Solar Thermal Panel with Drain-back
The principle is straight forward. When the sun is shining, water is pumped through the solar panel and is heated by solar energy. This heated water then flows through a heat exchanger, warming the water stored in the hot water cylinder.
The hot water in the cylinder can then be used for washing and bathing as required, with your boiler providing backup heating. In the summer the water in the cylinder can reach a temperature of 80 deg C within half a day, and the insulation on the cylinder will keep the water warm for the next day. Typically the solar hot water system will reduce your domestic hot water bill by 50%.
The Low Flow System
A characteristic feature of the ISL solar system is the low flow rate through the solar panel. Most systems in the UK use a full flow system, based on central heating technology.
The advantages of low-flow rate are:
This system has four main components:
1. A 2.7m2 solar collector panel (or more if required).
2. A pre-assembled unit comprising of a pump, control unit and small drain back bottle.
3. A hot water cylinder with solar heat exchanger.
4. A PV module, or mains, power supply.
These components are plumbed together using insulated microbore copper pipe, before filling the solar system with normal tap water. The solar hot water system is normally set up in conjunction with the existing boiler.
There are no running costs for electricity with a PV powered solar system! Due to the innovative drain back design of the system, no anti freeze is required and there are no maintenance problems due to pressure loss, as can occur in pressurised solar systems.
Solar Panel
Fully compliant with all British and European standards,
including BS EN 12975.
It is particularly attractive when roof integrated, but can be mounted on a framework above the roof, or on a flat roof. This means the panel is actually recessed into the roof, rather than sitting on top of the tiles. This provides an attractive low profile appearance, very similar to a low lying 'Velux' window.
Installing the panel into the roof is very simple and can be done in a day. The tiles are removed, the panel is laid on the roof battens and the tiles are put back to the edge of the panel in a watertight fashion.
The solar panel has a highly transparent, virtually unbreakable polycarbonate cover which has been treated to ensure long life.
- Innovative Dutch technology - designed with simplicity in mind
- No maintenance costs
- Tested under British Standards for solar water heating BS EN 12975
- Totally solar powered - pump & controls can be run by solar
electricity rather than mains power - Features drain-back technology - protected from summer overheating prevents freezing reduces maintenance requirements
- Designed for roof integration - Can also roof mount, install on flat roofs & walls.
- Easy plumb-in kit
- Full Installation in 2-3 days
- Compatible with most conventional water heating systems - including combination boilers.
- Includes pre-assembled pump, control unit and drain back vessel.
- Provided with new ‘solar compatible’ water storage cylinder - either vented, un-vented or thermal store
- All pipework run in copper microbore
- Planning not usually required as the collector does not stand more than 10cm from roof (same rules as for Velux window).
The principle is straight forward. When the sun is shining, water is pumped through the solar panel and is heated by solar energy. This heated water then flows through a heat exchanger, warming the water stored in the hot water cylinder.
The hot water in the cylinder can then be used for washing and bathing as required, with your boiler providing backup heating. In the summer the water in the cylinder can reach a temperature of 80 deg C within half a day, and the insulation on the cylinder will keep the water warm for the next day. Typically the solar hot water system will reduce your domestic hot water bill by 50%.
Principles of operation
- The system is managed by the control center, which includes a light sensor fitted inside the solar collector.
- When there is sufficient daylight water is pumped from a storage vessel and flows through micro-bore copper piping fitted beneath the solar collector.
- The water flowing through the copper piping collects the heat, and transfers it to the cylinder via a solar coil. Hot water is then ready upon demand.
- When insufficient solar hot water is produced the auxiliary fuel supply (e.g. gas-fired boiler) will fire and feed top-up heat into the hot water cylinder.
- With a combi boiler, pre heated solar water is supplied from the cylinder and fed top up heat by the combi if necessary.
- The pump unit will switch off at the end of the day, or when the hot water in the cylinder reaches the maximum temperature.
- All the water is drained-back out of the system into a storage vessel to guarantee boil and freeze protection.
- There is a two-minute time delay fitted to the pump to allow for dark clouds moving overhead.
The Low Flow System
A characteristic feature of the ISL solar system is the low flow rate through the solar panel. Most systems in the UK use a full flow system, based on central heating technology.
The advantages of low-flow rate are:
- Water passing through the solar panel will get heated up by about 30 deg C on a sunny day compared to about 3 deg C in a traditional solar system.
- The pump is only 3 watts instead of the 50 watts used on a full flow system making it ideal for powering with a small PV module.
This system has four main components:
1. A 2.7m2 solar collector panel (or more if required).
2. A pre-assembled unit comprising of a pump, control unit and small drain back bottle.
3. A hot water cylinder with solar heat exchanger.
4. A PV module, or mains, power supply.
These components are plumbed together using insulated microbore copper pipe, before filling the solar system with normal tap water. The solar hot water system is normally set up in conjunction with the existing boiler.
There are no running costs for electricity with a PV powered solar system! Due to the innovative drain back design of the system, no anti freeze is required and there are no maintenance problems due to pressure loss, as can occur in pressurised solar systems.
Solar Panel
Fully compliant with all British and European standards,
including BS EN 12975.
It is particularly attractive when roof integrated, but can be mounted on a framework above the roof, or on a flat roof. This means the panel is actually recessed into the roof, rather than sitting on top of the tiles. This provides an attractive low profile appearance, very similar to a low lying 'Velux' window.
Installing the panel into the roof is very simple and can be done in a day. The tiles are removed, the panel is laid on the roof battens and the tiles are put back to the edge of the panel in a watertight fashion.
The solar panel has a highly transparent, virtually unbreakable polycarbonate cover which has been treated to ensure long life.
Behind this is the solar absorber which is made of 0.2 mm copper sheet, covered with a black chromium oxide selective layer, and behind the absorber is 50mm of insulation.
As a result of these measures almost all the solar energy is absorbed and radiation losses are reduced to minimum, ensuring high efficiency.
Drain-back
- At night when there is no sun or in very cold weather there is no water in the panel to freeze, so plain tap water can be used in the solar system.
- No chemical antifreeze is required, so there no maintenance to check and maintain antifreeze protection for the system.
- In very hot weather with no water draw-off (e.g. whilst away on summer holidays) the system is protected from boiling by draining back the water when the cylinder exceeds 80 degrees centigrade.
- If you choose a mains powered system, then in the event of a power failure the system always fails safe, with water draining back out of the panel, where it will neither freeze or boil.
- Drain-back systems can be 'switched off' without harming the solar system, so we can offer high limit shut down at 80C or 65C, which makes the system ideal for use with un-vented cylinders.
- Plain tap water is a better heat transfer medium than antifreeze, so carries a greater density of heat from the panel in to the hot water cylinder.
Solar Power Supply
A solar power supply for the pump and controls, which replaces the mains electric power supply.
This comprises a photovoltaic (PV) panel measuring 638mm x 278mm, which comes complete with brackets for roof mounting. When fitted, the solar system is no longer dependent on a mains power supply, has no fuel running costs of any kind and will work in remote applications and during power cuts.
Installation is easier and safer, as a power socket is no longer required to be fitted and no 240 volt mains wiring is required. Also running costs are zero, the whole system running just on the occasional top up of plain tap water!
Hot Water Cylinders 
We supply various sizes of hot water cylinder, depending on your requirements. All have 60mm of CFC and HCFC free insulation for energy efficiency.
The cylinder is protected against overheating by a sensor which switches off the pump when the temperature reaches 80 deg C.
For safety, especially with children, we therefore recommend the installation of a Solar mixing valve to prevent scalding.