RUNNING 2 ELECTRIC SHOWERS

[OFS]

Can someone advise me as to whether or not it is safe to run 2 electric showers at the same time in the house ?

I already have 1 electric shower (Mira Sport) and am thinking of having another installed in the en suite

The locaL SHOWER SUPPLIER TOLD ME THAT WAS DANGEROUS AS THE HOUSE FUSE MAY BLOW IF RUN AT THE SAME TIME AND OTHER ELECTRICAL ITEMS ARE ON EG KETTLE? (oops sorry about capitals)

But a local electrician said it was safe to do so and asked me to check the amp shown in the electricity box for the house It said 100amp and he said it would be fine

Whose advice should I follow ?
Thanks

OFS

 

[the_jinj]

It's not dangerous - just need to take into consideration what else is drawing power, will they all be on at the same time, shower ratings etc.

 

[Steve]

It is possible to have 2 electric shower on the same single phase supply. But it all depends on the integrity of the mains supply to the house.

For example, my house has a fairly modern mains incoming, and the parts outside are also relatively new. However, the cable that enters my house is 16mm² Twincore. There are about 4 houses fed off a piece of this cable, and being rated at about 87A, it would not be very good if every house had 2 electric showers rated at 45A. They get over this fact by assuming that they wont all be using big appliances at the same time, which, on the whole is true.

It is, therefore, considered bad practise to allow a situation to occur where 2 showers can be used at the some time from one service. The best way to do this is with a 63A changeover switch hidden in a cupboard, but this is inconvenient if it is any distance from either shower.

Many houses have a supply direct from the road, if you're lucky it will be 25mm² SWA, which CAN take 2 showers no problem (given that the service head is up to the job). Just make sure the main fuse is rated at 100A, whatever you do.

Hope that helps.

 

[Adam_151]

It all depends on what rateing the showers are, what other stuff you have got, what size the service fuse is, etc

Why do you want two electric showers? why not have a pumped shower fed from the CH for the main shower and the electric one in the ensuite or something?

Crafty, sure its not 4 core and three houses....? , its AFAIK usually 16mm² to each house from a 95mm² three phase waveform cable under the street, the DNO do apply diversity, but not sure 4 houses is a big enough 'sample' they usually assume 2kw per house at the substation, and if its overloaded for a short time, the oil in the transformers and the ground the cables are burried in helps average it out thermally, if everyone in the same street ran seti farms or grew dodgy stuff in their attics then there would be problems

 

[Steve]

Crafty, sure its not 4 core and three houses....? , its AFAIK usually 16mm² to each house from a 95mm² three phase waveform cable under the street, the DNO do apply diversity, but not sure 4 houses is a big enough 'sample' they usually assume 2kw per house at the substation, and if its overloaded for a short time, the oil in the transformers and the ground the cables are burried in helps average it out thermally, if everyone in the same street ran seti farms or grew dodgy stuff in their attics then there would be problems

In our area, generally, one feed was taken off the poles on the street, and this was taken to the first house and strung between the next 4-5. The wires that came off the pole were 2 single cores (at the pole were 3 phases, neutral and switched for lights).

These 2 single cores went onto the house, and fed a concentric cable (16mm AFAIK). Then it got interesting. Wherever a branch for a house was required, the concentric split into 2 single cores again. For long distances (back of houses), they used 2 core "twin and earth" obviously without an earth. This is what enters our house.

A few years ago they put everything on the street underground, but left the 4 houses on a row arrangement. I think there's 5 on our run actually.

I dont see how they can assume 2kw per house. Thats ridiculous. What about all those immersion heaters? houses with storage heaters or other electric heating? I can see how it would average out though.

Its definitely not 4 core cable. I have seen a row of about 15 terraces with each single core phase cable on the front ending after so many houses, with just one phase left at the end 5 or so houses.

 

[Adam_151]

dont see how they can assume 2kw per house. Thats ridiculous. What about all those immersion heaters? houses with storage heaters or other electric heating? I can see how it would average out though.

The fact that it averages out is what matters, big overloads are taken care of the fact that both the oil in the transformers and the ground the cables are in have quite a high thermal capacity. The fact that the biggest loads occur when its cold outside also helps it work out ok. Remember as well that heating loads such as immersion heaters come in and out on a thermostat once the water is hot, which all helps to average out the load being drawn at any one time