Greenheck Fan VSU Make-Up Air Unit with Direct-Fired Gas Heater 470654 - Manual (Page 18)

18 Model VSU Make-Up Air
®
IMPORTANT
If the flame signal is not above 1.25 VDC and steady,
consult the troubleshooting section.
Flame Signal Check - Pilot Ignition
To measure the flame signal connect a standard DC
voltmeter to the flame amplifier test jacks + and - (com)
as shown to the
right. The flame
signal should be
above 1.25 VDC
and steady.
Check the flame
signal with the
burner at pilot only,
minimum fire, mid
fire and high fire.
DC Voltmeter and
Flame Amplifier
Maxitrol Series 44 – 9 Terminals: The Maxitrol
Series 44 should
be set to the
desired discharge
temperature.
The temperature
selector is a stand-
alone dial. The
stand-alone dial
may be mounted
remotely.
Maxitrol Series 14 – 8 Terminals: The Maxitrol
Series 14 should be set to the desired discharge
temperature mode. Place dipswitch in the “UP” position
for local control and in the “DOWN” position for remote
control. Keep LFST dipswitch in the “UP” position at all
times for 10 second delay.
Fig. A is required for remote control.
Set the Unit’s Operating Temperature
Set the operating temperature. The operating
temperature setting depends on which Maxitrol
controller is used.
Set the discharge temp
Typical: 65°F
Minimum: Typical: 55°F
Maximum: Typical: 90°F
Fig. A
Remote
controller
Low fire
setting
(LFST)
dipswitch
Discharge
temp
dipswitch
Maxitrol Series 14 — 8 terminals
Maxitrol Series 44 — 9 terminals
Maxitrol SC25S: The SC25S is an analog signal
converter that will change a 0-10 VDC or a 4-20 mA
control signal provided by an owner supplied Building
Management System into an output level capable of
driving one or more modulating gas valves. The SC25S
also limits the minimum and maximum discharge
air temperatures. Reference the unit-specific wiring
diagram and Maxitrol data sheets included in the IOM
packet.
Maxitrol SC25S
Terminal 3 - Remove wire to
send unit into maximum fire.
Maximum discharge
temperature setting
(Typical: 100ºF)
Minimum discharge
temperature setting
(Typical: 50ºF)
Low fire time delay setting
(75% of maximum)
Terminal 3 - Remove wire to
send unit into maximum fire.
Series 44 Temperature Setting
(shown as space temperature control)
Set the space
temperature
Typical: 70ºF