Johnson Controls
5513350-JTG-1018
119
Guide Specifications (Continued)
Hot Water Heat
A hot water coil shall be installed in the rooftop DA plenum.
1.
Construction -
The hot water coil shall have one
[two] row[s]. Primary surface shall be 1/2-inch OD
copper tube, staggered in direction of airflow. Con
-
nections have 1/4-inch FPT drain plug on each con-
nection. A structural galvanized steel casing shall
protect the coil. The coil shall be circuited to provide
free draining and venting through one vent and drain.
Freezestat shall be provided to prevent coil freeze up.
Access doors shall be provided for convenient access
to the valve for maintenance and inspection.
2.
Testing -
Completed coil including headers, connec-
tions, and return bends shall be tested with 325 pounds
compressed air under water. Coils shall be designed for
operation at 250 psig design working pressure.
3.
Valves -
Factory [field] shall provide three-way mod
-
ulating control valve and spring return valve actuator
capable of receiving 0–10VDC signal. Valve actuator
shall be controlled by factory-installed main unit con-
troller. [Field-provided valve shall match specifica
-
tions/ratings as recommended by unit manufacturer.]
Unit shall have hole markings for field to drill holes
through the base or side of the unit.
Steam Heat
A steam heating coil shall be installed in the rooftop DA
plenum.
1.
Construction -
The steam coil shall be constructed
in the non-freeze style. The steam coil shall have one
row. Tubes shall be 1-inch OD seamless copper tub
-
ing with a minimum wall thickness of 0.035-inch and
expanded into the fin collars for maximum fin-tube
bond. Inner distributing tubes shall be 5/8-inch OD
seamless copper tubing with a minimum wall thick
-
ness of 1/4 inch. All header connections shall be of
red brass, with male pipe threads and silver braze to
headers. Casing shall be galvanized steel. The core
shall be pitched in the direction of the condensate
connection for proper drainage. Freezestat shall be
provided to prevent coil freeze up. Access doors shall
be provided for convenient access to the valve for
maintenance and inspection.
2.
Testing -
The completed coil, including headers and
connections, shall be tested underwater with 325
pounds compressed air to ensure a leak-free coil.
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 bottom
[side] of the unit. Holes shall be capped for field to make
suitable connection. Bottom [Side] penetration option
shall be provided with piping to extend out of the unit.
Electric Heat
An electric slip-in heater shall be installed within the rooftop
unit DA plenum to provide the heating requirements per
the schedule shown on the plans. The electric heater shall
be wired in such a manner as to provide a minimum of
two steps of capacity. Heating element branch circuits shall
be individually fused to maximum of 48 Amps per National
Electrical Code (NEC) requirements. Unit shall be provided
with staged [modulating 0-10VDC silicon controlled rectifier
(SCR)] electric heat.
1.
Heat Element -
The heating element shall be an in-
dustrial grade design using an open coil made of the
highest grade resistance wire containing 80% nickel
and 20% chromium. The resistance coils shall be ad-
equately supported in the air stream using ceramic
bushings in the supporting framework. Terminals of
the coil shall be stainless steel with high temperature
ceramic bushings.
2.
Safety Devices -
The primary high temperature pro-
tection shall be an auto reset type thermal cut out.
Secondary protection shall be a manual reset type
thermal cut out.
3.
Agency Certification -
The operation of the elec-
tric heater shall be an integral part of the
rooftop's
control system. Power connection to the heater shall
be through the power panel of the unit. Electric heat
shall be tested and certified in accordance with UL
60335-2-40.