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Power vent water heater troubleshoot
Troubleshoot power vent water heater
Basic power vent troubleshoot/ pdf
burner assemblypower vent water heaterTypes of power vent water heaters
Power vent water heater derives all incoming air from inside the home and releases combustion gas in a sealed vent installed either horizontally through a side wall, or vertically through roof.
Power direct vent 
derives all incoming air from outside the home through a sealed intake pipe and has two pipes connected to water heater, one for intake and one for vent. Power direct vent can be vented through roof or side wall, and air suppy can come from roof or side wall.

Both types power vent heater
s require 120 volt electric outlet for operation. Improper grounding or reverse hot-neutral polarity can cause ignition failure and/or short cycling (repeat on-off attempts).

How power vent water heater works
-The gas valve thermostat senses that water inside tank is below set point and closes a circuit that turns on the 120 volt blower located on top of water heater. 
-The blower pulls air up from the combustion chamber into vent pipe and begins a cycle of releasing toxic combustion by-products, including NOx SO CO CO2 and acidic water vapor, into the atmosphere, where it creates an exciting new future for the planet. Alternative for some: Connect solar panels to electric water heater
-The vacuum safety switch is connected to blower via rubber tube. The rush of air through the vent pipe creates vacuum pressure. 
-The vacuum or pressure switch measures the vacuum created by the blower and verifies the blower is operating at speed. This ensures the blower can evacuate combustion gasses and support complete burning of fuel
. Complete burning prevents explosion hazard caused by ignitable fuel gathering inside combustion chamber or vent pipe. The efficiency of gas water heater combustion is typically 60-61%, with the remaining 39-40% of heat going up the flue pipe. Calculate efficiency
-Once the blower operation is confirmed by the vacuum switch, it closes (turns on) a small circuit that signals the gas valve thermostat that the blower is working. 
-If the 120 volt outlet has correct voltage, polarity and grounding, the gas valve electronic control board activates the hot surface igniter, igniter glows red with heat, and gas is released down the burner tube, through the orifice into the burner head.
-If the gas pressure good, and the orifice is clean and correctly sized, and hot surface igniter and burner head are clean and in good working order, and the igniter is correct distance away and positioned directly in front of a gas jet, the gas will ignite and burn blue. Flame sensor confirms that flame is present and signals the gas valve to continue releasing gas. Water temperature inside tank begins to heat.
-If the water heater has pilot light instead of hot surface igniter, the burner assembly has a pilot tube in addition to the burner tube that connects to gas control valve. The control valve releases gas into the pilot tube continually as long as thermopile is functioning and correctly positioned in the pilot flame so it sends small electric current to gas control valve, signaling that pilot flame is working. If the pilot flame and thermopile system are working, the ignition sequence can begin once the blower operation is confirmed.
-If the blower is not operating, or running at lower speed because of a brownout or lack of voltage or malfunction, the vacuum switch does not receive enough vacuum pressure and will not close, and the ignition sequence will not take place.
-The blower has a resettable thermal safety switch that monitors vent temperatures. If temperature on vent pipe at the blower exceeds 180, the thermal switch opens (shuts off) the circuit between gas valve and pressure switch. The vacuum switch resets to open position and gas valve thermostat turns off gas supply until vent pipe cools, after which the heat cycle begins again. Repeated failures in the ignition and heating sequence are recorded by the gas control valve. When errors exceed parameter, the gas control valve issues error code.
-If temperature of water inside tank exceeds high limit set point of thermostat, then gas control valve turns off all gas. Older style gas control valve may require replacement. Newer gas control valves can be reset (with exceptions) once repairs have been made to correct cause of overheating. If the thermostat comes out of calibration, and is no longer performing, it requires replacement of gas control valve.

