Contravening Regulations

[mikilianis]

I attach a few images one is of a contacter supplying a heating circuit apart from being able to touch the conductive metallic parts with a standard finger the supply voltage is connected to the lower terminals. The other image is of a fused supply again it can be touched with the standard finger also the live side is the lower terminals, Is this contravening the regulations SANS 10142-1

[AndyD]

I would say it's not a contravention for 2 reasons, firstly it's a control panel so SANS10142 (and the COC) is only applicable for the supply cable up to and including the point of isolation. Secondly the components that you indicate as insufficient IP ratings are mounted in an enclosure which has its own IP rating and requires a 'tool' to open it (assuming it hasn't been altered by vent holes being drilled for example). Therefore these components would be considered the same IP rating as the enclosure.

[Sparks]

Spot on Andy, another thing is that a 2nd, different, "tool" is required to remove the inner cover to expose the wires.

[bergie]

besides the enclosure ,a contactor can be connected load/supply top or bottom. would be wise to label load/supply on fuses. circuit breakers can also be reverse fed,if the manufacturer ok,s it and load/supply must be labelled.

[murdock]

my concern would be the thin wires connected to a 200 amp fuse...

unfortunately not know all the details about the installation...i would only be assuming things

the first thing i would be checking is the fault level to verify the cables can handle the fault level at the panel....this panel could be mounted close to a 1600 kva transfomer.

the other thing which concerns me is the fact that there are multiple cables coming off the top and bottom of the fuse holder...i can only assume that there is some type of isolator within arms reach.

the panels i have worked on which are imported from germany all have protective covers over all exposed conductive live parts even if the panel has to be opened with a key...but here in sa...this is not the case...it is just good practise to cover it...especially if it on the incoming side.

the other part which we dont see is there could be an isolator which is feeding these panels which cannot be opened unless the isolator is switched in the off position...which means that all these exposed conductors will be dead when the panel door is open...i have noticed the new isolators i have been working with dont have the hole anymore to bypass the unlock isolate feature...so you have to isolate before you can open the panel

[AndyD]

I would certainly agree there may be issues with the panel that should be addressed but none of them would fall under a SANS10142-1 or a COC if the circuit supplying the panel has a t/pole isolator. This panel is fairly typical of the locally built HVACR panels and further comment from me without more photos and info would be speculation.

[bergie]

what difference would the wire size make with the fault level?

[murdock]

fault level and wire size...now this is an interesting topic...you need to do your fault level calculation at the point where the cable is to be connected then only can you determine whether or not it is capable of carrying the fault...an example i installed a 200 kw motor with a soft start...i could have used 2 x 70 mm ecc cables according to my cable size calculations ...but because of the fault level at the point of connection was higher than normal because of the transfomer feeding the panel and the distance ...i had to use a 185 mm cable...aberdaire cables has a booklet which explains this in more detail...i think this is one of the least understood parts of electrical installations...in fact at the time i had another contractor who has installed a couple of panels already on the same site to the left of the transfomer but just as close...and he used 2 x 70 mm cables...i know my installation is correctly designed and installed i have all the documentation to prove it..so i sleep well at night...

[adrianh]

with a standard finger

What does this term mean?

[AndyD]

with a standard finger

What does this term mean?

[bergie]

fault level and wire size...now this is an interesting topic...you need to do your fault level calculation at the point where the cable is to be connected then only can you determine whether or not it is capable of carrying the fault...an example i installed a 200 kw motor with a soft start...i could have used 2 x 70 mm ecc cables according to my cable size calculations ...but because of the fault level at the point of connection was higher than normal because of the transfomer feeding the panel and the distance ...i had to use a 185 mm cable...aberdaire cables has a booklet which explains this in more detail...i think this is one of the least understood parts of electrical installations...in fact at the time i had another contractor who has installed a couple of panels already on the same site to the left of the transfomer but just as close...and he used 2 x 70 mm cables...i know my installation is correctly designed and installed i have all the documentation to prove it..so i sleep well at night...

mmm,makes sense,but what if you order pre wired panels?

[Justloadit]

Another way of looking at the fault level. If the cable you have used is too small, and there is a short circuit at the most furtherest point in the cable from the supply, the cable may act as a resistor, where the current flowing in the cable may not trip the main breaker. This in turn causes the cable to act like a wire wound heater, and start glowing red hot, which could cause a fire hazard. A good example is to take a 1 meter length of 5 amp wire, and short your car battery with it, ensure you have protective gloves, as you will see the wire get so hot, that the plastic cover on the wire melts off. Continuation of the short will make the wire glow red hot.

Sizing the wire to be able to take the fault current for the main breaker to trip, will force the breaker to trip because of the over current.

[bergie]

i,m presuming the wires are rated for there overload protection. for example the panel has a 60 amp breaker, 16mm wire to a 20 amp breaker feeding a 2,5mm wire,etc if the fault current is 1000 amps ,must we wire the panel with 1000 amp wire?

[AndyD]

The size of the cable doesn't get larger necessarily if the potential short circuit current is higher. If anything it might go the other way where multiple smaller cables are used to limit the short circuit fault current. Short circuit currents damage the device that disconnects the power, as the contacts separate there is much arcing and heat which can cause irreparable damage or even an explosion in extreme cases. Circuit breakers must be specified to handle the potential short circuit current of that particular circuit. The PSCC rating of a breaker is given as an Ics value in kA usually.

[AndyD]

I had a scratch around for some light bedtime reading on PSCC. There's a lot of very involved articles and white papers around but you can start with this which is fairly entry level and it's in an easily downloadable format.