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48VGUK: Installation Instructions
5. The evaporator fan will turn on 30 sec. after the flame has been
established. The evaporator fan will turn off 90 sec. after the
thermostat has been satisfied. Please note that the integrated gas
unit controller (IGC) has the capability to automatically reduce the
evaporator "ON" delay and increase the evaporator "OFF" delay in
the event of high duct static and/or partially-clogged filter.
Check Gas Input
Check gas input and manifold pressure after unit start-up (See
If adjustment is required proceed as follows:
• The rated gas inputs shown in
to 2000 ft (610 m) above sea level. These inputs are based on natural
gas with a heating value of 1025 Btu/ft
Table 3 – Altitude Derate Multiplier for U.S.A.
Altitude ft (m)
Percent of Derate
0-2000
(0-610)
*. Derate multiplier factors are based on midpoint altitude for altitude range.
When the gas supply being used has a different heating value or specific
gravity, refer to national and local codes, or contact your distributor to
determine the required orifice size.
CAUTION
!
UNIT DAMAGE HAZARD
Failure to follow this caution may result in reduced unit and/or
component life.
Do Not redrill an orifice. Improper drilling (burrs, out-of-round holes,
etc.) can cause excessive burner noise and misdirection of burner flame.
If orifice hole appears damaged or it is suspected to have been redrilled,
check orifice hole with a numbered drill bit of correct size.
Adjust Gas Input
The gas input to the unit is determined by measuring the gas flow at the
meter or by measuring the manifold pressure. Measuring the gas flow at
the meter is recommended for natural gas units.
Measure Gas Flow (Natural Gas Units)
Minor adjustment to the gas flow can be made by changing the manifold
pressure. The manifold pressure must be maintained between 3.2 and 3.8
IN. W.C.
ON/OFF SWITCH
INLET
PRESSURE TAP
Fig. 13 – Single-Stage Gas Valve (208/230 VAC Models)
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
Table
Table 5
are for altitudes from sea level
3
at 0.60 specific gravity.
Derate Multiplier
*
Factor
0
1.00
REGULATOR
COVER SCREW
PLASTIC
ADJUSTMENT
SCREW
REGULATOR SPRING
(PROPANE - WHITE)
(
NATURAL - SILVER)
GAS PRESSURE
REGULATOR
ADJUSTMENT
MANIFOLD
PRESSURE TAP
5).
Fig. 14 – Single-Stage Gas Valve with Tower Pressure Ports
If larger adjustments are required, change main burner orifices following
the recommendations of national and local codes.
NOTE: All other appliances that use the same meter must be turned off
when gas flow is measured at the meter.
Proceed as follows:
1. Turn off gas supply to unit.
2. Manifold pressure connections
a. For standard gas valves, remove manifold pressure tap cover
using an allen wrench. (See
and hose to connect to manometer. Turn on gas supply to unit.
b. For gas valve with tower pressure ports, loosen set screw on
manifold tower pressure tap no more than one full turn with a
3/32-in. hex wrench. (See
sliding 5/16" connecting hose over the manifold tower pressure
port. Turn on gas supply to unit.
3. Record number of seconds for gas meter test dial to make one
revolution.
4. Divide number of seconds in Step 3 into 3600 (number of seconds
in one hr).
5. Multiply result of Step 4 by the number of cubic feet (cu ft) shown
for one revolution of test dial to obtain cubic feet (cu ft) of gas flow
per hour.
6. Multiply result of Step 5 by Btu heating value of gas to obtain total
measured input in Btuh. Compare this value with heating input
shown in
Table 5
of gas is not known).
EXAMPLE: Assume that the size of test dial is 1 cu ft, one revolution
takes 32 sec, and the heating value of the gas is 1050 Btu/ft3. Proceed as
follows:
1. 41 sec. to complete one revolution
2. 3600 / 41 = 87.8
3. 87.8 x 1 = 87.8 ft
4. 87.8 x 1050 = 92,190 Btuh input
If the desired gas input is 89,000 Btuh, only a minor change in the
manifold pressure is required.
Observe manifold pressure and proceed as follows to adjust gas input:
1. Remove regulator cover screw over plastic adjustment screw on gas
valve (See
Fig. 13
2. Turn plastic adjustment screw clockwise to increase gas input, or
turn plastic adjustment screw counterclockwise to decrease input
(See
Fig. 13
and
and 3.8 IN. WC.
NOTE: Manifold pressure must be checked with the access door on.
A07551
16
Fig.
13). Install barbed pressure tap
Fig.
14.) Connect manometer by
(Consult the local gas supplier if the heating value
3
of gas flow/hr
and
Fig.
14).
Fig.
14). Manifold pressure must be between 3.2
A170118
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