Alternatively, we could make a permanent connection. This would involve either using a new underground cable from the garage to the house to deliver the power, or another option may be to use the existing garage GRID cable and reverse it to deliver the renewable power back to the house. Unfortunately, during my investigations I realised that the existing power cable feeding the garage also feeds my submersible pump in my well. Although I could have used the system to power the pump, my primary objective was to get the renewable power into the house. Using it for the pump would only leave less power available elsewhere, so I opted instead to use the spare underground conduit already in place between the garage and the house. If you are planning a similar system and neither option is available to you then you may have to consider running a new conduit - get your shovel ready.

Renewable Store Connections:

Firstly I ran a Steel Wire Armoured (SWA) cable, 3 core, 2.5mm, from the renewable store through this conduit, underneath the ground, over to the house and then into the roof space and across to the utility room, where my GRID fuse box is located. SWA cable should always be used when running permanent power outdoors. Remember to size the cable accordingly; as a rough guide a 1.5mm cable thickness can handle 3000watts of power, and a 2.5mm cable handles about 6000watts. Back at the renewable store, I have laid it out as follows:
 

• The SWA cable shown in the main picture above is the black one - I begin by terminating this in a suitable box, using a gland. A gland is a cable terminator for the type of cable which allows a strong connection to the box and also sheathes the cable and provides a method to allow the outer steel cable sheath to be linked to the inner earth core. You can see this coming in at the bottom of the box in the centre of the picture.
   
• At the left side of this box is a white 3-core 2.5mm cable, and all we do inside the box is to join up the Live, Neutral and Earth from this white cable to the Live, Neutral and Earth from the black SWA cable. The white cable terminates in an industrial male coupler, shown above joined to the right female receptacle. Both coupler and receptacle are rated at 230V, 32 amp.  
   
• The two mounted female receptacles to the left and right again have a 2.5mm 3 core cable coming from them. At the end of these cables is a 3-pin plug, as you can see in both the smaller pictures above. The right hand cable then plugs directly into the inverter, and the left hand cable plugs into an optional generator.
   
• The most important point here is to ensure that no power is left exposed. Note the use of 2 female receptacles and one male coupler - if I did it the other way round then the male couplers would be 'live', and could cause a shock if someone were to touch the pins. In the diagram above only the receptacles are live and are never exposed, so there is no danger of coming into contact with a live pin. Bear in mind the above layout is that bit more complex as I am allowing for two power sources; if you only have a single power source then you could make the connections much simpler.

Neutral Earth Bonding:

Before connecting up the inverter, we need to talk a little bit about the concept of neutral earth bonding. I confess to knowing nothing about this before I began to generate my own electricity. Now, having gone though the process, I understand it a bit better, so here is my own 2 cents worth of explanation. You or your electrician need to know something about this when installing permanent renewable power.

The GRID mains is "neutral earth bonded" at the local ESB substation, which means the neutral and earth wires are linked together before the electricity is sent on to our houses. So on our incoming GRID supply we receive 230v on live, 0v on neutral and 0v on earth (230,0,0). The consumer unit (CU) in the house and the Mini Circuit Breakers therein (MCBs) are designed to work with this type of electricity. Specifically, any Residual Current Detectors (RCDs) within the CU or inserted into any ring main monitor the voltage returning on the neutral wire once an appliance is connected. If that voltage fluctuates due to a faulty appliance or an incorrect flow of power from neutral to earth, then the trigger in the RCD trips and the current flow is stopped.

When using alternative power from an inverter or generator, it is often structured as +115v on live and -115v on neutral (115,115,0), as we have mentioned before. This is to allow these products to be used worldwide, with a wide set of voltage structures. But if we were to use this electrical structure with the RCD as mentioned above, because the power is balanced across both feeds, the RCD may not trip as accurately, or not at all, even if the appliance was faulty. This is why some people only connect Class 2 devices to inverters and generators - a Class 2 device is electrically shielded internally and does not require an earth wire, so the RCDs would have no benefit here as there is no escape route for the power.

