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Mains Fed Electric Shower

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  • 12-06-2018 9:31am
    #1
    John.G
    Registered Users Posts: 3,466 ✭✭✭


    I have a 11 year old Mira Sport mains fed electric shower rated at 9.0KW @ 230V.
    I clean the inlet filter very occasionally (every 2 years or so) and I also check the terminal screw tightness at the same time.
    As I had the cover removed I decided to take a few electrical readings which may be of interest, the readings were done with a fairly new but uncalibrated multimeter.
    I have always had a very high ESB voltage to my house so my shower operates more like a "240V" unit......here are my readings.

    Shower resistances 11.6 & 11.4 ohms. (some years ago I got 11&13 but dont know the accuracy or age of that particular multimeter)

    RCD voltage (shower off) 247V.
    Shower, full power, (2 elements)
    Voltage at RCD 240V
    Voltage at Shower terminals 237V
    Calculated power at 237V: 9.77KW (Measured as 9.66KW with the ESB meter)
    Shower, "1/2" power, (1 element, 11.6 ohm)
    Voltage at RCD 245V
    Voltage at Shower terminals 242V
    Calculated power at 242V: 5.05KW (Measured as 5.08KW with the ESB meter)
    Shower, Low power, (NO element on, cold water)
    Voltage at RCD 247V
    Voltage at Shower terminals 247V
    (Calculated power at 247V: 0.0KW, obviously)

    I was a bit surprised at the voltage drop of 7.0V at full power at the RCD but the 3V drop between the RCD and the shower terminals seems about right using 6MM2 cable with pretty long run of 14/15 meter (30 meter "to & from")


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    #2
    Wearb
    Moderators, Home & Garden Moderators Posts: 6,213 Mod ✭✭✭✭Wearb


    John.G wrote: »
    I have a 11 year old Mira Sport mains fed electric shower rated at 9.0KW @ 230V.
    I clean the inlet filter very occasionally (every 2 years or so) and I also check the terminal screw tightness at the same time.
    As I had the cover removed I decided to take a few electrical readings which may be of interest, the readings were done with a fairly new but uncalibrated multimeter.
    I have always had a very high ESB voltage to my house so my shower operates more like a "240V" unit......here are my readings.

    Shower resistances 11.6 & 11.4 ohms. (some years ago I got 11&13 but dont know the accuracy or age of that particular multimeter)

    RCD voltage (shower off) 247V.
    Shower, full power, (2 elements)
    Voltage at RCD 240V
    Voltage at Shower terminals 237V
    Calculated power at 237V: 9.77KW (Measured as 9.66KW with the ESB meter)
    Shower, "1/2" power, (1 element, 11.6 ohm)
    Voltage at RCD 245V
    Voltage at Shower terminals 242V
    Calculated power at 242V: 5.05KW (Measured as 5.08KW with the ESB meter)
    Shower, Low power, (NO element on, cold water)
    Voltage at RCD 247V
    Voltage at Shower terminals 247V
    (Calculated power at 247V: 0.0KW, obviously)

    I was a bit surprised at the voltage drop of 7.0V at full power at the RCD but the 3V drop between the RCD and the shower terminals seems about right using 6MM2 cable with pretty long run of 14/15 meter (30 meter "to & from")


    Did you measure drop at both sides of RCD? Did you measure at incoming L and N? I am curious as to whats causing that drop. Is it consumer side or ESB side?

    Please follow site and charter rules. "Resistance is futile"



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    #3
    John.G
    Registered Users Posts: 3,466 ✭✭✭John.G


    Wearb wrote: »
    Did you measure drop at both sides of RCD? Did you measure at incoming L and N? I am curious as to whats causing that drop. Is it consumer side or ESB side?

    Couldnt pick up any voltage drop across the RCD (0-200V scale) . ESB (side) tails, I couldnt get at the supply cable where it enters the Fuse holder (60/80A) but I was able to get the probe on the live and neutral where they exit from the Meter ( both are ~ 4.65MM OD with insulation). The tails from the fuse holder to the meter are ~ 6.75MM OD X ~ 0.5m long. I get a fluctuating volt drop reading of 0 to 1V between the each of the tails between the meter exit points and the corresponding + or - connections to the RCD. (Its actually a RCBO, 40A/30ma). It would seem that the voltage drop is on the ESB side, maybe with a bit of transformer regulation thrown in? although as I am living in a housing estate its hard to imagine 40A having much effect on what are probably multiple houses on one transformer.

    Daughter has a triton 90Z pumped shower (about 3 miles away) and if I just stick the probes in any of the sockets I get 234/228V with shower off/on with no other loading.


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