GMS8 Installation Manual

19
M odels using Single Stage Gas Valves
Altitude Gas Kit Orifice
Manifold
Pressure
Pre ssure
Switch
3.5" w.c.
None
Propane LPT-03 #55 10.0" w.c.
NOTE:
*MS81405DN** models utilize #43 orifices in Natural gas
applications.
0 - 5500
Natural None #45
M odels using 2-Stage Gas Valves
High
Stage
Low
Stage
Natural None #45 3.5" w .c. 1.9" w .c. None
Propane LPM-06 #55 10.0" w .c. 6.0" w .c. None
0 - 5500
NOTE:
*MH81405DN** models utiliz e #43 orif ic es in Natural gas
applications.
Gas Altitude Kit Orifice
Manifold Pressure
Pressure
Sw itch
Change
Contact your distributor for a tabular listing of appropriate
manufacturer’s kits for propane gas and/or high altitude instal-
lations. The indicated kits must be used to insure safe and proper
furnace operation. All conversions must be performed by a quali-
fied installer, or service agency.
GAS PIPING CONNECTIONS
T O AVOID POSSIBLE UNSATISFACTORY OPERATION
PM ENT , USE THE PROPER SIZE
OF NATURAL / PROPANE GAS PIPING NEEDED W HEN RUNNING PIPE FROM
THE M ETER / TANK TO THE FURNACE .
OR EQUIPM ENT
DAM AGE DUE TO UNDERFIRING OF EQUI
WARNING
When sizing gas lines, be sure to include all appliances which will
operate simultaneously.
The gas piping supplying the furnace must be properly sized based
on the gas flow required, specific gravity of the gas, and length of
the run. The gas line installation must comply with local codes,
or in their absence, with the latest edition of the National Fuel
Gas Code, NFPA 54/ANSI Z223.1.
Natural Gas Capacity of Pipe
In Cubic Feet of Gas Per Hour (CFH)
Length of Nominal Black Pipe Size
Pipe in Feet 1/2" 3/4" 1" 1 1/4" 1 1/2"
10 132 278 520 1050 1600
20 92 190 350 730 1100
30 73 152 285 590 980
40 63 130 245 500 760
50 56 115 215 440 670
60 50 105 195 400 610
70 46 96 180 370 560
80 43 90 170 350 530
90 40 84 160 320 490
100 38 79 150 305 460
(Pressure 0.5 psig or less and pressure drop of 0.3" W.C.; Based on
0.60 Specific Gravity Gas)
CFH =
BTUH Furnace Input
Heating Value of Gas (BTU/Cubic Foot)
To connect the furnace to the building’s gas piping, the installer
must supply a ground joint union, drip leg, manual shutoff valve,
and line and fittings to connect to gas valve. In some cases, the
installer may also need to supply a transition piece from 1/2" pipe
to a larger pipe size.
The following stipulations apply when connecting gas piping.
• Use black iron or steel pipe and fittings for the building
piping.
• Use pipe joint compound on male threads only. Pipe
joint compound must be resistant to the action of the
fuel used.
• Use ground joint unions.
• Install a drip leg to trap dirt and moisture before it can
enter the gas valve. The drip leg must be a minimum of
three inches long.
• Install a 1/8" NPT pipe plug fitting, accessible for test
gage connection, immediately upstream of the gas supply
connection to the furnace.
• Use two pipe wrenches when making connection to the
gas valve to keep it from turning. The orientation of the
gas valve on the manifold must be maintained as shipped
from the factory.
• Install a manual shutoff valve between the gas meter
and unit within six feet of the unit. If a union is installed,
the union must be downstream of the manual shutoff
valve, between the shutoff valve and the furnace.
• Tighten all joints securely.
• Connect the furnace to the building piping by one of the
following methods:
– Rigid metallic pipe and fittings.
– Semi-rigid metallic tubing and metallic fittings.
Aluminum alloy tubing must not be used in exterior
locations.
– Use listed gas appliance connectors in accordance
with their instructions. Connectors must be fully in
the same room as the furnace.
– Protect connectors and semi-rigid tubing against
physical and thermal damage when installed. Ensure