Tjernlund CPC-3 Constant Pressure Controller Startup Manual 8504125 - Manual (Page 15)

“SEALED” COMBUSTION AIR MODE:
The “Sealed” mode supplies combustion air to a Combustion Air Manifold. Heaters with a combustion air inlet collar may be connect-
ed to a Combustion Air Manifold. The pressure is measured between the manifold and the mechanical room space. As heaters con-
sume combustion air from the manifold, the “Sealed” mode recognizes the negative pressure and communicates to the Combustion
Air Blower to provide Combustion Air. The CPC-3 Set Point pressure range for the Sealed mode is +0.05" WC to -0.50" WC. The
default setting is 0.00" WC. NOTE: “Sealed” systems must use the TD-2 Transducer.
COMBUSTION AIR SET POINT: Once the Combustion Air is active and the COMBUSTION AIR SETUP screen is visible, press the
SET POINT key and the Set Point window will open on the bottom line of the display. Use the INCREASE and DECREASE keys to
make the Set Point adjustment and press the SAVE SETTING key to save. The new set point will be displayed on the second line
under the SET POINT field. To exit from the Set Point option back to the setup menu, press the SET POINT key again. WARNING:
The SET POINT pressure is the reference pressure the control will maintain the system static pressure at. Make sure an acceptable
static pressure is defined and used. Make sure to test fire each heater and all combination of heaters while monitoring the draft pres-
sure at each heater. In most cases, a Combustion Air Set Point of 0.00" is acceptable. Make sure the reference side of the Pressure
Transducer is in a non-turbulent area and is an acceptable reference area outside of the Mechanical Room. Tjernlund Products, Inc. is
not responsible for a Set Point pressure that results in misapplied Combustion Air pressures to the heaters, mechanical room, or any
other location that could cause damage. If needed, consult Tjernlund Products, Inc. for more details.
"OPEN" COMBUSTION AIR MODE SYSTEM START-UP
Mechanical room pressure CPC-3 set points are +0.05 to -0.05” WC. If a positive pressure set point is desired extra care must be
taken to insure that the mechanical room is tightly sealed to outside spaces. Based on mechanical room size and leakage factor C.A.
Blower performance may not be adequate unless a positive pressure set point was factored into original computations.
1. Turn ON the service switch to all of the heaters.
2. Momentarily cycle each heater to verify that its CPC-3 Amber CALL LED illuminates. If not, verify that wiring conforms to appropri-
ate heater interlock wiring diagram.
3. Close all doors and roof hatches within the mechanical room. Activate all exhaust fans and any other air consuming devices within
the mechanical room. Fire all heaters. VERIFY: A) The draft for each heater is within the heater manufacturer’s specified range. If
barometric draft controls are used they should be mostly closed when the heater is operating within its specified draft range. Adjust
weight on barometric draft control if necessary. B) That the VFD has not reached the factory set maximum hertz output. Reference
VFD installation instructions for maximum hertz output. If the VFD tops out with all heaters firing the probable cause is excessive
air leakage to connected spaces.
4. Verify draft levels on all connected heaters. Fire heaters in random order and simultaneously to ensure that draft levels remain
within the specified range. Note: The CPC-3 will stage the firing of interlocked heaters when more than one call for heat signal is
simultaneously received. In general, each successive heater will be released after the CPC-3 set point has been reached and a 10-
second time delay has occurred.
"SEALED" COMBUSTION AIR MODE SYSTEM START-UP
Duct pressure set points are +0.15 to -0.60 inches water column. The sensing tube for the TD-2 transducer should be installed after
the outlet of the VSUB-Series blower. The set point is not critical, as long as it can produce a neutral pressure in each individual
heater’s duct connection. Balancing baffles should be installed in each individual branch duct if the combustion air duct is directly con-
nected to more than one heater. Care should be taken not to create a positive pressure near the heater’s supply duct connection
because it may cause the heater’s internal draft inducer to draw excessive amperage.
1. Turn ON the service switch to all of the heaters.
2. Momentarily cycle each heater to verify that its corresponding CPC-3 Amber LED illuminates. If not, verify that wiring conforms to
appropriate heater interlock wiring diagram.
3. Verify that all balancing baffles are in the closed position. Fire each heater individually, starting with the heater farthest from the
VSUB blower. Slowly open balancing baffle until a neutral pressure is measured in the branch duct serving that heater. Measure
pressure on the heater’s side of the balancing baffle.
4. After adjusting the pressures on all connected heaters, fire each in random order and simultaneously to verify that pressure levels
remain at or near neutral. NOTE: The CPC-3 will stage the firing of interlocked heaters when more than one call for heat signal is
simultaneously received. In general, each successive heater will be released after the CPC-3 set point has been reached and a 10
second time delay has occurred.
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