A.O. Smith DSE-5, Руководство по обслуживанию

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OPERATION & SERVICE
Servicing should only be performed by a Qualified Service Agent
34
CONTACTORS
This section of the manual provides information on how contactors are constructed, how
they work and how to test contactor operation - see pages 8 & 9 for location.
Contactor Construction - How They Work
Magnetic contactors are used to energize and de-energize the heating elements. The water
heaters covered in this manual are equipped with either 3 pole or 4 pole contactors the
illustrations below show a 3 pole contactor - see Contactor Configurations on page 35 to
view 4 pole contactor illustrations. Power is supplied to the heating elements through three
or four switches (3 pole and 4 pole contactors) inside the contactor(s). Springs located inside
the contactor hold the switch contacts open; the springs are compressed and the spring
tension forces or holds the switch contacts in their “normally open” state.
The contactor’s switch contacts are closed by an electromagnetic coil located inside the
base of the contactor. When a call for heat is activated the control system sends 120 volts to
the contactor’s electromagnetic coil. As current runs through the coil it becomes
“magnetized” and overcomes the spring tension holding the switch contacts open. The
switch contacts then close which in turn sends power to the heating elements. When the call
for heat is satisfied the control system de-energizes the contactor coil and spring tension
returns the contacts to their “normally open” position.
3 Pole Contactor Side View
Electromagnetic
Contactor Coil Wiring
Terminals 120 VAC
Heating Element
Power Circuit
Wiring Terminals
3 Pole Contactor Internal Wiring
3 Normally
Open Switch
Contacts
Electromagnetic
Contactor Coil
3 Pole Contactor Side View - Cover Plate Removed
Contactor Springs
Hold Contacts Open
When Electromagnetic
Coil Is Not Energized