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VZ-VZH-VZT-IOM (08-24) 1047121-A
Table 17. Required Manifold (Outlet) Gas Pressure
Model
Gas
Type
Burner
Setting
Unit Size (MBTUh)
40 60 80 100 115 125 140 150 175 200
Gas Manifold Pressure (IN WC)
VZ
Natural gas
—
3.5
Propane 10.5
VZH
Natural gas
—
3.5
—
3.5
—
3.5
—
Propane 10.5 10.5 10.5
VZT Natural gas
Low-fire
—
1.7 1.6
—
1.7
—
1.8
High-fire 3.3 3.4 3.5 3.7 3.9
ADJUSTMENTS—CONTINUED
Measure and Adjust Manifold Gas (Outlet) Pressure—Continued
4. Open combination gas valve and operate heater.
5. To measure low-fire pressure on model VZT, disconnect wire from HI terminal on valve. Be sure to reconnect wire.
⚠ CAUTION ⚠
DO NOT bottom out the regulator screw on the combination gas valve. This can result in unregulated
manifold pressure, which can cause excess overfire and burner and/or tube damage.
6. Observe manometer gauge to measure outlet pressure of gas valve. If manometer reading does not indicate
that valve outlet pressure is in accordance with Table 17, remove cap from regulator screw(s) (see Figure 38)
and adjust pressure by turning regulator screw IN (clockwise) to increase pressure or OUT (counterclockwise)
to decrease pressure.
7. When manometer reading indicates that outlet pressure is in accordance with Table 17, disconnect manometer
and install cap(s) on regulator screw(s).
8. Re-install panel(s) removed in step 1. For models VZ and VZT, reconnect combustion air piping to blower if unit
is connected to outside combustion air and plug in blower motor power cable.
MAINTENANCE
⚠ WARNING ⚠
• Turn OFF the gas and electrical power supply and allow heater to cool before performing any
service or maintenance.
• Edges are sharp. Wear protective gear during installation and maintenance.
• Eye protection is recommended when cleaning the unit.
⚠ CAUTION ⚠
• When any service is completed, ensure that the unit is reassembled correctly so that no unsafe
conditions are created.
• When re-lighting, always follow the lighting instructions on the heater.
• If any of the original wire supplied with the appliance must be replaced, it MUST BE replaced
with wiring material having a temperature rating of at least 220°F (105°C) and 600V.
• If replacement parts are required, use only factory-authorized parts.
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