Speedy Jim wrote:
wrote:
This is what I got from the NEC handbook 2005 (Article 220, table
220.55):
"..the branch-circuit load for a counter-mounted cooking unit and not
more than two wall-mounted ovens, all supplied from a single
branch-circuit and located in the same room, shall be calculated by
adding the nameplate rating of the individual appliances and treating
this total as equivalent to one range."
The handbook also explains (has a picture 210.21) how to pick tap
conductors when installing oven and cooktop on the same circuit under
210.19(A)(3) Exception No. 1.
Table 220.55 lists the max demand for a 12KW range as 8kW (derating it
assuming the range is not used to its full capacity).
The handbook has an example that shows how to get a combined rating for
multiple appliances. In my case, the cooktop is rated at 9.6kW, and the
oven is at 7.2kW. According to their formula, my combined maximum load
is 10.4kW which requires 43.3 amps.
Is anybody familiar with all this? According to this rule, shouldn't I
be able connect the cooktop and the oven to the same circuit (60 amp)?
Thanks.
Matt
Yes, I would agree with your summary.
Note that the branch circuit is limited to a max of 50 Amp rating,
so you would replace the 60A breaker with a 50A unit.
On a side note, if the raceway will be used as the equip ground
(raceway does not contain a grounding conductor), I would
verify the integrity of the raceway connections (fittings)
to perform as an effective grounding means.
Jim
I havn't looked at this stuff since about 1903 but my reading of the
code is:
210.19A3 requires the circuit for a range to be at least the rating of
the range and/or cooktop
however
422.10A allows the branch circuit for household cooking units to be
sized from 220.55
220.55-table-note 4 allows combining the KVA values and treating as a
single unit
220.55-table-note 1 the value that can be used for your units is
8KW +(5x5%) = 10KW = 41.7A @ 240V
(this is different from the value you came up with but still a 50A circuit)
210.19A3-exception 1 allows tap conductors to your cooktop to be rated
20 amps (or larger) if
the circuit they are tapped from is protected at 50 amps
and tap conductors are large enough for cooktop
and the tap is only as long as it needs to be
(this requires you to reduce the 60A circuit to 50A as noted in Jim's post)
422.30 requires a disconnect for the units
422.31 allows a circuit breaker to be used as the disconnect but only if
in sight of the appliances or if equipped with a device to lock it open
(not likely in your case)
422.33A allows an accessible plug and receptacle to be used as the
disconnect (that is one reason ranges are commonly connected with plugs)
422.33B allows a plug and receptacle to be used as disconnect for a
range if it can be reached by removing a drawer
422.16B3 allows wall mounted ovens and cooktops to be cord and plug
connected if the plug and receptacle are rated for the temperature they
are exposed to
210.21 allows a receptacle to be sized acording to 220.55 (instead the
unit KVA size)
(Presumably you need to figure out a disconnecting means - I don't know
what is common for hardwired units. Good question for the inspector.)
bud--