Hi All,
I was at a house the other day and needed power outside for a fixed wire appliance (heatpump) the distribution board was in the center of a 2 story house and was impossible to get there without making a complete mess. The meter board was outside next to the where they wanted the heatpump so I fed directly from there - since chatting with one of my other sparky mates he told me that it was probably illegal as isolating the main switch from that distribution board wouldn't actually kill the heatpump circuit which is within that building. I've seen this done so many times before and never really questioned it but now I am beginning to think and have only just moved back to residential from industrial control.
I fed from the outgoing side of the 63A fuse, the same point that was feeding the main distribution board. I then put that through a 20AMCB (Labelled Heatpump) and then into my isolator. The MEN is at the meter board. At the main distribution board I label printed a note something along the lines of "HEATPUMP IS FED DIRECTLY FROM MCB IN METER BOARD ENSURE CIRCUIT IS ISOLATED BEFORE CONDUCTING ANY WORKS" as obviously if someone hits that main switch it won't actually isolate the heatpump circuit.
Thoughts?
Installing MCB at Meter board
Re: Installing MCB at Meter board
If the MEN is at the "meter board", and there's a main switch there as well, and there is a neutral bar and an earth connection, and the main earth conductor is connected to that earth connection, and there is outgoing circuit protective devices (you said 63A fuse for the other switchboard) - then that is the main switchboard, not just a "meter board".
So what you have done is probably fine.
A "meter board" wouldn't have all those things I listed. It may have a fuse, it might have a connection for the neutrals (and the meter neutral) and if the box is metal, it will be earthed - but without the main switch, neutral bar, MEN link and main earth conductor from the electrode, it isn't the main switchboard (it's not a switchboard at all).
So what you have done is probably fine.
A "meter board" wouldn't have all those things I listed. It may have a fuse, it might have a connection for the neutrals (and the meter neutral) and if the box is metal, it will be earthed - but without the main switch, neutral bar, MEN link and main earth conductor from the electrode, it isn't the main switchboard (it's not a switchboard at all).
Re: Installing MCB at Meter board
I agree that IF the metering is at the "main switchboard"; then it's OK to add a new final subcircuit fed from that switchboard.
Also that the key to whether it's a "switchboard" (as defined) is the presence of one or more circuit protection devices for submains and/or final subcircuits.
Clearly there's a circuit protective device, so the question is whether it's protecting either submains or final subcircuits.
It's true that If it's a switchboard, then as the switchboard closest to supply it mist be the "main switchboard", and therefore several other fittings must be located there, ie the main switch(es) main N-bar, main e-bar, MEN link, and the origin of the MEC to the earth electrode.
If the presence or absence of these fittings may be relevant, and certainly affects whether the installation is compliant; it doesn't affect the fundamental question of whether the assembly of fittings meets the definition of "switchboard".
In particular, the presence of an isolating switch upstream of meters makes no difference either; in most cases it's simply a means of isolating the meters when working on them. And that's also the most common reason for a 63A fuse being located upstream of the meters.
For the existing installation, whether it's a "switchboard" comes down to simply whether the 63A fuse that's there is protecting submains (it won't be a final subcircuit). If it's portection only part of the installation, with other device(s) protecting the rest; then reasonable to look at it as protecting a submain.
But it's probably 'protecting' the entire installation, and if so then it's much more likely to be 'protecting' mains - and therefore not a switchboard but just an 'extra' fitting that was required by the local network . In which case the "mains" continue on downstream of the meters all the way to the "main switch" & main N-bar" at the switchboard - and connecting anything to them, other than a revenue meter, would be "mains work" requiring inspection.
By adding a final subcircuit; the assembly of fittings is clearly now a switchboard, regardless of whether or not it already was.
As closest swbd to supply (ie providing the greatest level of control of the installation as per ESR 4) it is the main switchboard - and all those other things will have to be located there (if they aren't already).
It's possible - but not very likely - that it already complied as a switchboard. If it did, what you've done is probably OK.
But if not; then what you've done is far from OK.
A LOT more information needed to be sure; so suggest you find time to go back and check more thoroughly.
Also that the key to whether it's a "switchboard" (as defined) is the presence of one or more circuit protection devices for submains and/or final subcircuits.
Clearly there's a circuit protective device, so the question is whether it's protecting either submains or final subcircuits.
It's true that If it's a switchboard, then as the switchboard closest to supply it mist be the "main switchboard", and therefore several other fittings must be located there, ie the main switch(es) main N-bar, main e-bar, MEN link, and the origin of the MEC to the earth electrode.
If the presence or absence of these fittings may be relevant, and certainly affects whether the installation is compliant; it doesn't affect the fundamental question of whether the assembly of fittings meets the definition of "switchboard".
In particular, the presence of an isolating switch upstream of meters makes no difference either; in most cases it's simply a means of isolating the meters when working on them. And that's also the most common reason for a 63A fuse being located upstream of the meters.
