General 

The Honeywell C645 pressure switches are safety devices used in
positive-pressure or differential-pressure systems to sense
gas or air pressure changes.

Features 

• C645A,B models are for use on natural gas, LP gas,
or air.
• C645B1047 includes a scaleplate stop to meet
American Gas Association (AGA) requirements for
gas-fired boilers with inputs over 2-1/2 million Btuh.
• C645C,D models are for use on air only.
• C645E for use with distillate fuel oil.
• Spring-loaded diaphragm actuates snap-acting
Micro Switch.
• Switch can be wired to turn on alarm.
• C645A,C and D models break control circuit on
pressure fall.
• C645B models break control circuit on pressure rise.
• Lockout and manual reset optional in A and C models.
• Removable, zinc-plated cover protects scaleplate and
adjusting screw.
• Lockout models have external manual reset lever.
• Pipe tappings allow selection of positive pressure,
differential-pressure, or venting connections.
• Optional switch position indicator available.
• Models of C645A,B available with cover window for
setpoint visibility.
• Buna-N fiber-reinforced material for increased control
diaphragm strength.
• Two seal-off diaphragms for added reliability.

C645 Product Data (PDF)