If deciding on a permanent installation, I think the absolute safest way to do it is to imagine that the inverter or generator is simply replacing the GRID substation, i.e. treat it as an electricity substation, only much much smaller! Therefore, if the inverter or generator does not already output a 230,0,0 structure, see if it can be altered to the required output; that way all connections at the house should work exactly as before, because the power is not only identical in current, frequency and voltage, but is now identical in line structure to the GRID.

Integrating The Inverter:

Having settled on the appropriate inverter for your power requirements, there are a number of other factors that you should consider before using the inverter as a permanent power supply:

• The inverter should be fixed in position, preferably to the wall, ensuring that it is not located directly over the batteries, or if this is unavoidable, you should place a shield beneath the inverter to prevent battery gases harming the inverter electronics- just take care not to obstruct any inverter air vents. I placed some thin plywood above and below the inverter to help divert any gases.
   
• The outputs from the inverter need to be considered early on in your project. I did not do this, and ended up with a standard 3-pin plug inverter. The 3-pin plug is ideal for portable use as you can plug anything into it, but is not suitable for higher power requirements with a surge capacity of over 3KW. Remember that the fuse in a domestic 3-pin plug will only handle 3KW; higher currents may blow the fuse long before you reach a sustained surge power. So consider whether to opt for an inverter with hard wired AC output terminals, rather than sockets, if you are planning on running a washing machine and deep fat fryer at the same time! Naturally, the trade off here is flexibility - the hard wired outputs are unsuitable for plugging in appliances direct.
   
• As mentioned in the paragraph on neutral earth bonding, manufacturers state different requirements when connecting inverters into a house consumer unit. Some can be passed straight through as they already output the L+N+E as 230,0,0; others state that you can apply a neutral earth bond to the output of the inverter to amend the 115,115,0 to 230,0,0. And in the last category are those which output 115,115,0 but state that you cannot bond neutral to earth as the earth is already 'non floating' in the inverter and you would blow the inverter fuses if you joined neutral and earth. I confirmed with the inverter manufacturer and in my case was told not to bond neutral to earth but that the MCBs would still work. They did however say that RCDs would not work and advised not to use them with the inverter. In light of this, and my newly acquired knowledge on bonding, I may elect in time to change the inverter for another model which does allow me to create a true neutral earth bond on the output. 

 Adding A Generator:

When making a renewable energy supply, I had always planned to integrate the generator, to provide for additional backup if the GRID power was unavailable and there was insufficient power in the batteries. I already have a Honda 2kw generator (model EU20i) which has served me well during previous power cuts, and can power everything from my toaster to my PC. It is a very stable power source, with rock solid voltage and current, and comes in suitcase form rather than industrial form, as shown in the following picture:

This version runs on unleaded petrol and a full tank can provide up to 2kw continuous power for appx 3-5 hours, depending on load. There are other generators available, many which run on diesel, but I opted for an unleaded version as both my lawn mower and strimmer also run on unleaded. Having both diesel and unleaded in the same environment is just not worth it. Imagine if by accident I poured unleaded into my diesel generator - there goes EUR1500 worth of kit into the bin!

Whichever fuel source you opt for, of greater importance still is the quality of the power it generates. There are many 'industrial' generators available, some very cheap. They are all quite suitable for running power tools, but most of these units, in my opinion, are not suitable for running delicate equipment such as PC's and TV's, or any electronics for that matter. So if you are starting from scratch it is worthwhile spending the time to find good quality generators with smoothed power output designed for a wide range of applications, otherwise it will be of limited use.

Integrating The Generator:

Again some some do's and don'ts that you should follow when making the generator part of a semi-permanent or permanent install. Most domestic generators, like the model above, are designed to provide portable power and are not suited to permanent installations, until you have considered the following:

• Generator location- it must be sited such that all exhaust gases are ported to the outside. Portable generators give off exhaust fumes which are not suitable for use in enclosed interior spaces- failure to observe this could lead to harmful carbon monoxide poisoning.
   
• Ensure that the generator is not breathing in the exhaust fumes that it has expelled - this will cause the air filters to clog up and also lead to early breakdown and replacement of costly components.
   
• Keep the generator dry and away from wet sources - in my case I have an old cat flap in the garage door, therefore the unit can be located just inside the door and exhaust fumes can be directed outside through the cat flap. This allows me to keep the generator dry and port the dangerous exhaust fumes to the outside. 
   
