Installation
48 RT-SVX36K-EN
Gas Heat Units (SFH_)
All internal gas piping is factory-installed and pressure
leak-tested before shipment. Once the unit is set into
place, the gas supply line must be field-connected to the
elbow located inside the gas heat control compartments.
Access holes are provided on the unit as illustrated in
Figure 15, p. 29 to accommodate a side or bottom pipe
entry on 20 through 89Ton units and in Figure 17, p. 33 on
90-130Ton units. Following the guidelines listed below will
enhance both the installation and operation of the furnace.
Note: In the absence of local codes, the installation must
conform with the American National Standard
Z223-1a of the National Fuel Gas Code, (latest
edition).
1. To assure sufficient gas pressure at the unit, use
Table 24, p. 61 as a guide to determine the appropriate
gas pipe size for the unit heating capacity listed on the
unit's nameplate.
2. If a gas line already exists, verify that it is sized large
enough to handle the additional furnace capacity
before connecting to it.
3. Take all branch piping from any main gas line from the
top at 90 degrees or at 45 degrees to prevent moisture
from being drawn in with the gas.
4. Ensure that all piping connections are adequately
coated with joint sealant and properly tightened. Use a
piping compound that is resistant to liquid petroleum
gases.
5. Provide a drip leg near the unit.
6. Install a pressure regulator at the unit that is adequate
to maintain 7" w.c. for natural gas while the furnace is
operating at full capacity.
Note: Gas pressure in excess of 14" w.c. or 0.5 psig will
damage the gas train.
Failure to use a pressure regulating device will result in
incorrect gas pressure.This can cause erratic operation
due to gas pressure fluctuations as well as damage the gas
valve. Over sizing the regulator will cause irregular
pulsating flame patterns, burner rumble, potential flame
outages, and possible gas valve damage.
If a single pressure regulator serves more than one rooftop
unit, it must be sized to ensure that the inlet gas pressure
does not fall below 7" w.c. with all the furnaces operating
at full capacity.The gas pressure must not exceed 14" w.c.
when the furnaces are off.
7. Provide adequate support for all field installed gas
piping to avoid stressing the gas train and controls.
8. Leak test the gas supply line using a soap-and-water
solution or equivalent before connecting it to the gas
train.
9. Check the supply pressure before connecting it to the
unit to prevent possible gas valve damage and the
unsafe operating conditions that will result.
Note: Do not rely on the gas train shutoff valves to isolate
the unit while conducting gas pressure/leak test.
These valves are not designed to withstand
pressures in excess of 14" w.c. or 0.5 psig.
Connecting the Gas Supply Line to the
Furnace Gas Train
Follow the steps below to complete the installation
between the supply gas line and the furnace. Refer to
Figure 30 through Figure 33 for the appropriate gas train
configuration.
1. Connect the supply gas piping using a “ground-joint”
type union to the furnace gas train and check for leaks.
2. Adjust the inlet supply pressure to the recommended
7" to 14" w.c. parameter for natural gas.
3. Ensure that the piping is adequately supported to
avoid gas train stress.
WARNING
Hazardous Gases and Flammable Vapors!
Exposure to hazardous gases from fuel substances
have been shown to cause cancer, birth defects or other
reproductive harm. Improper installation, adjustment,
alteration, service or use of this product could cause
flammable mixtures. To avoid hazardous gases and
flammable vapors follow proper installation and set up
of this product and all warnings as provided in this
manual. Failure to follow all instructions could result in
death or serious injury.
When using dry nitrogen cylinders for pressurizing
units for leak testing, always provide a pressure
regulator on the cylinder to prevent excessively high
unit pressures. Never pressurize unit above the
maximum recommended unit test pressure as specified
in applicable unit literature. Failure to properly regulate
pressure could result in a violent explosion, which
could result in death or serious injury or equipment or
property-only-damage.
Table 17. Specific gravity multipliers
Specific Gravity Multiplier
0.50 1.10
0.55 1.04
0.60 1.00
0.65 0.96
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