Alternative water heating solutions

The 2011 amendment to the National Building Regulations requires 50% of an occupancy’s annual volume of heated water to come from alternative energy. Tracy Maher explores the reasoning behind this addition to the legislation, as well as how effectively it can be implemented.

Also referred to as the ‘new green laws’ for buildings, SANS 10400-XA governs the selection and installation of water heating systems from meter to tap in all new buildings, including renovations and add-ons, except for garages, storage areas, and buildings used for commercial and industrial purposes. Loosely translated, the regulation stipulates that conventional electric geysers may be used, provided at least half of the water supply is heated by an alternative energy source.

On paper, this appears to be a move in the direction of sustainability and energy efficiency for South Africa, but are the motives that ‘clean’? Or is it merely a smokescreen to hide the capitalist intentions of certain stakeholders that encourage consumers to dole out cash for new energy-efficient equipment they know very little about, to comply with National Building Regulations (NBR) and standards they don’t really understand.

SANS 10400 XA describes a competent person as one who is “qualified through training, experience and contextual knowledge” to implement the NBR. This must start with the rational design by architects and engineers, followed by the correct installation by contract plumbers. However, there is often a disconnect between this design and what is feasible when it comes to the building’s reticulation. The designer must prove the design makes use of an alternative heating source for water to meet the 50% NBR, including but not limited to solar, propane gas, heat pumps, or steam. The source selection criteria involve various factors, such as location, climate, outlay cost, and lifespan.

SOLAR
Ray Fernandez, business development manager at Averge Technologies, sheds a little light on why solar water heating (SWH) systems are a popular choice.

Multiple unit installation in Namibia. 
Image credi: SolahartColoured solar tank. 
Image credit: SolahartSilver solar tanks connected in parallel. 
Image credit: Solahart

How it works

SWH systems offer a decentralised solution to the total hot water supply need in warm, sunny climates. A gas in-line booster or in-tank booster may be required to offset the lack of solar radiation, especially in colder climates with more rainfall. With a lifespan of 20 years plus and the only moving part being water, operational and maintenance costs are much lower than the electric counterpart.

 Cost

Solar energy is free and renewable. Although SWH systems may be pricey to purchase and install, they pay for themselves over time in longevity and by not being influenced by drastic electricity price increases. In fact, these price increases will reduce the payback period. If saving approximately 85% of your heating cost or 45% of your total electricity bill is not enough to persuade you to go solar, perhaps the tax incentive will, or the fact that, in the age of unplanned outages, solar energy can supply an uninterrupted heat source.

Impact

If installed properly by a professional, SWH only takes a short time to reheat, depending on the available solar energy at the time and the type of boosting used, if any. In-tank boosters take approximately an hour to generate enough hot water to take a shower (at 45°C), while in-line boosters provide hot water instantaneously. The choice to go solar can also save the environment up to four tons of carbon dioxide emissions per system per year. This is equivalent to removing one small motor vehicle from the road per year.

Maintenance

According to the Solahart fact file provided by Fernandez, a SWH system operates on two natural phenomena: black objects absorb heat and hot water rises. Close-coupled SWHs are generally installed outside of the roof and have no moving parts; therefore, should anything happen, there is no collateral damage to the house by way of ceiling repairs or wall painting. The valves require routine maintenance, but not the system.

Challenges

Orientation is essential. As far as possible, SWH systems should be installed north facing, but more efficient systems can be installed from east to west. For indirect systems, the heat transfer fluid must be pressure tested on commissioning of the system to prolong lifespan and efficiency. The weight of the systems should be taken into consideration. When installing systems on roofs, a prop analysis must be done under the guidance of a roof structural engineer. Storage is also an important consideration, and a proper sizing analysis must be done to make sure there is enough storage capacity for the client/customer to maximise their savings.

LIQUEFIED PETROLEUM GAS (LPG)
Kevin Robertson, managing director of LPGSASA and chairman of South African Qualification and Certification Committee (SAQCC Gas), has a wealth of knowledge and experience when it comes to the gas alternative.

A Gasmate 20ℓ unit. 
Image credit: Kwikot

How it works

An LPG system can be used in virtually any application — domestic, commercial, or industrial — and is increasingly common in domestic and commercial use. When using an LPG water heater, there is no need for a large water tank or geyser to store and heat the water as is the case with an electric geyser. When the LPG water heater is activated, cold water passes through a pipe located just above a small flame (which is fed by the LPG) and this heats the water as it passes. Therefore, only the water that is needed is heated.

