Jandy LXi Gas Pressure Problems: Supply and Manifold Troubleshooting

Gas Pressure Specifications

• Natural Gas inlet supply: minimum 5.0″ WC, maximum 10.5″ WC
• LP inlet supply: minimum 11.0″ WC, maximum 14.0″ WC
• Natural Gas manifold: 2.5″ WC (with heater firing)
• LP manifold: 9.0″ WC (with heater firing)
• Burner throat pressure: 1.0″ WC (both gas types)
• Gas connection: 3/4″ NPT for both NG and LP

Step-by-Step Troubleshooting

Measure inlet supply pressure

1. Connect a manometer to the inlet pressure tap on the gas valve.
2. Measure with heater OFF (static) and firing (dynamic). Supply should stay within spec under load.
3. If dynamic pressure drops significantly, the gas line or meter cannot deliver enough gas.

If supply pressure is low

1. Check gas meter capacity. The LXi 250 draws 250,000 BTU/hr; the LXi 400 draws 399,000 BTU/hr. Add all other gas appliances for total demand.
2. Check gas line sizing. Pipe diameter must be adequate for BTU demand and run length. See manual Section 4.1, Table 5.
3. For LP: check tank level. Low tank = low pressure, especially in cold weather.
4. Check for restrictions: closed shutoff valves, kinked flex connectors, or debris in sediment trap.

Measure manifold pressure

1. Connect a manometer to the manifold pressure tap.
2. With heater firing: NG should read 2.5″ WC, LP should read 9.0″ WC.
3. If supply is adequate but manifold pressure is wrong, the gas valve regulator is likely faulty. Replace the gas valve.

Measure burner throat pressure

1. Locate the burner throat pressure tap and connect a manometer.
2. With heater firing, throat pressure should be 1.0″ WC.
3. Adjust using the air orifice slider on the blower intake.

Common Parts That Fix This Problem

• Gas valve/regulator assembly
• Gas orifices (if wrong size for gas type)
• Flex connector (if kinked or undersized)
• Sediment trap/drip leg (if clogged)

Model-Specific Notes

• The LXi 400 demands significantly more gas than the 250. Gas line sizing adequate for a 250 may not work for a 400 on long runs.
• Test with all gas appliances running simultaneously if possible.
• Propane heaters at high altitude may need orifice changes. Contact Zodiac Technical Support at 800.822.7933.