Electric Shower: Cold Water (Triton Riya)

jm1205

Hi,

We’ve moved into a house with a (~6 month old) Triton Riya (8.5kW) electric shower installed. We know that the cable feeding it is insufficient - the shower wasn’t working when we moved in and the electrician who came to fix it said it’s wired with a 5kW cable (although he said it should still function properly for a year or so until we get the cable replaced).

We believe the shower is plumbed into the mains water, because turning the cold tap in the bathroom on full reduces the pressure of the shower a little (plus there doesn’t appear to be a gravity-fed tank in the attic).

Unless the cold tap in the bathroom is turned on full, the shower barely gets lukewarm (and even with the tap reducing the volume of water through the shower it’s not exactly hot).

Do you think this is likely to be because:
a The shower is underpowered by the lower kW cable,
b The shower unit just isn’t powerful enough for our water pressure and we should invest in a more powerful shower (+ appropriate cabling), or
c The shower has a fault and the heating elements aren’t working correctly?

Any advice much appreciated!

Norman_Castle

The shower is underpowered by the lower kW cable,

Undersized cable would overheat rather than reduce water temperature.

Unless you have a very fast flow rate I would suspect the shower is faulty. What did the electrician advise?

As its only six months old try contacting the maker.

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keith969

Norman_Castle wrote: »

Undersized cable would overheat rather than reduce water temperature.

No - it would have higher resistance, and excessive power would be dissipated in the cable, lowering the power available to the shower. Depending on the cable length it may or may not be causing the issue.

Jonesya

You should never overload cables because when overloaded they can overheat leading to damage and potentially a fire.

If your electrician is saying the cable is rated for only 5kw, so around 20A and you've got an 8.5kw, or 35A shower connected to it then that is significantly overloaded and I don't know why he said to continue using it, because he really should have disconnected it because on the basis of what you've written, that shower is unsafe and shouldn't be used.

nofoollikeold

1. The shower could be getting insufficient power because of the undersized cable. An 8.5Kw shower requires a minimum 6mm diameter cable, more if the run from the incoming mains is long, and / or requires a lot of bends and / or runs through restricted space (e.g insulation). Running an appliance on under-rated cable is asking for a fire.

2. It's not the pressure of your supply than can cause the issue, but rather the rate of flow through the shower, although that in turn is of course driven by the pressure for any given system. You might try fitting a flow reducing valve in the feed to the shower. Your shower is designed to run at a minimum flow of 8 litres per minute at a pressure of 1 bar.

3. Its possible the element is faulty but pretty unlikely in a newish shower. The elements tend to either work or not work, rather than becoming partially faulty.

Ectophile

It's unlikely that the undersized cable would be the problem.

At this time of year, with the incoming mains water really cold, an 8.5kW shower will struggle to produce a good flow of hot water. Make sure the heater control is on maximum, and turn the flow control downwards to get hotter water. You should at least be able to produce reasonably hot water, but with no great flow.

If you're expecting to get water hot enough to boil a lobster, with a flow like the Niagara falls, then you'll be disappointed by an 8.5kW shower.

It's possible that one of the elements has failed. There are two of them to give the two power settings.

Risteard

nofoollikeold wrote: »

An 8.5Kw shower requires a minimum 6mm diameter cable, more if the run from the incoming mains is long, and / or requires a lot of bends and / or runs through restricted space (e.g insulation).

Cable sizes are not the diameter of the cable. Number of bends is not a factor in cable sizing either.