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33-1197 Solahart Owner‟s Manual – Thermosiphon Systems - Revision H – Nov 2013 6 Sub tropical / Tropical climate Minimum winter cold water supply temperature Thermostat set point Temperature rise = 20°C = 60°C = 40°C Booster Heating Unit 150 model 180 model 220 model 300 model 440 model 1.5 kW 2 ½ hours 3 hours 3 ½ hours 4 ¾ hours 7 hours 1.8 kW 2 hours 2 ½ hours 3 hours 4 hours 6 hours 2.4 kW 1 ½ hours 2 hours 2 ¼ hours 3 hours 4 ½ hours 2.5 kW 1 ½ hours 1 ¾ hours 2 ¼ hours 3 hours 4 ¼ hours 3.6 kW 1 hour 1 ¼ hours 1 ½ hours 2 hours 3 hours 4.8 kW ¾ hour 1 hour 1 ¼ hours 1 ½ hours 2 ¼ hours The recommended boosting periods are sufficient to allow the booster heating unit to heat up the boost volume of the solar storage tank to 60°C where the winter cold water temperatures do not fall below those shown. This may be necessary during periods of very low solar energy gain through the solar collectors, such as during constant rain or extremely cloudy weather, particularly in winter when the incoming cold water temperature is lower. The period will also provide a sufficient heat up time for the electric booster to operate, if required, to satisfy the requirements of AS 3498. The booster heating unit will only activate if heating is required and power is available from the timer. When the water is below the thermostat setting, the booster heating unit will turn on and heat the water. The booster heating unit will automatically turn off either when the temperature of the water reaches the thermostat setting or at the end of the timer period, whichever comes first. IN-SERIES GAS BOOSTING An in-series gas booster (also known as an instantaneous gas booster) can be installed between the solar water heater and the hot outlets in the house. This booster should be permanently active. The booster senses the temperature of the water passing through it: if the water temperature is above its temperature setting it does nothing; if below it will automatically heat the water up to the preset outlet temperature setting. This device ensures hot water delivery for a variety of hot water demands without the need for user intervention while enabling maximum solar energy contribution to the water heating. For more information on this booster, consult the owner‟s manual for the product. TEMPERATURE STABILISATION Temperature stabilisation is the reduction in water temperature as the hot water at the top of the storage cylinder transfers some of its heat to the cooler water in the lower section of the cylinder. This effect is often perceived as heat loss, but is actually the redistribution of stored heat more evenly over the entire contents of the storage tank. This may make it necessary to use the booster to raise the water in the top section of the cylinder back to an acceptable temperature. Over-night temperature stabilisation is most evident in the morning if the booster switch or time clock is left OFF overnight. It is more prevalent the more hot water is used the night before and also in the cooler months. Day time temperature stabilisation is quite evident on days of lower solar radiation particularly during the cooler months if the power to the booster heating element is not available, or the booster switch or time clock is left OFF. If higher temperature water is required, particularly in the morning, then use of the booster heating unit is necessary to raise the temperature of the water in the top section of the cylinder. Refer to “In-tank Boosting” on page 4.