We currently manufacture the manifold (where the pressure gauge is mounted and the pipes are connected to) on the pumping station in Woodbridge, Suffolk and are in the process of getting castings made in High Wycombe to replace the silver soldered unit made in Suffolk.

We have developed the solar pumping station ourselves so that we can insure that we can provide a quick and reliable solar heating installation, the unit is pressure tested before being taken to the customers site for installation to reduce the likely hood of leaks.

Starting at the top you will see the AVV, auto vent valve.  We have placed it hear instead of on the solar collector for a very good reason.  Some existing installations place the auto vent valve next to the header on the solar water heating panel on the roof on the there is one problem with this. When the solar collector vapour locks in extreme temperatures over one hundred and forty celsius the ball inside of the AVV will drop and allow some vapour out and a small amount of system fluid behind it, clearly over time you can lose enough system fluid to stop the solar water heating system from working. This is why we have placed our AVV down on the pumping station away from the vapour that can build up in the solar water heating panel.

Next you will see a chamber above the pressure gauge this is used to trap and collect any air that enters the solar heating system when you first install the unit and to remove any gas that would be released from the high heat transfer system fluid when the fluid gets hot (this usually occurs after the first two weeks of operation after the initial install.  Once the gas or air is trapped in the chamber you can remove it using the AVV and tap above and top up using the hand pump on the left with the high heat transfer fluid and hose pipe that we provide.

We have used a hand pump so that this unit can be placed anywhere and so that we  can use the high heat transfer fluid in the solar water heating panel, some units use mains water for the system which would does not have the same properties as the fluid and would possible mean you would have to install a long run of pipe to the mains supply which may limit where you can site the pumping station.

At the top right there is a non return valve that will prevent any hot system fluid backing up and damaging the pump, (grunfoss pump in red), when the temperature on the solar water heating panel exceeds one hundred and forty celsius. On the top left you can see a pressure relief valve which  is standard in all types closed circuit installations.  The pipe coming into the bottom of the grunfoss pump connects to the secondary coil in the new hot water cylinder and the non return valve (on the top right) connects to one side of the solar water heating panel on the roof.  The other side of the solar water heating panel connects directly to the second coil in your hot water cylinder.

We have used a standard grunfoss pump found in any normal central heating system in this unit so that it can be sourced from any DIY shop should you need to replace.  It should last far longer than a pump in a boiler as it is doing less work, it only operates when there is a 5 degree difference between the hot water cylinder and the solar water heating panel.  The four horizontal connections coming out of the manifold above the pump can be connecting in any way to suit your current plumbing in your house and the resol controller that regulates your solar water heating system can be removed from the backing board and place somewhere more suitable for yourself.

The last connection coming from the manifold (bottom right of the pressure gauge) is connected to the expansion vessel.

As the solar systems gets very hot it vaporises the fluid as part of their normal operation.  I thought it best to fit all the components in the RETURN (cold side). This includes the circulation pump, expansion vessel, pressure relief valve and flow meter etc. Then place the NRV (non return valve) between them and the solar collector to protect them from the fluid particularly when it vaporises. So you cannot really rearrange the solar water heating circuit to put the NRV after the zone valve.

So if the motorised valve closes at high temperatures and subsequently the NRV closes as the fluid vaporises this will give a section of the circuit that is completely closed and isolated from the expansion vessel or pressure relief valve.  Bearing in mind zone valves, unlike mid position valves, are meant to give 100% closure.  I would say that this will cause a dangerous build up of pressure in the FLOW side including the solar collector manifold’s internals.  I guess the zone valve will fail first, if it has not already succumbed to the high operating temps of the solar water heating circuit thus rendering this safety feature useless.  If not a joint may blow allowing the escape of very high temp vapour which would be particularly unpleasant if one of the high energy transfer fluids have been used.  An oil burn is much worse than a water burn.

I thought again about rearranging the circuit but could not because of the arguments in paragraph two. Even if regulations were written, say with two expansion vessels, I think it would only be a matter of time before someone got confused.  Basically putting two stop cocks on a circuit that could be heated and subsequently become pressurised is just bad engineering unless it had vent points in every section!

As a 2^nd safety back up the to solar controllers systems a high thermostat on the hot water cylinder could be fitted to break the power to the solar water heating systems circulation pump.  This would also protect against installation errors.

One solution to this is to fit a smaller dedicated solar pool pump in parallel with the existing filtration pump these pumps can be a tenth of the power of the filtration pump allowing for a great saving in operating costs.

When fitting the new pump you will need to install a non return valve in front of the existing filtration pump and in front of the new solar pool pump so that when either pump operates it does not drive the fluid back past the other pump and in the wrong direction.

Your new solar pool pump will be controlled by the Resol controller mounted on the Aztec Solar Water Heating pumping station backing board. Power will be supplied from the controller via a relay to the solar pool pump turning it on when required. Simultaneously power will be supplied from the controller to the flow switch.  This flow switch will then turn on the pump (this is a third pump used to drive around the solar system fluid from the heat exchanger to the solar water heating panel on the roof  and is not to be confused with the new pump that you have just fitted in parallel with the filtration pump).

The flow switch is fitted just in case the new solar pool pump that you have just fitted next to the filtration pump fails.  In this event the flow switch will turn off the solar system fluid pump and cool off the heat exchanger which will stop the empty plastic pipes from melting down.  Remember in this instance the new solar swimming pool pump has broken and there is no water in the plastic piping to take away the heat from the heat exchanger.

