you mean now - was being dim. That's not a bad idea at all. Unfortunately, having done the measurements, I don't think I can physically get the tank high enough to comply with the requirements of the T80SR.

If run off the mains, any issues with things like the kitchen tap or washing machine (fed from mains) being run at the same time as the shower? Would assume the Triton is expecting a fairly constant pressure?

 

[Johntheo5]

It will obviously affect it to some degree as the internal pump is boosting the supply pressure, but at least you still have control with the shower temperature control as you will have plenty of available pump head.

 

[Johntheo5]

A flow stabilisation valve is mentioned in the T80SR MIs, this is part of the temperature control, its allways installed on the mains supplied showers but a bit surprised its also on the pumped showers so should further help to maintain control. Strangely enough, its not mentioned in the T90SR (sold here) MIs.

 

[Ch_152]

A flow stabilisation valve is mentioned in the T80SR MIs, this is part of the temperature control, its allways installed on the mains supplied showers but a bit surprised its also on the pumped showers so should further help to maintain control. Strangely enough, its not mentioned in the T90SR (sold here) MIs.

Interesting! Thanks very much for your help