jar546
CBO
This is a situation that I would like to get a discussion going on. It is residential, so hopefully we will get more participation. This is an educational discussion.
A service disconnect is located in the garage on a wall that separates the garage from the interior and fed from underground. The meter is on the outside of the building on an exterior wall. No problems with this existing installation at all, even by today's standards as the conduit feeding the service conductors to the disconnect inside are underground and come right up into the panel. OK, no discussion for this part needed.
Here is the rub. Due to a need for a new circuit outside, the exterior service will be rebuilt and add a new service disconnect on a combo-pack. This will then force the interior panel to become a sub-feed and they will have to ensure separated grounds and neutrals along with ensuring they have a proper equipment grounding conductor run to the inside panel.
Now that the interior panel that was the service disconnect and main panel is a sub-panel it created a problem. You see, prior to 1996 you could run SE cable to a range as long as it comes directly from a service panel where the grounds and neutrals are tied together. Changing the service disconnect to a sub-feed now made this an illegal installation, albeit existing.
NEC addresses this issue in 250.140 and has an exception for existing branch-circuit installations.
250.140 Frames of Ranges and Clothes Dryers. Frames of
electric ranges, wall-mounted ovens, counter-mounted cooking
units, clothes dryers, and outlet or junction boxes that are part
of the circuit for these appliances shall be connected to the
equipment grounding conductor in the manner specified by
250.134 or 250.138.
Exception: For existing branch-circuit installations only where an
equipment grounding conductor is not present in the outlet or junction
box, the frames of electric ranges, wall-mounted ovens, counter-mounted
cooking units, clothes dryers, and outlet or junction boxes that are part
of the circuit for these appliances shall be permitted to be connected to
the grounded circuit conductor if all the following conditions are met.
(1) The supply circuit is 120/240-volt, single-phase, 3-wire; or
208Y/120-volt derived from a 3-phase, 4-wire, wye-connected
system.
(2) The grounded conductor is not smaller than 10 AWG copper or
8 AWG aluminum.
(3) The grounded conductor is insulated, or the grounded conductor
is uninsulated and part of a Type SE service-entrance cable and
the branch circuit originates at the service equipment.
(4) Grounding contacts of receptacles furnished as part of the equipment
are bonded to the equipment.
This is why plan review is so important and we must ask for details. Changing the service may trigger the requirement for the branch circuit to the range, dryer, oven, etc. to be replaced, and, in many cased, this would be a very difficult and expensive task.
Thoughts?
A service disconnect is located in the garage on a wall that separates the garage from the interior and fed from underground. The meter is on the outside of the building on an exterior wall. No problems with this existing installation at all, even by today's standards as the conduit feeding the service conductors to the disconnect inside are underground and come right up into the panel. OK, no discussion for this part needed.
Here is the rub. Due to a need for a new circuit outside, the exterior service will be rebuilt and add a new service disconnect on a combo-pack. This will then force the interior panel to become a sub-feed and they will have to ensure separated grounds and neutrals along with ensuring they have a proper equipment grounding conductor run to the inside panel.
Now that the interior panel that was the service disconnect and main panel is a sub-panel it created a problem. You see, prior to 1996 you could run SE cable to a range as long as it comes directly from a service panel where the grounds and neutrals are tied together. Changing the service disconnect to a sub-feed now made this an illegal installation, albeit existing.
NEC addresses this issue in 250.140 and has an exception for existing branch-circuit installations.
250.140 Frames of Ranges and Clothes Dryers. Frames of
electric ranges, wall-mounted ovens, counter-mounted cooking
units, clothes dryers, and outlet or junction boxes that are part
of the circuit for these appliances shall be connected to the
equipment grounding conductor in the manner specified by
250.134 or 250.138.
Exception: For existing branch-circuit installations only where an
equipment grounding conductor is not present in the outlet or junction
box, the frames of electric ranges, wall-mounted ovens, counter-mounted
cooking units, clothes dryers, and outlet or junction boxes that are part
of the circuit for these appliances shall be permitted to be connected to
the grounded circuit conductor if all the following conditions are met.
(1) The supply circuit is 120/240-volt, single-phase, 3-wire; or
208Y/120-volt derived from a 3-phase, 4-wire, wye-connected
system.
(2) The grounded conductor is not smaller than 10 AWG copper or
8 AWG aluminum.
(3) The grounded conductor is insulated, or the grounded conductor
is uninsulated and part of a Type SE service-entrance cable and
the branch circuit originates at the service equipment.
(4) Grounding contacts of receptacles furnished as part of the equipment
are bonded to the equipment.
This is why plan review is so important and we must ask for details. Changing the service may trigger the requirement for the branch circuit to the range, dryer, oven, etc. to be replaced, and, in many cased, this would be a very difficult and expensive task.
Thoughts?