A SH / S-TRAC MANUAL
21 of 29 Feb 06
Ambient reset
This option is activated by installing an Engineered Air TE6000 ambient air sensor to terminals AMB and U.
As the ambient temperature falls, the building outside walls and glass will cool down. Once the inside
surface temperature falls below the dew point temperature, condensate will begin to form. To prevent
moisture build-up the S-TRAC will automatically reduce the humidity setpoint. If the ambient sensor is to
be field installed care must be take to ensure the sensing location is not affected by external loads, such as
sunlight.
Setting the S-TRAC to an appropriate value with the window ‘R’ value pot can modify the amount of
ambient reset further. The pot on the face of the S-TRAC is labelled low, medium and high. If window
fogging continues to occur turn the potentiometer slightly towards the lower setting.
Duct Mounted High Humidity limit
Modulating or snap acting high humidity sensors are wired into RH-D and Z (+ to RH-D and - to Z). If the
supply air volume is too low or too cold it may be possible for condensate to form inside the supply duct. To
prevent this a modulating duct RH limit will reduce the S-TRAC RH setpoint automatically as the duct
humidity level approaches 80% (fixed) or disable the humidifier entirely using a make/break high humidity
limit set at 85% (also installed across RH-D and Z).
Warning:
m
Duct humidity high limits (either modulating or snap acting) and air flow proving
are required on all systems.
BURNER CONTROLS
Flame Failure
After closing the ENH (enable burner) output contacts, the S-TRAC must see proof of flame from a main
valve feedback wire into terminal VFB24 (24Vac) within a pre-set amount of time, or it will cause a flame
failure alarm. If the S-TRAC sees a signal indicating the main gas valve is energized when it does not
have the ENH contacts closed, it will also cause a flame failure alarm condition. The S-TRAC will enable
the dump cycle on flame failure.
DJM2 burner control (SH series 120, 240, 400, and 650)
The S-TRAC cannot directly control high turndown burner modulation. It can, however, provide a 2-10Vdc
output signal to an Engineered Air DJM2 (high turndown modulating burner controller). In this application
the DJM2 and its flame relay will control all the burner functions. The DJM2 must be set for full
proportional control and cycle off only when the input voltage from the S-TRAC is below 2Vdc. Consult the
DJM2 manual.
Direct modulating gas output (SH series 35, 60, and 90)
The S-TRAC can control most basic burner functions when modulating combustion air is not required. It
provides low fire light off and can directly control a modulating gas flow ratio valve.
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