-When temperature inside tank reaches the set point, for example 120F, the gas control valve thermostat turns off gas to burner, and a moment later turns off blower. The water heater goes into standby mode until water temperature drops below thermostat set point again.
Power vent Back to 14 things for troubleshoot gas water heater
12) power vent water heaters
Power vent water heater can vent combustion gas through a sidewall vent.If blower is not misaligned or damaged, check blower assembly: Turn off power to water heater. Remove vent from top of blower. Disconnect pressure tube going to pressure switch, and attach a manometer to the pressure tap. Turn on power to the blower. Pressure should be 1.3" w.c. to 1.4" w.c. at normal altitude (3000 ft)
How it works: "When the thermostat senses a need for hot water, a valve is opened which allows gas to flow to the closed solenoid valve. As gas pressure builds up within the solenoid,  the gas pressure switch closes and 24 VAC flows to the blower relay.  The  blower  relay  contacts  close and  send  115  VAC  to  the  vent  blower  which  turns  it  on.  Air  flow  from  the vent  blower  closes  the  air  pressure  switch    sending  24  VAC  to  the  solenoid  valve.  The  solenoid  valve  opens  and allows gas to flow to the burner which is lit by the pilot or igniter"
Blower: less than 5 amps consumption @ 120 volt. 120 volt x 5 amp = 600 watts running with 1200 watts start-up.

Power vents:
Power vent water heater issues
Anode covered by power vent

water heater blower motor  Blower
Power vent water heaters use a blower to vent gas by-product from water heater. Blower requires 120 volt grounded outlet. Electric outlet for power vent and flue damper water heaters should be dedicated. Do not use extension cord for power vent and flue-dampered water heaters.
Blower is connected to gas control valve with a wire, called the control cable. The gas control uses a firing sequence to activate the blower and start moving air upwards just before the burner fires up.
Blower, control cable, gas control valve, and pressure switch are part of troubleshooting. Eliminate the obvious: Check the blower first, and gas control valve last.
Make sure blower is aligned and opening is not obstructed by gasket and gasket is not damaged.
Other issues: excessive vent length, vent blockage, high vent temperature, bad wiring inside junction box,

Buy blower:
Water heater blowers at Amazon

Blower troubleshoot
Test pressure switch
Power vent troubleshoot
Troubleshoot power vent hot surface ignition
How to check blower motor
Check blower motor
Check the blower
If blower is not misaligned or damaged, check blower assembly: Turn off power to water heater. Remove vent from top of blower. Disconnect pressure tube going to pressure switch, and attach a manometer to the pressure tap. Turn on power to the blower. Pressure should be 1.3" w.c. to 1.4" w.c. at normal altitude (3000 ft)
water heater blowers Blowers: Fasco, AO Smith, Bradford White, Rheem power vent water heater exhaust draft-induced blowers
Buy blower
Water heater blowers at Amazon
Other types blowers
Fasco multi-purpose blowers
AO Smith multi-purpose motors and blowers
Furnace blowers
water heater pressure switchTroubleshoot Pressure switch / same as vacuum switch
Bypass or jumper around the pressure switch immediately after the inducer starts.
What does a vacuum switch do? What does a pressure switch do? The vacuum switch measures the vacuum created by the blower and verifies the blower is operating at speed. This ensures the blower can evacuate combustion gasses and support complete burning of fuel so no unburned fuel is inside the vent pipe.
Generally, to check if blower is good and pressure switch is bad, you bypass the pressure switch and connect blower directly to 120 volt outlet, running a pigtail to the blower or plugging blower directly into outlet.
At beginning of a call for heat, the vacuum switch is OPEN. The vacuum switch must close, like an ordinary on-off switch and complete a circuit that notifies gas control that blower is operating correctly.
Switch can fail to open if there is a vent obstruction or vent is too long. Correct venting.
"In troubleshooting pressure switches, you usually just jumper across it so it looks like a solid wire to the control.  Do this only when the unit is trying to fire up, so it is in the correct sequence. ~~ If you get no continuity however, it sounds like the contacts in the switch are shot and the switch should be replaced. Jumpering across it will let you know if that is what's keeping the heater from firing up. Do NOT leave the jumper in place as you're disabling a safety device." Source
"Because one of the two air chambers is vented to the atmosphere, the ambient (in the surrounding area) air pressure is critical. Ambient air pressure can push or pull on the diaphragm through the vent port. If the ambient air pressure is extremely high (positive) or low (negative) it may cause erratic pressure switch operation."

