DIY Solar Heating Plumbing Frequently Asked QuestionsThis DIY solar heating plumbing section is merely a guide. If you aren't sure about any aspect of installation I would recommend you hire a professional plumber.
Your diy solar heating system can be made to optimise solar energy during winter, but this would be at the expense of excess heat generation during summer, requiring frequent ‘dumping’ of the excess heat. Conversely, sizing the system specifically for summer, will limit the temperatures achievable during winter months requiring more input from the boiler. Therefore some compromise is required in conjunction with an assessment of the domestic water useage and the hot water temperatures required.
Do I need planning permission? With governments around the world promoting renewable energy - especially solar energy - it is becoming increasingly difficult for local Planning Departments to say 'no' to diy solar heating installations. Still, at the moment I would recommend that you contact your local Planning Officer before installation. You can never be too careful! Especially if you live in a conservation area. Or a listed building. You wouldn't want to upset the neighbours, would you? If you receive a letter stating that planning permission is not required then you are free to install your system.
Are Solar panels subject to Building Regulations? I would do as above and seek confirmation. It would help if you tell them the sort of roof and type of tiles you have. If you are installing an unvented (pressurised) cylinder please do not do the diy solar heating plumbing yourself. This must be carried out by a Regulation certified plumber who will provide a Commissioning Certificate.
What size pipe should I use for the solar loop? 10mm copper pipe allows suitable flow rates and reduces pipework thermal losses. You can use 15mm but its not quite as efficient.
What is an Expansion Vessel? As the solar panel is usually the highest point in the system, the solar installation has to run as a sealed system. When water is heated, it expands. In a plain sealed loop of pipework, there would be nowhere for the expanded water volume to go. The system pressure would grow until something bursts! And that wouldn't be pretty, would it? So the Expansion Vessel is a kind of pressure vessel containing a rubberised bladder. On one side is a gas (often nitrogen) pre-pressurised to 1.0 or 1.5 bar. The solar water loop is connected by a pipe to the other side of the bladder. As the pressure in the solar system increases, so the bladder compresses against the gas thus giving the increased water volume 'somewhere to go'. The added advantage of a pressurised system is that the boiling point of the solar loop is raised above 100 deg C - useful in the event of something going wrong. The Expansion Vessels in our diy solar heating kits has a 12 litre capacity which is easily enough for domestic solar installations. You can even get away with an 8 litre or even 4 litre capacity.
What other items are required for a diy solar heating system? Pressure Relief Valve If the expansion vessel fails, this protects the system. If the system pressure reaches 3 bar, the valve will automatically vent excess pressure in the form of water/steam into the overflow pipe to the outside. The valve also has a manual operating knob - handy for flushing the system whilst commissioning. Filling Loop This fills the system with mains water. It consists of a mains water valve and double check valve connected via a length of flexible hose. To comply with Water Byelaws, the hose should be removed once the system is filled and vented. The check valve prevents contaminated water from the solar system re-entering the mains water supply. Pressure gauge This indicates the system pressure. The system should be filled until the gauge pressure matches that of the Expansion Vessel pre-charge pressure as stated on the vessel. All these are available in my diy solar heating kits here.
Can I use pipe-lagging left over from my central heating system for my diy solar heating system? No no no!! The solar loop can reach high temperatures. This will melt standard pipe insulation. However, we supply Armaflex HT pipe lagging that is designed for high temperatures. This is essential on the flow pipework.
Can I use an automatic air vent like on my central heating system? This is not advisable! This is not recommended for the same reason as with the lagging above. Basically, the plastic components in the vent can melt! And we don't want that, do we? So it is best to use a radiator type manual air vent.
What pump do I use and what speed should it run at? Any standard domestic central heating pump with isolating valves is suitable. There is only around 1.5 litres of water in the manifold and the total water content of most systems will only be five to eight litres. Therefore start at the slowest speed position. Excessive flow rates will reduce the effectiveness of the high-efficiency solar coil in the cylinder.
Do I need a Thermostatic Mixing Valve (TMV) for my diy solar heating system? When fitting a diy solar heating kit it is always best to err on the side of caution. An optimised solar system will easily produce water in excess of 60 degrees C during the peak summer months. At this temperature, scalding could occur, especially in the case of the young or elderly. So fitting one or more TMVs to the hot water supply is vital. And you must fit a valve compliant with the industry TMV2 scheme. I would recommend to research the flow rate achievable through the TMV in conjunction with the water pressure (head) available prior to purchase. Some TMVs are only capable of delivering adequate flow rates to a single point (i.e. one tap) and are not adequate to supply the entire property direct from the cylinder. Also be aware that any if plastic push-fit fittings are already used within the DHW installation they are usually rated for 65 deg C maximum. Therefore the distributed water temperature must not exceed this temperature.
How do I make the holes in the roof tiles? The easiest way is to use an inexpensive tungsten-carbide tipped hole saw designed for concrete/brick. This will guarantee a clean hole with no mess. A masonry drill can be used with care. Just make sure you go at slow speed and definitely do not use hammer-action! :-) Also drill a separate 5-6mm hole (with a standard masonry drill) about 20mm in below the manifold flow pipe to take the temperature sensor cable. It is better not to use the same hole as the pipe - for one thing it will be a tight fit possibly damaging the insulation, and secondly the direct heat could cause degredation of the cable insulation in the longer term.
How do I seal the holes in the roof tiles? With just normal silicone sealant. Make sure that the drilled hole leaves a sufficient gap around the pipe to fill the depth of the tile. It is better not to make the hole so tight that only a smear is possible around the surface. This will not bond to the tile as good.
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