Once you have determined whether your pool heating needs will be best met by solar, heat pump or gas, the next decision will be how to select the correct sized heating system and how to differentiate differing quotes for installation.
Heating capacity should be your first point of comparison of heating systems. It will be the size of heater selected that determines the temperature, swimming season and length of time to heat the pool.
Solar systems will be compared according to the total collector area, measured by m2 and expressed as a percentage of the pool surface area. Increased collector provides a direct proportional increase in heat transfer. The base guideline has been that the the area of solar collector should equal the total surface area of the pool, with this being denoted as 100% cover.
Gas heaters are rated by energy input, expressed as Megajoules (MJ) per hour. The higher the MJ rating, the higher the heat output.
Heat pumps are rated by heat output, in this case expressed in Kilowatts (KW). The manufacturer determines the KW output at a specific water/air temperature and relative humidity value. To accurately compare one unit to another, these test values must be the same. Look for the KW output and efficiency at a common rating value to ensure a valid comparison. This is a complicated issue for potential heat pump purchasers but critically important if correct product selections and price comparisons are to be made. We have provided more advice on this in a separate page.
What size best suits you
Knowing how to compare the heating capacity of a heater is great but just as essential, is choosing the heater that meets your expectations for the use of the pool.
For pool owners who have chosen gas heating and want to achieve maximum flexibility in heat-up times to suit ad-hoc use of the pool or spa, the input MJ rating is the key. The larger the figure, the faster the heat rise per hour. The relatively small increase in price between Raypak's smallest residential pool heater (the Raypak PO200) and its largest (the PO430) means that the larger heater can be readily chosen.
Selecting the right size Raypak Gas heater for your pool or spa
Note: Temperature rise is provided as a guide only and is based on outdoor installations ands an average wind speed of 2.2km/h and depth of 1.3m. Temperature rise will be greater with indoor installations or lower with higher wind speeds.
This same approach is not transferable to the selection of heat pumps can be readily seen when it is understood that the Raypak 430 (420MJ natural gas input) is equivalent to 94KW nominal output. In contrast, a typical heat pump for a domestic pool would be 20KW output. So the gas heater does raise temperature at a much faster rate and would continue to achieve the target pool temperature under any weather conditions.
For pool owners who seek to maintain a constant temperature by the use of a heat pump, the selection will rely on a detailed evaluation of the pool's heat loss characteristics, a thorough understanding of the heat pump's rating and potentially some site specific aspects such as required run-hours or electricity tariff structure.
Pool Heat Load Modelling
Each pool and home is unique. However, most of the heat loss from a pool is suffered through the surface. A pool loses heat whenever the surrounding air temperature is less than the pool water temperature. The rate of heat loss is quantifiable, and this rate is used to determine the amount of heat needed to keep a pool at a given temperature. The determination of the rate of heat loss for a pool is based on several factors, including the size and shape of the pool, pool shading, geographic location, swimming season, desired pool temperature, wind exposure, blanket use, etc
At Rheem Pool Heating, we pride ourselves on the level of expertise which we bring to client advice in relation to heat load. Our work is based on the use of the University of New South Wales Poolheat Model. The Poolheat Model examines the hourly heat loss characteristics of a pool based on all the variables of design such as wind and sun exposure.
We believe that is vitally important that our clients understand not only the output of this type of facility but also the design assumptions which have been applied. We will undertake this analysis and provide a report of our work including a summary of the analysis in an easily read form.
The Poolheat Model outputs will be essential in allowing a comparison of the relative economics of the gas and heat pump options and will also allow us to review the impact of differing energy price options on heater sizing and overall heating costs.
If you would like us to provide you with a proposal for a Pool or Spa Heating application, please either fill in the attached form below and email: email@example.com fax it back to (02) 8706 8477 or call us on 1300 132 950
Rheem_Pool_Heating_Profile_Questionnaire.pdf (209.46 KB)