A
G-TRAC2
IOM-25
12 of 42
Mar 99 R7
XI.
AUTO BYPASS LOW LIMIT
NOTE:
Low limit can be disabled (Dipswitch C-5).
The low limit set point is fixed at 40ºF. There are two low limit bypass timers, start-up and anti noise. The 6 minute start-up
auto bypass low limit timer is started every time the night terminal energized status changes
(on-off or off-on transition)
or
when the "SA"
(supply air blower)
contactor is energized.
An anti-nuisance low limit bypass timer is started every time a low limit condition is detected and the 6-minute auto bypass
timer has timed out. This timer is designed to prevent nuisance low limit lock outs caused by any electrical noise which may
be picked up by the discharge sensor. If the low limit condition exists for more than 15 seconds, a low limit lockout will
occur. When the low limit trips, the G-TRAC2 closes its alarm contacts
(LK)
. Also, LED 3 will be turned on steady. A flame
failure can also activate this output.
Whenever the discharge temperature is below 40ºF but one of the bypass timers is operating, LED 3 will flash every second.
To reset the low limit, turn the power off to the G-TRAC2 terminal "T1"; or interrupt power to terminals "FS, HS, and K" all
at the same time. Most units can be reset remotely by turning the remote panel control switches
(often-labelled fan or unit
switch)
off and then on. This will toggle power to the "FS, HS, and K" terminals.
NOTE
:
On some applications with large amounts of outside air being switched while unit is in day time operation,
terminal “K” may be switched to simulate coming out of night function. This will reactivate the six minute
low limit bypass thus allowing the heat to catch up to falling discharge air temperatures if cold outside air
has been introduced into the system.
XII. DAY AND NIGHT OPERATING STRATEGIES
Supply Fan, Damper and Heat Operation
Standard G-TRAC2 Supply Fan Function (Temperature Priority Program)
In normal operation dipswitch A-4 is off. The supply fan is operating with discharge temperature authority. During morning
start-up, if there is no initial heat call
(due to a warm discharge sensor being exposed to building heat)
the supply fan will
start after the outside damper is open. However if the discharge sensor is rapidly cooled, the G-TRAC2 senses a need to
start the burner. As it takes time to start the burner and warm the heat exchanger the G-TRAC2 will shut off the supply fan
until the main flame has been firing for about 64 seconds. This reduces the amount of cold air dumped into the building
during start up. If dipswitch A-4 is turned ‘on’ after the fan starts, it stays on,
(Air Delivery Authority)
. For other set ups, note
below.
Day/Night General Description of Fan/Damper Operation
The combination of energized night (K) and fan (FS) terminals set the blower and damper operation in day and night mode.
DAY
(FS on, HS on)
Continuous Blower, Dampers Open, Discharge Control
NIGHT
(FS off, K on, HS on)
Intermittent Blower, Dampers Off, Room Control
ALTERNATE NIGHT OPERATION
(HS, FS,
K terminals all energized)
Continuous Blower, Dampers Off, Discharge Control with Room
Reset
Fan/Damper During Day (Terminal “K” No Power) Dipswitch A-4
During day operation Terminal ‘K’ has no power. The unit dampers
(if controlled by the G-TRAC2)
will open before the
blower starts and close after blower stops
(64 seconds)
.
Содержание EngA G-TRAC2
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