Electric shower [Thermal cut-out has operated]what to check

Every electric shower has a thermal cut-out, and it is the single most misunderstood component in the category because the same three words describe genuinely different devices depending on who made the shower. What they have in common is the job: sense a temperature inside the unit that should not be there, and disconnect the heating elements before it becomes dangerous. What they do not have in common is what happens next, and that is the part that decides whether this is a five-minute wait or an engineer. Triton fit a device that is not resettable at all. Their own wording is that it "will require a visit from a qualified engineer to determine the nature of the fault and replace the safety device once the unit has been repaired" — note that it is a replacement part, and note the order, repaired first and then the device replaced, because the cut-out operating is a symptom of something else.

Redring fit a two-stage device. Stage one is cyclic and the owner resets it by running the shower: their instruction is simply to allow cold water to run through. Stage two operates only at an extreme temperature, switches off permanently and is replaced. Bristan describe two behaviours across their range. On the Glee and its relatives the Temperature Control Device cycles on its own: it switches the elements off, they come back on once the unit has cooled, and the cycle repeats until the temperature is turned down, which is why a Glee that has tripped it cycles between hot and cold rather than going dead. On the Joy Care, whose display shows LP when the TCO has activated, the instruction is to turn the unit off and wait five minutes for it to cool.

Mira’s Advance does not give the owner a cut-out to reset at all: an over-temperature comes up as code D or F on the lights and the published action is a purge of the flow valve, with the thermal switch listed only as a spare. Confusing them produces the two classic errors in this category. Somebody with a Triton waits for a reset that is never coming and concludes the shower is dead. Somebody with a Redring or a Bristan books an engineer for a fault that would have cleared itself. The other half of the answer matters as much: a cut-out that has operated once is protection working, and a cut-out that operates repeatedly is reporting an underlying problem, usually restricted flow, that will keep tripping it whatever you do to the device.

1. 1

   Find out which kind you have before doing anything else. Triton is non-resettable and needs an engineer. Redring resets by running cold. A Bristan Glee cycles back on by itself once it has cooled and wants the temperature turned down; a Bristan Joy Care wants five minutes off. A Mira shows a code and has its own pages here.

2. 2

   On a Redring, run the shower with the temperature wound fully to cold so cold water passes through the heater and resets the cyclic cut-out. Redring give no time for it; the device resets once the heater has cooled. If it stays cold after that, stage two may have operated, and that one is replaced.

3. 3

   On a Bristan Joy Care, switch the unit off, wait a full five minutes for it to cool, and try again; Bristan give five minutes specifically, so it is worth timing rather than guessing. On a Glee, Cheer, Smile, Solis or Noctis, whose guides all describe the Temperature Control Device the same way, there is nothing to wait for: turn the temperature control anticlockwise, which is Bristan’s remedy, and the device stops cycling.

4. 4

   Whatever the brand, deal with the flow before you use it again. Descale or replace the showerhead, make sure the hose is not kinked behind the riser, and have the inlet filter cleaned: yourself on a Bristan, where the cap unscrews from outside with the electricity and water isolated, and by the installer or a competent person on a Triton, Mira or Redring, where it is inside the case.

   Isolate the shower at the pull cord and turn off the water at the servicing valve before touching the inlet filter on a Bristan, and do not remove the front cover of any brand to reach one.
5. 5

   Turn the temperature down a little and run at higher flow. A shower asked for slightly less heat at more litres a minute stops tripping its own protection.

6. 6

   If it trips again after a clean showerhead and a clear filter, stop resetting it and get it looked at. The device is reporting something it will keep reporting.