TM 5-3895-374-24-2 Table 7 Suggested Firebox Boiler Combustion Chamber Dimensions Oil (C) Gas Input Minimum Model Input GPH (W) (L) Tube Number MBTU Hr. #1, #2 Oil Width Length Height C1-GO-10 300 2.5 13 17 3 C1-G-10 500 3.5 16 22 3 C1-0 800 6 19 25 3 980 7 20 28 3 C1-GO-12 700 5 13 17 3 C1-G-12 900 6.5 20 28 3 C1-0 1150 8 22 30 3 1260 9 23 33 3 C2-GO-15 1000 7 21 29 5 C2-G-15 1300 9 23 33 5 C2-OA 1600 13 25 38 5 2100 15 27 42 5 C2-GO-20 1500 11 25 38 5 C2G-20 2000 14 27 42 5 C2-OB 2500 18 29 46 5 2900 22 30 48 5 Oil (C) Gas Input Minimum Model Input GPH (W) (L) Tube Number MBTU Hr. #1, #2 Oil Width Length Height C3-GO 2400 17 27 44 5 CG-3 3300 24 33 53 6 C3-O 4200 30 37 62 8 5250 37.5 40 68 9 C4-GO-30 4000 29 35 58 8 C4-GO-30 5500 40 42 70 9 C4-O 7000 50 45 76 12 7840 56 48 79 13 C5-GO-30 6000 43 43 72 10 C5-G-30 7500 53 48 79 13 C5-O 9000 65 50 80 13 10500 75 54 84 15 C6-GO-30 8000 57 48 79 13 C6-G-30 10500 75 54 84 15 C6-0 12500 89 60 90 17 14215 101.5 64 95 18 Note: These  dimensions  are  to  serve  as  a  guide only, and may be modified providing approximate area is maintained. 3.  MECHANICAL OPERATION OF FUEL/AIR CONTROL MODES Figure 18 Typical Gas Burner with On-Off Fuel/Air Control Mode (Model CR-G) MECHANICAL   OPERATION:   This   system   uses   a   combination Diaphragm   Gas   Valve   and   Integral   Pressure   Regulator   (1)   to control the on-off operation of gas to the Firing Head (2).  A proven spark  ignited  gas  pilot  provides  ignition  for  the  main  flame.    Gas flow  control  rate  is  accomplished  by  adjustment  of  the  main  gas pressure  regulator  and  by  a  Limiting  Orifice  (a  limiting  orifice  is used  wen  the  gas  flow  rate  -  BTU  input  -  through  the  gas  train components is higher than desired), located in the Side Orifice Tee fitting (5) at the inlet to the gas manifold.  The Air Dampers (6) are adjusted  and  locked  in  place  with  the  Air  Damper  Arms  (7)  for  a fixed firing rate.  When the gas pilot’ has been proven by the flame detector’, the Diaphragm Gas Valve will open slowly, allowing gas to the Firing Head.  Firing head gas pressures are measured at the 1/4 Plugged Gauge Test Port (8) in the Side Orifice Tee.  Refer to page 33, Table 10 for orifice sizing information.  See page 32, Fig.  33 for side orifice detail. *Not shown in this depiction.  See page 3, Fig.  1. Note 1 Component     operational sequencing will vary    with    the    specific    Flame    Safeguard Control  being  used.    Refer  to  the  specific Flame  Safeguard  Control  bulletin   supplied with the burner for complete information. Note 2 Optional  On/Off   systems   may   be   supplied using a separate gas pressure regulator and separate  diaphragm  or  motorized  gas  valve in  place  of  the  combination  regulator/valve unit   depicted.      Other   components   would remain as described. (page 3 - 965)