After a water heater is installed a crucial procedure is sometimes overlooked. Jon Palfrey explains.

Installing a water heating system is a typical job for most plumbers.

Whether the system is going into a new project or replacing an old model, connecting the associated pipe work is the initial step.

Turning the system on, checking its correct operation, checking and/or adjusting gas pressure, checking fluid levels in a solar indirect system, etc, are commissioning procedures documented in installation instructions from the manufacturer.

In addition to commissioning procedures, plumbers advise the users about safe operation, temperature adjustment in appropriate models, how to re-light the pilot, the normal function of valves and even the noises to expect from the system.

The following steps are typical of Rheem Australia’s commissioning procedures for some of the most common of water heater types.

Even if installing a water heater is part of your day to day work, take the time to familiarise yourself with the following commissioning examples.

Domestic gas storage type 

The gas pilot or burner must not be lit until the heater is filled with water, then:

• Open all hot water taps (don’t forget the shower).
• Open the cold water isolation valve fully to the heater.
• Air will be forced out of the taps.
• Close each tap as water flows freely from it.
• Check pipe work for leaks.
• Open the gas isolation valve fully.
• Check the gas pipe work for leaks.

Warning: On completion of the installation and commissioning, leave the guide with the householder. Do not leave the guide inside the cover of the heater, as it may interfere with safe operation or ignite when the heater is turned on. Explain to the householder the functions and operation of the heater.

Gas inlet pressure

Important: Check the gas supply pressure at the inlet to the water heater with the water heater and all other gas burning appliances in the premises operating (burners alight). The minimum gas supply pressure is:

• Natural gas – 1.13kPa
• Propane – 2.75kPa
• Universal – LPG 2.75kPa
• Butane – 2.75kPa.

If this minimum cannot be achieved, the meter or gas line to the heater may be undersized.  Ensure an adequate gas supply pressure is available to the heater when all other gas appliances on the same supply are operating.

Testing

• The operation of the water heater must be thoroughly checked by the installer.
• The burner flame must light smoothly and quickly from the pilot flame, and must go out quietly and completely.  The main burner flame must be stable, although slight lifting at the front edge of the burner is acceptable when the burner is cold.
• The main burner flame should be blue, with a clearly defined inner cone. Luminous yellow or ‘floating’ flames are not acceptable and must be corrected by opening the air shutter.
• Check the test point pressure and compare it with the rating label.
• The pressure regulator is not adjustable. If the test point pressure is not within 5% of the specified value, refer to the manufacturer’s service division or the nearest accredited service agent.
• When satisfied everything is working properly, you should then instruct the user in the correct method of operation.

Lighting instructions

• Stop and read the safety information in the instructions, then remove the access cover.
• Turn the gas control knob fully clockwise to the l (off) position.
• Wait five minutes so any built-up gas can escape.
• Danger: If the main burner or pilot flame is extinguished for any reason during the lighting process, always turn the gas control knob to the l (off) position and wait five minutes.
• Failure to wait five minutes may result in a fire or explosion.
• Turn the gas control knob to the Õ (pilot) position.
• Depress the knob fully (until the Õ disappears below the housing) and hold the knob down until the end of Step 7.
• If it is not possible to depress the knob fully, turn the gas control knob to the l (off) position and begin again at Step 3.
• After waiting 30 seconds and with your face clear of the combustion chamber opening, press the igniter button repeatedly (for up to a further 40 seconds) until the pilot flame lights.
• Continue to hold the knob down for 20 seconds after the pilot flame lights.
• Release the knob and check that the pilot is still alight. Look through the combustion chamber opening below the gas control.
• If the pilot has failed to light or has not remained alight, turn the gas control knob to the l (off) position and begin again at Step 3.
• The next step will cause the main burner to light, if the water in the tank needs heating. The flames may be noisy at first. This is normal and will cease after 2-seconds.
• If the pilot flame remains alight, turn the knob anticlockwise to the numbered setting of ‘6’ for a water temperature of about 60°C. This setting is also shown on the
  rating label.
• Turn the knob to a higher number if a higher water temperature is required. Refer to ‘temperature adjustment’ in the procedure.
• Replace the access cover.
• The main burner will now automatically ignite when heating is required and extinguish when the water has reached the set temperature. If the main burner does not light at the selected setting, the water may already be at the right temperature.

Gas continuous flow

All Rheem continuous flow gas water heaters are tested and adjusted before dispatch from the factory, but further adjustments may be necessary due to local conditions.

