JOHNSON CONTROLS
86
FORM 100.50-NOM12
ISSUE DATE: 04/02/2019
SECTION 5 – SEQUENCE OF OPERATION
Single Enthalpy
• Economizer type is single enthalpy.
• Economizer is User Enabled.
• The IPU board must see a valid OAT and outside
air relative humidity.
• When the current OAT is 2.0°F less than the out-
side air dry bulb setpoint
AND
The current outside air enthalpy is less than the
outside air enthalpy setpoint
THEN
The economizer becomes active
• The IPU board modulates the outside air damper
to try to achieve and maintain the active cooling
SAT setpoint.
Dual Enthalpy
• Economizer type is dual enthalpy.
• Economizer is User Enabled.
• The IPU board must see a valid OAT, outside air
relative, RAT, and return air relative humidity.
• When the current OAT is 2.0°F less than the out-
side air dry bulb setpoint
AND
The current outside air enthalpy is 1 BTU/LB less
than the return air enthalpy
THEN
The economizer becomes active.
• The IPU board modulates the outside air damper
to try to achieve and maintain the active cooling
SAT setpoint.
Best Method
• The IPU board gives the option to set the econo-
mizer method to use to best method.
• When set to best method, the IPU board moni-
tors the different sensors used for the three dif-
ferent economizer types. When a sensor reading
becomes invalid, the economizer method used
switches to a different method.
• For example, when the economizer type
is dual enthalpy and the return air humid-
ity sensor reading becomes invalid, the IPU
board tries to control the economizer as sin-
gle enthalpy if the economizer method to use
is set to best method.
HEATING
• The Series 100 unit can be ordered with an op-
tional heating system installed.
• Natural gas is the standard for staged and modu-
lating gas. Optional propane kits can be ordered.
• There are four heating options:
1. Staged natural gas heat
2. Modulating natural gas heat
3. Electric heat
4. Hot water/steam heat
• Each of these four options has different sub-op-
tions that can be ordered, which is covered in fur-
ther detail under their sections.
• Both natural gas heat options can also be oper-
ated with LP (propane) gas with the appropriate
conversion kit.
Heating Setpoints
• The IPU board looks at different temperature val-
ues to determine when there is a heating demand
present.
• When the unit type is SZVAV, see Figure 26 on
page 66.
• When the unit type is VAV, see Figure 32 on page
72 and Figure 33 on page 73.
• When the unit type is FlexSys, see Figure 56 on
page 107 and Figure 57 on page 108.
Staged Natural/Propane Gas Heat
• Staged natural gas heat can be ordered with one of
three heating capacities
1. 375 MBH (1 furnace section)
2. 750 MBH (2 furnace sections)
3. 1125 MBH (3 furnace sections)
• The heating capacity determines the number of
furnaces installed.
• Each furnace has a 2 stage gas valve, an ignition
control module, and an induced draft fan motor.
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