A customer has a machine that has four separate
processes. The first section requires a
start button to be CLOSED in order for a magnetic motor starter with memory to
become energized, which then energizes a light. The magnetic motor starter
sends power to the second section. In
this section one NC and three NO buttons are used to control a control relay
that also has memory. The control relay
sends power to the third section. The
third section contains one NC and two No pushbuttons. Both pushbuttons must be CLOSED in order to
energize a control relay with memory.
The relay will also energize an indicating light as well as send power
to the fourth and final section. This
section consists of a limit switch controlling a magnetic motor starter with
memory. The customer also wants a safety
stop switch installed so that the supervisor can shut the entire machine
down.
1. Draw a line/ladder diagram
and label and number all devices and lines.
2. Create a price list for this
job. Use the attached pricing sheet and
calculate how much time you think this job will take and how much per hour your
labor is worth.
3. The machine measures 200
feet in length ( each of the four sections measures 50 feet) and the supervisors
office is 10 feet away from the machine.
All indicating lights are to be installed in the supervisors
office. Wire will be #14 AWG THHN solid
copper. The price list should be ONLY
for the controls NOT any 3 phase for mags, etc.
4. All devices will already be
mounted in enclosures. Enclosures are installed two feet from the ends of each
section and ten feet apart within the section.
Devices must be connected using liquidtight flexible metal conduit
(seal-tite). Seal-tite will be secured using 2-hole 3/4" EMT straps with
self-tapping sheet metal screws.
5. Limit switches will require
the use of 45 degree angle seal-tite connectors. Stop/start stations will require 90 degree
connectors. All other devices including
lights can use straight seal-tite connectors.
6. An equipment ground must be
pulled and connected to every device.
7. Assume 120 volt power is
available in the supervisors office and at the first location of the machine.
