General Information
OAU-SVX007A-EN 21
Modulating 3-Stage Gas Heat
With modulating 3-stage gas heat, heat 1 and 2 are a single,
split manifold burner, with each stage being 25% of the
capacity (totaling 50% of the total capacity). Heat 3 is 50% of
the total capacity and equal to the size of both heat 1 and heat
2. The burners are staged in different orders to achieve the full
modulating range.
Heat 1 is enabled whenever the heating capacity is above 0%.
Heat 2 is enabled when the heating capacity is between 25-
50% and from 75-100%. Heat 3 is enabled when the heating
capacity is above 50%. The modulating heat signal is scaled 0
to 100% between each of the stages see Figure 2. Each time
a burner is staged off/on, the PID is locked to prevent
overshooting the setpoint.
Space Temperature/Humidity Sensor
All units ordered with Space Control or Single Zone VAV
Control (with or without thumbwheel) come standard with a
hardwired space temperature/humidity combo sensor
(BAYSENS036A). In all cases when controlling to space
conditions, a space temperature sensor is required, either
using the factory provided hardwired sensor, a field provided
wireless sensor, or communicated via BAS.
Space humidity is required on all lab/critical applications, and
is highly recommended (but not required) for other applications
controlling to space conditions.
Fans
Condenser Fans
The following pictures represent the condenser fan numbering
for each Horizon cabinet from the top view. The ones labelled
with VFD are the fans that are on a VFD when the unit is
equipped with Active Head Pressure Control, while the others
are on/off.
Figure 3. Modulating heat signal and staging for 2-
stage gas heat
Figure 4. Modulating heat signal and staging for 3-
stage gas heat
Figure 5. Top view of OAB 3 to 9 tons
Figure 6. Top view of OADG (rev 6) 10 to 20 tons
standard DX; and 10 to 15 tons air source
heat pump
Figure 7. Top view of OADG (rev 6) 25 to 30 tons
standard DX; and 17 to 30 tons air source
heat pump; and OAK 12 to 30 tons
Figure 8. Top view of OAG 10 to 12 tons (left) and 15 to
30 tons (right)
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