Gas Hot Water Cylinder

Gas hot water heaters are a familiar fixture in a lot of homes. They use convection, a law in physics which describes how heat rises, to heat the water. Gas water heaters burn either natural gas or LPG to heat the water supplied to the outlets. 

There are certain advantages to using gas to heat your water over using electricity.

  • Quick Recovery & Heating Gas hot water system work twice as fast to heat your water than electric hot water cylinders, they also recover much faster than electric models, meaning your hot water supply is replenished faster. A gas water heater can heat 190L of water in roughly an hour, while an electric model may take several hours longer. If you have a large household or your household has high hot water usage, then a gas hot water heater is by far a better option than an electric heater.
  • Low Energy Cost Gas water heaters also have lower energy costs when compared with electric models. While gas models suffer heat loss from exhaust gases and the walls of the tanks; electric models are far more energy efficient. However; in terms of energy costs, gas heaters are far more affordable to operate since natural gas and LPG are far less expensive than electricity. Gas heaters cost more upfront to install, but they make up the difference in operation costs.
  • Easy to retro-fit into your existing cylinder installation These systems are also easy to install, especially if you already use reticulated gas in your home. 

There are two main systems for heating water in your home.

  • Gas hot water cylinder system.
  • Gas continuous flow system.

Continuous Flow Gas Hot Water System

These systems are extremely popular and it’s easy to see why: they never run out of hot water and they are energy efficient. The unit delivers a pre-determined flow rate (10 to 32 litres per minute) every minute for as long as it runs; it does not make use of a water storage tank.

Gas continuous flow systems burn gas to heat water as it runs through a califont, this system can run on both LPG and natural gas. Gas continuous flow systems are more efficient that gas hot water cylinders, heat water on demand and do not require a tank to store water.This hot water solution is good if you already use reticulated gas for space heating or cooking and want to continue this.

While this system provides unlimited hot water, using more hot water than you need is a waste of water, energy and money. Gas continuous flow systems have digital controllers that allows for a specific water temperature to be selected, a safety feature that can prevent scalding in small children. 

Working of Instantaneous/Continuous Gas Hot Water Heater

This system works when you open the hot water outlet and a sensor detects the water flow out of an outlet. This sensor is connected to the Electronic Control Unit (ECU) which controls how gas flows through the heater. The combustion fan is started and ignition begins, this is electronic and requires electricity. The ECU also opens the gas valve and once the flame is established, the appliance will heat the water until the tap is turned off.

Advantages of Continuous Gas Hot Water Heater

  • The biggest advantage to using this system is that it provides unlimited hot water.
  • Other advantages include saving energy and money when compared to traditional hot want cylinders
  • Gas continuous flow systems are also an excellent option for homes with small spaces, as the unit does not have a tank to store water and can be mounted outside.
  • Gas continuous flow systems have reduced gas emissions compared to other gas systems.
  • The water is also cleaner as it is not stored in a tank.
  • The design is safer.
  • The gas continuous hot water units come in size ranging from 16 litres of hot water per minute to 32 litres of hot water per minute.

Disadvantages of Continuous Gas Hot Water Cylinder

  • It is important to note that with this system you may need to pay a fixed charge for reticulated gas supply and running costs are high if you use LPG. As with hot water cylinders, gas continuous flow systems also contribute to climate change by producing greenhouse gases.
  • Another disadvantage of this system is that it will not work during a power outage as most systems require an electrical supply. However, there are units that do not require power like Hydropower Ignition.

Gas Hot Water Cylinder

Gas hot water cylinder systems are storage water heaters and are the most popular type of water heater installed in homes in New Zealand. Natural gas hot water cylinders can be installed using both low pressure and mains pressure, with the latter being the preferred style. 

A gas hot water cylinder burns gas to heat water in insulated tank to a temperature set by the thermostat; these normally run on natural gas. This system does not use electricity to run and can continue to heat and supply hot water during power outages. They can also be installed outside your home to free up space inside.

  • It’s important to keep in mind that the running costs for this system is relatively expensive, as you will need to pay a fixed charge for reticulated gas supply.
  • Another factor to consider is that this system will produce emissions, so while burning gas a relatively clean, it will contribute to climate change. Unlike electric hot water cylinders, you can’t put a cylinder wrap around gas hot cylinders. This may obstruct airflow and extinguish the flame. As with electric hot water cylinders, this system will also need to be set up correctly to ensure the tank water temperature is maintained at 60°C to prevent the growth of legionella bacteria. 

Working of Gas Hot Water Cylinder

In short, gas water heaters convert gas into heat energy, transferring the heat to the water. They are connected to a system of pipes, a cold water supply pipe and an outgoing hot water pipe that supplies hot water to your outlets.

Cold water enters the tank at the bottom of the cylinder through a cold water supply tube; the dense cold water at the bottom of the cylinder is then heated by a gas burner located beneath the sealed tank. As the water heats up, it rises to the top of the cylinder. A hot water discharge pipe draws off hot water when needed.

The gas burner is controlled by a gas regulator assembly mounted on the side of the water heater, this includes a thermostat that measures the temperature of the water inside the cylinder and turns the burner on and off as needed to maintain the set temperature of the water. The exhaust flue runs through the centre of the tank and allows potentially toxic emissions from the burner to flow up through the tank and out of the house via a chimney or vent pipe. The hollow flue is fitted with a spiral metal baffle that captures heat and transfers it to the surrounding water to maximise the efficiency of the gas hot water cylinder. The hot water cylinder tank consists of a steel outer jacket that encloses a pressure-tested water storage tank. The inner tank is made of high quality steel with a vitreous glass or plastic layer bonded to the inside surface to prevent rust. A layer of insulation sits between the inner storage tank and the outer steel jacket to reduce heat loss. There is a sacrificial anode inside the tank and prevents corrosion through electrolysis.

A key safety feature of this system is the temperature and pressure relief valve; it acts to prevent excessive pressure of temperature inside the tank. The system also has a drain valve at the bottom of the cylinder, which allows you to drain the tank for maintenance or flush out sediment. 

Tanks come in a range of sizes varying between 130L to 350L to suit your requirements depending on your hot water use needs.

Contact our plumbing team to discuss what Gas Hot Water Systems in Auckland are right for your property.