Shower circuit design supplies

[pc1966]

His point is the MCB can provide only fault protection (i.e. not overload as well) for the cable to fixed loads.

The fundamental aspect is the shower load is too much for the cable if it is thermally insulated. Changing the MCB is not going to alter that situation, and would only add another part that would be overloaded under normal operations.

So the real issue is the cable getting too hot due to thermal insulation? That may be hard to check [in any sane way] if you can't inspect enough to know the typical route. But if you can see sections and they show no sign of thermal stress it should be OK.

If it is a risk then the best option would be to replace the cable with a higher capacity one.

 

[davesparks]

If it is a risk then the best option would be to replace the cable with a higher capacity one.

The OP is doing an EICR their only option is report on it accordingly.

Carrying out the remedial work will be up to the contractor appointed to do this.

 

[westward10]

This is an issue doing periodics as in most situations it is not possible to verify the full installation method of the cable. According to Table 4D5 unless you can confirm Reference Method C can be applied then 6mm cable is undersized for an 8.5kw shower. That's how I read it.

 

[Ian1981]

This is an issue doing periodics as in most situations it is not possible to verify the full installation method of the cable. According to Table 4D5 unless you can confirm Reference Method C can be applied then 6mm cable is undersized for an 8.5kw shower. That's how I read it.

I don’t fully agree as for all you know the cable has been installed correctly during the original install.
If there’s no evidence of damage and the circuit has been in use for years as is the case with this situation (red and black coloured conductors) then it’s pessimistic to give it a potentially dangerous code without evidence of any danger present or potential danger.
That said I think the OP has indicated they has been alterations done to the original circuit.

I think that the reference method on an EICR which you record can be a bit pointless tho as you said, it’s sometimes impossible to verify, but we could end up applying that scenario to every circuit present including ring final circuits that may have the ccc below the required 20 amps minimum but I wouldn’t code that without evidence of thermal damage or insulation present surrounding the cables.
[automerge]1587121839[/automerge]
To be honest, if it’s ran up the pipe boxing (which is dubious) I’d be tempted to give it’s reference method as method B

 

[telectrix]

if it's in soil pipe box then it's gotloads of free air around it, unless some muppet has fille the box with itchy-poo. i'd class it as ref. C.

 

[Ian1981]

if it's in soil pipe box then it's gotloads of free air around it, unless some muppet has fille the box with itchy-poo. i'd class it as ref. C.

Smelly free air ?

 

[westward10]

I would go with B.

 

[telectrix]

I would go with B.

yeah, but B refers to encosed in conduit usually with very little air space. and the ref. tables make no mention of T/E in conduit.

 

[westward10]

yeah, but B refers to encosed in conduit usually with very little air space. and the ref. tables make no mention of T/E in conduit.

Table 4A2 references cables in building voids as Method B.

 

[telectrix]

so what about cables in the voids between floors.? surely these aren't B. i'd class then as in free air, unless clipped to joists, i.e C.

 

[westward10]

so what about cables in the voids between floors.? surely these aren't B. i'd class then as in free air, unless clipped to joists, i.e C.

According to Table 4A2 Method C applies to cables fitted direct to walls and ceilings, in masonry walls and cables on unperforated trays. Strictly speaking according to this Table cables in floor voids would be Method B.

 

[R-fur]

I am dealing with a similar case just now. A house I own and rent out was due for its 5 year EICR. While doing the EICR I asked the tenant if there was any problems with the installation, just the shower they said, if two people have a shower one after the other or the daughter is in it for a while it trips out. Turns out the tenant had up graded the shower without my knowledge to a 8kW on a 6mm cable with 32A MCB. I know the cable is clipped in the floor void then up inside an uninsulated lath and plaster wall and there is no sign of any distress at the connections so I am going to change the 32AMCB to a 40A RCBO once the current madness is over.

 

[Buzz1980]

Yeah looking at table 4D5 it should be reference method C clipped direct. As the cable is not in 100mm insulation in wall. I think that will be best option remove any insulation around the cable in attic away and check electrical connections for any damaged insulation/over heating etc. That way don’t have to change 40amp to 32amp In Case of potential constant overload and I have made the current rating of the cable better with clipped direct and check that there is no signs of over heating ? This like said will get done when current climate get back to normal