5
WIRING
The MPCI must be wired by a qualified installer (an individual properly licensed and/or trained) in accordance with these instruc-
tions and in accordance with all local codes or in their absence, with the current editions of NFPA 70, National Electrical Code in
the U.S. or CSA C22.1-12 Canadian Electrical Code in Canada.
All 120 V wiring from the MPCI to the Fan junction box must be appropriate Class 1 wiring as follows: installed in rigid metal con-
duit, intermediate metal conduit, rigid non-metallic conduit, electrical metallic tubing, Type MI Cable, Type MC Cable, or be other-
wise suitably protected from physical damage.
The maximum distance the 1-10 VDC output from the MPCI to the VFD or ECM motor is 300 feet. Exceeding this distance can
result in lower than desired signal strength. 1-10 VDC wiring should be in metal conduit or utilize shielded cable. Non-shielded sig-
nal wiring can be influenced by outside conditions resulting in undesirable operation of the MPCI control.
IMPORTANT:
Installer must supply overload and disconnect protection as dictated by local and national codes. Do not use a fused disconnect.
MPCI Control supply power may be switched through a building management system, pressure switch or other 120 VAC switch.
IMPORTANT:
MOTOR ROTATION MUST BE VERIFIED PRIOR TO OPERATION CHECKS.
If using the model MPCI in conjunction with a VFD, fan rotation must be checked to validate that the motor is turning in the correct
direction. Fans should have rotation stickers on the housing or motor mount. Activate the MPCI as directed below and then disrupt
operation so that motor rotation can be detected as the motor coasts down. If rotation is incorrect, change by switching any two of
the 3 power output leads from the VFD to the fan motor. Verify proper rotation by repeating steps above.
SUPPLY MAKE-UP / COMBUSTION AIR PRESSURE SET POINT
MPCI Controllers are defaulted to a 0.10” w.c. set point. To enable
the SET POINT 2, default setting (0.00” w.c.) for Supply Make-up /
Combustion air, a jumper wire must be installed between terminals
8 & 9 on the right hand side of the Pressure Control terminal strip,
(See Figure E). Remove Pressure Control cover with small phillips
screwdriver to access terminal strip.
MPCI SEQUENCE OF OPERATION
An intercepted call for heat is sensed at terminals A & B or 1 & 2 of the integral UC1 Interlock Control or MAC-Series interlock
expansion modules. The Amber LED of the UC1 will turn on.
1. This closes the motor relay of the UC1 sending 120 V to the MTR terminal of the Power Terminal Block (can be used to power
120 VAC intake damper motors up to 5 amps or energize the coil of a line voltage VFD activation relay). The Green LED on
the UC1 will turn on.
2. Simultaneously it energizes the 24 VAC transformer to supply power to:
The 24 VAC hot of the external Green run light on the MPCI cover.
Terminal 5 of the Pressure Control to power the common of its N/O alarm relay contacts.
The 24 terminal of the Pressure Control Terminal Block. (Used to energize Tjernlund Products VFDxxx-MPC Series VFD
activation relay within VFD electrical enclosure)
Terminal 1 of the Pressure Control, activating it to measure system pressure and to output a proportional 1-10 VDC signal to
the 1-10 terminal of the Control Terminal Strip. The 1-10 VDC signal from the Control Terminal Strip is wired directly to an ECM
motor input or to a VFD input to vary the fan speed to maintain the set point as volume, stack effect, wind loading and reference
pressure change.
As long as the pressure set point is made within 10 seconds (field adjustable) of the pressure control producing 10 VDC (max.
output) and the PSA-1 Fan Prover is closed, the UC1 interlock control will complete the circuit to the burner(s) through terminal
4 of its terminal strip. The Blue LED on the UC1 will turn on.
IMPORTANT:
The PSA-1 Fan Prover is not used for Supply /
Make-Up air applications since its operating range is outside of the 0.00” w.c. set point of the Pressure Controller.
When the call(s) for heat is satisfied the circuit from terminal 4 of the UC1 to the burner(s) is disrupted and the UC1 starts its post
purge cycle. Red LED’s 4 & 5 of the UC1 will flash in unison during post purge. The Pressure Control will maintain set-point for a
2-minute post purge cycle and then disrupt 120 VAC power from the MTR terminal of the UC1, powering off the 24 VAC trans-
former and shutting off the Pressure Control, Green run light and the 24 VAC output from the Control terminal strip. Red LED 6 on
UC1 will stay lit and Red LED 5 will blink on and off every 3 seconds until a call for heat is sensed.
FIGURE E
JUMPER WIRE MUST BE
INSTALLED ON PRESSURE
CONTROL BETWEEN TERMI-
NALS 8 & 9 TO ENABLE SET
POINT 2.