I have been getting conflicting information.
Scenario: I am installing recessed lights.
amps per light (75 watt divided by 120 volts = 0.625 amps)
80% rule to circuit loading = 12 amps
divide amps per light = 19 lamps
This seems like an awful lot on one circuit. Even using 100 watts per light
would put 15 lights on the circuit. I had read that 10-12 should be the
Opinions please. thank you.
You are both right but you are missing one point. When you install 14, 12 and
10 guage wire (the ones likely to have receptacles) the code builds in the 80%
safety factor in the breaker you are allowed to use. They know the installer
has no control over what the user will plug in.
Look at 310.16 and you see 14 ga copper is good for 20a but 240.4(D) limits the
breaker to 15a. There is your 80%. There are also rules about the size of any
single piece of plug connected equipment and that can be 80% or even 50% in the
case of a fixed in place unit. That uses the 240.4(D) breaker size.
There are also exceptions that could allow up to a 40a breaker on 14ga wire but
we don't need to kick that tar baby. ;-)
A 15a circuit has a capacity of 1800 watts, or 1440 watts for an 80% load.
1440 / 75 watts = 19 fixtures. But since most recessed cans will easily accept
a 150 w lamp with the appropriate trim, or no trim at all, some inspectors like
to see no more than 9.
Then there are full size cans which accept R-40 size lamps, (generally 150
watt) medium which accept up to R-30,(generally 75 watt) and small cans which
accept up to R-20.(generally 40-60 watt) Since any of these lamps are
available up to 150 watts (and there are par lamps of 250 watts as well) an
inspector who is a stickler for the rules may demand a 180 watt calculation per
can no matter what size it is. IME no inspector has balked at placing a few
more smaller cans on a circuit even if they are somewhat picky.
1500W of heat may be a inconvinient in the summer, consider fluorescent
that screw right in the same holder. They are more expensive but will pay
for themselves (if do not fail).
Screw in, built in ballast fluorescents turn on slowly though.
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