I heard that Smoke Detectors are not allowed on these circuits. If this is true, what is the rationale behind it?
In the Canadian Electrical Code, Part I - 19th edition (2002 issue)the following will be added to Section 26.
(f)	Branch circuits that supply receptacles installed in sleeping facilities of a dwelling unit shall be protected by an arc-fault circuit interrupter; and
(g)	For the purpose of Paragraph (f), an arc-fault interrupter means a device intended to provide protection from the effects of arc-faults by recognizing characteristics unique to arcing and functioning to de-energize the circuit when an arc-fault is detected.
A smoke alarm shall be supplied from a lighting circuit, or from a circuit that supplies a mix of lighting and receptacles, and in any case shall not be installed where prohibited by Rule 26-704; or protected by a GFCI or AFCI.
The requirement for AFCI protection is for the circuit supplying receptacles in bedrooms – thus AFCI breakers will typically be installed in the panelboard. It is important to stress that smoke detectors may not be connected to a circuit fed from an AFCI breaker. Smoke detectors may be connected to a lighting circuit, or a combination lighting / receptacle as long as the receptacles are not in bedrooms requiring an AFCI (e.g. bathroom circuit ahead of the GFCI)
Thanks for your response. I am still trying to figure out how I personally feel about having the Smoke Detectors on a Bedroom AFCI circuit. I was just wondering if you had any compelling arguments either way.
I heard today that it will be up to the individual Electrician where I am. The local Inspection Agencies will not enforce the 2002 NEC requirement that smoke detectors in a bedroom must be on a AFCI protected circuit.
In Ontario, AFCI breakers will not be required retroactively, even if the service is upgraded. They would however be required for an addition containing a bedroom.
I am installing a set of 4 (phase A, B, C & Neutral) in a 4" PVC conduit, 6 times, for a 2000amp service.
How would you handle the length issue in this installation? Cut all the same length, based on the longest, and loop where needed?
What method is best to help train this wire? Has anyone used that new device that fits on a ratchet? I saw one at a trade show, looked like a good idea.
The shorter the length of wire and the higher the load, the more critical the length becomes. I normally lay the conductors out and cut them all the same length before installing them. Finding space for the excess wire is sometimes a problem.
If you look at your installation and assume 4 sets of 600 kcmil with a calculated load of 1680 amps and multiple service disconnects and cable lengths of 20', 21', 22' and 23', we will find that the two shortest cables will be carryign more than there rated 75 degree ampacity. The 21' would be at 452, the 21' at 428, the 22' at 409 and the 23' at 391 amps. The rated ampacity of 600 kcmil is 420 amps.
It is important to get them close, but reality says that there will be some difference because all of the conduits don't enter the service equipment in the same place. I can't speak for the ratchet device. I've always used a hydraulic wire bender.
I used to have a problem from a class that I took that showed in theory how important it is to have the conductors the same length.
I need to find out how inspectors are treating this rule that all conductors need to be the same length. Is there any standard percentage length difference that they allow?
I find that if there is a 10% difference in length between two conductors, there is approximately a 10% difference in the current through each conductor, with the shorter conductor carrying the larger portion of the current.
Also, do inspectors look at the whole installation as to how important it is for conductor length to be exactly the same.
For example, if you have 2 parallel - 1/0 conductors, 75C rated 150A feeding a 300A load. If there is any difference in length between the conductors, the shorter conductor would exceed it's ampacity rating.
But, if those same two conductors are feeding a 250A load, the ampacity of the shorter conductor is not exceed until it there is over a 30% difference in wire length.
i am a canadian electrician and was taught this many moons ago,but if i have time i will look through the code book to see if i can locate this rule.
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