To turn on the water heater:

• Open all hot taps in the house (don’t forget the shower).
• Open the cold water isolation valve fully at the inlet to the water heater. Air will be forced out of the taps.
• Close each tap as water flows freely from it.
• Check the pipe work for leaks.
• Open the gas isolation valve fully.
• Check the gas pipe work for leaks.
• Plug in the water heater at the power outlet and switch on.
• Turn on a controller, if one is fitted, by pressing the on/off button. The on/off operating light and the priority light will glow.
• Open a hot tap. The water heater will operate automatically.
• Check to ensure that the flow from each connected hot tap is sufficient to operate the water heater.

The minimum operating flow rate for the Rheem 26L continuous flow gas system is 2.0L per minute. Check and, if required, adjust the pre-set outlet temperature setting of the water heater.

The automatic water governor incorporated in the water heater is not adjustable.

To complete the installation, you must check the gas supply pressure at the inlet to the water heater, the minimum test point pressure and the maximum test point pressure.

Upon completion and testing of the installation, ensure that any controllers are turned off.

Explain to the householder the functions and operation of the water heater and any controllers.

Warning: After commissioning the water heater, give the guide to the householder.

Gas inlet pressure

Important: Check the gas supply pressure at the inlet to the heater, with the unit and all other gas appliances in the premises operating (burners alight). The minimum gas supply pressure is:

• Natural gas – 1.13kPa
• Propane and ULPG – 2.75kPa.
• If this minimum cannot be achieved, it may indicate that the meter or the gas line to the heater is undersized. It is important to ensure that an adequate gas supply pressure is available to the water heater when other gas appliances on the same gas supply are operating.

Gas inlet test point pressure

To check the gas inlet pressure:

• Close any hot taps and ensure the burners are not operating.
• Close the gas isolation valve at the gas inlet to the water heater.
• Locate the gas inlet test point on the gas connection to the heater.
• Remove the test point screw and washer from the test point orifice and connect the manometer.
• Open the gas isolation valve fully at the gas inlet to the heater.
• Observe the gas pressure reading on the manometer.

If the manometer reading is between the minimum and maximum inlet gas pressure ratings on the rating label, no adjustment is required.

If the reading is below the minimum rating, then either the gas pipe to the heater is undersized and needs to be rectified or adjustment is required at the gas regulator.

If the manometer reading is above the maximum rating, then adjustment is required at the gas regulator.

• Switch on the electrical supply at the power outlet to the water heater if it is not already switched on and turn on a controller, if one is fitted, by pressing the on / off button.
• Open a hot tap fully and ensure the burners are fully ignited. It may be necessary to open a second tap.
• Turn on all other gas burning appliances in the house which are on the same gas supply.
• Observe the gas pressure reading on the manometer.

If the manometer reading is between the minimum and maximum inlet gas pressure on the rating label, no adjustment is required.

If the manometer reading is below the minimum inlet gas pressure rating, then either the gas pipe to the water heater is undersized and needs to be rectified or adjustment is required at the gas regulator.

If the manometer reading is above the maximum inlet gas pressure rating, then adjustment is required at the gas regulator.

• Turn off the other gas appliances in the house.
• If an adjustment was made during Step 9, repeat the procedure from Step 5.
• Close the hot tap(s).
• Close the gas isolation valve at the inlet to the heater.
• Remove the manometer and refit and tighten the test point screw and washer.
• Open the gas isolation valve fully at the gas inlet.
• Open a hot tap again so the burners ignite.
• Test for gas leaks.

Gas boost for solar

Australian Standard AS 3498 requires that a water heater should provide the means to inhibit the growth of Legionella bacteria in potable water.

When the water heater is used as an in-series booster for solar hot water it can satisfy this requirement provided that it is energised, the booster pre-set outlet temperature setting is 70°C or higher and a remote temperature controller is not used.

It will be necessary to check and, if required, to adjust the pre-set outlet temperature setting of the continuous-flow water heater when:

• It is installed as an in-series gas booster for solar hot water; and,
• It is an existing continuous-flow heater and solar water heating is then installed.

Solar

For ‘indirect’ gas or electric boosted solar water heating systems, the associated commissioning procedures need to be carefully followed to ensure heat exchange fluid levels are correct.

Summary

The commissioning procedure is designed to complete the installation to the manufacturer’s requirements and to leave the customer with a reliable, safe, durable and efficient water heating system.

By following the stipulated commissioning procedure you will be able to confidently leave the job without your fingers crossed.

Jon Palfrey is Rheem Australia’s Training Manager. He conducts training to plumbers and specifiers across the southern states.