Pressure switches fail when a few drops of water condense in the small tube the connects to the switch, or some other internal problem with contacts happens.  Using a volt meter on the switch while gently blowing /sucking on the tube will confirm it's operation... or lack of operation.
Pressure switch troubleshoot
Intellivent pressure switch troubleshoot and testing
Test pressure switch
Air pressure switch testing
Intellivent wiring
Pressure switch replacement
Bradford White pressure switch replacement
Check pressure switch
Construction, operation, and testing for pressure switch .pdf

The Vacuum line can be clogged
Check pressure switch and vacuum line
"How to check the vacuum line
Requires the use of a magnahelic gauge.
1. Place inline “T” fitting between vacuum switch and vacuum line from the blower motor.
2. Turn heater on and adjust so water heater turns on. Blower motor turns on..
3. Check  pressure on the magnahelic gauge. If gauge shows 0.6 to 1.5 inches water column, then blower motor is inducing the proper draft and vacuum lines are not obstructed.
4. If gauge does not read between 0.6 and 1.5 inches water column -
a. Move the inline “T” fitting and place it between the blower motor and the vacuum tube at the top of the heater.
b. Check the pressure on the magnahelic gauge. If the gauge shows 0.6 and 1.5 inches water column, then the blower motor is inducing the proper draft and vacuum lines are obstructed. Replace the heater.
 c. If the gauge does not read between 0.6 and 1.5 inches water column, then the blower motor is not inducing the proper draft. Replace the blower motor."  Resource: Power vent troubleshoot / pdf
Buy: magnahelic gauge
water heater pressure switch Pressure switch/ Vacuum switch for water heaters
There are 3 major water heater manufacturers, AO Smith, Bradford White, Rheem, that make all the other brands from Kenmore, Craftmaster, Whirlpool, American, Reliant (AO Smith) to Reliance (Rheem)
Buy water heater pressure switch:
Rheem water heater pressure switch
Bradford White pressure switch
AO Smith pressure switch
Outlet polarity Polarity
Power vent is connected to 120 volt outlet. No electricity, no hot water.
The outlet polarity must be correct, and water heater must be grounded. Poor ground can prevent flame. GFCI circuit can cause short cycling. If outlet is not dedicated or has GFCI, or line has other loads such as florescent lighting, these factors can cause short cycling.
Unplug cord. Test for continuity between ground prong on plug and manifold tube on gas valve.
Test for continuity between ground prong and blower assembly mounting screw.
Connect water heater to different outlet. Test outlet polarity with circuit analyzer
Circuit analyzer

Power vent circuitIntellivent gas control circuit
Vent temperature limit switch monitors the flue gas temperature in blower assembly. If temperature exceeds set point, the limit switch opens and turns off circuit that is routed from gas control valve through the limit switch and pressure switch. This signals to gas control valve to shut down gas flow to burner and water heater stops heating water.

Defective vent temperature limit switch; this is a normally closed switch that opens its contacts on a rise in temperature. Turn off power and disconnect wires to the vent temperature switch.

With the switch at room temperature (77 F), check for continuity between the two wiring terminals on switch with an ohm meter. If switch contacts are open (no continuity) at room, or below 160F - replace the switch.

power vent flue restrictorAt top of heater is a flue restrictor plate that is located on vent pipe under the power vent assembly. If restrictor is missing or dislodged, the flow of combustion gas will increase causing more hot gas to reach limit switch. If heat exceeds 160F limit, the limit switch opens and burner shuts down.

Missing flue baffle can create turbulence inside combustion chamber, that can sweep gas away from burner causing ignition failure, and short cycling where water heater turns off for a few moments and then cycles on again several times before shutting down.
Turbulence can also be caused by improper or missing seal around combustion chamber access door

Intellivent wiring
Read about replacing rubber seal
Minimum distance of vent pipe from window   
Larger image with more information
Minimum distance of vent pipe from window
Side-wall vent pipe must be 4 feet away from windows and doors. And 3 feet away from inside corners.