Cost

The complexity of the installation determines the costs and an LPG water heater would generally be more expensive than a standard electric geyser to purchase and install. However, considering the effectiveness of the water heater and the fact that it only heats the water required, the running costs are far more efficient. The longer you keep and use it, the more it saves. There is a large number and a broad range of LPG water heaters available to suit various cost and application requirements, bearing in mind that only appliances that carry a Permit Verification number are approved for use.

Impact

With traditional geysers, all the water in the geyser is kept hot and when required for a bath or a shower, cold water flows through the tap until hot water flows. This means there was unused and therefore wasted water, noting that cold water still needs to be added to make the temperature comfortable for use. With an LPG water heater, the temperature of the water can be set to an acceptable limit so that it can be immediately used without moderating with additional cold water.


Compliance is mandatory, and all tradespeople, installers, and technicians should be well trained, fully registered, and accredited.


In current water heating models, once the water has been turned off, the flame automatically shuts off, so no gas is burnt unnecessarily, and you only heat the water that is used.

Maintenance

The system needs to be designed and installed according to the requirements and by properly trained and registered LPG practitioners. It should be noted that only registered practitioners (installers) are permitted to undertake the installation of any LPG appliances — including LPG water heaters. These practitioners should be trained by the Liquefied Petroleum Gas Safety Association of South Africa (LPGSASA), which is mandated by the Department of Labour (DoL) to undertake this training. They should then be registered through an independent body (SAQCC Gas), which is also mandated by the DoL to do so. This is a requirement in terms of the Occupational Health and Safety (OHS) Act and the Pressure Equipment Regulations (PER). Like any working appliance, there is a need for maintenance, which should only be undertaken by a trained practitioner.

Challenges

LPG is becoming the alternative energy source for many households in South Africa due to its increased availability, effectiveness, and efficiency. Both natural gas and LPG can be used for water heating. However, because natural gas is only available in certain areas it is not vastly used. LPG is portable and transportable; this makes it a friendlier alternative. Whether the water heater is in an upmarket suburb or a more rural environment, it would be possible to get an LPG cylinder (bottle) to the site. Calculating the size and number of LPG cylinders required to ensure a sufficient flow of hot water and establishing the pipe sizing requirements can be a challenge, which is best left to trained and registered LPG practitioners who are also competent in ensuring that the entire installation complies with the various regulations that cover LPG installations. Installations not undertaken by such an installer could be potentially hazardous and may not be covered by insurance companies.

HEAT PUMPS
Wil Jansen, divisional director of Alliance heat pumps, explains more about the intricacies of heat pumps, with input from the director of SARACCA, John Parry.

Heat pumps. 
Image credit: Alliance Heat pumps are effective water heating systems for schools. 
Image credit: AllianceHeat pump for industrial use. 
Image credit: Alliance Heat pump for residential use. 
Image credit: AllianceHeat pump for industrial use. 
Image credit: AllianceHeat pump for industrial use. 
Image credit:  Alliance

How it works

Parry explains that water heat pumps work on a similar principle to air conditioners and chillers. The refrigerant gas is compressed, condensed to a liquid, expanded back to a gas and then back to the compressor. In the process of condensing the compressed refrigerant to a liquid, heat is rejected, which is absorbed by the water in the condenser heat exchanger. The liquid is then expanded before it enters the evaporator (heat exchanger). Ambient air is then drawn through the evaporator, removing the cold air at approximately 8°C and ‘dumping’ it into atmosphere. A heat pump replaces the electric elements of a geyser and uses a third of the electricity.

The heat pump heats small quantities of water at a time and recirculates it with the aid of a pump to and from a tank (the geyser), heating the water gradually until it reaches the desired temperature. The water from the mains enters near the bottom of the tank and the hot water exits at the top. An expansion relief safety valve is also fitted on the tank. The temperature in the tank that can be obtained from a heat pump is approximately 55°C, but if higher temperatures are required, electric elements can be installed in the tank to raise it.

Cost

Jansen admits that installation can be more expensive than conventional electric geysers and solar geysers. However, as with SWH, the payback period becomes shorter as the electricity prices increase. A heat pump can effectively save domestic and commercial users as much as 70% of their geyser heating costs. Since the Eskom rebate system stopped, there has been a definite drop in the number of specialist heat pump installation companies, but Jansen says there are several good partners that have been “around the block” and know their stuff, meaning there is growth potential in the foreseeable future.

