Johnson Controls
5513350-JTG-1018
118
Guide Specifications (Continued)
11.
Supply Airflow Measurement [Optional]
capability
shall be provided. Supply fan airflow shall be viewable
on the control panel and communicable across the
BAS.
Discharge Air Plenum
Note:
Select one of the following heat/no heat configura
-
tions.
Cooling Only
The DAT sensor shall be located in the DA plenum and be
located such that it accurately measures the DAT.
Staged Gas Heat
The heating section shall include an induced draft furnace
in two [four] [six] stages of heating capacity. Furnaces
are designed in 250 MBH and 500 MBH modules. [Op-
tional high altitude kit shall be shipped loose from the fac
-
tory.] [Optional liquid propane (LP) conversion kit shall be
shipped loose from the factory.]
1.
Heat Exchanger -
The heat exchanger shall be con-
structed of tubular aluminized steel [stainless steel]
and flue assembly.
2.
Burner and Ignition Controls -
The burner shall
include a direct-driven induced-draft combustion fan
with energy efficient intermittent pilot spark ignition,
redundant main gas valves with pressure regulator.
3.
Combustion Air Fan -
The inducer fan[s] shall main-
tain a positive flow of air through each tube to expel
the flue gas and to maintain a negative pressure within
the heat exchanger relative to the conditioned space.
4.
Safety Devices -
A high limit controller with automat
-
ic reset to prevent the heat exchanger from operat-
ing at an excessive temperature shall be included.
A centrifugal switch on the induced draft fan motor
shaft shall prevent ignition until sufficient airflow is
established through the heat exchanger. A rollout
switch shall provide secondary airflow safety protec
-
tion. The rollout switch shall discontinue furnace op
-
eration if the flue becomes restricted.
5.
Flue -
The furnace flue shall be shipped loose to pro
-
tect it from damage during transit. The flue shall be
field-mounted by the installing contractor. The flue
outlet shall be located above the unit to help prevent
recycling of combustion gases back through the heat
exchanger.
6.
Agency Certification -
Gas heating units shall be
designed in conformance with ANSI Z83.8-2016/CSA
2.6-2016 standards and shall carry a CSA listing. All
gas heating units shall have 81% steady state effi
-
ciency rated in accordance to 2023 Department of
Energy Efficiency code.
7.
Valves -
Factory provided gas heater isolation valve
shall be shipped loose for installation in the field by
others. Punched holes shall be provided in the bot-
tom [side] of the unit. Holes shall be capped for field
to make suitable connection. Bottom [Side] penetra
-
tion option shall be provided with piping to extend out
of the unit.
Modulating Gas Heat
For applications requiring gas heat for morning warm-up,
supply air (SA) tempering, or other heating needs, a modu
-
lating natural gas furnace is available for finer temperature
control. The furnace is located in the DA plenum, down
-
stream of the supply fan. The DAT sensor is located across
the face of the supply duct opening in the unit. Furnaces
shall be designed in 250 MBH and 500 MBH modules. Fur-
naces shall be capable to achieve a minimum turndown of
25 MBH. Ignition and safety controls shall be included and
factory wired. [Optional high altitude kit shall be shipped
loose from the factory.] [Optional LP conversion kit shall be
shipped loose from the factory.]
1.
Heat Exchanger -
The heat exchanger shall be con-
structed of tubular stainless steel and flue assembly.
2.
Burner and Ignition Controls -
The burner shall
include a direct-driven induced-draft combustion fan
with energy efficient direct spark ignition, redundant
main gas valves with pressure regulator.
3.
Combustion Air Fan -
The inducer fan[s] shall main-
tain a positive flow of air through each tube to ex
-
pel the flue gas and to maintain a negative pressure
within the heat exchanger relative to the conditioned
space.
4.
Safety Devices -
A high limit controller with automat
-
ic reset to prevent the heat exchanger from operat-
ing at an excessive temperature shall be included.
A centrifugal switch on the induced draft fan motor
shaft shall prevent ignition until sufficient airflow is
established through the heat exchanger. A rollout
switch shall provide secondary airflow safety protec
-
tion. The rollout switch shall discontinue furnace op
-
eration if the flue becomes restricted.