RCD requirements
RCD requirements
For a "tiny home" that's plugged in (16 or 32A supply), does the "minimum of two RCD" requirement apply in a transportable if there is more than one final subcircuit? (2.6.2.4(b)(ii) )
Re: RCD requirements
Yes.
Being a 'tiny home' it's domestic; so RCD is required as per 2.6.3.1.
Domestic is a sub-set of Residential.
Being plugged in, it's a connectable installation, so must also comply with "3001";
so now RCD is required for all FSs ( not just as per 2.6.3).
2.6.2.4 (a) is universal (where RCDs are required).
and 2.6.2.4 (b) applies to residential (again where RCDs are required).
Often with CIs there's only one final subcircuit (as defined), all off the one RCBO.
But if, for some reason, the protection is configured as RCCB upstream of mcbs, then there will be 2 subcircuits so needs 2 RCDs.
Being a 'tiny home' it's domestic; so RCD is required as per 2.6.3.1.
Domestic is a sub-set of Residential.
Being plugged in, it's a connectable installation, so must also comply with "3001";
so now RCD is required for all FSs ( not just as per 2.6.3).
2.6.2.4 (a) is universal (where RCDs are required).
and 2.6.2.4 (b) applies to residential (again where RCDs are required).
Often with CIs there's only one final subcircuit (as defined), all off the one RCBO.
But if, for some reason, the protection is configured as RCCB upstream of mcbs, then there will be 2 subcircuits so needs 2 RCDs.
Re: RCD requirements
Thanks Alec. Good point about all FSCs requiring RCD protection. So that would also cover ovens etc which normally wouldn't need one.
Great that we can always rely on you to cover all aspects of a question!
Great that we can always rely on you to cover all aspects of a question!
Re: RCD requirements
Is the CI considered its own installation? Otherwise could you consider upstream RCDs in the installation to contribute towards the minimum of two per installation when 2 or more FSCs?
Re: RCD requirements
A CI is dealt with as being complete by itself.
The fact that there may be an RCD in the installation that the CI plugs into can't be taken into account;
because there's no control over whether or not that's actually the case.
True ESR 60 requires both caravan parks and other sites to comply with site supply rules of the relevant Standards; which all require RCD for any supply intended for use by CIs. But that only covers new work, and only where the socket is installed with intent that the socket be used to supply a CI. There are legacy sites that pre-date these requirements, and there is no way to prevent people plugging CIs into sockets that don't have RCD.
Looked at from the fixed installation, an electrical installation stops at a socket outlet, and anything that is plugged in is excluded from being part of the installation by definition.
For fixed wiring, we have 3 clear and mutually-exclusive groups of "fittings" that are assembled together; all defined in the Act:
- "works"
- "installations"
- "appliances".
There's also generation, which is generally upstream of 'works", but in some cases is part of an installation.
A CI is yet another sort of assembly-of-fittings, which fits into none of these categories but has aspects of several of them.
The fact the definition of an "electrical installation" specifically excludes "appliances" (directly connected or plugged in), while the "CI" definition specifically includes both; shows that a CI is not a subset of "electrical installation" but a separate & different thing.
Determining whether a particular assembly of fittings is a CI or not requires looking at the definition in the Act, the additional detail in ESR 7 (which limits it to external supply at SLV), and then the scope of "3001", which specifies (among other things) detachable connection (ie it plugs in).
And even then it's not always possible to make a clear and indisputable distinction. Due to the very wide definition of "vehicle"; lots of mobile plant would fit the definition of CI - but can instead be treated as an appliance.
What IS clear is that once a decision has been made to treat the assembly as a CI; ESR 60 requires compliance with not only "3000" but also "3001".
The fact that there may be an RCD in the installation that the CI plugs into can't be taken into account;
because there's no control over whether or not that's actually the case.
True ESR 60 requires both caravan parks and other sites to comply with site supply rules of the relevant Standards; which all require RCD for any supply intended for use by CIs. But that only covers new work, and only where the socket is installed with intent that the socket be used to supply a CI. There are legacy sites that pre-date these requirements, and there is no way to prevent people plugging CIs into sockets that don't have RCD.
