4
Midco
International
Inc.
8470 70
Installation
When natural draft is used and the chimney height is over 25 feet, a barometric damper of the same
size as the vent connector should be installed. If the chimney is high enough to make it diffi cult for
the barometric to maintain a maximum incineration chamber over-fi re draft, (0 to minus 0.5″ W.C. for
Model J81A-3, 0 to minus 1.0″ W.C. for Model J121A-3), a fi xed damper should be installed in the
vent connector between the barometric and chimney to restrict the chimney draft to a point within
the controlling capacity of the barometric. After fi nal setting, the damper should be permanently
fastened into position per ANSI Z223.1-1992 “National Fuel Gas Code”, or latest edition available
from American National Standards Institute to prevent tampering.
_______________________________________
The supply piping to the burner should branch off from the main line as close to the source as
possible (NATURAL gas meter or PROPANE tank regulator). When branching off from an existing
gas line, do not tap off the bottom of a horizontal section. Use new black pipe and malleable fi ttings
free from cutting and threading burrs or defects.
Use pipe joint compound resistant to liquid petroleum gases when using either NATURAL or
PROPANE gas. Piping must comply with the local and national codes. If the burner piping must be
rearranged because of space limitations, be sure to carry out the general confi guration shown in
Figure 3.
A suitable Main Gas Pressure Regulator should be installed as shown in Figures 1 or 3. Choose a
regulator(s) to adjust the available gas pressure to the pressure shown in SPECIFICATIONS, page
2.
CAUTION: The regulated gas pressures must not exceed 14
″
W.C. or Main Automatic
Gas Valve and Ignitor Regulator will be damaged. If excessive gas pressure is prevalent, the
regulator must be a tight shut-off type to prevent high pressures from developing during
stand-by. The regulator must have a minimum fl ow regulating capacity for the ignitor gas rate
(see Table 4). It is strongly recommended that a separate smaller regulator be used for ignitor
gas, connecting to the gas line ahead of the Main Gas Pressure Regulator and downstream
of any intermediate Regulator.
For full input, refer to SPECIFICATIONS, page 2, for minimum gas pressure required. For reduced
capacities, refer to Firing Rate Curves, Table 2 or 3.
CAUTION: If gas supply pressure is below its specifi ed range during adjustment, an
over-fi re condition could result when pressure returns to normal, particularly if the regulator
adjustment screw is bottomed out. ALWAYS confi rm that at least the minimum rated pressure
is being supplied during regulator adjustments, and NEVER BOTTOM OUT regulator screw.
When selecting the burner supply piping size per Table 1, the permissible pressure drop must
be based on the pressure available at the inlet to the supply pipe branch line when all other gas
equipment fed by the same source (NATURAL gas meter or PROPANE tank regulator) is fi ring at full
rate. Also take into account any other INCINOMITE burners to be attached to the same branch line.
NPT Approximate Capacity - MBH
Pipe Type Length of Pipe / Feet
Size of Gas 10 20 40 60 100
3/4″ Natural 275 200 130 100
Propane 450 300 200 165 125
1″ Natural 520 350 245 195 150
Propane 820 550 385 300 235
1-1/4″ Natural 1050 730 500 400 300
Propane 1200 1150 790 630 480
1-1/2″ Natural 1200 1100 760 610 460
Propane 1200 1200 960 725
2″ Natural 1200 1200 1150 870
Propane 1200 1200
Capacities shown are for total pressure drop of 0.3
″
W.C. For higher
permissible pressure drops consult your fuel supplier.
Source
: Gas Engineers Handbook-1974 Industrial Press Inc. NY, NY
Table 1 - Schedule 40 Pipe Capacities in MBH
V Piping
!
!
IV Chimney, Vent
Connector and Draft
Control
Continued