Impact

According to Parry, heat pumps are a great energy-saving, cost-effective water heating method that is becoming increasingly popular in South Africa. Water heating in a domestic setting accounts for a large portion of electricity use. With escalating costs of power, a more energy efficient source has become vital. Jansen adds that aside from reducing reliance on a national electricity supplier, heat pumps have also become more environmental friendly by using R410a, a more energy efficient and ozone-friendly gas alternative to R-22. Less reliance on electricity also results in fewer carbon dioxide emissions being released into the atmosphere, and usage times and temperatures can be controlled remotely.

If, for example, the hot water is only required by a factory for showers for the staff at the end of the day, Parry explains that the heat pumps can be set to heat the water from midday. Of interest, says Jansen, is the increase in applications of heat pumps, especially providing heating and cooling for various industry segments. Other than normal domestic and commercial hot water, Jansen says Alliance has supplied heat pumps to hydroponic farmers, crocodile farms, industrial cleaning companies, and Olympic-sized swimming pools, to name just a few.

Maintenance

Water pumps do not take up much space and can be discreetly installed in both residential and commercial properties without any advanced plumbing work. Parry says that heat pumps require regular servicing and when maintenance is required, it must be done by a SAQCC Gas-registered practitioner. For more information, visit the SARACCA website.

Challenges

The reliance on electricity to operate leaves heat pumps vulnerable to unplanned power outages. They may also be less effective in low temperatures, which makes correct placement in the northern part of the building crucial to energy efficiency. There has been a definite reduction in the number of heat pump suppliers in the market. For example, at the height of the Eskom approval programme, there were approximately 30–35 suppliers on the approved list. Today, there are only a handful of importers that specialise in heat pumps, so it is imperative to have a good stock and spares holding, keep pricing competitive, and support clients with good technical backup.

STEAM
Francisco Habib from Allsteam Engineering cc explains the basics of steam as a water heating source.

Steam boiler in Charlotte Maxeke Hospital nurses’ quarters. 
Image credit: Ilana Koegelenberg

How it works

Steam boilers do not require electricity to function, as steam is used as an energy conveyor by means of burning a fossil fuel as energy source. Gas or diesel hot water boilers are a more efficient and quieter option for simple hot water needs.

Cost

Steam boilers and steam reticulation involves an extremely expensive outlay cost, but there is a decent return on investment when you consider that steam will be used for all heating, cooking, and sterilisation. Gas or coal is often used as a water heating medium, as you can put together a large high-kilowatt system at a fraction of the cost of any other heating system.

Impact

Steam as a heating source is not seen as an eco-friendly water heating system and is usually used where energy consumption is greater than what the municipality can provide. However, modern technology has allowed for more efficient fossil fuel water heating with steam. Hot water boilers show efficiency rates of up to 93% and with economisers and heat exchanges, all the heat from the combustion process is used. LPG and compressed natural gas (CNG) running costs as well as the carbon footprint of steam and hot water boilers are significantly lower than traditional resistance element heating systems, falling within the 50% alternative heating criteria.

Maintenance

Boilers generally have a long life, but require regular servicing by a qualified technician to keep the steam traps and pressure relief valves functioning.

Challenges

It is difficult to set up the infrastructure required for a steam water heating system in energy-remote areas. Other factors to be considered are the quantity of water to be used, electrical supply, temperature required, and the layout of the facility. While most government and private sector hospitals and prisons use steam as their primary heating source, gas and coal are often used for large-scale water heating systems. For example, Egoli gas is piped to many streets of the Johannesburg CBD and surrounding areas, and high-rise buildings often make use of this effective fuel source. Military bases also use gas for water heating.

The verdict

It may be a ‘50% regulation’, but there are no half measures when it comes down to it. Compliance is mandatory, and all tradespeople, installers, and technicians should be well trained, fully registered, and accredited. NBR aside, water heating is estimated to be one of the top five household electricity consumers, according to Parry, and the shift to alternative energy sources benefits not only cash-strapped consumers, businesses, and industries, but maps the way forward for an environmentally friendly and sustainable water heating solution.


Click below to read the February 2018 issue of Plumbing Africa

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