Manual 01 - Section 12

Residential Solar Information Manual
Section 12 - Solar I.C.S Unit HotTop


The HotTop Solar hot water system is a low pressure integrated collector storage tank system. The water storage tank functions both as the collector and the potable water storage tank. This is accomplished by using a flat tank, with a large exposed surface area to volume ratio.

The tank comprises two sheets of steel, drawn into identical shapes to form the top and bottom halves. After forming the sheets are trimmed and holes (2 rows of 5) are punched to accommodate reinforcement tubes. The tank halves and tubes are shot blast to ensure maximum adhesion potential for the vitreous enamel lining. The two halves are butt welded together along the outside seam. The system is completed by welding the 10 reinforcing tubes, neck ring, element flange and hot water outlet socket to the main tank assembly.

After welding the tank is subjected to an air pressure test at 250 kPa to ensure that the tank is free of leaks and to weld integrity.

After passing this pressure test the inside of the tank is coated with vitreous enamel, a brush coat of vitreous enamel is also applied to the outside surfaces and baked in a furnace at 860°C.

Following the enamel application, the flange and anode are fitted and a final 150 kPa hydrostatic pressure test is performed to ensure that the seals are all water tight. The completed tank is placed in a Zincalume casing that is lock seemed together to ensure good weather proofing.

The tank is held in place within the case by expanded polystyrene insulation blocks on both ends and expanded polystyrene strips are used for side stability and insulation. A 60 mm thick polyester batt is placed under the tank for rear insulation.

Low iron tempered glass is used to cover the HotTop tank/ collector and is held onto the case by P.V.C closed cell foam tape with acrylic adhesive on both sides. A second foam tape seal is applied along the glass edge and the completed seal secured to the case by an aluminium glazing angle fixed into place with blind rivets.

A standard 4 bolt element flange is provided on every HotTop. The flange is sealed at production with a flat EPDM rubber gasket and backing plate. An energy saver kit is available as an optional extra to provide electrical boosting back-up. The energy saver kit comprises an element, gasket, adjustable thermostat, and a one shot relay. The kit is pre-wired into a metal tray that replaces the factory fitted flat access cover on the HotTop unit.


The HotTop unit is specifically developed for use in more isolated regions, and summer holiday homes. Typically in these locations conventional forms of power are unavailable, as is the luxury of hot water.

The HotTop system is capable of regaining heat quickly during the hours of sunshine, however, because the collecting surface can not be covered with insulation some heat will be lost overnight

Solar energy input is greatest between 10 AM and 3 PM, with the greatest amount of solar heated hot water available towards late afternoon. Therefore the highest use of hot water is recommended during these hours or early evening.

When an Energy Saver electric booster kit is fitted, it's recommended that the one shot boost is activated at least two hours before hot water is needed.

DWG. No. 52-0005 REV. G



Maximum working pressure                     120 kPa (17.4 psi / 1.2 bar)
Air test pressure (without enamel lining)    250 kPa
Final hydraulic leak test (enamelled)        150 kPa
Nominal capacity                             100 litres
Weight empty                                 65 kg
Weight full                                  165 kg
Outlet scoop                                 Fitted to hot water outlet.
                                             Polypropylene, PPK 2032
Inlet scoop                                  Fitted to cold water inlet. 
                                             Polypropylene, PPK 2032
Water connections                            Mild steel sockets 3/4" BSP female(RP 20 - 3/4")
Insulation                                   Container end and sides expanded polystyrene
                                             Container back 60 mm polyester batt.
Anode (AZ 31)                                Magnesium with a max. of 0.003% iron content
Anode support                                40mm diameter. tube polypropylene, PPK 2032


Material Mild steel, non oiled low carbon HE 1006 made to AS1594 and SAE1006 Material thickness 2.2 mm Lining One coat X-Class vitreous enamel (860C) Enamel thickness 0.16 mm Outside surface finish Brush coat vitreous enamel Reinforcement tubes Mild steel 38 mm diameter/ 1.6 mm wall Element flange Provided at the RH side of the container, blanked off. Element Not fitted, optional extra (straight elements only) Closure flange Mild steel vitreous enamelled, fitted with anode and cold water inlet sockets.


Material 0.6 mm Zincalume Construction Bottom and sides folded from one sheet, both ends snap locked to the bottom and sides. Element access 232 x 80 mm at the RH side. GLASS One sheet of low iron tempered glass Iron content Max. 0.03% Transmittance Min. solar radiation transmittance 90% Standard Made to standard ANS1297-1-1975, BS6206A and JIS-R3206 Temper Tempered to AS2208-1978 and U.S. Federal spec DDG 403C Weight 8 kg Size 1434 x 695 x 3.2 mm GLASS TO TRAY SEAL Material Closed cell PVC Foam tape. Acrylic adhesive on both sides. Size Bottom seal 12 x 3.2 mm Top seal 18 x 1.6 mm GLAZING ANGLE Material Aluminium Extrusion Alloy 6060 Temper T5 Size 19 x19 x1.2 mm OPTIONAL Energy saver kit Recommended element rating 2.4 kW (straight)