• According to the manufacturer, for my generator to function correctly when permanently installed it requires a "neutral earth bond" to be added at an appropriate point in the generator output*. I did this on the feed in to the left female receptacle, by linking the neutral and earth wires with an additional wire. Oddly enough, rather than send the 115v down the earth cable, as you would possibly expect it to do, what actually happens is that the 115v on the neutral is forced back though the live cable, therefore increasing the voltage on the live cable to 230v and reducing the voltage on the neutral to 0v. Wow! 
  * On the advice of Honda UK, who state this should be done for any permanent or semi permanent installations using the EU20i generator. The 3-pin plug should also have a warning label attached, e.g. 'WARNING- FOR GENERATOR USE ONLY, NEUTRAL-EARTH BOND APPLIED'

When swapping to generator power, we simply start the generator, and insert the 3-pin plug coming from the left receptacle. Then I remove the male coupler from the right receptacle and swap it to the left one instead. Now the generator is sending the power to the house, in the same way that the inverter was doing before.

There are complete 'fail over' systems available where a generator would start up and automatically feed the supply if it becomes exhausted, but I doubt if many householders would need such a complicated or expensive solution.

Using The Generator As A Battery Charger:

Even more options - I noticed that my generator could produce a 12V output to power car batteries etc. Again in theory you could have the generator power the batteries, which in turn powers the inverter, in turn powering the house circuits! But if you think about this, we are using 3 steps to get the final power to the house, and at each stage a certain amount of power is consumed by the process itself. So this is really only a sensible solution if you were running, say, a 12V lighting system direct from the batteries and needed to recharge them in an emergency if the wind/solar source was unavailable.

House Side Connections:

The process of installing any changes around the house fuse box and environs must be done by a competent electrician. For this type of work, you should also ensure that he or she is a member of the Register Of Electrical Contractors Of Ireland (R.E.C.I), for insurance, when making alterations of this nature. The electrician now works with the SWA cable coming into the house, and he installs the new change over switch (CO) and consumer unit (CU).

• The incoming SWA cable is stripped back, allowing the earth to be connected directly into the new CU, and onwards to the common house earth rod. This is now protecting the SWA cable from damage or intrusion. Note: if you do not have a standalone protecting earth rod at your house then you will need to run to a new earth rod, otherwise power could be sent back through the GRID earth in the case of a fault when running on renewable power. Your electrician can confirm the house side earthing system once he inspects the property.
   
• The live+neutral from the SWA is then connected to one side of the CO, with a new live+neutral feed from the existing GRID CU coming in at the other side. The output cable from the CO switch is then fed into the renewable CU. Shown above is the renewable CU and CO switch on the left, and the original GRID CU on the right.
   
• Now the electrician takes out some of the circuits in the GRID CU, and moves these into the renewable CU. In the pictures above you can see three circuits have been moved, my utility room sockets, my study sockets and my living room sockets. 
   
• Testing is done to ensure that the change over switch correctly swaps both Live and Neutral. This can be tricky but one way of testing is to have either the inverter or generator send 115v on live and neutral (i.e. unmodified). Then, using a simple phase tester, check the plug sockets in one of the rooms switched to the renewable power. The sockets will show power on both live and neutral. When switched back to GRID power, you should only have power on the live contact! 

The Change Over Switch:

The switch, sometimes called a make-break-make switch, will allow a feed from either the grid power or renewable power to be directed to the second fuse box. The central position is off, which means that power must be broken first before restoring. At no point does the renewable power join with the grid power. This keeps the renewable system totally isolated from the GRID, i.e. it is termed "OFF GRID". 

As mentioned before, the importance of connecting the changeover switch correctly is paramount. Because we require both L+N to be switched, a double pole changeover switch (or greater) is required to enable switching of both live and neutral at the same time. 

You could install without a changeover switch if you also had a backup generator to service the supply directly, but having the switch makes for a very practical solution. If the power from the renewable system or generator is no longer sufficient, then the switch is turned back to feed the new CU from the grid, until such time as the batteries have been recharged. There is also an automatic changeover switch which would do the swapping without any user input, but I have been told that this kind of switch is not cheap !

Now let's see how it all works, in real day-to-day operation: