We have had a number of inspectors ask about codes that apply to wires that cross the hot bus in panel-boards and whether or not this should be considered a defect or not.
We searched through the codes as well as manufacturer’s installation instructions we could not find anything specific with respect to wires and bus bars.
In section 2-304 of the Ontario Electrical Safety Codes we did find a vague reference that might apply.
In sub-section (1) of that code, is states “No repairs or alterations shall be carried out on any live equipment except where complete disconnection of the equipment is not feasible” and in section (3) of the same code it states “Adequate precautions, such as locks on circuit breakers or switches, warning notices, sentries, or other equally effective means, shall be taken to prevent electrical equipment from being electrically charged when work is being done”
How this applies to our opinion will be discussed later.
Throughout the various codes and installation instructions, there is a multitude of diagrams, drawings and images. In none of them could we find a diagram gives an indication of any wire of any type running across the bus.
Taking a look at an empty panel, we can see that there appears to be an adequate area for cable routing.
There is a distinct open space between the panelboard and the cabinet in which to run the cables connecting to breakers, neutral bars and ground bars.
If you look at panels that have two neutral bus bars on either side of the hot bus bars, the bonding jumper is routed away from the exposed hot bus bar even though this is a rigid bar.
We can find no reasoning, other than laziness as to why a wire of any sort would be routed across the hot bus bar.
We have reached out to a number of electricians and almost all have come back and said that this is not allowed when asked why not we get responses that range from the in-depth response to “it’s an unwritten rule”.
We’ve collated the in-depth responses and grouped them into what we, as inspectors see as three potential risk areas.
The risks are caused by routing either the ground (earth) wires over the hot bus bar, the grounded (neutral) wires over the hot bus bar and the hot wires over the bus bar.
Ground wires over the bus bar.
This is probably the most obvious, and as at least one electrician put it “are you nuts?”, risk. Ground wires are in most cases unsheathed conductors made of copper, tinned copper or aluminium, depending on the wiring. The ground is connected at one end of the branch circuit to the receptacle ground and onwards to the appliance ground (generally the bit people touch). The other end of it is connected to the panel and onward to ground (earth) via a bonding jumper to a grounding source. Imagine if you will a ground conductor in a branch wire touching the hot bus in an electrical panel. This applies a 120v charge to the conductor with a current rating limited only by the gauge of the conductor or the main disconnect whichever is the higher. Anything connected to either end of the ground wire now becomes hot. This includes the appliances plugged in, the panel and the grounded conductors which are joined to the ground at the panel.
If the connection between the ground conductor and the bus bar is solid, this errant energisation of the panel and appliance won’t last long as either the main-disconnect will trip or the dead short between hot and ground along the conductor will melt it. It would likely melt in the panel closest to the hot connection which is in the panelboard area causing untold damage to the panel. There goes another $1,200.
If the connection between the conductor and bus bar is intermittent (arcing or vibration) then there is a greater risk the main-disconnect will miss the short and the current will present a risk to either anyone touching the panel or using a grounded appliance. Sure the risk is small, but the same minimal risks are taken into account with the double tapping of neutral conductors under a single lug. The reasoning applying to one should apply to both.
Obviously, the risk could be minimised by sheathing the ground wire, but why go to the extent of doing this when routing the cable around the panel board is so much more sensible and present zero risk?
Our advice to inspectors? Ground wires should NEVER cross the hot bus bar.
Grounded wires over the bus bar.
Here’s where things take a turn for the peculiar. A ground wire (Neutral) is (or at least in a panel should be) a sheathed wire, so what the risk? Well, if the sheathing is damaged in any way, either during installation or over the lifetime of the installation then similar risks apply as a ground conductor crossing the bus with respect to the energising of the panel and errant current in the ground/grounded circuits.
However, because this is the return for current in an appliance should the compromised neutral touch the bus bar on the opposite side of the transformer split as the hot wire servicing a receptacle a 240v circuit can be established in the branch circuit. If this was an intermittent touch-down (arcing or vibration) appliance damage would likely ensue as a minimum. A more permanent connection would create at least appliance damage and at worst any of the above.
Our advice to inspectors? Grounded wires should NEVER cross the hot bus bar.
Hot wires over the bus bar.
This is the least obvious risk and also the least likely but it’s a risk nevertheless. If a hot wire with a damaged sheath crossing the bus touches down.
Most lay people would think that it a hot wire, so what if it’s touching the hot bus? Well as an inspector you know differently. There are, in a residential panel, two hot busses. Each one carrying one side of a split single-phase 240v a/c circuit. Depending upon which side of the split the wire touches there is the opportunity for either a dead short or an unprotected branch wire where the breaker that protects that conductor being circumnavigated.
Let us explain that a bit better.
Let’s assume that the two bus bars are called A and B and the hot wire is connected to a single pole breaker on bus A.
If the wire touches down on busbar B, then there is a dead short between busbar A and B running along the wire from the bus bar to the breaker. The likelihood is the breaker will trip and never allow itself to be reset.
If however, the wire touches down on busbar A what’s the problem? It’s the same side of the transformer split so it wouldn’t cause a problem with the circuit. EXCEPT the branch circuit would no longer be protected by the breaker, relying solely on the gauge of the wire or the main-disconnect for over-current protection.
In most cases there would probably never be an issue as rarely do we overload circuity in a home to the extent that the gauge of the wire is insufficient, do we?
The major concern here would be the fact that if the breaker was flipped off, the current could still flow through the branch wire because the hot was in contact with the bus bar, hence kicking in the Ontario Electrical Safety Code 2-304. The power could not effectively be shut-off from the branch circuit because the hot wire touching the bus bar was effectively circumventing the over-current and disconnect of the breaker.
Our advice to inspectors? Hot wires should NEVER cross the hot bus bar.
For those that need further information, no wires should ever cross the exposed hot bus bars of an electrical panel. There are wire channels down each side of a panel and along the end furthest away from the protected main disconnect. All wiring needed to cross the panel should be routed along these channels and NOT across the exposed bus. Ideally, the wiring should be routed externally to enter the panel at a location closest to the breaker avoiding the need for any cross panel wiring
These opinions and reasons came from Electricians. We understand the reasoning and would agree with their opinion.
Until such time as we are told otherwise by the ESA, who we have asked for an official opinion, If you, as an inspector, see any wires in a panel crossing a bus bar call it as a defect and refer a qualified electrician. These wires can be routed by a qualified electrician around the cable channels of the panel, with short wires being made longer by pig-tailing.
Sure you may get called a deal killer, but it’s better than being responsible for a real killing.
Just because you can, it doesn’t mean you should
As and when we hear from the ESA you will be the second to know. (We will be the first).