American Water Heater STCE3-52/80/119 ユーザーズマニュアル

Servicing should only be performed by a Qualified Service Agent

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This section of the manual provides information on how contactors used on Electronic 
Control Models are constructed, how they work and how to test contactor operation - see 
Figure 2 on page 9 for location of the contactors on these models. Surface Mount Control 
Models are not equipped with contactors.

Magnetic contactors are used on Electronic Control Models to energize and de-energize the 
heating elements. Power from the fuse blocks is supplied to the heating elements through 
three switches (3 poles) inside the contactor. 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 switches are closed by an electromagnetic coil inside the base of the 
contactor. When a call for heat is activated the electronic 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 open position.