92
(3.) No basepan penetration, other than those authorized by the manufacturer, is permitted.
10. Component access panels (standard)
a. Cabinet panels shall be easily removable for servicing.
b. Unit shall have one factory installed, tool--less, removable, filter access panel.
c. Panels covering control box, i ndoor fan, indoor fan motor, gas components ( where applicable ), and com-
pressors shall have molded composite handles.
d. Handles shall be UV modified, composite. They shall be permanently attached, and recessed into the pane l.
e. Screws on the vertical portion of all removable access panel shall engage into heat resistant, molded com-
posite collars.
f. Collars shall be removable and easily replaceable using manufacturer recommended parts.
23 81 19.13.I. Gas Heat
1. General
a. Heat exchanger shall be an induced draft design. Positive pressure heat exchanger designs shall not be al-
lowed.
b. Shall incorporate a direct--spark ignition system and redundant main gas valve.
c. Gas supply pressure at the inlet to t he rooftop unit gas valve must match that re quired by the manufac turer.
2. The heat exchanger shall be controlled by an integra ted gas cont roller (IGC) microprocessor.
a. IGC board shall notify users of fault using an LED (light--emitting diode).
b. IGC board shall contain algorithms that modify evaporator fan opera tion to pre vent future cycli ng on high
temperature limit switch.
c. Unit shall be e quipped with anti--cycle protection with one short cycle on unit flame rollout switch or 4
continuous short cycles on the high temperature limit switch. Fault indication shall be made using an LED.
3. Standard Heat Exchanger construction
a. Heat exchanger shall be of the tubular --section type constructed of a minimum of 20--gauge steel coated
with a nominal 1.2 mil aluminum--silicone alloy for corrosion resistance.
b. Burners shall be of the in--shot t ype construct ed of aluminum--coated steel.
c. Burners shall incorporate orifices for rated heat output up to 2000 ft (610m) elevation. Additional accessory
kits may be required for applic ations above 2000 ft (610m) elevation, depending on local gas supply condi-
tions.
d. Each heat exchanger tube shall contain multiple dimples for increased heating effectiveness.
4. Optional Stainle ss Steel Heat Exchanger construction
a. Use energy saving, direct--spark ignition system.
b. Use a redundant main gas valve.
c. Burners shall be of the in--shot type constructed of aluminum--coated ste el.
d. All gas piping shall enter the unit cabinet at a single location on side of unit (horizontal plane).
e. The optional stainless steel heat exchanger shall be of the tubular--section type, constructed of a minimum
of 20--gauge type 409 stainless steel.
f. Type 409 stainless steel shall be used in heat exchanger tubes and vestibule plate .
g. Complete stainless steel heat exchanger allows for greater application flexibility.
5. Optional Low NO
x
Heat E xchanger construction
a. Low NO
x
reduction shall be provided to reduce nitrous oxide emissions to meet California’s Air Quality
Management District (SCAQMD) low--NO
x
emissions requirement of 40 nanograms per joule or le ss.
b. Primary tubes and vestibule plates on low NO
x
units shall be 409 stainl ess steel. Other components shall be
aluminized steel.
6. Induced draft combustion motor and blower
a. Shall be a direct -- drive, single inlet, forward--curved centrifugal type.
b. Shall be made from steel with a corrosion--resistant finish.
c. Shall have permanently lubricated sealed bearings.
d. Shall have inherent thermal ove rload prote ction.
e. Shall have an automatic reset feature.
23 81 19.13.J. Coils
1. Standard Aluminum Fin -- Copper Tube Coils:
a. Standard evapora tor and condenser coils shall have aluminum lanced plate fins mechanically bonded to
seamless internally grooved copper tubes with all joints brazed.
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