Does the term conduit/conduits include underground cable ducts?
I often hear people referencing ducts as different installation rules and they are often installed by landscaping contractors. Many people don't seem worried but as far as I'm aware they should meet all the relevant requirements of conduits seeing as I can't see a separate option for ducts and in saying this it's up to us to make sure they are suitable regardless who installs them before running cables through.
I believe they should still be HD (for cat A, MD for cat B), still have the relevant protection, depth of burial etcetc can anyone correct me otherwise or help point me in the right direction?
If this is the case then what's the point in light duty duct? Purposes outside of the scope of installations/3000? Works?
3.11 Underground Wiring Systems - Ducts
Re: 3.11 Underground Wiring Systems - Ducts
Duct is a term defined in "3000" [1.4.42].
Basically something intended to have cables drawn in.
Conduit is a form of wiring enclosure, and is generally part of a "wiring system"
refer 3.2 & Table 3.1.
The terms are not synonyms; but also not exclusive.
Conduits less than 75 mm cannot be ducts (by definition).
Conduits 75 mm & larger could be.
Similarly ducts could be manufactured to comply with "conduit" Standards.
Since your question is headed "underground wiring systems", I'll limit response to that context.
All underground ducts have the primary function as defined: installed to facilitate subsequent installation of cables.
Whether an (underground) duct needs to have any particular qualities depends on the nature of the cables installed.
There may of course be several different lots of cabling in a duct, and each must be considered on its own merits.
A wiring system is more than just the cable type; it's a combination of cable type and wiring enclosure (if any).
Underground wiring must be one of the wiring systems specified in Table 3.5; many if which include a specified type of wiring enclosure.
If the duct used is one of the types of wiring enclosure listed in columns 2 - 7, then the duct can be part of the wiring system for that cable;
and will have the resulting Category.
If the duct used is not one of the listed wiring enclosure types (eg light duty duct); then it can't count as the wiring enclosure for any of the permitted cable types. They would instead need to be treated as 'unenclosed'.
For some types of cable, that won't matter much. If they can be installed buried direct; then they can be installed in a duct of any sort.
However as 'unenclosed' cables, bedding requirements still apply; and also additional mechanical protection for Cat B systems.
Other cable types may require a complying wiring enclosure to be installed through the duct.
Installing duct is mostly about managing the timing of various aspects of a job.
Installing underground cables early may expose them to additional risk over an extended period.
However if care is taken when specifying the type of duct; it can not only allow installation of cables to be postponed, but may do double-duty as part of the final "wiring system".
Basically something intended to have cables drawn in.
Conduit is a form of wiring enclosure, and is generally part of a "wiring system"
refer 3.2 & Table 3.1.
The terms are not synonyms; but also not exclusive.
Conduits less than 75 mm cannot be ducts (by definition).
Conduits 75 mm & larger could be.
Similarly ducts could be manufactured to comply with "conduit" Standards.
Since your question is headed "underground wiring systems", I'll limit response to that context.
All underground ducts have the primary function as defined: installed to facilitate subsequent installation of cables.
Whether an (underground) duct needs to have any particular qualities depends on the nature of the cables installed.
There may of course be several different lots of cabling in a duct, and each must be considered on its own merits.
A wiring system is more than just the cable type; it's a combination of cable type and wiring enclosure (if any).
Underground wiring must be one of the wiring systems specified in Table 3.5; many if which include a specified type of wiring enclosure.
If the duct used is one of the types of wiring enclosure listed in columns 2 - 7, then the duct can be part of the wiring system for that cable;
and will have the resulting Category.
If the duct used is not one of the listed wiring enclosure types (eg light duty duct); then it can't count as the wiring enclosure for any of the permitted cable types. They would instead need to be treated as 'unenclosed'.
For some types of cable, that won't matter much. If they can be installed buried direct; then they can be installed in a duct of any sort.
However as 'unenclosed' cables, bedding requirements still apply; and also additional mechanical protection for Cat B systems.
Other cable types may require a complying wiring enclosure to be installed through the duct.
