Newly installed gas tank water heater with its flue, gas line and water connections
9 components covered

Field manual · Water Heater

A.O. Smith and State residential power-vent gas tanks with Intelli-Vent hot-surface control (GPVL, GPVT, GPVH, GPSH, GPDH; State PR6 power vent): quick sheet (diagnostic and electrical side)

Covers: A.O. Smith residential power-vent and power direct-vent gas tanks with a blower on top and a hot surface ignitor: ProLine XE GPVL-40/50 (40,000 BTU/h, short), GPVT (tall), older GPVH, GPVR, GPSH and GPDH (power direct vent). State equivalents such as PR6 40/50 XCVIT / CCVIT (power vent) and XBPDT / CBPDT (power direct vent), and State GP6 power vent. Search terms: AO Smith power vent, GPVL-50, GPVT-40, Intelli-Vent, Intellivent error code, power vent pressure switch, power vent water heater won't light. The error-code section applies to units with the 6-LED Intelli-Vent gas control (two temperature buttons, LED bar). Atmospheric ProLine/Signature tanks with the thermopile control and Vertex condensing units are different (separate sheet).

Single sourceBrands: A.O. Smith, State9 components

A 40 or 50 gal gas tank with a 120 V blower that pushes flue gas out through 2, 3 or 4 in plastic pipe, a sealed FVIR combustion chamber and a hot surface ignitor (no standing pilot). The Intelli-Vent combination control (an Emerson / White-Rodgers part) handles temperature, ignition, blower, flame sensing and gas regulation, and reports faults as LED combinations. Most no-heat calls come down to power (polarity and ground), the air pressure switch circuit, the ignitor, lint-clogged intake screens or the flammable-vapor sensor. The gas control, burner, flame sensor, flue baffle and vent piping are blocked for this library.

Safety first

  • Gas control, burner, flame sensor, ignitor assembly replacement, manifold or supply gas pressure, flue baffle and vent piping are blocked: refer to a licensed plumber or gas technician. Gas odor: leave and call the utility.
  • 120 V AC at the control, blower and ignitor: unplug before handling plugs or switches.
  • Never jumper the air pressure switch or vent temperature limit; they prevent flue gas spillage (carbon monoxide).
  • Hot water and tank surfaces can scald.
  • After a flammable-vapor lockout, remove the vapor source before any reset.

How it works

On a call for heat the control first checks that the air pressure switch circuit is OPEN, then starts the blower. Within about 5 seconds the switch must CLOSE (the residential power-vent switch is normally open and closes on a fall in pressure as the blower pulls). Only then is the ignitor powered. The control keeps watching this circuit for the whole burn; if it opens even briefly, the gas valve closes.

Sequence on the Intelli-Vent (A.O. Smith training literature): about 5 s pre-purge, about 20 s ignitor warm-up, a 4 s trial for ignition, 5 s inter-purge and 5 s post-purge. It allows 2 retries (3 trials) and 2 recycles (3 flame losses) before it locks out; the ignition lockout clears itself after one hour or when power is cycled.

The temperature probe on the control holds a thermistor and the ECO. Residential controls ship at a 70 F 'vacation' setting and range 70-160 F; the recommended start is 120 F. Holding both temperature buttons about 1 second wakes the display to show the setting; with no input it sleeps after about 30 seconds and all LEDs go dark. In normal operation no LEDs are lit; a lit LED combination is an error code (residential controls show it steady, commercial controls flash it).

Later FVIR versions carry a flammable-vapor (FV) sensor on the base ring. If it sees vapors the control locks out hard and needs a manual reset after the hazard is removed. An LDO (lint, dust, oil) lockout is set when the pressure switch / vent temperature limit circuit opens repeatedly in one cycle, usually from clogged intake or dilution-air screens.

Components & tests

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Official manufacturer documentation

Always confirm values against the tech sheet for the exact model.

OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work. © 2026 OnCall Tech. Original content; not a reproduction of any manufacturer document.Generic part photos (not of this brand): Newly installed gas tank water heater with its flue, gas line and water connections by Tim Evanson, CC BY-SA 2.0

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A.O. Smith and State residential power-vent gas tanks with Intelli-Vent hot-surface control (GPVL, GPVT, GPVH, GPSH, GPDH; State PR6 power vent): quick sheet (diagnostic and electrical side) · OnCall Tech