For the existing installation, whether it's a "switchboard" comes down to simply whether the 63A fuse that's there is protecting submains (it won't be a final subcircuit). If it's portection only part of the installation, with other device(s) protecting the rest; then reasonable to look at it as protecting a submain.
But it's probably 'protecting' the entire installation, and if so then it's much more likely to be 'protecting' mains - and therefore not a switchboard but just an 'extra' fitting that was required by the local network . In which case the "mains" continue on downstream of the meters all the way to the "main switch" & main N-bar" at the switchboard - and connecting anything to them, other than a revenue meter, would be "mains work" requiring inspection.
By adding a final subcircuit; the assembly of fittings is clearly now a switchboard, regardless of whether or not it already was.
As closest swbd to supply (ie providing the greatest level of control of the installation as per ESR 4) it is the main switchboard - and all those other things will have to be located there (if they aren't already).
It's possible - but not very likely - that it already complied as a switchboard. If it did, what you've done is probably OK.
But if not; then what you've done is far from OK.
A LOT more information needed to be sure; so suggest you find time to go back and check more thoroughly.
Re: Installing MCB at Meter board
Elliot said that he fed the circuit breaker for his circuit from the load side of the fuse.
I would just assume that he's not an idiot, and that fuse is after the meter, not before it, so that might make it a protective device for a submain. (Normally though, his circuit breaker should have be connected to the line side, which would be somewhere on the load side of the main switch).
Along with the fact that there is a MEN link, so presumably there is a neutral bar. The earth connection point doesn't necessarily have to be a "bar", so presumably wherever the earth end of the MEN link goes, is the installation earthing point, with the submain earth and MEC etc connected - maybe.
So possibly the only thing that we are unsure of is the main switch? And whether that is before the meter or after the meter, probably doesn't make any difference in this case.
So yes, the only certainty is not enough information at this point to be sure
I would just assume that he's not an idiot, and that fuse is after the meter, not before it, so that might make it a protective device for a submain. (Normally though, his circuit breaker should have be connected to the line side, which would be somewhere on the load side of the main switch).
Along with the fact that there is a MEN link, so presumably there is a neutral bar. The earth connection point doesn't necessarily have to be a "bar", so presumably wherever the earth end of the MEN link goes, is the installation earthing point, with the submain earth and MEC etc connected - maybe.
So possibly the only thing that we are unsure of is the main switch? And whether that is before the meter or after the meter, probably doesn't make any difference in this case.
So yes, the only certainty is not enough information at this point to be sure
Re: Installing MCB at Meter board
Right I guess technically it's not just a meterboard (that just what we'd always referred the ones on the external of houses where the mains is fed into with meters), at this switchboard there is the mains coming from the road through the main switch > meter > fuse > submains feed.
The main earth connection/bar and main neutral bar are there with the MEN link. I am feeding my MCB off the load side of the fuse at the same point at which the internal distribution board is fed. I am happy what I did was electrically safe and that my circuit has the appropriate protection.
So I guess its whether or not the "meter board" I was working on was classed as the main switchboard or not to whether my connection was legal.
The main earth connection/bar and main neutral bar are there with the MEN link. I am feeding my MCB off the load side of the fuse at the same point at which the internal distribution board is fed. I am happy what I did was electrically safe and that my circuit has the appropriate protection.
So I guess its whether or not the "meter board" I was working on was classed as the main switchboard or not to whether my connection was legal.
Re: Installing MCB at Meter board
That's about the size of it.
Another thing about having MSB located at outdoor metering position, is that switchboards and especially main switches have to be readily accessible; whereas many enclosures intended for meters only need the lid / door screwed shut to prevent access to basic insulation.
Assuming your metering point is the MSB, then - as DougP said - your mcb feed would normally come from the line side rather than the load side of the fuse. However there is no rule against a submain (the output of the fuse) supplying more than one DB (the big one in the house, and another one consisting of just your new mcb. Not common in domestic, but very common in high-rise with tee-offs to switchboards on each floor.
And likewise there's no rule against a DB sharing an enclosure with the MSB; noting that all these terms are defined in terms of the fittings, and not in terms of structures or enclosures.
It can be tricky to work through; as there are a lot of variations, and a particular one may be common in one area but never seen in other areas.
And not all of them are kosher.
Equally there are many configurations that are perfectly OK but rarely encountered.
The only real problem with adopting a non-standard solution, especially one that isn't obvious, is that if it ever gets considered by EWRB they are likely to adopt a very conservative approach. So you need to be confident that you have ticked every box - and best to fully record and fully label so that your line of thinking is clear to anyone coming along later. Which might discourage them from lodging a complaint just because they don't like what you've done.
