Shower pump supply

[dawdle]

Is it wrong to run a 2.5mm t&e spur off of the RCD protected downstairs ring to supply a shower pump on the first floor? It would be easier for me at this point but I'm not sure it would be 'good practice'. ie a circuit downstairs feeding something upstairs?

Thanks.

 

[Chri5]

Best avoided, most would assume an upstairs item would feed via the upstairs circuit.

Why isn't the upstairs on an RCD ?

 

[dawdle]

Thanks. That's what I was thinking. But hoped someone would say 'no problem' as I will have to try to get 3x 2.5's into 400mm of 20mm conduit or make holes to get into the upstairs ring.

 

[ColJack]

why would you need to get 3 in one tube?

can't you pull a leg back and route it to the new spur, then pull a new leg in from the spur back to the socket? ( IE make the spur part of the ring.? )

 

[dawdle]

I could pull it in to the ring but it would be a lot more work. I can access the conduit to a nearby socket from below if I take down a sheet of plasterboard.

Is there any reason not to put 3x flat t&e 2.5's in 20mm plastic conduit apart from they won't fit easily?

Thanks

 

[Taylortwocities]

You'd be lucky to get them in there. Also, did you not hear about space factor? See this http://www.kopex.co.uk/guide.asp?chaptercount0=5&id=55

If you stuff them all together then you may need to derate the cable....

 

[ericmark]

Interesting as to comments it has been a source of debate between my son and I many times.
My Sisters house was wired side to side for sockets instead of upstairs and downstairs which has some advantages with less cable used so better ELI and more even distribution of the power between both circuits.
My son feels electricians may not realise and could work on the system and in error open a live socket.
I consider if they don't test each socket they deserve all they get and one should never assume anything.
If it were not in a house we would not worry as to were supplied from as long as it meets the regulations.
The only way it could be a problem is if as a result we were exceeding floor area covered with a ring main but personally I would say let common sense prevail and so long as the ELI etc. will allow it's use then why not?
I have seen conservatory's feed from upstairs and switches for immersion heaters were often put down stairs and when removed these are often converted into a radial with one socket downstairs and one upstairs more to fill gap were switch was then anything else.
So it is common in houses to get a odd socket or light feed from wrong place.
And if I was doing a periodic inspection can't see how I could enter any of the 4 fail options against it. I think I would have to pass.
Even though I know my son would not agree.
Big point is who is signing paperwork. If would every is signing minor works is happy with it then why not?

 

[dawdle]

You'd be lucky to get them in there. Also, did you not hear about space factor? See this http://www.kopex.co.uk/guide.asp?chaptercount0=5&id=55

If you stuff them all together then you may need to derate the cable....

Thanks. So 60% free space in conduit to allow ventilation for cables. I think that means I'll have to use either the D/S ring, U/S lighting or just leave it on the immersion feed which is where it's supplied from at the moment (Poor descision). None of which I like the sound of.

Any opinions as to which of the above is best?

I think my U/S light circuit can handle it. I have to derate the cable as there is a fair bit of insulation in the attic. Can anyone tell me if I'm correct in thinking a derated for insulation 1.5mm t&e on a <15M radial gives me a max load of about 7A? The max load on the circuit (All bulbs maxed out) is less than 4A and currently about 2A.

I'll have to pull up the carpet, gripper and screwed down boards to pull it into the ring as I'll have to use a socket on the other side of the room. Why is the best option always most difficult.

Thanks.

 

[Chri5]

just leave it on the immersion feed which is where it's supplied from at the moment

I take it the radial cct for the immersion is fused at 20 amp and run in 2,5 TE ?

A 3kw immersion loads at 13/14 amp and thus has spare capacity for a shower pump via a fused spur.

Since immersions tend to run as an emergency form of heating (boiler HW fail) or simple water top up I see no reason why you can't hang the pump off the immersion circuit.

Why do you think that's a 'poor' idea ?

 

[dawdle]

It is in 2.5 and will be on a 16A MCB. Only said poor as its 'recommended' it has it's own fixed supply I knew the cable could handle the load but wasn't aware of the recomendation when I wired it. I also didn't allow for derating from insulation.

Can someone please tell me what the capacity of 20M of derated 2.5 t&e would be if one side is on insulation for more than 500mm? The other side is clipped to timber at the moment. I can pull it and lay it on top of the insulation if necessary/better.

I do currently have a shorter route open with no insulation. If I have to I can pull it out and reroute it (I hate doing things twice!).

I just found some leaks in the roof too

 

[maltaron]

Surely if you label the socket as on the downstairs ring then it should be no problem. In my bungalow ther are 3 socket circuits in the kitchen, one dedicated kitchen only, one main house ring with original kitchen sockets still there and one old cooker point converted to twin 13 amp. This was done before I bought the place and I have a cert fron an electrician who rewired the kitchen, but no mention of different circuits. For my own safety I have put coloured stickers on all sockets and on the MCBs that control them.

 

[Chri5]

what the capacity of 20M of derated 2.5 t&e would be if one side is on insulation for more than 500mm? The other side is clipped to timber at the moment.

A 2.5mm TE x 20m x the whole route touching plasterboard (with insulation) at 30 deg, will allow a 20 amp fuse / load.

If you could confirm that your immersion runs as the emergency HW, rather than x hours per day, that the element is 3000w and the pump no more than 1400w (most run 400-700w) I'd add the pump on.

Mines in the same cupboard as the immersion and the f/spur is beside the immersion 20a switch.
Our immersion gets turned on, for 15 minutes every blue moon.


Maltaron, if you admit that you had to put effort in to 'discovering' what socket and light was on what fuse at the CU, then the original and subsequent installers have not done the works to absolute best practice.

These things do happen and are sometimes the only option. Consider things like tiled, laminate, buried, plastered routes.
Houses with middle divides where front and rear lights and rings incorporate a number of floors are a good example.
When additional works are done some will take the cheap cost option rather than the correct design option. That explains 75% of borrowed landing light neutrals.

Every electrician will endeavour to keep the installation logical, but sometimes it can't always be. Where it can't you have done the right thing and clearly documented the deviations.

 

[dawdle]

Thanks for the cable calc. I'm guessing the pump is 230W/1A as there is only 230/1/50 on the box. It's only a 1.4 bar. I'll double check next time I have the bath panel off (It's under the bath in zone 0).

The immersion isn't used at the moment as the CH is on for a couple of hours a day. It may be used in the summer though. There is no timeclock on the immersion so it's on or off.

I think I'll leave it and mark the CU immersion and shwr pump. the FCU's are side by side in the HW cyclinder cupboard (and will be labelled when I get my hands on one.) so no confusion there.

There's that 20A DP switch that keeps popping up. Should I swap out the 13A fused switch spur?

Thanks.