Manual 02 - Section 02

Non-Residential Solar Information Manual
SECTION 2: Solar Hot Water System Packages


Non Residential Solar Hot Water System Packages are manufactured in three standard sizes - 2500J, 3500J and 6500J. The numerals indicate the capacity of the Heat Store in litres and the 'J' indicates a jacketed (or a closed circuit) system.

To complete the packaged system each Heat Store requires an appropriate number of collectors to meet the hot water demand of the proposed installation.

Typically the package's collector combinations will be:

Only in extremely high or low radiation areas, should collector quantities outside the above ranges be installed. Refer to the Solar Contribution Factor (SCF) Programme for selection assistance or to Solahart for individual system calculation.


              Draw off        Litres for 12'c              
 Package          in        Temperature Decrease
           (Litres/minute)  Solar / Gas Capacity     Electric (Only) Capacity

  2500J           20               1600                       1200         
  3500J           30               2500                       1800         
  6500J           40               4000                       3000         


Each Heat Store is manufactured, tested and assembled in a weather-proofed enclosure requiring only minimum on site installation work. The on site installation work is usually limited to collector mounting plus water and electrical supply connections to become a fully operational hot water system.

The combined potable water storage and closed circuit heat transfer fluid system design, enable the use of mains pressure potable hot water system with all the advantages of a closed circuit collector heat transfer system.

The total volume of potable water can be drawn at the stored temperature without a heat exchange penalty, irrespective of the rate of water draw.

The Heat Store is designed to have exceptionally large heat exchange capacity that effectively transfers the energy in the closed circuit fluid reservoir to the potable water circuit with minimal heat exchange penalty. The exterior surfaces of all potable water storage vessels become the heat exchange surface. This surface is many times greater than the heat exchange surface in most conventional coil heat exchanger systems.

The lower row of potable water storage vessels are supplied with potable water at ambient temperature, and through the use of a parallel-series interconnection method, the water is exposed to the maximum possible heat exchange surface area en route to the hot outlet connection in the upper row of potable water storage vessels.

The layout of the potable water storage vessels and their parallel-series method of interconnection enables the input energy to cascade through the system enhancing the natural stratification within the Heat Store. This ensures the availability of the total stored energy at the hot outlet and at the maximum possible temperature.

The automatic drain back feature of the closed circuit system, prevents wet stagnation of the closed circuit fluid in the collector array. This eliminates potential damage due to freezing or boiling of the fluid induced by wet stagnation and also ensures that the collected energy remains in the Heat Store.

The open, accessible and simple design of the Heat Store enables easy access to all components by service personnel for preventative maintenance procedures.

The Heat Store is designed with large, low fouling, readily cleanable, vitreous enamel lined internal heat exchange surfaces in the potable water circuit. Large removable access plates are located in the front of each potable water storage vessel to facilitate cleaning when necessary. It is important to note however, that this facility would only be necessary in extremely hard water areas.

The Non Residential Solar Hot Water Systems can be installed and plumbed together in multiple unit combinations to cater for large hot water demands. It is preferable to install multiples of the same capacity of the Heat Store and not varying Heat Store capacities.

For example, to meet a hot water demand of, say 12,000 litres per day @ 600 C, the following multiples of Heat Stores would be recommended.

1) 6 off 2500J Heat Stores or
2) 4 off 3500J Heat Stores or
3) 2 off 6500J Heat Stores

A combination of one 6500J and two 3500J Heat Stores or any other combination of varying capacities of Heat Stores is not recommended.

The Heat Store package is designed to be connected to systems requiring both domestic hot water and space heating hot water supplies. The sizing and design of these systems is not covered by this Manual and enquires of this nature should be referred directly to Solahart.


The Heat Stores are designed to have auxiliary boosting by either electricity, gas or a combination of both electricity and gas.

Each potable water cylinder can be fitted with an electric element to a maximum rating of 4.8 kW. The local supply voltage of the proposed installation location will determine the voltage rating of the package produced.

The table below indicates the boosting capacity fitted as standard to each electrically boosted Heat Store.

   Heat Store     No. of Elements    Element Rating    Total Boost Input

     2500J               4               4.8 kW            19.2 kW     
     3500J               7               4.8 kW            33.6 kW     
     6500J              10               4.8 kW            48.0 kW     

To provide a gas boosting option, the closed circuit fluid of the Heat Store can be circulated through remotely mounted gas heater unit (s) by an independent booster circulating pump.

Two alternate types of gas booster connections are available. The choice between types normally remains with the client and is made based on the available services and service expertise at the location of the proposed installation.

Both types of gas boosters are available for Natural Gas or LPG installations.

Multiple, temperature and flow controlled gas instantaneous package units mounted outside the Heat Store. A thermostat is located in the Heat Store to sense the temperature of the closed circuit fluid. If the temperature is below the designed set point of 65 C, the thermostat energises the closed circuit booster circulating pump. The booster circulating pump draws the closed circuit fluid from the bottom third section of the Heat Store and circulates it through the gas boosters before being returned to the top of the Heat Store. The thermostat switches the circulating pump OFF when the system reaches the set temperature.

The gas boosters are normally mounted onto one side of the Heat Store. However, they can be mounted on a wall within the plant room or on an adjoining wall outside the plant room.

If the gas boosters are located inside a plant room appropriate fluing arrangements should be made to comply with statutory requirements.

A single, temperature and flow controlled boiler unit with an electronic ignition device is located adjacent the Heat Store. This boiler unit is controlled as detailed for the gas instantaneous units (Gas Type 1) with the exception that the one boiler unit is sized to provide the total boost requirement. This boiler is a stand alone device with internal ignition and protection devices. For best results the boiler is typically located on the right hand side of the Heat Store adjacent the plumbing connections.

Both internal and external boiler models are available to suit the particular requirements of the installation.

For internal installations, appropriate fluing arrangements should be made to comply with statutory requirements.

The table below indicates the boosting capacity fitted as standard to each gas boosted Heat Store.

                   Gas Boost Type 1         Gas Boost Type 2     
  Heat Store    No.   Input    Total     No.   Input     Total

    2500J        2    100 MJ   200 MJ     1    277 MJ    277 MJ    
    3500J        2    130 MJ   260 MJ     1    343 MJ    343 MJ    
    6500J        4    100 MJ   400 MJ     1    420 MJ    420 MJ    

The Heat Stores are designed to be simultaneously compatible with both forms of boosting.

Where a facility has off peak electricity tariff, electric boosting is conducted overnight to capitalise on the lower cost electrical supply.

During days of low solar radiation or high day time hot water demand, auxiliary boosting is performed by the auxiliary gas device thereby avoiding the need for higher cost day time electrical boosting.

This method of connection ensures that the most cost effective method of axillary boosting is utilised minimising the total operating costs of the installation.