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Low Voltage Garden Lighting - Tips For Sizing and Fitting Techmar Transformers!

Low Voltage Garden Lighting - Tips For Sizing and Fitting Techmar Transformers!

Questions about low voltage garden light transformers often get raised.  So I've put together this simple high level explanation about sizing-up and fitting that hopefully helps! 

We have more information at in our 'FAQ's page'.

Background: In the UK, if you want to run low voltage garden lighting then you need a transformer!  Why?  To take unsafe 230v 'mains electricity' and convert it to 'safe 12v electricity'.  

The transformers are no different in principle to 'phone chargers'.  The charger takes unsafe 230v electricity and puts out a very safe and low voltage that your phone's rechargeable battery can handle!  We know them as chargers but in reality they are transformers!

Techmar's high quality transformers come pre-fitted with a UK 3-pin plug and approximately 2 metres of 230v cable. They also have their own internal fuse.  

The 2 metre cable allows the transformer to be sited in a convenient position next to your 230v socket outlet.  Just plug it in, switch on and the UK mains and 230v power is reduced to safe 12v power.   

On the 12v output side of the transformer a 'one-way 12v fly-lead' is connected (approximately 30cm)

One end connects to the transformer's 12v output and the other end fits all 'Plug & Play' cables by TECHMAR. 

First and most importantly! Make Sure Your Transformer is 'big enough' for the job!

Each 12v LED light bulb that you put in your garden or other outdoor area uses some electrical energy.  It's calculated in 'watts'.

To get the correct sized transformer add up the number of 'watts' your complete low voltage lighting system will use by counting the energy that each low voltage LED light bulb uses. (e.g. one LED uses 3 watts.  So ten low voltage LED light bulbs will use 30 watts).

If the total power consumption of your low voltage garden lights is very near to, or exceeds, the transformers total power 'output rating' then you should either upgrade to a more powerful transformer or split your cabling runs and use more than one transformer. 

In this example the 30 watts falls well below a transformer rated at 60 watts so go for that one.  Don't use a 22 watt's just not big enough for the job!

Where does the transformer go and how do I fit it?

The transformer can be fitted safely outdoors but if the 3-pin plug is to be sited outdoors then it should be fitted in a waterproof electrical socket housing similar to the one shown below:

230V 2 Gang RCD Switched Socket Housing

The image shown above is from the Screwfix catalogue (BG Nexus 13A 2G RCD Switched Socket - Product Code: 91095) but equivalents are readily available from good electrical wholesalers.

An RCD is a residual-current device, or residual-current circuit breaker (RCCB), is a device to quickly disconnect current to prevent serious harm from an ongoing 230V electric shock.

All transformers are weather proof but we just think it's good practice to house them.  It keeps the British weather off the transformer's casing and cables; and just helps tidy the view! You can paint the boxes too if you don't like grey!

We use simple weatherproof boxes (e.g. from Screwfix - IP55 Enclosure) but again readily available elsewhere. 

IP55 Weatherproof Housing Box

TIP: If you leave the transformer outdoors, whether or not it's housed, make sure it's lifted and fitted well off ground to avoid being flooded or buried in snow; and use common sense when near to water bearing fittings such as down pipes, leaking gutters, ponds etc.

The Techmar transformers can be found at

Low Voltage Garden Lighting - Transformer

The basic dimensions and fitting tips are shown below.

Base plate footprint:  

Width 150mm x Depth 95mm x Height 100mm with four mounting holes for fixing screws.

NB: If housing the transformer in a weatherproof box or fitting into a tight area then remember to allow some room for the pre-fitted and sealed 230v input cable and the 12v exit cable (fly lead - see picture).

The following dimensions should be adequate (allowing for normal cable entrance/exists etc). 

Base plate footprint plus cable entrance and exits:

Width between 235 - 260mm x Depth 95mm x Height 100mm with four mounting holes for fixing screws.

If in any doubt use the larger width (260mm) and this will ensure the pre-fitted cables are cleared before normal flexible cable can be manipulated to the final position.

If this helps good...and feel free to share!

Thank you for reading our blog....from the team at


0121 416 0408

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