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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.

Location

Rise above ambient (OC)

Outer front casing

25OC

Inner channel air temp

38OC

 

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.

 


LED Lamp Modification

A simple refit of the internals of the lamp housing can be undertaken to make use of LED lights, with significant power reduction, temperature rise and long term reliability.

 

Fig 6. LED strips

 

 

 

 

 

 

 

 

 

 

 

 

Fig. 6 12V 12W LED Strips

 

Some 12V 12W LED strip lamps were purchased (http://www.dealextreme.com/p/12w-3500k-800lm-warm-white-led-emitter-metal-strip-12-14v-80310). These are operated from a 12V power source and are as bright as the 18W fluorescent tube. They emit a ‘warm white’ (3500K) light and are able to be bolted directly to the internal channel for heat sinking. One of these LED strips was used in place of each fluorescent lamp, each drawing only 700mA from a 12V switching power source. This is a total of 16.8W for two LED strips, less than half the power of the existing 2x18W fluorescent fitting.

 

Fig. 7 LED PSU

 

 

 

 

 

 

 

 

 

 

 

Fig. 7 LED Power Supply fits where the ballast was

 

The power supply used is a 12V 30W LED driver imported from China by Victoria ECO LED lighting. These fit neatly into the channel where the electronic ballast was previously fitted. Since there are also fewer wires going through the holes from the lights to the power supply, there is more ventilation for the centre channel.

The images in fig 8-9 show the internal refit for LED operation. Fig 10 shows the LED (right) and the fluorescent (left) in operation together, showing similar light brightness output.

 

Fig 8

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig 8. LED strips fitted in place of 18W fluorescent lamps

 

Fig 9

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig. 9 View of internal components with LED strips and LED PSU fitted

 

Fig 10

 

 

 

 

 

 

 

 

 

 

 

Fig. 10 Wall lamps using LED strips in place of fluorescent tubes


The same temperature measurements were taken as for the original fitting, ambient, external case and internal channel air temperatures and graphed over a 2 hour period. The graph is shown in fig 11.

Fig 11

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig. 11. Graph showing significantly reduced temperature rise for LED fittings

 

The temperature rises are significantly lower, as shown in the table below.

Location

Rise above ambient (OC)

Outer front casing

11OC

Inner channel air temp

16OC

 

The power supply produces an insignificant amount of heat, and most of the heat is produced by the LED strips bolted to the internal channel, as can be seen by the small difference in temperature between the external case and the internal enclosure.

The cost of the LED strips ($15 each) and the power supply ($20) comes to $50 for the LED re-fit. As spares, the cost of the fluorescent lamps ($8 each) and the ballast ($30) comes to $46, so it is not significantly more expensive, however the anticipated lifetime of the LED wall lamp is significantly greater given the reduction in temperature and the longer lifespan of LED lamps.