| RD SERIES ROOFTOP GAS
DUCT FURNACE The Hastings RD series is a
complete line of weatherproof duct furnaces for rooftop installation. Both gravity
vented (RDG models) and power vented (RDF models) furnaces are available with balanced
flue design to assure good combustion at all operating conditions.
The RD series utilizes Hastings patented airfoil shaped heat
exchanger, shown in Figure 1. with horizontal radiation ribs and large free area
between tubes to yield heat transfer and low pressure drop.
Internal baffles are included to lengthen the path of the
hot flue gas, increasing heat transfer. External vertical airfoil baffles are placed
between each pair or tubes to cause the air to scrub the tube surfaces and pick up more
heat. The external baffles also deflect more air towards the bottom of the tubes where
heat pickup is greatest. On high airflow applications
(50 F temperature rise and less), the air velocity is so
great that external baffles are unnecessary, and they are removed to reduce
even further the already low air pressure drop. As a consequence, by-pass ducts and
dampers are eliminated., saving both cost and space. The potential problems of air
stratification and heat exchanger burnout associated with furnace by-pass systems are also
prevented. Nor is it necessary to oversize the duct furnace to avoid by-pass ducts.
To provide a broad range of production against the effects
of high temperature and corrosion, heat exchangers for the RD series are available in
three steels. Aluminized steel, as standard, is cold-rolled steel with silicone aluminum
fused to both sides to provide a material much superior to ordinary or ceramic-coated
steel. Type 409 heat exchanger stainless steel is a low carbon steel containing
about 12% chromium and a small amount of nickel that offers greater corrosion
resistance than aluminized steel at slightly more cost. For extremely high resistance to high
temperature and corrosion, type321stainless steel a titanium stabilized steel containing
18% chromium and 10%nickel, is recommended.
Single furnaces are available from 100 MBH to 400 MBH heat
input. Two identical furnaces, each with individual gas manifold, may be factory assemble
for the inputs of 500 to 800 MBH Models with suffix "A" consist of two furnaces
arranged side by forl high airflow, suffix "B" models have two furnaces in
series for high temperature rise.
Several types of modulation are offered to adapt RD series
furnaces to space heating, make-up air, and combined heating and ventilating
applications.
All RD series duct furnaces are A.G.A./C.G.A. design
certified and approved for installation downstream from cooling coils
Standard Equipment
Cabinet:
Aluminized steel weatherproof construction of 20 gauge
thickness with enamel exterior finish.
Heating Section:
Choice of three all electric -welded heat exchangers:
1. Aluminized steel, 18 gauge tubes and 16 gauge header
plates. Internal baffles are .032". Type 409 stainless steel with stainless steel
tips.
2. Type 409 stainless steel 044" tubes and .050"
header plates.Internal baffles are 32". Type 409 stainless steel with stainless steel
tips.
3. Type 321 stainless steel, .041" tubes and
.060" Type 409 header plates Internal baffles are .02" Type 409 stainless steel
with stainless steel tips.
Burners are 18 gauge aluminized steel with Type 430
stainless steel ribbon inserts to provide automatic proportioning of primary combustion
air. Burners and pilot are mounted in side-out burner tray to ease of maintenance. Pilot
is intermittent with non-100% shut off as standard for natural gas and 100% shut off as
stand.and for propane.
Venting System:
Gravity vented units(" RDG " models) feature a
balanced flue design in which combustion air is drawn down a partitioned vent cap while
flue gas products are vented up the exhaust section of the same cap.
Power vented units ("RDV" models) also feature a
balanced flue design with an integral power venter operating to draw combustion air evenly
across the burner while venting the products of combustion at the same time.
Gas and Electrical Components:
Main gas cock, main and pilot gas pressure regulators,pilot
gas cock, main solenoid gas valve, pilot solenoid gas valve, electronic spark
ignition system, high limit control, 115/24 volt control transformer
Electrical System:
115 volt primary with 24 volt control circuit to produce
even temperature.
Gas System:
For inlet gas pressure of 6" to 14" w.c. natural
gas , or 11" to 14" w.c. propane. |
