Hot Water Cylinders Explained – How They Work
Thursday, March 9th, 2017
In New Zealand the most common form of hot water heating system is the humble hot water cylinder, low installation costs and proven reliability have made a firm favourite across the country for many many years. Although electricity is historically the most popular, these days hot water cylinders can be powered by gas, solar energy, heat pumps and wetback systems or mixed combinations of these methods.
How Do Hot Water Cylinders Work?
Simplicity has always been the key to the success of hot water cylinders, they deliver hot water right where you need it with a minimum of fuss. Similar to an electric jug, hot water cylinders rely on an element encased within an insulated and reinforced storage tank to heat and maintain the surrounding water to the required temperature, which is regulated by the cylinders thermostat. (In New Zealand the recommended hot water temperature is 60 degrees in the cylinder and no more than 55 degrees at the tap).
Essentially cold water automatically enters the cylinders storage tank when hot water exits, resulting in a lowering of the water temperature in the bottom of the tank, this then triggers the thermostat which allows the element to activate and heat the water to the set temperature again. This process continues 24/7 keeping you in a constant supply of perfectly heated hot water.
What Are The Components Of A Hot Water Cylinder?
- The Storage Tank. Modern mains pressure hot water storage tanks will usually have a steel inner cylinder which is lined with glass or vitreous enamel, insulation and a steel outer lining. Depending on their age low pressure tanks may have a copper lining.
- The Thermostat. Essentially a thermometer, the thermostat controls the water temperature inside the storage tank. The thermostat is fully automatic meaning power is only used when heating is required.
- The Element. One and in some cases two immersion elements are located inside the storage tank, it creates the heat needed to heat the water. Some tanks will have two heating elements, each controlled by its own thermostat, only turning on when the water goes beneath the pre-set temperature.
- The Temperature Pressure Relief Valve. This is there to protect the hot water cylinder from excess pressures and temperatures and hopefully avoid major damage to the cylinder and/or your house!
- The Anode Rod. Wherever there is water there is going to be corrosion. In order to prolong the lifespan of the storage tank and reduce corrosion over time an anode rod is suspended within the tank to act as a sacrificial piece of metal. The Anode Rod is usually made of magnesium or aluminium with a steel core.
- The Drain Valve. Used to drain the hot water cylinder of its water in order to make repairs, move or replace etc.
What Are The Benefits Of Electric Powered Hot Water Cylinders?
- Energy Efficiency. It may surprise many people to learn that electric hot water cylinders are actually more energy efficient than gas water heaters. Conventional electric hot water cylinders average about a 90% efficiency rating, while a conventional gas water heater averages about 60%.
- Easy Shutdown. Turning off the hot water cylinder while you are away is easy, just flip the switch on the wall. Great for saving power when away on holiday.
- Large Storage Capacity. There is always plenty of water on hand.
- Low Upfront Costs. The upfront costs of electric hot water cylinders will come in well under other forms of water heating here in New Zealand.
- Tried And Tested Reliability. Electric hot water cylinders have been around for many many years, the components have been refined and perfected providing excellent reliability and extended life expectancy.
- Good Flexibility. Hot water cylinders are available for purchase with future proofing in mind. They can be solar ready, wetback ready, or suited to hot water heat pumps. Allowing for greater adaptation if/when you circumstances change or hot water demands alter. Mains pressure and low pressure options are also available.
- External Installation. Certain types of hot water cylinders are now able to be installed outside the house, freeing up space within the home and providing easier access when servicing is needed.
What Are The Drawbacks For Electric Powered Hot Water Cylinders?
- Slow Recovery Rates. The speed at which your hot water cylinder heats its water to temperature in an hour is referred to as its recovery rate. Electric hot water cylinders tend to have slower recovery rates than gas hot water heaters.
- Electricity costs. It is thought hot water heating amounts to roughly a third of a household’s electricity bill. High electricity costs in New Zealand are a definite motivator for some people to look for water heating alternatives.
Need help deciding which hot water cylinder is right for you? Talk with the experts in Hot Water Cylinder repairs and replacements at The Cylinder Guy. Whether it is mains pressure hot water cylinders, low pressure hot water cylinders, gas hot water heating, an outdoor cylinder, solar or wetback powered hot water cylinders or the increasingly popular hot water heat pump system, the nationwide network of installers at The Cylinder Guy will provide you with the best match for your home or business.