Consult product manual and local codes for specific vent installation.

Power direct-vent clearances
Venting a gas water heater
Conditions where outdoor air supply is needed

Formation of condensation in the venting system of Power Vented water heaters is dependent upon installation conditions including, but not limited to:
ambient temperature and humidity of installation location;
ambient temperature and humidity of venting space;
vent distance and slope; and product usage.in order to effectively control condensate from adversely affecting the mechanical components of the water heater several methods may be employed:
1. For horizontal installations the vent pipe can be installed with a downward slope (not less than 1/8 inches (3 cm)) and away from the blower.
2. In order to prevent condensate from draining back into the blower(vertical or horizontal runs), an optional condensate kit is available as a service part (Condensate kit, p/n 238-45875-00). A factory supplied exhaust adapter with drain outlet mounts directly to the blower outlet and is secured with two hose clamps, one to the blower and the other to the vent pipe. Tubing is provided to drain any accumulated condensate away from the water heater and to a suitable drain. The kit comes complete with instructions for proper installation.
Flame rod sensor
Location of flame sensor and igniter vary by model and brand of water heater.
Sand carbon deposits off igniter.
Avoid touching igniter
Larger image
Hot surface igniter troubleshoot
Hot surface ignition basics
Troubleshoot hot surface ignition
Hot surface igniter troubleshoot
Power vent hot surface ignition

Tip of flame sensor must be directly in front of burner port.
Use a nickel to set 7/64 gap.
Natural gas flame sensor will be bent, while propane will be straight.
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Intellivent troubleshoot Manual
Power vent surface ignition
Gas burner without piezo igniter
Larger image
Burner flame is yellow
Power vent Venting for power vent models
Read product manual for venting specifications
Example power vent manual p17
Minimum vent distance from window
Power vent tables
Power vent troubleshoot
Typical power vent manual
Typical power vent manual2
Typical service manual
Bradford White power vent service manual
Gas venting specs
Conditions where outdoor air supply is needed
Soot on gas burner
Soot on top of heater also implies danger of improper vent and backdraft.
Improper location of vent on roof, and incorrect clearances, or windy location can stop vent gas from leaving vent pipe. If vent gas cannot escape at top of pipe, it can be entering house at the vent hood. Soot on top of heater is evidence. If pilot goes out, the improper draft can be blowing out pilot light.
Soot on top of heater can be caused by backdraft where vent gasses are being blown back onto water heater because of shared vent pipe with furnace or other gas appliance. Read next section.
Negative inside air pressure, Negative pressure
Backdraft Is your furnace causing water heater to malfunction? Furnace, kitchen-bath bent fans etc can affect vent draft on water heater. Called negative pressure.
Is there evidence of rusting etc on top of heater, next to the draft hood? Is the furnace room particularly cold or wet? This is evidence of backdraft.
Here is a simple, but telling test. When the water heater first fires up, a little heat will spill from the draft hood. It should only spill for a second or two under normal circumstances. So, with the furnace off, turn the temperature on your heater up to cause it to fire up (you might make a mark on the thermostat dial so it can be put back to the same place). Quickly, put the back of your hand to the draft hood to feel any heat spilling out. Count the seconds. Return the heater to normal. Now wait a bit and fire up the furnace. Feel for any spillage at the water heater draft hood with the water heater off. Count seconds. Now fire up the water heater (furnace running) and check for spillage again.
If furnace and water heater both vent into same chimney, the draft might not work properly. Water heater should have dedicated vent. For example the chimney vent pipe is is eight inch, but the two vents (from furnace and water heater) going to it are both four inch. That bigger vent might be oversized and hard to warm properly for good drafting.
If the furnace is power vent, and fan or vent will overpower natural draft. Having the furnace and water heater vents combined will cause problems. Likely the
right fix is to run two, separate three inch vents. Resource: Venting combustion byproduct .... issues: vent in disrepair, other vents in house drawing air
Water on top of heater. Rusted vent pipe. White condensate on pipes.
Inadequate draft, or improperly installed vent pipe can cause condensation inside pipe that will rust and cause white condensate.
Missing roof cap will cause water on top of heater that will rust out the water heater.

