Tjernlund HST_HS115_HSUL-J, 1, 2 Series (Discontinued) 8504060 Rev A 11/99 - Manual (Page 9)

ELECTRICAL WIRING
WIRING RESTRICTIONS
1. All wiring from the Power Venter to the appliance must be appropriate class 1 wiring as follows:
Installed in rigid metal conduit, intermediate metal conduit, intermediate metal conduit, rigid non-metallic conduit, electrical metallic
tubing, Type MI cable, Type MC cable or be otherwise suitably protected from physical damage.
2. The electrical contact ratings for the diaphragm Fan Proving Switch are as follows:
3 amps (full load) at 120 VAC
28VA Pilot Duty (1.16 amps) at 24 VAC
125 VA Pilot Duty at 120 VAC
The Fan Proving Switch and Power Venter are not suitable for use with loads which exceed the above limitations.
TJERNLUND POWER VENTER SEQUENCE OF OPERATION
HSUL OR HST SERIES WIRED AT 24V GAS VALVE:
As the thermostat senses a need for heat, 24V is applied to the Power Venter relay. The 24 volts applied to the relay coil bring in the
115 volt power to the motor. The air movement generated by the Power Venter closes the Fan Proving Switch contacts which allow
the thermostat signal to reach the 24 volt gas valve. The Fan Proving Switch actually becomes the burner controller and will allow the
appliance to operate only when the thermostat is calling for heat and the Power Venter is operating. DO NOT OPERATE THE APPLI-
ANCE WITHOUT THE FAN PROVING SWITCH WIRED INTO THE 24V APPLIANCE CIRCUIT!
HSUL OR HST SERIES WIRING TO THERMOSTAT ON SINGLE ZONE FURNACE/BOILER INSTALLATIONS
As the thermostat senses a need for heat, 24V is applied to the Power Venter relay. The 24 volts applied to the relay coil bring in the
115 volt power to the motor. The air movement generated by the Power Venter closes the Fan Proving Switch contacts which allow
the thermostat signal to reach “W” on the 24 volt burner control. The Fan Proving Switch actually becomes the burner controller and
will allow the appliance to operate only when the thermostat is calling for heat and the Power Venter is operating. DO NOT OPER-
ATE THE APPLIANCE WITHOUT THE FAN PROVING SWITCH WIRED INTO THE 24V APPLIANCE CIRCUIT!
HS115 SERIES WIRED AT 115V GAS VALVE OR BURNER MOTOR:
As the thermostat senses a need for heat, 115V is applied to the Power Venter motor. The air movement generated by the Power
Venter closes the Fan Proving Switch contacts which allow 115V to be applied to the gas valve or burner motor. The Fan Proving
Switch actually becomes the burner controller and will allow the appliance to operate only when the thermostat is calling for heat and
the Power Venter is operating. DO NOT OPERATE THE APPLIANCE WITHOUT THE FAN PROVING SWITCH WIRED INTO THE
115V APPLIANCE CIRCUIT!
HST SERIES WIRED TO OIL BURNER:
Control signal from thermostat, aquastat or primary control is intercepted and routed to the ORANGE of Relay/Timer and BLUE from
HST Fan Prover with either 24 VAC or 120 VAC. The Relay/Timer receives current and HST motor is energized. After draft is estab-
lished within the HST, the Fan Proving Switch closes completing the circuit allowing burner to fire.
The ORANGE wire from Relay/Timer can accept either a 24 VAC or 120 VAC control signal. For most furnace applications it may
be easier to interlock with the 24 VAC thermostat circuit. For most boiler applications it may be easiest to interlock with the 120 VAC
primary control circuit to the burner motor. For boiler applications with solid state primary controls it is recommended that the interlock
be made between the aquastat and the primary control to avoid the need for a field installed isolation relay. This relay is necessary to
eliminate false triggering of the HST by circuit checks that are common with solid state controls. Choose the interlock method that
best fits your application. DO NOT OPERATE THE BURNER WITHOUT THE FAN PROVING SWITCH WIRED INTO THE BURNER
CIRCUIT!
NOTE:
The following wiring diagrams are designed to satisfy most installations. Should your installation be different from those shown in
these instructions, please contact the Tjernlund Technical Service Department for assistance at 1-800-255-4208, 7:30 - 4:30 CST.
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DISCONNECT 115 VAC POWER TO THE APPLIANCE BEFORE PROCEEDING WITH POWER VENTER WIRING. THE POWER
MAY BE DISCONNECTED BY TRIPPING THE CIRCUIT BREAKER OR REMOVING THE FUSE PROTECTING THE APPLIANCE.
ELECTRICAL CONDUIT AND 24 VAC WIRING MUST BE ROUTED AWAY FROM ANY HOT SURFACES. USE ADEQUATE CON-
DUIT SUPPORTS WHERE NECESSARY. ALL WIRING MUST COMPLY WITH APPLICABLE CODES AND ORDINANCES. ALL
115 VAC WIRING MUST USE RIGID OR SEMI-RIGID METAL CONDUIT WITH 18 AWG, 300 VAC, 90 DEGREE C-RATED COP-
PER WIRE.