There is one more potential advantage in using a smaller powered solar pool pump which is that the flow rate of the water through the piping and in turn the heat exchanger is a lot slower and therefore should allow for a better transfer of heat from the exchanger and allow for better performance of the whole solar water heating system and potentially save you more money on the operating costs for your swimming pool.

Are you better off investing in solar water heating than putting money into a savings accounts?

Unless you are  willing to invest in a high risk bond in a far off land and potentially lose all your money (all though option is no longer available due to the collapse in the Icelandic banks and the credit crunch) you will have to choose a UK based bank or building society (which have not been so financially secure recently due to the credit crunch).

The current domestic savings products are earning about 4.5 percent gross interest on a bond and after a tax of twenty percent or forty percent for a higher income rate earner this will amount to a net interest rate of 3.6 percent for the lower tax band and 2.7 percent for the higher tax band.

When you consider that this would mean that you would only earn  £108  or £81 for the higher tax band on  an investment of £3000 isn’t it worth considering another option.  For £3000 you can install solar water heating that can add top the value of your property and saving up to 25 percent of your overall heating bill which would prove attractive if you use gas central heating and even more attractive if you are using the more expensive fuels such as oil and electric boilers.

Furthermore the Bank of England are going to meet in early   January of 2009 and are expected to cut base rate by another 0.5 to 1.0 percent which would mean that savings rate may fall to 4 or 3.5 percent on a bond which would mean at worst that you would only earn  2.8 percent net or 2.1 percent net on a higher income band which equates to

£84 interest for a lower band income earner and £63 for a higher income band earner now the fuel bill savings associated with solar water heating must be an even more attractive proposition compared to the savings rates earned with your bank or building society.

In addition to this we must also consider the benefits that solar water heating can bring with regards to the recent events happening between Russia and the Ukraine and its effect on the security of gas supplies to the UK.  Due you want to secure your hot water heating supplies and no longer be held to ransom by Russia!

A direct solar heating system uses the existing hot water tank.  The cold water supply to the solar  panel is drawn from the cold water feed pipe to the existing hot water cylinder. This is the pipe that runs from the header tank down to the bottom of the hot water cylinder. This water is then heated by the panel and then fed back to the water cylinder y a pipe that connects to the hot water output that comes out of the top of the cylinder both connections can be made easily using a t piece.  The disadvantage with this system is that the solar water heating panel will only allow you to heat up the top of the hot water cylinder due to the existence of thermoclimes. A may have come across a thermoclime in  the sea before where you go swimming and find a freezing cold band of water around your legs but the water above this is warm.  It is for this reason that all existing hot water cylinders have the coil at the bottom for the traditional boilers and have done for years.   One further floor with these systems is that you obviously cannot add any fluid to stop freezing as you would loose it down your plug hole the first time you turned your taps on so these systems rely on using plastic piping that can expand in freezing conditions but of course if you have allowed the pipe to freeze your solar water heating panel can no longer be supplying any free energy! Furthermore, the temperatures reached by solar water eating panels can be in excess of one hundred and forty Celsius which also brings into question the lifespan of plastic piping under these temperatures.

To sum up a direct system is faster for the installer to fit and should only take one day and is far more profitable for them as they do not have to supply a new tank and they have saved on a days installation but it will not work anywhere as well as an indirect system and will not work under freezing conditions as it merely allows the pipes to freeze and top the supply of hot water and the lifespan of the plastic pipe under the extreme temperatures is questionable.

Indirect solar water heating panels

An indirect solar heating system uses a secondary coil in a new hot water cylinder the new coil is places at the bottom of the hot water cylinder so that it operates like a traditional boiler by avoiding the issue of thermoclime and heats the entire body of the hot water unlike a direct system that just heats the top of the tank it also has the added advantage of being able to operate in winter because it uses its own sealed system containing high heat transfer fluid that can withstand freezing temperature that runs in a loop from the solar  heated panel to the secondary coil in your new tank and back up to the solar heated panel.  The systems should only take two days to fit, the first day is used to switch the hot water cylinders and get the existing system working again and the second day to fit the solar water heating panel and connect to the panel to the secondary coil in your new tank.

Recently I have noticed people trying to create a indirect system using a secondary coil inserted through the emersion heater port at the top of the existing hot water cylinder.  Although this saves on the cost of replacing the hot water cylinder it suffers the same problems as the direct system where you are confronted by thermoclimes and can only ever heat up the top of the cylinder leaving the bottom of the hot water cylinder cold.  I have seen one cylinder that does have an emersion heater port at the bottom of the cylinder (Megaflow).  But I have yet to find an adapter coil that can be inserted through this port that matches the large surface area of the curly fin coil supplied in the brand new cylinders.  You would need an adaptor coil in a large C shape to try and generate the same heat energy of the new hot water cylinders with the secondary coil included and the only ones that I have found have looked very similar in area to a emersion heater so they would not transfer that much heat energy from the solar water heating panel.

To summarise the indirect system is more expensive but actually works and would work all year around  but only if used in conjunction with a new cylinder, placing an adaptor coil at the top of the cylinder suffers the same problems as a direct system (thermoclimes) and a decent adaptor for exiting cylinders which have an immersion port at the bottom of the cylinder does not exist and because of the surface area required even if it did exist it maybe quite hard to fit.