Keeprite LO Error Code

What does Keeprite LO mean?

The LO fault on the Keeprite PGD4/PGS4 packaged gas-electric unit indicates that the low gas pressure switch (LGPS) has opened, interrupting gas flow to the burners. The LGPS is a safety device that opens when manifold or supply gas pressure drops below the minimum threshold required for safe, stable combustion. The unit shuts down gas heat until adequate pressure is restored.

Symptoms

• Gas burners fail to light or extinguish shortly after ignition
• Unit displays LO on the diagnostic indicator during a heating call
• Heating failure occurs most often during periods of high neighborhood gas demand
• Other gas appliances in the building may also show reduced flame or ignition difficulty

Common causes

• Insufficient gas supply pressure from the utility, especially during peak demand periods
• Partially closed upstream manual gas shutoff valve reducing pressure at the unit
• Failed or undersized gas meter or service regulator providing inadequate flow
• Low gas pressure switch out of calibration, opening at pressures above the minimum threshold
• Wiring fault or open circuit in the LGPS circuit causing a false low-pressure indication

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Diagnostic steps

1. Check all gas shutoff valves

   Verify that the main gas shutoff, service cock at the unit, and any intermediate shutoff valves are fully open. A partially closed valve is the most common and easily corrected cause of low gas pressure.

2. Measure supply gas pressure

   Connect a manometer to the inlet pressure tap on the gas valve. Measure pressure with the burners firing; supply pressure must not fall below 4.5 in. w.c. for natural gas at full fire. Record the reading for comparison.

3. Test the low gas pressure switch

   With power off, disconnect the LGPS and measure continuity across its terminals. The switch should be closed at atmospheric pressure. An open switch at rest is failed and requires replacement.

4. Inspect LGPS wiring and connections

   Trace the LGPS wiring harness and check for loose terminals or damaged insulation. Secure any loose connections and repair any wire damage before retesting.

5. Contact the gas utility if pressure is confirmed low

   If measured supply pressure is below 5 in. w.c. under load, the gas meter, service regulator, or service line is undersized or malfunctioning. Contact the gas utility to investigate and correct the service.

When to call a professional

If supply gas pressure is below specification and all shutoff valves are open, the issue is upstream of the unit and requires the gas utility or a licensed gas contractor to inspect the meter and service regulator. If gas pressure is correct and the LGPS is still tripping, a licensed HVAC technician must replace the switch or investigate for wiring faults. Do not operate the unit with an unverified low gas pressure condition.