NOTE: THIS IS A CLOSED CIRCUIT SYSTEM
COLLECTORS MUST BE SEALED AND TESTED FOR COMPLETE AIR TIGHTNESS.
The Non Residential range of systems has been designed to cater for applications where the hot water demand is in excess of 2,000 litres per day.
Although multiples of Residential Systems are capable of meeting such large demands, quite often the structure and location of the roof prevent such an installation.
1.2 SYSTEM DESIGN
The Non Residential System is pre-engineered for simplicity of operation and a minimum of site installation. The collector array installed on the roof of the building connects by flow and return pipe work to a Heat Store typically located at ground level.
1.3 HEAT STORE SYSTEM
The Heat Store is an integral unit consisting of potable water storage and closed circuit heat exchange systems. The potable water storage system is a set of vitreous enamel lined storage vessels housed inside an outer shell. The vacant space between the outer shell and the potable water storage vessels forms a reservoir for the fluid of the closed circuit heat transfer system.
1.4 ENERGY COLLECTION AND TRANSFER METHOD
The closed circuit fluid is drawn from the lowest point of the Heat Store by a circulating pump, and circulated through the collector array. The fluid is heated as it flows through the collectors and returns into the top third of the Heat Store closed circuit reservoir. This continual heating and recirculation process raises the temperature of the closed circuit fluid in the Heat Store. The energy accumulated in the reservoir by this transfer process is conducted through the walls of the storage vessels to the potable water they contain.
1.5 HOT WATER OUTPUT RATING
The cold supply water connects to the bottom row of the potable water storage vessels. Each row of vessels is connected in parallel with each other, then in series to the row above. This method of piping ensures that the total volume of potable water is ready for immediate use at the maximum possible draw off rate with minimal heat exchange penalty. The remaining energy within the Heat Store closed circuit system reservoir is also readily transferred to the potable water circuit at the maximum possible rate with minimal heat exchange penalty. A system with a rated draw of 2500 litres indicates that 2500 litres of hot water can be drawn from the Heat Store before a 12 C drop in hot water temperature at the outlet occurs. Each system's performance has been tested and witnessed by an independent qualified Testing Authority.
1.6 TEMPERATURE DIFFERENTIAL THERMOSTAT
The Heat Store is fitted with a temperature differential thermostat and a cold sensor located in the base of the Heat Store. This location measures the coldest point of the entire system. A hot sensor also connected to the thermostat and located alongside the collector array in a hot sensor box, measures the hottest point of the system. The thermostat is pre-set to energise the closed circuit pump and circulate the closed circuit fluid through the collectors only when there is sufficient solar energy available to increase the closed circuit reservoir temperature.
The temperature differential thermostat has an override system set to turn the closed circuit circulating pump 'OFF' when the temperature of the cold sensor reaches 75 C. This function is fully automatic and will allow the pump to restart when the cold sensor temperature falls below 60C and the hot sensor box temperature is greater than 60 C.
1.7 RAPID COLLECTOR REFILL AND DRAIN BACK
The collector hot return pipe is connected into the Heat Store in two positions. The top-most connection contains a check valve. The connection at the top third of the Heat Store contains an orifice plate to control the closed circuit flow rate.
The check valve is designed to close when full closed circuit heat transfer fluid flow is established. Until full flow is established the check valve remains open to allow rapid replacement of the nitrogen protection blanket from the collectors to the Heat Store reservoir. Once full flow has been established the check valve closes and the system flow rate is controlled by the orifice plate.
When the circulation pump turns OFF, the check valve opens and the closed circuit fluid contained in the collectors drains back to the Heat Store. As the closed circuit fluid drains back to the Heat Store it is replaced in the collector array by the nitrogen protection blanket.
The drain back feature of the closed circuit fluid, prevents the undesirable collector wet stagnation conditions of high temperature and pressure within the collector closed circuit and potable water systems.
For this reason the collector array must always be mounted above the Heat Store.