Elbows slow venting, can cause backdraft if vent pipe is not large enough, or serves too many gas appliances..
Gas venting specs
Direct vent clearances
Conditions where outdoor vent is required
Vent Gas Odor
Lack of air supply
  -Clean air intake screen, open window
  Ventilating tight-house/ pdf
Improper vent
  -Read product manual for vent requirement
Poor combustion
  -Clean combustion parts, service unit
CO poisoning
If joints fall apart, or vent is improperly installed, hot gases enter home posing risk of odorless CO poisoning. Symptoms: headache that goes away when outside in fresh air. Unconsciousness.
Remove affected people from home and lay on sides, not on back. Call emergency help.
call plumber. Attach vent pipe sections with 3 screws and then cover joints with aluminum tape.

Vent tape
Carbon monoxide detector
Water leak issues
A. Water at the blower assembly is water vapor which has condensed out of the combustion products.  This is caused by a problem in the vent.
B.  Condensation may be seen on pipes in humid weather or pipe connections may be leaking.
C.  The anode rod fitting may be leaking (anode is located under the Blower Assembly).
D.  Small  amounts  of  water  from  temperature-pressure  relief  valve may be due to thermal expansion or high water pressure in your area.
E.  The temperature-pressure relief valve may be leaking at the tank fitting.
F.  Water from a drain valve may be due to the valve being slightly opened.
G.  The drain valve may be leaking at the tank fitting.
H.  Combustion products contain water vapor which can condense on the cooler surfaces of the tank.  Droplets form and drip onto the burner or run on the floor. This is common at the time of start-up after installation and when incoming water is cold.
I.   Water  in  the water  heater  bottom or on the floor may  be  from condensation,  loose  connections, or the relief  valve.   DO NOT replace the water heater until a full inspection of all possible water sources is made and necessary corrective steps taken.

Resources: Power vent troubleshoot/ pdf
Bradford White power vent service manual

For power vent models
Range Low 90 - very hot 160
Average bath 110F, typical water heater temp 120
ECO limit 199 F, ECO trips, gas valve fails
Average bath 110F
ECO limit 199 F
TP release water  at 170
Example Honeywell gas control valve at Amazon
Reliance NG at Amazon
Replacement instructions
How to replace water heater gas valve

Adjust temperature/ error codes on Honeywell
How to light Honeywell gas valve
Dampered Fury gas troubleshooting codes
Induced draft troubleshoot codes
Error codes, troubleshoot for gas valve
Error codes
Error codes2
Error codes
Icon gas valve error codes
Service manual
Bradford White service manual 2
Test gas control/ from BW service manual
Sequence of operation
How to clean burner

Water heater safety precautions
Water heater precautions/ pdf
Gas valve safety
Thermal expansion
Insulation blanket

For power vent models
Range Low 80 to Hot 150
Error C flashes at 160
Buy Intellivent gas control at Amazon
White Rodgers/ Rheem Intellivent gas control
AO Smith intellivent
AO Smith Intellivent at Amazon
AO Smith White Rodgers at Amazon

Replacement instructions
How to replace water heater gas valve

AO Smith Intellivent troubleshoot and FVIR test/ pdf
Error codes and adjust temp on Intelli-vent gas valve
How to light water heater
Troubleshoot Intellivent/ pdf
FVIR intellivent troubleshoot .pdf
Intellivent service manual
Intellivent FVIR troubleshoot and reset
Sample manual
Intellivent wiring
Power direct vent troubleshoot
Sequence of operation
Intellivent error codes-troubleshoot
Promax gas water heater manual
For resetting controller: After the unit has been off for at least a minute, plug it in, turn on the switch; within a few seconds, depress both arrow buttons on the controller, and hold them until the left light begins to blink.  Release them, and within a few seconds, push those arrow buttons in the following sequence:  L/R/L/L/R/L/R/R.  This should reset the controller.
gas valve setting
Larger image
Gas control valve thermostats at Amazon
Gas water heater thermostats at Amazon
Rheem gas control valve at Amazon
Gas control valve at Amazon
Camco White Rodgers at Amazon
Gas water heater timer fits this valve
Replacement instructions
How to replace water heater gas valve
Service manual
Service manual 2
Service manual 3
Operation and safety
How to light water heater/pdf
General troubleshoot manual /pdf
White Rodgers gas control valve replacement pdf
Power vent water heater issues
Magnet testing
Test thermocouple
Gas valve testing
How to light gas water heater
White Rodgers NG replace, install, set temp