Last year a sparky was "convicted' by EWRB on exactly that point - he left a label on a DB that said "main switch" but didn't isolate everything in the outbuilding . There was / is no rule requiring a single point of isolation; and while there's a rule requiring actual main switches to be labelled as such, there's no rule prohibiting other switches (such as incoming supply isolators for DBs) from being mis-labelled as "main switch". But they found the label to be misleading.
So the obvious thing is that the DB inside the house probably has an isolating switch for the incoming supply (which if it's a DB it doesn't actually need); and that switch is almost certainly labelled "main switch" (which is incorrect for a DB - but very common). Your new warning label will help; but removing the "main sw" label from there and ensuring that the one it the outdoor MSB is correctly labelled would be better.
Another thing about having MSB located at outdoor metering position, is that switchboards and especially main switches have to be readily accessible; whereas many enclosures intended for meters only need the lid / door screwed shut to prevent access to basic insulation.
Assuming your metering point is the MSB, then - as DougP said - your mcb feed would normally come from the line side rather than the load side of the fuse. However there is no rule against a submain (the output of the fuse) supplying more than one DB (the big one in the house, and another one consisting of just your new mcb. Not common in domestic, but very common in high-rise with tee-offs to switchboards on each floor.
And likewise there's no rule against a DB sharing an enclosure with the MSB; noting that all these terms are defined in terms of the fittings, and not in terms of structures or enclosures.
It can be tricky to work through; as there are a lot of variations, and a particular one may be common in one area but never seen in other areas.
And not all of them are kosher.
Equally there are many configurations that are perfectly OK but rarely encountered.
The only real problem with adopting a non-standard solution, especially one that isn't obvious, is that if it ever gets considered by EWRB they are likely to adopt a very conservative approach. So you need to be confident that you have ticked every box - and best to fully record and fully label so that your line of thinking is clear to anyone coming along later. Which might discourage them from lodging a complaint just because they don't like what you've done.
Last year a sparky was "convicted' by EWRB on exactly that point - he left a label on a DB that said "main switch" but didn't isolate everything in the outbuilding . There was / is no rule requiring a single point of isolation; and while there's a rule requiring actual main switches to be labelled as such, there's no rule prohibiting other switches (such as incoming supply isolators for DBs) from being mis-labelled as "main switch". But they found the label to be misleading.
So the obvious thing is that the DB inside the house probably has an isolating switch for the incoming supply (which if it's a DB it doesn't actually need); and that switch is almost certainly labelled "main switch" (which is incorrect for a DB - but very common). Your new warning label will help; but removing the "main sw" label from there and ensuring that the one it the outdoor MSB is correctly labelled would be better.
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Re: Installing MCB at Meter board
And just one other point to consider. As Alec said, the main switch in the outdoor "main switchboard" must be readily accessible. But also, there can't be any primary insulation in the enclosure that is accessible without the use of a tool (to be "readily accessible").
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Re: Installing MCB at Meter board
Thanks Alec and Doug both for your very helpful and informative responses.
The outdoor "main switchboard" was not screwed shut and only had two plastic latches keeping it shut.
Yes you are right the isolator at the DB was labelled as main switch (as in many residential installations), upon looking at AS/NZS 3000 Figure 5.1 I am confident that the switchboard I used was in fact the main switchboard as similar arrangement. I am going to drop into the job and label the main switch as it is not done so.
The outdoor "main switchboard" was not screwed shut and only had two plastic latches keeping it shut.
Yes you are right the isolator at the DB was labelled as main switch (as in many residential installations), upon looking at AS/NZS 3000 Figure 5.1 I am confident that the switchboard I used was in fact the main switchboard as similar arrangement. I am going to drop into the job and label the main switch as it is not done so.
Re: Installing MCB at Meter board
Just to clarify about dB not needing a main isolation switch is that true for all dbs apart from DB in outbuilding that also
-has a maximum demand of 100 A or more per phase; and
- is provided with a switchboard.?
-has a maximum demand of 100 A or more per phase; and
- is provided with a switchboard.?
Re: Installing MCB at Meter board
2.3.4.1 (a) requires such outbuildings to be treated as separate installation; which therefore needs one or more "main switch(es).
2.3.4.1 (b) requires outbuildings (with or without switchboards) to have "an isolating switch or switches" that between them isolate everything on the outbuilding.
And 2.3.3.1 requires any alternative supply (eg genset) that is connected at a DB to have a "main switch".
Otherwise
- all main switches are at main switchboard; and
- all other DBs are not required to have isolators on incoming supplies.
2.3.4.1 (b) requires outbuildings (with or without switchboards) to have "an isolating switch or switches" that between them isolate everything on the outbuilding.
And 2.3.3.1 requires any alternative supply (eg genset) that is connected at a DB to have a "main switch".
Otherwise
- all main switches are at main switchboard; and
- all other DBs are not required to have isolators on incoming supplies.