Category Archives: Order of Operation

Troubleshooting Power Vent Water Heaters

Venting

When troubleshooting a Power Vent water heater the venting often goes unnoticed even if there is an issue. The venting is so important to inspect on Power Vent Water Heaters because if they are sloped the wrong direction condensation will makes its way to the blower and damage it. Power vents don’t always form condensation, but there are a couple different variables that do cause them to condensate.

-Ambient temperature and humidity of installation location

-Ambient temperature and humidity of venting space

-Vent distance, slope, and correct product usage

-Vent has slope minimum of 1/8″ AWAY from the blower – Horizontal Applications

-Know the proper vent lengths for the model water heater (see table below)

These are the variables you need to pay especially close attention to when inspecting the venting. If you do notice an issue where the Power Vent is condensating a condensate kit is available to install. This is a Fernco exhaust adapter with a drain outlet that you pipe to the drain using vinyl tubing. An inexpensive part that will solve the condensate problem.

Check for vent blockage and determine if the vent could become clogged by surrounding vegetation. If so, consult with the home owner on a solution to make sure the problem does not repeat itself.

Its extremely important to make sure there is adequate air for combustion and ventilation. An insufficient supply of air will cause re-circulation of combustion products resulting in air contamination that may be hazardous to life. In Such conditions you will notice a yellow,luminous burner flame, causing carbon build up or sooting of the combustion chamber, burners and flue tubes with possible damage to the water heater.

Vents are susceptible to freezing and can be very easy to overlook. If the burner wont stay lit you should check to make sure there are no obstructions and investigate the possibility of frozen vent.

Troubleshooting codes and Vent Length Table

The link below includes a table to troubleshoot any issues you may have

The link also includes Maximum vent length including number of allowed elbows

vent-length-table-troubleshooting-codes-and-cause

Proper Combustion Air

Combustion air is very important for a water heater to run correctly. All different variables should be considered. When an exhaust fan is installed in the same room with a water heater, sufficient openings for air must be provided in the walls. Undersized openings will cause air to be drawn into the room through the venting and causing circulation of combustion products. A very common solution to this problem is the installation of a louvered door.

The formula to correctly determine proper openings

All air coming from inside the building: an opening must have a minimum free area of 1 inch² (6.5 cm²) per 1000 BTU (0.29 kw) per hour of the total input rating of all gas utilization equipment in the confined space, but not less than 100 inches² (645 cm²). One opening must be within 12 inches (31 cm) of the top and one with 12 inches (31 cm) of the bottom of the enclosure.

All Air coming from Outdoors: The confined space must be provided with two permanent openings, one commencing within 12 inches (31 cm) of the top and one commencing within 12 inches (31 cm) from the bottom of the enclosure. The openings must communicate directly, or by ducts, with the outdoors or spaces (crawl or attic) that freely communicate with the outdoors.

  1. When directly communicating with the outdoors, each opening must have a minimum free area of 1 inch² (6.5 cm²) per 4000 BTU (1.2 kw) per hour of total input rating of all equipment in the enclosure.
  2. When communicating with the outdoors through vertical ducts, each opening must have a minimum free area of 1 inch² (6.5 cm²) per 4000 BTU (1.2 kw) per hour of total input rating of all equipment in the enclosure.
  3. When communicating with the outdoors through the horizontal ducts , each opening must have a minimum free area of 1 inch² (6.5 cm²)  per 2000 BTU (0.6 kw) per hour of total input rating of all equipment in the enclosure.
  4. When ducts are used, they must be of the same cross-sectional area as the free area of the openings to which the connect. The minimum dimensions of rectangular air ducts must be not less than 3 inches (7.5cm)

Specially Engineered Installations

The requirements noted under the CONFINED SPACES above must not necessarily govern when special engineering, approved by the authority having jurisdiction, provides an adequate supply of air for combustion, ventilation, and dilution of flue gases.

Sequence of Operation

The sequence of operation is important to know so you can properly diagnose the problem.

Control Sequence of Operation

Start up sequence

Upon powering up, the control checks for the presence of the resistive plug, if the resistance is in the expected range the control will begin normal operation after 5 to 8 seconds.

Normal Heating Sequence

  1. The thermostat senses a need for heat.
  2. The control checks the pressure switch condition.
  3. If the pressure switch is open, the control sends power to the blower motor.
  4. The blower starts moving combustion air through the combustion system.
  5. The pressure switches closes.
  6. The control senses the closed pressure switch and starts the ignition process by providing a spark at the pilot electrode and allowing gas to flow to the pilot.
  7. When the pilot is lit the gas control senses the pilot flame and opens the main gas valve.
  8. The main burner is lit.
  9. The main burner and blower continue to operate until the thermostat is satisfied.
  10. When the thermostat is satisfied the main and pilot gas valves close.
  11. The blower operates for a short post purge period before shutting down.
  12. The water heater remains in the stand-by mode until the next call for heat.
  13. Make sure Power Vent is plugged into a grounded outlet.
  14. Make sure you have correct continuinty

Maintenance

  1. Annually check the operation of the thermostat
  2. The flow of combustion and ventilation air MUST NOT be restricted. Clear the combustion air openings of any dirt, dust, or other restrictions. WARNING! The ventilation air system may be HOT.
  3. At all times keep the water heater area clear and free from combustible materials, gasoline and other flammable vapors and liquids.
  4. Bi-annually conduct a visual check of the main and pilot burner flames to determine that they are burning properly. see Burner Flame Check. If sooting or other burner anomalies are evident, shut down the water heater by turning off the gas per the instructions listed in this manual or as listed on the water heater.
  5. Annually remove the inner door and main burner assembly to clean orifices and related parts of any dirt or other foreign material. Inspect the burner ports for obstructions or debris and clean with a wire brush as needed. Wire brush and/or vacuum clean the combustion chamber as needed to remove scale deposits and debris. NOTE: It is imperative for proper operation of the water that the inner door replaced in the original location.
  6. At least once a year, check the combination temperature and pressure relief valve to insure that the valve has not become encrusted with lime. Lift the lever at the top of the valve several times until the valve seats properly without leaking.
  7. Monthly drain off a gallon of water to remove silt and sediment.
  8. If the combination temperature and pressure relief valve on the appliance discharges periodically, this may be due to thermal expansion in a closed water supply system. Contact the Ace Hi Plumbing, Heating and Air to help correct this problem. Do not plug the combination temperature and pressure relief valve outlet.
  9. A combination sacrificial anode rod/hot water outlet nipple has been installed to extend tank life. The anode rod should be inspected annual and replaced when necessary to prolong tank life. Water conditions in your area will influence the time interval for inspection and replacement of the anode rod. The use of a water softener may increase the speed of anode consumption. More frequent inspection of the anode is needed when using softened (or phosphate treated) water.
  10. The blower has sealed motor bearings and does not require adding oil.
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