Installed one of these ~ 2 years ago to replace a long lasting (16 years) Mira Sport (more about this shower later).
My mains pressure for years was a static 3.5bar so no problem with shower pressure required for the diaphragm switch to close the microswitches, for the past year or so the water board has reduced this static pressure to exactly 2.15bar, at my normal showering temp of 40C, 4.61LPM from a present 12C mains temp, this, allowing, 0.65bar, (elevation + pipe loss +very small mains loss), results in a, 2.15-0.65, 1.5bar pressure at the 9kW shower, workes fine as only two of us in the house and nobody opening other taps in the house while showering.
For the past few months the mains pressure is further reduced during the night until 0630 hrs to 1.75/1.78bar static which results in 1.1bar at the shower, this sometimes results in the microswitches not closing so have to reduce flow to get the pressure up that tiny amount to close the microswitches, can then increase the flow to normal again. On test, by throtting the mains, the microswitches require 1.12bar (at the shower) to close the switches, they then reopen at 0.75bar, hysteresis of o.37/0.4bar, probably normal for this model??.
Major mains water pipe renewal was going on for weeks one winter with no mains water available for up to 8 hours daily so I installed a X over lever valve from the CWSC to the house mains with a DCV (double check valve at the mains) and a single NRV on the CWSC outlet, to my amazement, the Mira Sport would close its microswitches at a shower pressure (gravity head) of around 1.5M, 0.15bar and supply a measured 3.9LPM, enough to use both elements at 41C from the mains 8C.
I assume there was a "fault" in this diaphragm switch to operate at such a low head, if so, then it must have been like this from new. For interest, I tested the Triton on this gravity feed but it only flower ~ 1.5LPM and obviously (and correctly) didn't close the microswitches. Its a bit illogical IMO, to have a 1bar closing pressure (for safety reasons) and yet allow a flow of 2.0LPM when the temperature control is turned to fully hot, the Mira flowed 2.2LPM & the Triton flows 1.7LPM, at a 2.0LPM flowrate, 9kW will raise the temperature by almost 65C, in the unlikely event that the 48C TCO not opening then serious scalding could result as the second TCO doesn't open until 75C, one might think that a closing pressure of say 0.75bar would satisfy all requirements.
That said, I wouldn't dream of installing a mains supplied electric shower unless a minimum dynamic pressure of 3bar is available. If I get fed up with having to play around with the temperature setting on the infrequent times I have a pre 0630hr shower then I will just install a integrally pumped gravity fed one like the Triton T90SR or the like.
My mains pressure for years was a static 3.5bar so no problem with shower pressure required for the diaphragm switch to close the microswitches, for the past year or so the water board has reduced this static pressure to exactly 2.15bar, at my normal showering temp of 40C, 4.61LPM from a present 12C mains temp, this, allowing, 0.65bar, (elevation + pipe loss +very small mains loss), results in a, 2.15-0.65, 1.5bar pressure at the 9kW shower, workes fine as only two of us in the house and nobody opening other taps in the house while showering.
For the past few months the mains pressure is further reduced during the night until 0630 hrs to 1.75/1.78bar static which results in 1.1bar at the shower, this sometimes results in the microswitches not closing so have to reduce flow to get the pressure up that tiny amount to close the microswitches, can then increase the flow to normal again. On test, by throtting the mains, the microswitches require 1.12bar (at the shower) to close the switches, they then reopen at 0.75bar, hysteresis of o.37/0.4bar, probably normal for this model??.
Major mains water pipe renewal was going on for weeks one winter with no mains water available for up to 8 hours daily so I installed a X over lever valve from the CWSC to the house mains with a DCV (double check valve at the mains) and a single NRV on the CWSC outlet, to my amazement, the Mira Sport would close its microswitches at a shower pressure (gravity head) of around 1.5M, 0.15bar and supply a measured 3.9LPM, enough to use both elements at 41C from the mains 8C.
I assume there was a "fault" in this diaphragm switch to operate at such a low head, if so, then it must have been like this from new. For interest, I tested the Triton on this gravity feed but it only flower ~ 1.5LPM and obviously (and correctly) didn't close the microswitches. Its a bit illogical IMO, to have a 1bar closing pressure (for safety reasons) and yet allow a flow of 2.0LPM when the temperature control is turned to fully hot, the Mira flowed 2.2LPM & the Triton flows 1.7LPM, at a 2.0LPM flowrate, 9kW will raise the temperature by almost 65C, in the unlikely event that the 48C TCO not opening then serious scalding could result as the second TCO doesn't open until 75C, one might think that a closing pressure of say 0.75bar would satisfy all requirements.
That said, I wouldn't dream of installing a mains supplied electric shower unless a minimum dynamic pressure of 3bar is available. If I get fed up with having to play around with the temperature setting on the infrequent times I have a pre 0630hr shower then I will just install a integrally pumped gravity fed one like the Triton T90SR or the like.