Installing duct is mostly about managing the timing of various aspects of a job.
Installing underground cables early may expose them to additional risk over an extended period.
However if care is taken when specifying the type of duct; it can not only allow installation of cables to be postponed, but may do double-duty as part of the final "wiring system".
Re: 3.11 Underground Wiring Systems - Ducts
Interesting
Just to be clear I was specifically curious about insulating ducts, much like iPlex and Marley's range
Just for clarification, would an HD duct be suitable as a cat A system? Or would the cables inside still be regarded as there own wiring system and be classed as unenclosed underground or was that more directed towards the light duty rating?
Just to be clear I was specifically curious about insulating ducts, much like iPlex and Marley's range
Just for clarification, would an HD duct be suitable as a cat A system? Or would the cables inside still be regarded as there own wiring system and be classed as unenclosed underground or was that more directed towards the light duty rating?
Re: 3.11 Underground Wiring Systems - Ducts
Depends in the basis of the claim of the duct being "HD".
I'm no expert on details of the manufacturing standards that apply; but I see no reason a duct (ie > 75 mm) could not be manufactured to comply with a conduit Standard. In which case I'm sure that fact would be clearly marked on it - as either MD or HD.
And assuming such a product exists; it would certainly qualify as one of the enclosures permitted by Table 3.5:
(Col 2: HD conduit, Col 3 MD conduit, or Col 7 MD encased in concrete.
Marley's 'power duct' brochure states that (most of) it is manufactured to AS/NZS 61386, which is one of two Standards accepted for conduits used as wiring enclosures under 3.10.2.1 (a).
On that basis, I would have no hesitation in using it as a wiring enclosure for purposes of 3.11; if any of the cables to be installed within needed one to get the Cat rating.
Eg TPS within HD duct / conduit would get Cat A (Col 2); or in MD duct / conduit would be Cat B (Col 7).
N/S (u/g) cable in same duct would be Cat A even without the duct, and adding the duct (of any duty rating) doesn't alter that fact.
Need to be careful of making assumptions based on a quick read of a brochure.
Seems not all of Marley's 'powerduct' is to "61386". There's a range of "non-rated duty" that's marked by an asterisk; and when you follow through to the relevant Notes you find it's made to AS/NZS 1260 instead. Which would be OK for duct-only purposes but wouldn't contribute to achieving category for clause 3.11.
But product to "61386" will be clearly marked accordingly.
One draw-back from drawing multiple cables through a duct is you may then need to apply de-rating factor for grouping, as per "3008.1.2".
I'm no expert on details of the manufacturing standards that apply; but I see no reason a duct (ie > 75 mm) could not be manufactured to comply with a conduit Standard. In which case I'm sure that fact would be clearly marked on it - as either MD or HD.
And assuming such a product exists; it would certainly qualify as one of the enclosures permitted by Table 3.5:
(Col 2: HD conduit, Col 3 MD conduit, or Col 7 MD encased in concrete.
Marley's 'power duct' brochure states that (most of) it is manufactured to AS/NZS 61386, which is one of two Standards accepted for conduits used as wiring enclosures under 3.10.2.1 (a).
On that basis, I would have no hesitation in using it as a wiring enclosure for purposes of 3.11; if any of the cables to be installed within needed one to get the Cat rating.
Eg TPS within HD duct / conduit would get Cat A (Col 2); or in MD duct / conduit would be Cat B (Col 7).
N/S (u/g) cable in same duct would be Cat A even without the duct, and adding the duct (of any duty rating) doesn't alter that fact.
Need to be careful of making assumptions based on a quick read of a brochure.
Seems not all of Marley's 'powerduct' is to "61386". There's a range of "non-rated duty" that's marked by an asterisk; and when you follow through to the relevant Notes you find it's made to AS/NZS 1260 instead. Which would be OK for duct-only purposes but wouldn't contribute to achieving category for clause 3.11.
But product to "61386" will be clearly marked accordingly.
One draw-back from drawing multiple cables through a duct is you may then need to apply de-rating factor for grouping, as per "3008.1.2".