LED Replacement for Halogen MR8 Light Bulbs

MR8 is a reflector lamp with a 35mm diameter.  They are a small low voltage bulb and are usually used whether directional light is required, such as display cabinet lighting and fibre optic lighting.

Understanding MR8 Halogen Bulbs

MR8 bulbs like all other halogen bulbs are energy inefficient and produce a significant amount of heat with a short life span.  These bulbs normally operate on 12 volts and normally have a G4 pin base.

Can you get LED versions of halogen MR8 light bulbs?

Yes there are now LED versions of the MR8 which are designed to fit in the same fixtures and operate at 12 volts.  The LED MR8 offers comparable light output whilst only consuming 80-90% less energy.

Can I just swap halogen bulbs for LED?

In some cases you can just have a direct swap but you must be aware of your existing transformer as it may need replacing to a LED version.

The transformer compatibility challenge

The main problem you can have when changing from low voltage halogen bulbs to LED’s is the transformer. The MR8 uses a 12V transformer which converts the standard 240V down to the 12V required.

There are 2 types of low voltage transformers:

 Magnetic Transformers - These are the older, heavier models and tend to work well with LED’s as they do not have a minimum load requirement.

Electronic Transformers - These tend to be more problematic as they are designed to operate efficiently when a certain minimum load is placed on them.

The minimum load issue

A fixture may have 3 x 10W halogen MR8 lamps running from 1 transformer which equals 30W in total and if you swap those 10W halogen bulbs for 3 x 1W LED MR8 bulbs you would only have a total load of 3W which may on register on the transformer.

When the total wattage of the LED bulbs fall below the transformers minimum load you could encounter:-

Flickering - Bulb may flash or strobe

Buzzing - Either the transformer or the bulbs could emit a humming noise

No Light - The  transformer may not be able to power the LED at all

Reduced Lifespan - The LED or the transformer could fail prematurely

Solutions to ensure a successful swap

If you do encounter any of the above issues you have 2 options available 

1.  Replace the transformer - The most sensible option would be to replace the 12V halogen transformer with a 12V LED driver as they are designed for the very low wattage of LED bulbs.

When selecting a LED driver - You must ensure that it is rated for 12V DC (direct current) as most LED bulbs require DC power.

The transformers maximum wattage should not be exceeded

2.  Install a load resistor - If replacing the transformer is too difficult (if hard wired in or not accessible) you can install a load resistor in parallel with the LED bulbs.  This component will increase the electrical load, for example if the minimum load is 20W and the LED’s are only 5W a 15W load resistor will bridge the gap.

Conclusion

LED MR8 bulbs are available and a plug and play swap may be possible but you may need to upgrade the transformer to a LED version or install a load resistor.