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Table 9: Modulating Gas Heat Control Board Flash Codes
Flash Code
Heart Beat
1 Flash
2 Quick Flashes Followed By
1 Slow Flashes
2 Slow Flashes
3 Slow Flashes
4 Slow Flashes
3 Quick Flashes Followed By
1 Slow Flashes
2 Slow Flashes
3 Slow Flashes
4 Slow Flashes
4 Quick Flashes
5 Quick Flashes
6 Quick Flashes
7 Quick Flashes
8 Quick Flashes
9 Quick Flashes
14. Electric Heat Option: A call for heat stages electric heat
on. Electric heat is available as 40kW [one stage], 80kW
[two stages], or 108kW [three stages]. There is one over-
heat limit for electric heat, regardless of the number of
stages - contrasted with gas heat, which has individual
over-heat limits on each module.
On units with the Electric Heat Option, a call for heat (W1)
will initiate the main blower. The blower will produce static
in the supply and the Air Proving Switch (APS) contacts will
close. The control recognizes closure of the APS and ener-
gizes the H1 terminal to complete the circuit to the first
stage of electric heat.
In Occupied mode, if additional heat is required, the W2
signal will energize the second stage of electric heat
through terminal H2; W3 / H3 function similarly. When the
W2 call for heat has been satisfied, W2 will be de-ener-
gized and will in turn de-energize H2 second stage heat.
As the call heat (W1) has been satisfied, W1 will be de-
energized. If the unit is in Unoccupied mode, the fan will
shut off and the APS will open. For units in space sensor
®
control, the Simplicity
maintain space sensor temp, or SAT temp if the space sen-
sor signal is lost.
All electric heat modules have an auto-reset primary limit
and non-restartable back-up limits. Dirty filters, broken
belts, fan motor burn-out or running this unit below 6,000
CFM will cause the limit to trip on the auto-reset primary
Johnson Controls Unitary Products
Description
Normal Operation
Not Applicable
Module Limit Switch Failure
Module 1 Limit Switch
Module 2 Limit Switch
Module 3 Limit Switch
Module 4 Limit Switch
Module Gas Valve Failure
Module 1 Gas Valve
Module 2 Gas Valve
Module 3 Gas Valve
Module 4 Gas Valve
Not Applicable
Supply Air Temp. (SAT) Sensor
Input Failure
Mixed Air Temp. (MAT) Sensor Input
Failure
Air Proving Switch (APS) Input
Failure
Low Voltage (Non Failure)
Module Locked Out Due To
Mechanical Cooling (Non Failure)
will stage on heat as required to
limit. In addition to the primary limit, back-up limits may trip
under these conditions. The back-up limits are one-trip
devices and will have to be replaced should they trip.
15. When the space temperature rises above the Unoccupied
cooling setpoint, the control enables optional duct pressure
control and optional power exhaust system; power is
applied to the airflow proving switch (APS) and to the coil
of starter 5M to engage the supply fan motor. If the supply
fan operates correctly (proper rotation) the pressure differ-
ence between the heating section and the supply fan sec-
tion increases and APS closes to allow mechanical cooling
operation. The unit operates as though it were in the Occu-
pied mode (see above) until the space temperature falls
below the cooling setpoint or Occupied mode is engaged.
16. Duct Pressure Control - Inlet Guide Vane Option: The
duct pressure controls are powered with a call for the sup-
ply fan. Once powered, the pressure transducer DPS pro-
vides a voltage signal input to the Simplicity
control calculates a 2-10VDC signal to the inlet guide vane
actuator.
17. Duct Pressure Control - VFD (Variable Frequency
Drive) Option: The duct pressure controls are powered
with a call for the supply fan. Once powered, the VFD
responds to a VDC control signal from the DPS (Duct Pres-
sure transducer). In the heating mode the VDC, DPS pres-
sure signal forces the fan to full volume. VAV boxes should
be tied to the H1 terminal to signal the boxes to full open.
18. Electronic Economizer Option: The control directly con-
trols the position of the outside air / return air dampers
through a 2-10 VDC signal to ACT1 (economizer actuator).
The economizer is powered only after supply fan operation
has been verified (APS closed) and the unit is in Occupied
or Recovery mode. When the control is not powered or is in
Unoccupied mode, the outside air dampers spring return
closed. When in Occupied or Recovery mode and there is
no Y1 call or if free cooling is unavailable, the Simplicity
control opens the economizer dampers to the minimum
position setting made in the parameters.
With a Y1 call where the outside air is appropriate for free
cooling (see below), the control modulates the vanes for
free cooling in place of first stage cooling. (Please see the
compressor staging chart above.) The control modulates
the economizer dampers to maintain a Mixed Air Tempera-
ture (Return Air / Outside Air Mixture, sensed between the
filters and the DX coil) between 50 °F and 55 °F (adjustable
between 40 °F and 65 °F).
®
The Simplicity
control uses one of three methods to deter-
mine when free cooling is available. The method used is
determined by the option selection.
Dry Bulb: The control refers to input from the OAT, and
will allow free cooling when the outdoor temperature falls
below the Economizer First Stage temperature setpoint.
Free cooling will be available until the outdoor tempera-
ture rises above the temperature setpoint.
351579-YTS-B-0608
®
control. The
®
25
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