replacing a power shower

[Mike Wright]

So, some background.

The house is 1978 ish build, brick and tile.

It's never been rewired.

The old wire fuses are all plug in mcb's except one which I can't identify and is either a direct connection to the immersion circuit that isn't working or the feed to the old bar heater I took out.

The existing shower is switched outside the bathroom and voltage dropped via a transformer.

I intend to replace switch with a wall mounted mcb's thing as new shower takes 240volts into shower unit. This will also hopefully be earthed as 3core cable is used. 

Will this be enough? I assume the original earth bonding is still present but how would I know? If I check continuity of the existing feed pipes to the earth running back to consumer unit, and it's less than 0.05 ohms, can I be satisfied bonding is good.? 

Mike

 

[Andy™]

of course the shower will take 240v. thats the standard voltage. (well, on paper its 230v, in reality its usually closer to 240).

the wall mounted heater was most likely connected to your lighting circuit,not this unknown mcb

i have no idea what you mean by replace switch will wall mounted MCB's. if you mean the CU then its not really a DIY job. if its the isolation switch adjacent to the shower, then you wont need an MCB there. additionally, if its a power shower, its unlikely that the wiring will be adequate for a normal electric shower either. and i doubt its fed from a transformer either, although i guess a power shower could be but ive never seen any like that

and you  will know if original bonding is in place by looking and a continuity test between it and the MET (with the earth removed from the pipe to avoid parallel paths

 

[Mike Wright]

Sorry, bit confusing I know. The existing shower is a power shower but it runs on 24 volts via a step down transformer outside the room.

A switch outside isolates it. The power comes from a spur off the ringmain. I though I would replace the existing switch with a built in mcb type thing but ring main is protected at consumer unit by mcb anyway,  so probably don't need too.

Currently shower isn't earthed!!  new one will be.

 

[Andy™]

never seen a 24v power shower before. but im not surprised its not earthed. it will be specifically not earthed for a reason. and if its from the ring, you cant get 'mcb thing'. im guessing what you have may be an RCD spur or just a normal spur.

you could replace with another power shower which if its mains voltage will most likely require an earth (and will probably need a new cable to the spur / switch), but you would need to install a dedicated shower circuit to have an normal electric one

your new shower will most likely also require RCD protection (definitely if its 230v inside the bathroom), you will need to fit this if the circuit doesnt already have RCD protection

 

[Rob_the_rich]

Sounds like the existing one is just a pump, can you confirm the replacement one is also just a pump. How much power does it use?

 

[M107]

Mike  I would do as Andy has said, get somebody in that knows what they are doing, the following was yesterdays job post somebody doing DIY work to replace an old shower with a new one. Only one picture I'm afraid as my phone died.

Had a call last week from a fella who was in a bit of a panic.

Smoke coming out of the cupboard in the lounge. The 7 year old was down stairs on his own watching tv while his mum was having a shower, the lad saw the smoke & raised the alarm.

Some months ago they had an old 8Kw shower removed & a new 10Kw put in by friend who "knew how to fit showers".

The "shower" BS3036 was linked out & feeds the BS60898 plug in to the left, that in turn feeds the RCD & on up to the shower switch in the fist floor bathroom..........the switch cabling was interesting 6mm² supply 10mm² to the load :Applaud

I should have taken pics of the RCD as it was also severely melted on the line terminals.

Parent had the presence of mind to switch off at the main switch.

I didn't get any other pic's sorry, but the new board replacing all this lot is one of SBS Dave's units using his standard RCBO's

 

[Mike Wright]

"wall

Sounds like the existing one is just a pump, can you confirm the replacement one is also just a pump. How much power does it use?

Amounted heater was most likely connected to your lighting circuit,not this unknown mcb"

 

[Mike Wright]

New unit recommends a spur fused separately at 3amps, it's hot and cold water feed so no internal heating elements!! 

It recommend a 30ma mcb in circuit or at the consumer board - I shall put one in spur.

The spur is already there - serving exist unit - so just need to run new cable from switch to unit.

Other than checking earth, does this sound ok?

 

[Andy™]

you cant get a 30mA MCB. you can get a 30mA RCD. but unles you know for sure that you have an RCD..

 

[Mike Wright]

you cant get a 30mA MCB. you can get a 30mA RCD. but unles you know for sure that you have an RCD..

Erm yeah that thing.

 

[Mike Wright]

Mike  I would do as Andy has said, get somebody in that knows what they are doing, the following was yesterdays job post somebody doing DIY work to replace an old shower with a new one. Only one picture I'm afraid as my phone died.

Good advice!! 

 

[Mike Wright]

Good advice on here,  really appreciate it all.

From the sounds of it, it's pretty straightforward and should not be out of my abilities. 

It won't overload the existing wiring as it's running a 3amp maximum rating which is fused. Or at least will be.

 

[Andy™]

you still havent answered my question if you have an RCD or not...

and i very much doubt you have the required test equipment to ensure that the RCD is working correctly

 

[Mike Wright]

you still havent answered my question if you have an RCD or not...

and i very much doubt you have the required test equipment to ensure that the RCD is working correctly

I have RCDs on consumer unit anyway, they have tripped appropriately so happy with these. I should be able to put a standalone RCD in the spur, I've seen them in other applications.

 

[Andy™]

are you sure they are RCD's (with a button marked 't' or 'test')?

and since you would appear to have an old wylex with plug in MCB's, i very much doubt you have RCD protection at the board unless its been fitted before on the tails (which could be the wrong rating) or fitted after the board on certain circuits

and how do you know they have tripped appropriately? you do know the trip times are measured in mS, dont you?

 

[bluetobits]

How do you know it was "appropriate"? 

Did you measure the leakage current and monitor the time taken to open the circuit? 

 

[Mike Wright]

you still havent answered my question if you have an RCD or not..

.I have RCDs on consumer unit anyway, they have tripped appropriately so happy with these. I should be able to put a standalone RCD in the spur, I've seen them in other applications.

Consumer unit has 4 two 32 amp, ringmain and cooker feed and two 6 amp lighting - and a 16amp fuse block
existing shower is a spur on ring main.
i'll fit a dedicated RCD in the spur.

 

[Mike Wright]

http://www.diy.com/departments/wylex-63a-sp-230v-30ma-shower-protection-unit-rcd/177830_BQ.prd this kind of thing, on the actual spur.

 

[Andy™]

if thats between socket circuit & shower, i hope you have something else with a fuse, since that alone does not comply...

 

[Mike Wright]

Yes, there is a switch already in the circuit now with a replaceable 3 amp fuse. It will be reused. Does this RCD thing need to be between switch and shower or spur and switch? I assume before the fused switch.