Gas hot water

Gas Hot Water Wellington

There is a trend to continuous flow water gas hot water heating these days, to gain the space occupied by the water heater storage tank, and have more hot water. The new continuous flow gas hot water heaters are normally mounted on the outside wall, as they are usually, more expensive to mount inside due to the flue cost. The job of changing over normally involves taking out an electric storage tank inside, and fitting a gas continuous flow unit outside. A check is needed to determine if sufficient gas pressure is available from the gas supplier. A new gas supply is run from an existing gas supply in the building, and a cold water pipe taken to the new position and a hot water pipe taken to the existing hot water piping from the new unit.

An external electric hot point is installed outside below the new unit to power the ignition and control mechanism. You can also specify optional control pads which are installed in the bathroom, and or kitchen. These give a digital readout on the temperature. They can also control the temperature by setting the control pad to a set temperature. This can be used instead of a shower mixer and have bath fill options. The maximum temperature for a domestic unit is 55 degrees C’.

Some of the Installation Requirements for Continuous Flow gas water heaters

The gas supply has to be large, to get enough energy to the unit, and is often a big part of the job. It cannot be taken from a pipe less than 20mm in diameter, and not more than 9m of 20mm pipe can be installed. After that the rest of the pipe must be 25mm and that rules out taking a branch of cookers, fires, and storage water heaters.

So we have to find a bigger pipe e.g. 25mm usually. This is because the water heaters need a lot of energy quickly to heat 20-26 liters of water in one minute. In fact 50Kw of energy input is why gas has an advantage over electric, where 2-3 Kw is normal.

The Continuous flow units can only be installed in certain positions –

  • 300mm away from internal and external corners
  • 300mm away from an opening windows
  • 1.5m below and opening window
  • 500mm away from electrical meter boxes vent openings

On completion a gas installation needs to be certified  Gasfitter, and a Registered Electrician which is done as part of the job.

Gas Hot Water Wellington

The Old Mechanical units

Many people are familiar with the old mechanical units which deliver a lot less hot water and used to suffer from pilot outage – this is no longer a problem with the new units. The old mechanical gas units used to deliver 10-13 liters per minute the new units deliver 20-32 liters per minute of shower temperature water.

The older units have improved considerably in recent times and are now able to generate their own electricity for ignition purposes.  That means no pilot any more to go out and no batteries either.

Benefits of Gas Hot Water

  1. Endless showers in the case of continuous flow water heaters
  2. Smaller size of gas heaters over electric or gas storage tanks.
  3. Improves the value of buildings.
  4. Better for the environment.
  5. Better shower flow.

See Improved shower pressure page here