Midco G69B - Manual (Page 6)

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FIGURE 9 Draft Hoods
FIGURE 10 Barometric Dampers
Figure 3 and 4 : Copyright by the American Gas Association.
Used by permission of the copyright holder.
If a draft hood is used, it should be of the same size as the
vent connector and should be located higher than the
highest part of the heating appliance flue passage.
If a barometric damper is used, it should be of the
double-swing type, which opens freely outward to afford
downdraft protection irrespective of settings made to the
balancing weights for updraft control. The damper should
be located so it is free to swing without interference from
surrounding objects so that the velocity pressure of the
flue gases does not interfere with its operation. See Figure
10 for proper installation.
When any vent connector passes through a partition the
draft control must be located in the same room as the
heating appliance. A device which will automatically shut
off gas to the burner in the event of sustained backdraft is
recommended if such backdraft might adversely affect
burner operation or if flue gas spillage might introduce a
hazard. If such a device is used, it shall be of the listed
type and installed and adjusted by a qualified service
technician in accordance with the manufacturerÕs
instructions.
V ELECTRICAL
The burner, when installed, must be wired and grounded in
accordance with local codes, or, in the absence of local
codes, with the National Electric Code ANSI/NFPA No.
70-latest edition. In Canada, refer to CSA Standard C22.1,
"Canadian Electrical Code Part 1."
CAUTION: REFER TO THE SEPARATE WIRING
DIAGRAM INCLUDED WITH EACH BURNER.
When wiring, be sure that the electric power take-off is
connected to a permanently live circuit and use multiple 14
gage copper wire conductors. Provide a fused disconnect
switch in the burner circuit. Each installation must include
a limit control to guard against excess temperature or
steam pressure. Steam or vapor systems will require a low
water cut-off.
VI PIPING
For the usual low pressure gas supply system, 5" to 14"
W.C. NATURAL (11" to 14" W.C. PROPANE) use Table 3
to find the recommended gas supply line size.
Piping follows normal practices and should be
connected to the burner in the manner shown in Figure 12.
If the piping must be rearranged because of space
limitations be sure to carry out the sequence of
components illustrated. While the pilot regulator can be
mounted in any position, the main regulator should be
mounted upright and in a horizontal run of pipe.
Run full size pipe or tubing from regulator vent openings
to outside of building. Provide no traps in the vent lines
and terminate away from all doors and windows; also
make provisions for keeping rain and foreign objects from
entering the vent piping.
When high supply gas pressure is encountered, as in
the case in many industrial plants, the gas line size can be
reduced to allow for a greater pressure drop; however, the
size must be sufficient to delivery burner rating pressure.
CAUTION: High gas pressure supply lines require
the proper pressure reducing regulators. Install two
separate high pressure regulators, of the Tight
Shut-Off type upstream of the low pressure regulators.
One sized for main gas input, and one suitable for the
minimum flow regulating capacity of the pilot.
The high pressure regulators may be substituted for the
low pressure regulators. If high pressure regulators are
used as substitutes, they must be adjustable down to a
minimum of 2"W.C. outlet pressure for the pilot and 5"
W.C. for the main gas. They must be adjustable down to
the maximum burner inlet pressure rating (14"W.C.).
DANGER: Explosion hazard.
Do not use oxygen for pressure testing. An
explosion could occur during initial start-up.
When the gas supply line is about to be put into service
it must be tested to insure that it is gas tight. Use air or
inert gas under pressure and test with soap and water or
other liquids to locate leaks.
CAUTION: Because it is difficult to accurately
control pressure, disconnect all low pressure (14"W.C.
max.) components (main and pilot) during supply pipe
leak testing. Exposing low pressure regulators and
valves to a pressure over 1Ú2 PSIG (14"W.C.) will
damage components and void their warranties.