4. Slowly turn VFD speed control knob counter-clockwise in 5 Hz increments every 5 minutes until a decrease in the draft in the
heater furthest from the chimney termination is measured or when any of the heaters starts to spill flue gases. Turn PSA-1 adjust-
ment screw clockwise in 1/4 turn steps waiting 30 seconds between each turn until the PSA-1 switch opens, causing the heaters to
be disrupted. Turn the PSA-1 adjustment screw 1/4 turn counter-clockwise and replace electrical box cover.
5. Note the frequency displayed Hz _____ (speed) on the VFD display and turn VFD speed control knob clockwise until 5 additional
Hz. is displayed Hz _____ (speed). Verify that all heater’s draft falls within the manufacturer’s recommended range. Increase
VSUB Blower speed if necessary to help achieve desired draft range.
SAFETY INTERLOCK TEST
1. Adjust the appliance thermostat(s) or aquastat(s) to call for heat.
2. Determine that the VSUB Blower operates before the gas valve or burner becomes energized.
3. With the appliance(s) and VSUB Blower operating, disrupt power to the VSUB Blower and determine that the appliance
gas valve(s) or burner motor(s) shut off.
Do not operate an appliance that does not shut off with the VSUB Blower disabled.
COMBUSTION AIR
Adequate combustion air is vital for proper combustion and for safe venting. Likewise, for proper inducer performance, adequate
combustion air must be available to the appliance. Many installers assume adequate combustion air is present, especially in older
structures. In some cases this is a false assumption because many structures have been made "tight" due to weatherization. Size
the combustion air opening(s) into the equipment room as outlined in NFPA 31, 54 & 211. Tjernlund’s IN-FORCER
TM
or Auto-Draft®
VSUB combustion air intake systems provide a convenient, automated way to supply combustion air to the equipment room. When
installing the VSUB Blower as a draft inducer, it is not necessary to supply any more combustion air than normally required when con-
ventional venting.
MAINTENANCE, SERVICE & HOUSING ROTATION
Disconnect the power supply when making wiring connections or when working around the fan impeller and motor. Failure
to do so can result in electrical shock, personal injury, death or property damage.
The Tjernlund VSUB Blower is designed for continuous use. The motor is equipped with permanently lubricated sealed ball bearings
which do not require regreasing.
A vent/duct pipe inspection must be performed annually. The inspection should include checking all vent/duct pipe and connections
for blockage and leaks. A safety interlock test must also be performed.
Inspect impeller after (3) months and set up a periodic inspection and cleaning routine as necessary.
Intake Hood and prefilters when Using VSUB as a combustion air intake:
Intake Hood screen, prefilters and blower impeller should be clear of any foreign material such as leaves, lint or other items.
SLIDE-OUT SERVICE & HOUSING ROTATION
The VSUB Blowers feature a slide out motor/blower impeller assembly for
easy servicing. The blower housing can be rotated 180° in 45° increments
so the discharge orientation best matches the job requirements. The
motor/blower impeller assembly must be completely slid out prior to rota-
tion of the housing.
TO SLIDE OUT MOTOR/BLOWER IMPELLER ASSEMBLY:
NOTE: Nuts on bottom can be removed through access openings.
Do not overtighten stainless steel fasteners.
1. Remove (8) nuts and washers from motor mount plate.
2. Remove (2) nuts and washers from the bottom stud of each side of
the motor mount flange.
3. Loosen nuts on motor mount base and slide motor/blower impeller
assembly out of housing.
13
ACCESS OPENING
MOTOR MOUNT BASE
MOTOR MOUNT FLANGE
SUPPORT BRACKET
(VSUB16 & 20 ONLY)
INLET
HOUSING
SUPPORT BRACKET
HOUSING STUDS
MOTOR MOUNT
PLATE STUDS
L
E
T
R O
T A T E
S
1
8
0
°
I
N
4
5
°
I
N
C
R
E
M
E
N
T
S
T
U
O
MOTOR
MOUNT
PLATE
