It's Pool Heating Time
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Holiday patrons expect pool heating as a standard facility.
But pool heating is a major expense for most resorts and it is important that your equipment is serviced by an authorised technician and fine tuned to avoid unnecessary high running costs and of course after hour callouts to repair the equipment.
What temperature the pool water should be is the most frequent question asked by most resort managers.
The accepted standard for water temperature in swimming pools is 27° to 28°C maximum. Pool water at 30°C and above affects the chemical balance of the water and this can cause the water either to become corrosive or scale to form which can damage the pool heater, heat exchanger or the pool filtration equipment.
Spa water temperature is 36° to 38°C maximum. Water temperature above 38°C can breed bacteria and cause health issues with patrons. Spa pools also require more regular water testing to keep the water balance in check.
Some resorts have indoor pools that are used by elderly owners and set these pool temperatures at 30° to 32°C, thus risking the damage that may arise from imbalanced water.
The major heat loss in a pool generally occurs from the surface area of the pool water. The coldest portion of the pool is usually the top 50mm. This is more noticeable when patrons "toe dip" to check the water temperature and complain that the pool is cold. When testing water temperature for accuracy, the reading will be more reliable from approx 300mm deep.
Patrons should be told to insert their arm or leg into the water (giving time for body temperature to adjust) and note the difference.
Excessive heating bills are mainly caused by:
1. Pool heater is undersized and cannot replace the heat loss in adverse weather conditions. When purchasing a pool heater ensure that the supplier has experience in design and installation.
2. A modern feature of pools is water fountains or waterfalls. These features act as cooling plants and should only be turned on when required, especially in adverse weather conditions.
3. The pool heater is not balanced correctly and the water travelling through the heater is not getting the required temperature rise – in other words the inlet temperature of the water to the heater is say 20°C, then the outlet temperature should be approximately 24° to 28°C, giving a heat rise of 4° to 8°C. On gas pool heaters above 500 MJ/H the temperature rise should be between 14° and 16°C.
Which type of heating system is best?
Solar pool heating: Solar heating systems work by direct heat transfer. The water from the pool is circulated through the collector that is usually located on the roof.
Most systems utilise a digital controller that sends water to the roof whenever there is sufficient solar gain. These systems are usually supported with another form of heating (usually gas) to compensate for no solar gain.
These systems are not usually suited to resorts because of lack of roof space to place the collectors. As a general rule the collector should be equal to the surface area of the pool.
The collectors or absorbers should have UV resistance in the material – beware some cheaper absorbers generally break down in a few years and require replacement. Look for a product that has at least a 10 to 15 year guarantee.
Electric element heaters: Element heating works much like an electric kettle in that there is direct heat transfer between the immersed element and the pool water. The small physical size of the units makes them ideal for use where plant space is restricted or where gas supply is not available and the special installation needs of heat pump cannot be met.
Electric element heaters usually have high running costs, depending on the electric tariff.
Gas heating: Gas heaters are used in large numbers on pools and spas and give great flexibility to the manager because of their rapid heating ability and robustness.
Gas heaters can easily maintain any desired water temperature as typical sizing is based on providing heater capacity capable of achieving a 14°C rise in water temperature in 24 hours.
When purchasing a gas pool heater, ensure that a commercial grade heater is installed.
Most major brands have cuprous nickel heat exchangers (90 per cent copper – 10 per cent nickel).
Electric heat pump: Heat pumps work like a reversed air conditioner. The heat pump takes large quantities of air from the atmosphere; the heat contained in the air is removed and transferred to the water from the pool water passing through the unit. The characteristic of the heat pump of absorbing heat value from the air means that the unit has a low electrical input relative to its heat transfer.
These heaters are usually two to three times the cost of a gas heater but the running costs can be two thirds cheaper.
Disadvantages are usually fan noise, heater size and supply of three phase power.
Just recently one major pool heater supplier has developed a gas pool heater that reduces greenhouse emissions and claims that the heater has operating efficiencies of up to 97 per cent and can reduce operating costs by 20 per cent. Not bad considering most gas pool heaters have an efficiency rate of approximately 85 per cent.
This heater is also smaller than conventional models, which is a bonus where space is limited.
Another major feature is that the heater produces approximately 10 litres of condensation per hour that can be piped back to the pool or spa, saving on water usage costs.
Worth looking into.
Ken Adams
KW & WM Plumbers & Gasfitters
