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Safer Homes, Save Money! Setting hot-water thermostats Want to save money while making your home safer for children and older people? You can do this simply by reducing the thermostat setting on your electric hot-water system. And why would you want this done? Simply because most hot-water systems are set at too high a temperature, often presenting a risk of scalding. T o be specific, hot water that is at or above 60°C can cause scalding in the wrong circumstances. Consider if an older person is having a shower and accidentally bumps the cold water tap so that the shower suddenly runs very hot. The person might be unable to quickly step out of the torrent of hot water and may not be able to quickly turn off the hot tap. In fact, they might suddenly lose their balance and fall over in the shower, in which case they may be even less able to avoid the hot water. This could lead to very serious scalding which could mean a stay in hospital . . . or worse! Or consider a young child in the bath and cavorting about, as they are wont to do. They could easily bump or turn on the hot tap and get a blast of hot water which could be very dangerous to their delicate skin and they can very easily get third-degree burns. Third-degree burns, by the way, are sometimes known as full thickness burns. They go through the epidermis (outer layer of skin – first degree) and the dermis (lower layer of skin – second degree) and affect deeper tissues. If enough of the body is involved, they are considered life-threatening. (Never, ever, take hot water temperature for granted when running a bath for young children. Always test the 80 Silicon Chip A typical thermostat, fitted to a hot water heater. The temperature adjustment control (circled in yellow) goes from 50° (too cold!) to 80° (way too hot!). Celebrating 30 Years by LEO SIMPSON temperature with your elbow to see if it is OK; your elbow is more sensitive than your hand. Then make sure that even if the child does turn on the hot water tap, that it will first run cold. But you need to be present at all times when young children are in the bath!) There are two requirements to avoid scalding. First, no hot water tap in a home should be able to deliver water at a higher temperature than 50°C. But setting your hot water tank’s thermostat to 50°C is (usually) definitely not recommended. Why? Because tank temperatures below 60°C can encourage the growth of Legionella spores. So the tank thermostat should be set to 60°C, no less. But there are a few qualifications in this requirement. If the pipe run from the hot water tank is long, and/or is either poorly insulated or not insulated at all, it may mean that the water temperature drops to an unacceptable level before it arrives at the closest tap or mixer. In that case, the thermostat should be set higher to ensure that the closest tap delivers water at no higher than 50°C . Why aren’t hot-water systems set to 60°C as a matter of course? These days any new tank should have the thermostat set by the installer to 60°C but it appears that in many cases this siliconchip.com.au Tempering valves This article would not be complete without mention of tempering valves. These devices mix hot and cold water to achieve a pre-set temperature, (usually) set by rotating a knob. While generally not required where the system delivers hot water to existing dwellings at less than 50°C in bathrooms, the Plumbing Code of Australia (PCA) requires that the delivery temperature of hot water for personal hygiene purposes (primarily bathroom taps) is not to exceed 45°C for early childhood centres, primary and secondary schools, and nursing homes or similar facilities for young, aged, sick or disabled persons. Considering that the PCA also requires a minimum tank temperature setting of 60°C (Australian Standard AS3500.4.2 Clause The interesting part about this thermostat is that lugs on the temperature adjustment control (orange, in centre) prevent it from being set outside the range of 60° to 75°C, despite the 5080° clearly visible on the dial. requirement is ignored and tanks can come from the manufacturer with the thermostat set at 70°C and above. This really can cause scalding to anyone, let alone more vulnerable children and older people. If your hot water seems too hot, the solution is to reduce the thermostat to around 60°C. Strictly speaking, this should only be done by an electrician or a plumber qualified to do the electrical and plumbing work for electric hot-water systems. But this can be done very simply and safely in just a few steps. (1) Go to your meter box and switch off the circuit breaker for the hotwater system. (2) Remove the plate on the tank which has the entry point for the electrical connections. (3) Identify the thermostat dial and check its setting. (4) If it is above 60°, use a flat-bladed screwdriver with an insulated shaft to rotate the thermostat dial to 60°C. (Most tank thermostats now have a minimum temperature setting of 60°C). (5) Replace the plate on the hot-water tank. (6) Turn on the circuit breaker for the hot-water system. Note that while the thermostat on siliconchip.com.au older hot-water systems is relatively easy to identify, the thermostat “dial” on new systems can be much smaller and the numbers harder to read. However, even setting your hot water tank thermostat to 60°C may still result in tap water temperatures above 50°C. If this occurs, the outlet of the hot water tank should be fitted with a water tempering valve (see above). This is defintely a job for your local plumber. By the way, the only way to be sure that your water temperature, as delivered by the tap closest to the tank, is 50°C or less, is to measure it with a mercury thermometer or a calibrated thermocouple and digital multimeter. (Do not use a meat thermometer – they are not sufficiently accurate.) Energy saving Reducing the thermostat setting by 5 or 10°C will give an energy saving over a year of use. But unless you have an electric hot-water system which permanently powered, ie, not off-peak, the cost saving is not large. Celebrating 30 Years A typical Tempering Valve with adjustment under the blue dust cover. The cold and hot inlets are marked with C & H cast into the body of the valve 1.6), the 45°C requirement can only be met by the fitting of tempering valve. These valves have an inbuilt thermostat element and a sliding valve that varies the ratio of hot and cold water that is allowed to pass. The temperature setting can be adjusted and is typically controlled to within ±3%. The PCA also now requires that tempering valves be installed on all new homes or renovations. So, when an old hot water system is replaced, a tempering valve should also be installed, to reduce the temperature to 50°C in bathrooms. Kitchen and laundry applications are still permitted to bypass the tempering valve and use the hot water directly from a standard electric or gas heater. The main reason for reducing the thermostat setting to 60°C is to reduce the risk of scalding. There is another possible benefit of having a lower temperature setting in that there will be lower stresses in the tank due to heating and cooling and this applies particularly to larger tanks which are usually run overnight to benefit from off-peak tariffs. Will the tank last longer? Maybe. But you also need to ensure that the sacrificial anode is replaced at every five years or so (something that even many plumbers don’t know about!). See our articles on this topic in the November 2012 issue: siliconchip. com.au/Article/417 and siliconchip. com.au/Article/409 By the way, electric hot-water systems are being phased out and are usually not allowed to be installed in new homes where solar and gas hot-water systems are used instead. Nevertheless, these should also be set to ensure that hot water inside the home is no more than 50°C. SC October 2017  81