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Instruction Book
IB182012EN March 2017 www.eaton.com
50DH-VR-50AXU / 50XU / 75U / 75ARU - 600 / 1200A
Replacement Circuit Breaker
5.2.2 CELL CLEARANCE AND SHUTTER MODIFICATIONS
FOR 50-DH-50XU & 75ARU (REAR RACKING)
In addition to the circuit breaker compartment channel modifications
detailed in 5.2.1 for front racking circuit breakers, the rear racking
versions require cell channel clearance modifications and changes to
the shutter operator mounting brackets. After these modifications
to the shutter are made, the original air magnetic DH circuit breaker
cannot be re-installed in this circuit breaker compartment. If it is
desirable to allow the original circuit breaker to be installed, the
shutter parts must be removed according to the procedure below
but the new parts from the kit should not be installed. Follow this
procedure for shutter modifications that allow shutter operation with
the replacement circuit breaker:
1. Before starting any modifications, confirm that the switchgear
primary and secondary circuits are completely de-energized.
2. Protect all primary disconnects and secondary disconnects and
terminal boards from the metallic dust that will be generated
during the cutting process. This must be done with drop cloths
or tarps that are sealed along their edges with duct tape or
equivalent means.
3. Remove the hardware used to attach the shutter operators to
the cell frame and shutter. Keep the shutter arms for later use.
New hardware is provided in the shutter modification kit shipped
with the vacuum replacement circuit breaker.
4. Refer to Figure 5.3 for diagrams of the necessary shutter bracket
modifications. The brackets used to attach the shutter operators
to the middle channel need to be removed. These brackets are
welded to the frame so they must be cut away before any other
modifications can be performed.
5. Use Figure 5.4 for dimensional information on channel
modifications for the Rear Racked circuit breakers. These
dimensions are different from the ones for the front racking
circuit breakers.
6. With a suitable marker, outline the material to be removed
according to the appropriate diagram. Put on the appropriate
personal protective equipment including safety glasses or a
shield, hearing protection, and gloves.
7. Using a power saw with a metal cutting blade, remove the metal
within the outline. A grinder may be needed to clean up the
cuts after grinding.
8. With an industrial vacuum cleaner, remove all of the metallic
dust from inside the cell. Wipe down any areas that may trap
these metallic particles, taking care not to be cut by any sharp
edges or metal burrs. Gray primer paint may be optionally
applied to the exposed metal surfaces.
9. Attached the left and right shutter arm mounting brackets that
were supplied as a kit with the vacuum replacement circuit
breaker. See detail A of Figure 5.3.
10. Attach the left and right cell extension arm assemblies according
to Figure 5.3, detail B using the supplied hardware.
11. After assembly of the extension arm assemblies, the shutter
arms can be reassembled in the cell per Figure 5.3 using the
hardware supplied.
12. Remove the drop cloths or tarps used to protect the primary
and secondary circuits. Carefully inspect these areas to ensure
that no metallic dust has penetrated these areas. It may be
necessary to manually operate the shutter to inspect the primary
connections. If dust is observed, remove it with the industrial
vacuum cleaner. The insulation on the primary bottles may also
be cleaned with isopropyl alcohol and a soft cloth.
DANGER
FAILURE TO COMPLETELY REMOVE METALLIC DUST COULD NEGATIVELY
AFFECT THE OPERATION OF THE CIRCUIT BREAKER AND / OR
SWITCHGEAR STRUCTURE. THIS COULD RESULT IN EQUIPMENT DAMAGE,
PERSONNEL INJURY, OR DEATH.
13. Verify that enough metal has been removed by slowly racking
the new 50-DH-VR circuit breaker to the “TEST” position.
Adequate clearance should be available on each side of the
circuit breaker such that it does not contact the steel channels.
If contact is observed, this process must be repeated to remove
enough metal to allow the circuit breaker to be installed.
14. Figure 5.5 shows the modification for rear racking types.
15. After all modifications are complete, test rack the circuit breaker
to the fully “CONNECT” position noting the operation of the
shutter as the circuit breaker is racked. If all is satisfactory, the
circuit breaker can be racked to the “TEST” position for electrical
tests of the charge, close, and trip systems.
16. After these modifications, the new circuit breaker front cover
will align with the channels on each side to conceal the channel
modifications and create the dead front barrier required for
metal-clad construction.
Figure 5.5. Completed Cell Modification (Rear Racking)
