Downsizing Cable ?

[tomodo]

Hi new to this website . I was wondering what excatly are the regulations to downsizing cable . I was wiring up a pillar drill the other day which had 1mm internal wiring but the only cable i had was 2.5 swa which i used coming from the distribution board to the connector blocks which in turn was the connected to the 1mm internal wiring inside the pillar drill. - protected with 6 amp breaker still though . is this okay to do? Thanks

 

[trev]

I'm not sure there are any regs governing this. 2.5 has a larger ccc than 1.0 so I don't really see a problem, you could wire a 2 point lighting circuit in 10mm swa if you could terminate it properly mate
I wouldn't have done it myself but you were the man on the ground there so if that's all there was to hand that's it.
Was this some sort of emergency job where the drill had to be up and running because I'd have taken a look at it and made whatever call I felt necessary rather than waste cable on a job which, potentially, could have been done cheaper and eaiser.

 

[Eddiesparks]

I've needed to finish downlights and ended up the last 2 being in 2.5mm. Was rough and a pain to terminate in the newlec made in china terminals but it was more than safe !!

 

[7029 dave]

Nothing wrong it that, bigger the csa ,lower the resistance that's basic physics. lol

 

[tomodo]

It was only a short run of around 3 metres so wasnt too bad. I was just wondering because if later on someone came along and seen the 2.5mm in the distrubution board and for whatever reason decided to uprate the MCB to lets say a 16A then the 1mm wouldnt be protected would it? Would it be their responsibility to check the full run of the cable before changing an MCB size? Thanks for the replys.

 

[Engineer54]

It was only a short run of around 3 metres so wasnt too bad. I was just wondering because if later on someone came along and seen the 2.5mm in the distrubution board and for whatever reason decided to uprate the MCB to lets say a 16A then the 1mm wouldnt be protected would it? Would it be their responsibility to check the full run of the cable before changing an MCB size? Thanks for the replys.

If this SWA from the DB is only supplying the Pillar Drill, then anyone upping the MCB rating would be totally responsible for his actions and any subsequent damage therein!!

 

[davesparks]

I'm a tad more concerned by what sounds like an swa running straight from DB to the machines terminal box without a means of isolation. Doesn't sound like good installation practice to me.

 

[tomodo]

Cheers for the help! Also does go through a rotary isolator before the drill

 

[Spoon]

I'm a tad more concerned by what sounds like an swa running straight from DB to the machines terminal box without a means of isolation. Doesn't sound like good installation practice to me.

Isn't the MCB the means of isolation. The SWA is only 3 meters long.

 

[Farmelectrics]

say the db was locked an isolator local to pillar drill would be better

 

[Spoon]

The drill is 3 meters away mate. No one should be messing about with the drill unless they have assess to the DB.

 

[trev]

say the db was locked an isolator local to pillar drill would be better

Say it wasn't lockable, say the OP was the man on the ground and made an assessment (rightly or wrongly) that because of the proximity of the MCB that would suffice as local iso.

 

[davesparks]

Mcb as an isolater? Not on my watch thanks!

 

[Spoon]

Mcb as an isolater? Not on my watch thanks!

Read Table 53.4

 

[davesparks]

Assuming that is the table that details all of the different switching and isolating devices and what they can/can't be used for then I know perfectly well what it says about the subject.

I still won't have MCBs installed as the only means of isolating a machine on my watch though.

 

[Spoon]

Assuming that is the table that details all of the different switching and isolating devices and what they can/can't be used for then I know perfectly well what it says about the subject.

I still won't have MCBs installed as the only means of isolating a machine on my watch though.

Yes mate, that the one.
Fare comment, but for 3 meters of SWA cable then I'm saying it can be used. (within reason)

 

[davesparks]

The length and type of cable is irrelevant!
An mcb is a protective device, an isolator is a means of isolation.

 

[Spoon]

The length and type of cable is irrelevant!
An mcb is a protective device, an isolator is a means of isolation.

What Im saying is that it can be used as an isolator. It all depends on other factors if you want an additional isolator in the circuit nearer to the equipment its feeding.

 

[Darkwood]

For maintenance purposes having a separate isolator that can e locked off in case of fault or servicing on the machine... you can't have a service engineer coming to replace, repair mechanical parts of the drill then be expected to remove the cover of the DB to remove the cable from the mcb... switching off would not be adequate isolation on its own .... if their was a safety protocol in place where the DB was always padlocked and under control of 1 person only then possible argument but really not a situe' to be in in the first place.

Isolator on the wall adjacent to the drill is the common standard practice and allows for correct lockable isolation to any trade that needs to isolate the drill without the need for them to Electrically trained.

 

[davesparks]

What Im saying is that it can be used as an isolator. It all depends on other factors if you want an additional isolator in the circuit nearer to the equipment its feeding.

I never said it can't be used as an isolator.

I said it would not happen on my watch!