Tjernlund CPC-3 Constant Pressure Controller Startup Manual 8504125 - Manual (Page 3)

The Patented CPC-3 Controller can simultaneously control both draft and combustion air so only one is needed when both Draft
Inducers and Combustion Air Blowers are installed in conjunction with the same heating system. For the remainder of this guide
Inducer will be synonymous to Induced Draft Exhaust and C.A. Blower will be synonymous to Combustion Air Blower.
AUXILIARY DEVICES
The CPC-3 auxiliary devices include an Audible Alarm Buzzer (circuit board mounted), an Auxiliary Device relay for activating a motor-
ized damper in series with the draft and/or combustion function, and a sensor input for a damper end switch. The sensor input can
also be configured to accept a signal from a CO detector and lock out all interlocked burners.
CPC-3 AUTOMATIC / MANUAL MODE SEQUENCES OF OPERATION
CPC-3 AUTOMATIC MODE SEQUENCE OF OPERATION, SEE DIAGRAM A
An aquastat, sequencing control or building management system signals a call for heat. This signal is intercepted and routed
through the CPC-3.
The CPC-3 compares actual pressure levels in vent connector and/or mechanical room with previously entered set points.
The Inducer speeds up to achieve the vent pressure set point and/or the combustion air blower simultaneously speeds up
to achieve desired pressure set point. These separate functions happen in parallel but are based on software and toler-
ances unique to the respective draft or combustion air function and to the differential between actual and set point. When
the set point is reached the CPC-3 completes the circuit to the heaters allowing ignition sequence to begin.
Pressures are constantly monitored by the transducer during the heating cycle. The Inducer / C.A. Blower motor speeds
are independently and continuously adjusted to maintain set points entered into the CPC-3. Winds, outdoor temperatures,
natural chimney draft, flue gas temperatures, modulating firing rates and building pressure changes will all be compensated
for automatically.
The heaters will be disrupted for 1 minute if at any time the draft cannot be maintained within the times and tolerances of the soft-
ware. After this restart delay the CPC-3 will once again try to reach the system set points. If successful, the system will sequence nor-
mally. If not successful, the CPC-3 will lock out the heaters until it is manually reset. Up to 5 fault codes will be stored memory.
CPC-3 MANUAL MODE SEQUENCE OF OPERATION
Manual Mode is a method of setting Draft and/or Combustion Air at a fixed speed. It was developed to be used in emergency cases
where a transducer is not operational. In Manual mode, the heaters are allowed to operate as long as the manual mode PSA-1 Fan
Prover Switch is closed. WARNING: Because Manual Mode is a method of setting a fixed speed for Draft and/or Combustion Air, con-
sideration must be given to over-drafting and/or excessive combustion air supply, See “Manual Mode Operation and PSA-1 Fan
Prover Switch Adjustment”, page 16. Deactivate heaters not necessary in an emergency situation to reduce the chance for these con-
ditions. To shut off heater calls from being processed, refer to the “SET STAGES” option, page 16 or shut off the service switch to
each heater.
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DIAGRAM A