Robert shaw gas control valve
Robert Shaw 120Volt input gas control valve
Wiper Control and Gas Valve assembly
Triangle pointed upward is 120 degrees F
Replacement for Rheem power vent/ 

Rheem wiper SP20123A thermostat KIT
Wiper SP20123B valve/ no thermostat

Larger image 
Error Codes and troubleshoot
Guardian power vent Robert Shaw error code
Check the blower motor, gas control etc
Rheem parts list
American power flex parts
General manual with lighting instructions
Replace water heater gas control and FV
Check pressure switch, blower, gas control
Sequence of operation
How to light water heater
To reset: turn the red control knob on and off 6 times within 30 seconds to reset the board.
White Rogers thermostat

Camco White Rodgers at Amazon

Troubleshooting/ pdf
How to light gas water heater
How to replace water heater gas valve

Remove gas valve
Buy universal gas control wrench

Gas water heater thermostats at Amazon
Robert Shaw natural gas
Robert Shaw propane gas
Replacement instructions
How to replace water heater gas valve

Robert Shaw models
Robert Shaw/ Unitrol troubleshooting/ pdf
General troubleshoot/ pdf
General troubleshoot manual /pdf
How to light water heater/pdf
Magnet testing
Test thermocouple
Gas valve testing
Operation and safety
Recalibrate gas control/ pdf
How to light gas water heater
Adjust pilot on unitrol gas control valve
How to test White Rodgers gas valve p14
How to test Honeywell Icon gas valve p23
How to test Robertshaw gas valve p14
14 things needed for gas water heater & .pdf resources
What you need for operation of gas water heater.
General troubleshoot
1) Basic parts and operation
2) Adequate incoming air supply ... issues: closed doors, tightly insulated house, very hot attic.
3) Adequate air supply getting to burner... issues: dirty vent screen, dirty environment, maintenance.
4) Thermal cutoff  ... TCO ... issues: failed part, maintenance, vent.

5) Flammable vapor lockout .... issues: exposure to vapors, bad FV sensor, failed FV system,
6) Fuel supply to gas valve thermostat ... natural gas and propane are different ... issues: wrong gas, low pressure, moisture in pipe, undersized gas meter, supply line too small for BTU rating.
7) Gas valve thermostat regulates fuel supply ... issues: not enough gas, failed thermostat, failed gas control valve.

8) Fuel supply from thermostat to burner ... issues: maintenance, thermocouple-thermopile, gas control valve.
9) Clean and replace burner ... issue: periodic maintenance requires burner inspection, cleaning, and possible replacement

10) Functioning thermopile-thermocouple-pilot light ... issues: misalignment, failure of part.
11) Ignition of fuel supply by pilot light or hot surface igniter ... issues: pilot light, piezo igniter, electrode.

12) Power vent water heater troubleshoot ... issues: pressure switch, blower, blower sequence from gas control, outlet polarity
13) Venting combustion byproduct .... issues: vent in disrepair, other vents in house drawing air

14) Misc troubleshoot manuals
Additional links
gas water heater timer Gas water heater timer
Fits Honeywell, White Rodgers, Robert Shaw
Both Propane and Natural gas models

Gas water heater timer
Gas and electric water heaters Support the economy:
Buy water heaters  from my associate links:

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Reliance 80 gallon heat pump at Amazon
Air tap: add to existing electric water heater at Amazon

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