| Optional Items Intermittent Pilot with 100% shut-off - Provides increased
safety for natural gas firing (standard on propane fired units). It pilot fails to ignite
within a given time period, system will lockout and require manual restarting.
230 volt primary /24 volt control circuit
- For higher voltage applications.
High fuel pressure regulators :
a. 8" to 15" line pressure (pilot regulator only)
b. 1/2 lb. to 5 lb. line pressure
c. 6 lb. to 40 lb. line pressure (specify gas pressure)
Two-stage gas valve - For applications
requiring only make-up air. Direct-acting non-electric valve modulates gas flow to provide
constant leaving air temperature.
Modusnap gas valve & by-pass manifold
- For application requiring both make-up air and space heating. Modusnap valve provides
minimum leaving air temperature and by-pass valve admits full gas input whenever
thermostat calls for space heating. Thermostat is a required extra.
"Selectra" Modulation Systems
MS-1 For applications requiring only
make-up air, Maxitrol solid state electronic modulating system provides constant
leaving air temperature. Wall mounted "Selectrastat" permits adjustment of
discharge air temperature from convenient location.
MS-2: For space heating only applications.
Maxitrol solid state electronic modulating system provides continuous blower operation and
extremely close control of space temperature. Sensitive to 1/10 F.
MS-3: For make-up air and space heating
applications. Same as MS-1, but with two-position overriding room thermostat for space
heating as well as make-up air.
Selection Procedure
1 Determine required model size from performance tables
using desired Btuch output with desired temperature rise, read pressure drop and
corresponding airflow.
2. Choose either gravity vented ("RDG") or power
vented ("RDV") model.
3. Also specify heat exchanger type., and any optional
items or accessories. Note: For applications where furnace inlet air temperature is 40 F
or less, type 409 or type 321 stainless steel heat exchanger is recommended.
Example : Select rooftop duct furnace for
304,000 Btuch output with 40F temperature rise.Application is space heating with
inlet temperature of 60 F in non-corrosive environment. Fuel is natural gas.
Selection :
1. From Table 1, model size no, 400 is chosen with 304,000
Btuch output. For 40F rise,pressure drop = 0.07" W.C. and airflow = 7.040 SCFM.
2. RDG model is picked for gravity venting.
3. Aluminized heat exchanger is chosen.
Selection is thus complete :
RDG-400 with aluminized heat exchanger for natural gas
firing. Unit develops 304,000 Btuch output at 0.07"w.c. pressure drop with 40 F rise
and 7,040 SCFM. |
