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Problem: The Envirolux 'Radia' wall lamp appears to overheat and destroy ballasts if left on for long periods of time. Here's an analysis of the problem and a potential solution using LED lamps.


The Envirolux ‘Radia’ wall lamp is a satin steel finish 2x18W fluorescent wall lamp. It is an all-steel construction and has an 18W (Philips 18W/840/4P) fluorescent lamp fitted at the top and bottom, behind frosted glass panels. It was purchased as a new fitting from Beacon Lighting.

Internally the lamp has a central channel housing the Ultralamp B218P electronic ballast and providing support for both the fixture to the wall bracket and for the lamp sockets. Surprisingly this compartment is unventilated.

The accompanying photographs show the wall fitting and components (figs 1-3).


Fig. 1















Fig. 1 Lamp mounted to wall



Fig 2




















Fig. 2 Top glass removed, showing 18W fluorescent lamp.



Fig 3
















Fig. 3 Removed from wall showing internal components.


During extended periods of operation (ie 30 mins or more continuously) the lamp housing would become very hot to touch and in three of the six lamps installed, the electronic ballasts were destroyed by excessive internal temperature. The three ballasts destroyed were fitted in lamps that remained on over several hours each evening.

A set of temperature probes (DS18B20) attached to a networked data acquisition system were used to gather and graph the temperature of the unit over a 3 hour period of operation. One temperature probe was used to measure ambient temperature, one was taped to the outer front casing and one was inserted into the internal ballast space, to measure the air temperature inside the channel. The measuring apparatus is shown in fig 4 and the resulting graph is shown in fig 5.


Fig 4















Fig. 4 Temperature measuring and logging apparatus


Fig 5

















Fig. 5 Plot of temperature over time at locations indicated whilst lamp is on.


The following table shows the temperature rises recorded after settling for a couple of hours.


Rise above ambient (OC)

Outer front casing


Inner channel air temp



The temperature graph shows a rise of approximately 25OC on the outer casing. On a hot evening (eg 35OC) the outer casing would reach 60OC which could lead to wall paint discolouration and minor burns if touched. Internally the temperature rise reached 38OC. Again, on a 35OC evening, the internal air temperature in the ballast compartment could reach 73OC. The ballast is rated for a case temperature of 70OC maximum (according to the label on the device), so this appears to violate the manufacturer’s recommendations. The component temperature would easily be 85OC or more inside the ballast itself, exceeding the component temperature recommendations as well. There is little surprise, given these measurements, that the ballasts were being destroyed by overheating.