| SD SERIES INDOOR GAS DUCT FURNANCE HIGH CFM-LOW STATIC PRESSURE -NO BY-PASS
The Hastings SD series is a complete line of gas fired duct
furnaces for indoor installation. These duct fur nances feature low air pressure drop
heat exchangers which reduces motor horsepower requirements or eliminates expensive
by-pass ducts.
The Sd series utilizes Hastings' patented air foil shaped
heat exchanger shown in Figure 1, with horizontal radiation ribs and large free area
between tubes to yield high heat transfer and low air 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 of 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 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 the 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 protection against the effects
of high temperature and corrosion, heat exchangers for the SD 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 stainless steel heat exchangers offer greater corrosion resistance than
aluminized steel at slightly more cost. Type 409 exchangers are recommended for use with
make-up air units or with duct furnaces downstream of cooling coils. Type 321 stainless
steel heat exchangers are available for those applications requiring the greatest
corrosion resistance.
Single furnaces are available from 50 MBH to 400 MBH heat
input. Two identical furnaces, each with individual gas manifolds, may be factory close
coupled for heat inputs of 510 to 800 MBH. Double furnace banks may, in turn, be assembled
for inputs up to 1,600 MBH.
Several types of control systems, one or two stage,
modulation or combination, are offered to adapt SD series duct furnaces to space heating,
make-up air and heating and ventilating applications.
All SD series ducts furnaces are A.G.A. /C.G.A. design
certified and approved for installation downstream from cooling coils.
Standard Equipment
Cabinet:
Side panels of 20 gauge cold rolled steel. 20 gauge
aluminized steel drain pans on all models except SD-400 which is constructed of 18 gauge.
Side panels and drain pans are finished with baked enamel.
Slip-joint type ducts flanges on both air intake and
discharge. Adjustable two-point suspension hangers on DU-50 and SD-100 thru 160. Fixed
four-point hangers on all other SD models.
Draft Hood:
22 gauge aluminized steel.
Heating Section:
Choice of three all electric-welded heat exchangers:
- Aluminized steel, 18 gauge tubes and 16 gauge header plates.
All electric welded construction. Internal baffles are 032" type 409 stainless
steel with stainless steel tips.
- Type 409 stainless steel .044" tubes and .050"
header plates. Internal baffles are .032" Type 409 stainless steel with type 442
stainless steel tips.
- Type 321 (chrome-nickel) stainless steel, .041" tubes
and .060" type 409 header plates. Internal baffles are .032" type 409 stainless
steel with stainless steel tips.
Burners are 18 gauge aluminized steel with type 430
stainless steel ribbon inserts to provide automatic proporating of primary combustion air.
Gas and Electrical Components:
24 volt combination gas valve consisting of main and pilot
gas cocks, main and pilot gas pressure regulators,s redundant solenoid gas valves, pilot
solenoid gas valve and 100% safety shut-off; also high limit control and 115/24 volt
control transformer. Model SD-300, 400, 600 and 800 are furnished with electronic ignition
systems are standard.
Electrical System:
115 volt primary with 24 volt control circuit.
Gas System:
For inlet gas pressure of 6" to 14" w.c. natural
gas, or 11" w.c. propane. |
