A.O. Smith INTELLI-VENT, Troubleshooting Manual

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Air Pressure Switch Types
Normally Open = NO
Normally Closed = NC
Contact States Contact Actions
Close on a rise in pressure
Close on a fall in pressure
Open on a rise in pressure
Open on a fall in pressure
Application Normal State Activated State
Normally closed contacts, open on a fall in pressure.
Blocked Intake
Air Pressure Switch
Cyclone BTH 120-400 Models
Normally open contacts, close on a rise in pressure.
Blower Prover
Air Pressure Switch
Cyclone BTH 120-400 Models
Normally closed contacts, open on a rise in pressure.
Blocked Exhaust
Air Pressure Switch
Cyclone BTH 120-400 Models
Normally open contacts, close on a fall in pressure.
Blocked Exhaust
Air Pressure Switch
Power-Vent & Power Direct
Vent Residential Models
Blower Prover
Air Pressure Switch
BTI/BTN 120 – 400 Models
AHSA02307 7 of 8