Looked at from the fixed installation, an electrical installation stops at a socket outlet, and anything that is plugged in is excluded from being part of the installation by definition.
For fixed wiring, we have 3 clear and mutually-exclusive groups of "fittings" that are assembled together; all defined in the Act:
- "works"
- "installations"
- "appliances".
There's also generation, which is generally upstream of 'works", but in some cases is part of an installation.
A CI is yet another sort of assembly-of-fittings, which fits into none of these categories but has aspects of several of them.
The fact the definition of an "electrical installation" specifically excludes "appliances" (directly connected or plugged in), while the "CI" definition specifically includes both; shows that a CI is not a subset of "electrical installation" but a separate & different thing.
Determining whether a particular assembly of fittings is a CI or not requires looking at the definition in the Act, the additional detail in ESR 7 (which limits it to external supply at SLV), and then the scope of "3001", which specifies (among other things) detachable connection (ie it plugs in).
And even then it's not always possible to make a clear and indisputable distinction. Due to the very wide definition of "vehicle"; lots of mobile plant would fit the definition of CI - but can instead be treated as an appliance.
What IS clear is that once a decision has been made to treat the assembly as a CI; ESR 60 requires compliance with not only "3000" but also "3001".
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Re: RCD requirements
Further question, is a CI considered a residential installation? I would assume not unless it was a sleepout or something designed for such purpose and if it's not, like simply an office, 2.6.2.4 (b) wouldn't apply? Because 2.6.2.4 (b) applies only to "in a residential installation"
Obviously the above post specifies "tiny home" so safe to assume 2.6.2.4 (b) applies but obviously many types of CIs so would depend on the type and intended purpose
Obviously the above post specifies "tiny home" so safe to assume 2.6.2.4 (b) applies but obviously many types of CIs so would depend on the type and intended purpose
Re: RCD requirements
Agree it can't be taken as read that a CI will be domestic, or even residential.
However there are very few rules that change based on this distinction.
RCDs are one that would - but the the complexity of RCDs under 2.6.3 of "3000" is replaced by the simplicity of RCD for all final subcircuits under "3001" , "6115", & "3004".
However there are very few rules that change based on this distinction.
RCDs are one that would - but the the complexity of RCDs under 2.6.3 of "3000" is replaced by the simplicity of RCD for all final subcircuits under "3001" , "6115", & "3004".
Re: RCD requirements
My main purpose for the question above is if the limitation of 3 FSCs per RCD would apply and I understand in most cases it would never be an issue due to CIs usually being fairly small in nature but just curious from a technical point of view
Also the requirements of a minimum of two RCDs, in a non-residential CI, 2.6.2.4 (Ii) (b) would not apply and one RCD could be suitable for multiple FSCs
Also the requirements of a minimum of two RCDs, in a non-residential CI, 2.6.2.4 (Ii) (b) would not apply and one RCD could be suitable for multiple FSCs
Re: RCD requirements
I believe most people would accept a typical caravan or motorhome as being domestic; on the grounds that people live in it.
That is consistent with the apparent intent of the requirements; and I don't think anyone would argue that following the "residential" rules WRT RCDs would result in a non-compliant installation.
So your question really is, in the event that the particular CI had multiple subcircuits, would it be non-compliant to install only one RCD.
The answer depends on the exact configuration and the type of RCD.
Definition of "final subcircuit" [1.4.88] says it starts at the N-bar and at the load terminals of the circuit protective devices.
This is usually taken to mean the overcurrent devices; which provide over-current (overload & short-circuit) protection; and are required for every FS.
Other devices, such as RCDs & AFDDs, are not always present; so it would be stretching things to argue that the origin of the FS is the load terminals of an RCCB upstream of a group of mcbs. So if there's a RCCB upstream of several mcbs, then there are multiple FSs - as many as there are mcbs.
And therefore, being residential, all parts of 2.6.2.4 apply, and a minimum of 2 RCDs must be installed.
It's common for older caravans that have N-E links (and no RCD) to have several FSs.
Sometimes when upgraded they are fitted with an RCCB upstream, which is non-compliant as there should be at least) two RCDs.
Another common configuration is where instead of an RCCB an RCBO has been used upstream of the mcbs / fuses for the FSs.
This configuration seems almost identical; but the rules apply very differently.
