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PRESSURE FAULT SEQUENCE
If either the alarm circuit of the Pressure Control closes or the PSA-1 fan prover opens for more than 10 seconds, the UC1 inter-
lock control will disrupt the circuit from terminal 4 to the burner(s). The MPCI external Red fault light with audible alarm will come
on and sound alarm. The auxiliary alarm contacts will change state. Red LED 4 on the UC1 will flash continuously.
The Pressure Control will continue to try to obtain the set point for 10 minutes. If the alarm circuit opens and the PSA-1 fan prover
closes during this 10-minute period, the UC1 interlock will automatically reset and complete the circuit to the burner(s). The UC1
interlock will go into a hard lockout after 10 minutes without an automatic reset. Disrupting the call for heat or shutting off the MPCI
internal 120 VAC power switch for 10 seconds will reset the UC1 interlock control.
MPCI BURNER INTERLOCK FEATURING THE UC1
The UC1 is the standard interlock control for Tjernlund's full line of Power Venters, Draft Inducers and Combustion Air fans. It can
be interlocked with virtually any burner control circuit. Features include: adjustable pre & post purge, LED status / diagnostic indi-
cators, 10 second prover switch delay to avoid burner start up and wind induced short cycling. Interlocks with any 24-115 VAC
burner control circuit and also includes “dry” contact actuation option. After each burner cycle, the UC1 will continue to operate in
post-purge mode to allow the fan to purge the heater and vent of residual flue gases. A factory post-purge time is set at 2 minutes
and is adjustable up to 16 minutes, see “Pre / Post Purge and Prover Status Check Dip Switch Settings” on page 9.
1. The UC1 Pre-Cycle Prover Status Check is deactivated from the factory to avoid nuisance lock out in applications where
exhaust shafts or vents may be capable of creating enough chimney effect to make the pressure set point prior to a call for
heat. When activated, the UC1 Universal Control checks across the P1 & P2 safety circuit Fan Prover to verify that the Fan
Prover switch is “Open” upon a call for heat and not stuck “Closed”. See “Pre-Cycle Fan Prover Status Check”, page 9 for details.
2. A post-purge on the UC1 has been factory set at 2 minutes. Confirm that dip switch #5 is in the up or "on" position. A longer
post-purge may be necessary for longer vent runs or high heat retention, refractory lined combustion chambers. A shorter post-
purge may be desired for short vent lengths. If using the UC1 to control a combustion air fan a post-purge may not be desired.
See “Pre / Post Purge and Prover Status Check Dip Switch Settings”, page 9 for details.
CAUTIONS
Disrupt supply power to the MPCI and heating equipment when making wiring connections and servicing the UC1 Control. Failure
to do so may result in personal injury and/or equipment damage. UC1 LED #6 (Red) should be off with power removed.
All installation restrictions and instructions in the Exhaust/Supply Air Fan and/or VFD installation instructions must be adhered to.