Solar Panels | Solar Water Heating | Solar energy Ireland | Solar Tubes » Frequently Asked Questions

By: Ecologics Solar Solutions  05/12/2011
Keywords: solar panels, solar energy, Water Heating

What Size is the collector?

The 20 tube collector is 1680x1580x130mm (LxWxH)
The 30 tube collector is 1680x2280x130mm (LxWxH)

What warranty is there on the panels?

We offer a 15 year warranty on the evacuated tube panels and a 10 year warranty on our Gasokol Flat Plate panels. All other components are guaranteed for the manufacturer guarantee period.

Vacuum flasks have a design life of 20 to 25 years, after which the flasks themselves may lose their vacuum. However, these are relatively cheap to replace and are a standard size so they are interchangeable with other brands and can reasonably be expected to be available from numerous suppliers.
Price for a replacement flask is currently €5 ex VAT.

Gasokol Flat Plate panels are rated to last for 30 years if maintained correctly. We have seen some flat plate installations still operating after 35 years!

What size solar cylinder should I fit?

We recommend that the 20tube panel is used with cylinders between 135L and 160litres, and the 30tube panel is used with cylinders up to 240litres. Larger cylinders can be heated with 2 or more panels, and it is possible to add an extra panel to benefit from higher temperatures in the winter. In fact, if you fit a smaller cylinder, you will have hotter water, but of course less of it. We would recommend fitting a tank of 135litres if you prefer a smaller amount of hotter water.

An interesting and popular option is to put a smaller cylinder in and set the controller to allow this cylinder rise to 75 degrees – but you MUST fit a thermostatic mixing valve on the outlet to bring the temperature back down and prevent scalding. This increases the effective heat storage and at the same time, on partially cloudy days you are more likely to have water at an acceptably high temperature

What is the output of the panel in terms of kWh?

This varies according to the time of year – in summer we get almost 10times the amount of solar energy that we do in the winter. In the summer, you can expect to get at least 4kWh of heat per day from a single 20tube panel, whereas in December you can expect only 0.4kWh per day on average. Even in the winter, it is possible to preheat the water to 40C or more if the sun comes out. In fact, if you fit multiple panels, it is possible to heat your hot water to 100C in January (we have seen this in Cornwall).

How hot will the water get?

This depends on the size of the cylinder you chose, and the amount of water you use. A smaller cylinder will be heated to higher temperatures, whereas a larger cylinder will heat more water, but not to the same extent. Systems are generally designed to heat water to 65C or so, although during the winter, it may be necessary to ‘top-up’ the heat on less sunny days. Large arrays, running high temperature solar antifreeze at high pressures can be designed to achieve temperatures of 170C or more!

Where do these need placing and at what angle?

Panels should be sited on a south facing wall or roof. In fact, anywhere between South-West and South East will give good results. If you are limited to an East-West facing system, then you will need two panels to provide the same amount of hot water as a single south-facing roof slope. The most frequent solution to this problem is normally to mount one panel on the east slope and a second panel on the west slope. A special controller is available for East/West facing installations.

The panels should be mounted at the angle of your lattitude. In Ireland, this is approximately 52 degrees. This is AVERAGE optimum angle. In fact, in winter the optimum angle is 15degrees steeper, whereas in the summer it is 15 degrees shallower. The panels will function anywhere between 15 and 90 degrees angle of inclination. This is actually academic, a variation of 15 degrees will make very little difference to the output, so most people simply settle for whatever angle their roof slope is. The extra cost of trying to stand panels off the roof to achieve better efficiency would probably be better spent on purchasing a second panel!

Are spares available?

Yes, spares are always available, should you need them. With no moving parts, it is very unlikely that you will need to replace anything, but occasionally customers break tubes during the installation process, in which case you can purchase a modestly-priced replacement. However, it is not possible to post a replacement tube, so you will need to collect it. The tubes are made of borosillicate glass (aka ‘pyrex’) so they are actually very tough.

Can I fit this system DIY?

Yes you can! These systems are very easy to fit, and anyone with basic plumbing and electric skills can carry out a DIY installation. Mounting the panel on the roof is sometimes daunting, although it is actually quite simple.

Will the system need to be inspected by a plumber or be installed by a

No, you can do this yourself. However, you can call in a plumber to carry out the work if you feel you are not able to tackle to plumbing yourself.

What is the recommended system type, pressurised or unpressurised and why?

How much maintenance does the system require?

Very little maintenance is required for solar water heating systems. If you have a pressurised system, you should occasionally check the system pressure, to make sure there has been no water loss, and to check for any air in the system. The only other requirement is to ensure that there is an electricity supply connected at all times, otherwise without pump circulation, in strong sunshine, the panel could overheat, and start to boil off water.

What about freezing in Cold Weather?

The solar panel is very well insulated – the manifold is surrounded by 2"of rockwool insulation. This is better than your outdoor water pipes, so it is unlikely to freeze except in exceptionally cold weather. However, it is recommended that you take precautions to prevent the possibility of freezing, by either adding antifreeze to the system (use a non-toxic solar antifreeze) or you can use a DELTASOL BS3 controller which has ‘freeze protection’ – this controller monitors the temperature of the collector – and if it falls below 4C, it will turn on the pump, allowing water to circulate and heat the manifold. You should turn this function off if you use antifreeze.

Can I use Solar Power with a Mains Pressure Hot Water Cylinder?

Yes. There are two ways to achieve this. You can either purchase a mains pressure unvented water cylinder (these can be expensive). Please note that you will have to have a pressure vessel certificate to install these. Alternatively, you can fit a ‘solar store’ cylinder (see below)

What is a Thermal Store?

A thermal store is a tank which has an additional large surface area high efficiency coil fitted. The mains cold water is fed into this coil, thus heating the water on its way through. The mains water exits the tank as hot as the hottest water in the tank, but without losing any pressure – thus providing mains pressue hot water to the household taps.

Can I get a grant for these systems?

Do I need planning permission?

Can I power the pump with solar energy?

Yes, this is possible. For flat plate collectors, manufacturers will specify a 5W photovoltaic panel, and a 5-10W low voltage pump. This is because flate plate collectors do not work efficiently in low sun conditions, so the pump only needs to function in bright sunlight. This is insufficient for evacuated tubes, which due to their high efficiency, will require pump circulation even in overcast conditions. For this reason, the pump should be rated at least 10W, and the panel 20W to provide sufficient circulation. At the moment, there is no cost-effective low voltage pump on the market suitable for pumping hot water. The most popular 12v solar pump, the ‘ivan’ retails at around £150-200, making this an expensive option. It is possible to use a solar photovoltaic panel to drive a mains inverter, powering a standard 220v circulation pump, but most customers do not want the complexity of such as system.

If you are concerned about electricity use, you may be better off mounting your panel on the ground and placing the hot water cylinder close-by and as close as possible to directly above it. Hot water rises, and this may allow the panel to "thermosyphon" water up to the cylinder. If the coil on your tank is, say 8′ above top of the panel, the panel can be up to a maximum of 16′ away horizontally. Your should 3/4" pipe with no elbows (use a pipe bender) and keep the pipe runs as short as possible. It is best to consult a plumper about whether or not the system will thermosyphon.

The information in this article was current at 02 Dec 2011

Keywords: evacuated tube, Flat Plate, hot water, solar energy, solar panels, Solar Tubes, solar water heating, Tube, Water Heating

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