That's because we can now consider it as being either multiple FSs origination at the mcbs / fuses; or one FS originating at the upstream RCBO
- which is after all just as much a 'circuit protection device" as the downstream over-current-only devices.
So when installing an upstream RCD; the choice of RCCB vs RCBO makes a big difference.
Both these configurations, one perfectly fine and the other non-compliant, are commonly found when carrying out WoEF assessments.
But even though the RCCB version is non-compliant work; these rules are not part of the assessment for WoEF, so can't decline to issue WoEF on those grounds.
However generally the installers have failed to ensure that current limitation has been provided for the supply lead & associated fittings; as the RCCB can't provide it and the mcbs / fuses generally add up to more than 16 A.
Swapping RCCB to 16A RCBO solves both issues - and only an ESC required.
Others try to save the cost of the RCBO by altering the configuration of the mcbs;
but the alteration requires a CoC - and any config that still has multiple FSs remains non-compliant.
That is consistent with the apparent intent of the requirements; and I don't think anyone would argue that following the "residential" rules WRT RCDs would result in a non-compliant installation.
So your question really is, in the event that the particular CI had multiple subcircuits, would it be non-compliant to install only one RCD.
The answer depends on the exact configuration and the type of RCD.
Definition of "final subcircuit" [1.4.88] says it starts at the N-bar and at the load terminals of the circuit protective devices.
This is usually taken to mean the overcurrent devices; which provide over-current (overload & short-circuit) protection; and are required for every FS.
Other devices, such as RCDs & AFDDs, are not always present; so it would be stretching things to argue that the origin of the FS is the load terminals of an RCCB upstream of a group of mcbs. So if there's a RCCB upstream of several mcbs, then there are multiple FSs - as many as there are mcbs.
And therefore, being residential, all parts of 2.6.2.4 apply, and a minimum of 2 RCDs must be installed.
It's common for older caravans that have N-E links (and no RCD) to have several FSs.
Sometimes when upgraded they are fitted with an RCCB upstream, which is non-compliant as there should be at least) two RCDs.
Another common configuration is where instead of an RCCB an RCBO has been used upstream of the mcbs / fuses for the FSs.
This configuration seems almost identical; but the rules apply very differently.
That's because we can now consider it as being either multiple FSs origination at the mcbs / fuses; or one FS originating at the upstream RCBO
- which is after all just as much a 'circuit protection device" as the downstream over-current-only devices.
So when installing an upstream RCD; the choice of RCCB vs RCBO makes a big difference.
Both these configurations, one perfectly fine and the other non-compliant, are commonly found when carrying out WoEF assessments.
But even though the RCCB version is non-compliant work; these rules are not part of the assessment for WoEF, so can't decline to issue WoEF on those grounds.
However generally the installers have failed to ensure that current limitation has been provided for the supply lead & associated fittings; as the RCCB can't provide it and the mcbs / fuses generally add up to more than 16 A.
Swapping RCCB to 16A RCBO solves both issues - and only an ESC required.
Others try to save the cost of the RCBO by altering the configuration of the mcbs;
but the alteration requires a CoC - and any config that still has multiple FSs remains non-compliant.
Re: RCD requirements
Ignore the label of tiny home. It depends on what the designer intended. If the designer of the electrical installation intended it to be a 'normal' installation then it is one. If the designer intended it to be a transportable installation, then it is one.
Re: RCD requirements
Agree the term "tiny home" has little meaning, other than indicating a residential purpose.
But designer's intent is equally useless.
Legally, if it meets the definition of "connectable installation"(in the Act) then it is one.
Meaning must comply with Part 2 & with 3001; and WoEF required before plugging into any supply.
There's a bit of "grey area" around mobile plant, which can be argued as better dealt with as an appliance;
but if people are living in it (or intend to) and it can be plugged in, there's no room for argument.
But designer's intent is equally useless.
Legally, if it meets the definition of "connectable installation"(in the Act) then it is one.
Meaning must comply with Part 2 & with 3001; and WoEF required before plugging into any supply.
There's a bit of "grey area" around mobile plant, which can be argued as better dealt with as an appliance;
but if people are living in it (or intend to) and it can be plugged in, there's no room for argument.