Is it to code to connect live wires to the bottom instead of the top of a disconnect switch?

[dmnichol]

I know it's not commonly done but is it acceptable according to the Canadian Electrical Code (or American Electrical Code) to connect live wires to the bottom instead of the top of a non-fused rotary disconnect switch (Socomec model 27003021; Link to website:

https://www.socomec.us/datasheet/27003021/

) inside a control cabinet if it is used a disconnecting means for that control cabinet and is door interlocked? This would make the routing of the cables into and out of the cabinet easier and cheaper. A finger guard would be installed on the bottom of the switch where the live wires are connected and I would put a sign on the outside of the cabinet door.

The only reference I could find in the 2021 version of the Canadian Electrical Code (CSA C22.1:21) was section 14-506 Connection of switches.

14-506 Connection of switches
Manual single-throw switches, circuit breakers, or magnetic switches shall be connected so that the
blades or moving contacts will be dead when the device is in the open position, except that the
following need not comply:
a) branch-circuit breakers that have all live parts other than terminals sealed and that are constructed
so that the line and load connections can be interchanged;
b) switchgear that is provided for sectionalizing purposes and has a suitable caution notice attached
to the assembly;
c) switches that are immersed in a liquid and have a suitable caution notice attached to the outside
of the enclosure;
d) switches that are designed so that all live parts are inaccessible when the device is in the open
position; and
e) magnetic switches, when preceded by a circuit breaker or manual switch that is located in the
same enclosure or immediately adjacent and is marked to indicate that it controls the circuit to the
magnetic switch, unless this is obvious.

I think condition d) applies to this situation as all the live parts are inaccessible when the device is in the open position.

Thanks in advance

 

[waross]

After over 50 years in the trade, my first reaction is:
"Try harder."
The origin of the "In at the top, out at the bottom" convention may be interesting.
When the code was first developed, knife switches were common.
Several rules were developed pertaining to knife switches:

14-502 Mounting of knife switches
(1) Single-throw knife switches shall be mounted with their bases in a vertical plane.
(2) Single-throw knife switches shall be mounted so that gravity will not tend to close them.

(There are some exceptions for double throw switches.)
This led to the universal convention that disconnect switches are always fed at the top.
Interestingly, a similar rule in the NEC is interpreted differently.
In Canada, residential breaker panels are often mounted horizontally.
Under the NEC, residential panels must not be mounted horizontally.
Rule (2) "Single-throw knife switches shall be mounted so that gravity will not tend to close them", is applied to the circuit breakers and the top row of breakers are moved downward to close the breaker.
Electricians will expect the disconnect to be fed from the top.
But the final word will be from the AHJ.
I suggest a query to the local Authority Having Jurisdiction.

And as a side note, I have just finished installing a 100 Amp generator transfer switch.
It utilizes two knife type disconnect switches.
The fast, cheap way to manufacture the switch would be to mount the disconnects back to back, one up and one down.
However the manufacturer chose to follow the two rules, even though it meant a larger enclosure, jumper cables, and a more elaborate and expensive mechanical interlock.
(Not all transfer switches are built this way.)


--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[mparenteau]

I would say convention is to wire the disconnect such that when the switch is opened, the knife side of the switch is de-energized (switch base side is hot, knife side not). I'm not sure voltage separation/clearances can be maintained if the switch is opened as the knives will be energized so the question is, "how close are the knives to the enclosure?" Can you do it? Possibly. But as waross mentioned, check w/ your AHJ.

Mike

 

[che12345]

Mr. dmnichol (Electrical)(OP)27 Jun 23 16:48
"....I know it's not commonly done but is it acceptable according to the Canadian Electrical Code (or American Electrical Code) to connect live wires to the bottom instead of the top of a non-fused rotary disconnect switch (Socomec model 27003021; Link to website:

https://www.socomec.us/datasheet/27003021/

) inside a control cabinet if it is used a disconnecting means for that control cabinet and is door interlocked?...."
I look at it this way, for your consideration:
1. Besides the cable connection terminals, all other electrical parts are enclosed. Therefore, the blades shall be dead on open position is irrelevant.
2. The terminals are NOT marked "Incoming" and "Outgoing" . That is, there is no change in the ratings, irrespective of the direction of the current flow, i.e. down/up or L-R/R-L.
3. "A finger guard would be installed on the bottom of the switch where the live wires are connected and I would put a sign on the outside of the cabinet door" is certainly strongly recommended.
3.1 I would strongly recommend to add warning sign "DANGER LIFE INCOMING
ISOLATE ELSEWHERE FOR SAFTY..... to be placed at the incoming terminals.
Che Kuan Yau (Singapore)






r

 

[waross]

Good advice Mr. Che.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[jraef]

It matters on FUSED disconnects, because the fuse holders are on the bottom, so if you feed from the bottom, you cannot kill power to the fuses when you have to replace them.

But IMHO non-fused is not an issue if the condition d. is applicable (the entire switch assembly was enclosed). In know that was the case on the Siemens VB-II non-fused disconnect switches, they even said in the installation manual that they could be fed either way, because their blades break the circuit in two places by rotating in between two slots, so the moving blades are never hot when open, no matter which direction the line power is coming from.


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