![background image](http://html1.mh-extra.com/html/desa/vsf20nt/vsf20nt_safety-information-and-installation-manual_2485667010.webp)
www.desatech.com
116307-01A
10
INSTALLATION
Continued
CONNECTING TO GAS SUPPLY
WARNING: This appliance
requires a 3/8" NPT (National
Pipe Thread) inlet connection to
the pressure regulator.
WARNING: A qualified ser-
vice person must connect heater
to gas supply. Follow all local
codes.
WARNING: For natural
gas, never connect heater to
private (non-utility) gas wells.
This gas is commonly known
as wellhead gas.
IMPORTANT:
For natural gas, check gas line
pressure before connecting heater to gas line. Gas
line pressure must be no greater than 10.5" of wa-
ter. If gas line pressure is higher, heater regulator
damage could occur.
CAUTION: For propane/LP
gas, never connect heater di-
rectly to the propane/LP supply.
This heater requires an external
regulator (not supplied). Install
the external regulator between the
heater and propane/LP supply.
For propane/LP gas, the installer must supply an
external regulator. The external regulator will
reduce incoming gas pressure. You must reduce
incoming gas pressure to between 11" and 14" of
water. If you do not reduce incoming gas pressure,
heater regulator damage could occur. Install the
external regulator with the vent pointing down
as shown in Figure 10. Pointing the vent down
protects it from freezing rain or sleet.
CAUTION: Use only new,
black iron or steel pipe. Inter-
nally-tinned copper tubing may
be used in certain areas. Check
your local codes. Use pipe of
large enough diameter to allow
proper gas volume to heater. If
pipe is too small, undue loss of
volume will occur.
Typical Inlet Pipe Diameters
20,000 Btu/Hr Models - 3/8" or greater
30,000 Btu/Hr Models - 1/2" or greater
Installation must include equipment shutoff valve,
union and plugged 1/8" NPT tap. Locate NPT
tap within reach for test gauge hook up. NPT
tap must be upstream from heater (see Figure
11, page 11).
IMPORTANT:
Install an equipment shutoff valve
in an accessible location. The equipment shutoff
valve is for turning on or shutting off the gas to
the appliance.
Apply pipe joint sealant lightly to male NPT
threads. This will prevent excess sealant from
going into pipe. Sealant in pipe could result in
clogged heater valves. Most flex gas tubing does
not require sealant. Read instructions supplied
with flex gas tubing.
WARNING: Use pipe joint
sealant that is resistant to liquid
petroleum (LP) gas.
Install sediment trap in supply line as shown in
Figure 11, page 11. Locate sediment trap where
it is within reach for cleaning. Locate sediment
trap where trapped matter is not likely to freeze.
A sediment trap traps moisture and contaminants.
This keeps them from going into heater controls. If
sediment trap is not installed or is installed wrong,
heater may not run properly.
Install male connector and flex gas line to equipment
shutoff valve as shown in Figure 11, page 11.
Figure 10 - External Regulator With Vent
Pointing Down
External
Regulator
Propane/LP
Supply Tank
Vent
Pointing
Down