Wednesday, 13 November 2013

Lighting Revisited.

It's one year on and I have decided to revisit our led lighting upgrade.

A "normal light bulb" has a very thin tungsten filament that is housed inside a glass sphere. They typically come in sizes measured in 10, 25, 40, 60 or 100 watts. The idea is simple, electricity runs through the filament. Because the filament is so thin, it offers a good bit of electrical resistance to the flow of electricity. It is this resistance that turns electrical energy into heat. The heat is enough to make the filament glow white hot, and the "white" part of the glow is light.

The problem with tungsten filament light bulbs is that the heat created is wasted electricity. Heat is not light and the main purpose of the light bulb is to give light. So all of the energy spent creating the heat is wasted. Incandescent light bulbs are therefore very inefficient.

When we purchased Rosie the lighting configuration was as highlighted in the list below. The figures in brackets are the power consumption for each bulb which is expressed as watts.
Saloon:      6 halogen (20w) and 4 tungsten filament (20w)
Kitchen:      4 halogen (20w)
Bathroom:  4 halogen (20w)
Bedroom:    6 halogen (20w)
Aft cabin:    2 halogen (15w)
Navigation: 3 tungsten (15w)
Tunnel:        1 tungsten (40w)

Saloon        10 x 20 = 200 watts.
Kitchen        4 x 20 =   80 watts.
Bathroom    4 x 20 =   80 watts.
Bedroom      6 x 20 =  120 watts.
Aft Cabin      2 x 15 =    30 watts.
Navigation   3  x 15 =   45 watts.
Tunnel          1  x 40 =   40 watts.

Giving a grand total of 595 Watts. The conversion of Watts to Amps at fixed voltage is governed by the equation Amps = Watts/Volts

595/12 = 49.58 Amperes.  However, when I measured the actual amps used with all the items turned on. Power consumption measured 56.2 Amperes (674 watts) on Rosies digital ammeter. The actual power used will vary a little for each bulb. The figures quoted on the packaging are nominal. All the little additional bits in our case totalled about 6 amps or 72 watts just over 2 watts per bulb.

The one thing that we did notice was that the lighting appeared to be extremely bright for such a confined area. The other was that the halogen type also seemed to create a great deal of heat. So I went through the boat and took out half of the lights in each area except for the bathroom. Leaving lights in place over work areas in the kitchen. It was hard to detect a significant difference in the actual overall light level. Many of the lights that were removed were removed from our eye-line and this made reading and watching TV much more comfortable. We actually preferred the apparent lower light ambiance as being a much more comfortable lighting level. 

I decided that I would look at reducing the power budget from the whole lighting system. There was one obvious contender. That was to use light emitting diodes or LED's. There were direct replacement bulbs available. However, the light fittings had reflectors. The more modern LED bulb is of a different shape and would not therefore use the reflector. I thought about replacing the light fittings.

I asked around to get advice from people who were using them. Most of it was inconsequential and so I used the 'suck it and see' method.  Then I decided to test a couple of led's before going to the extra expense of changing fittings. I purchased a couple of cheap devices and replaced a couple of  the bulbs. I was pleased with the amount of illumination.

I read everything I could find on LED lights, including the kelvin range of light colour.  Led's are very efficient and seemingly improving all the time. We now needed to select the correct type of lights. The lights would be where possible in the appropriate part of the colour spectrum for best effect.

Also the brightness of the LED lights would be tailored to our needs.  When we watch TV, we like to have a warm subdued colour from the wall lights. However, where we sit and read we wanted an overhead light that would approximate to a more natural white. In the bathroom and kitchen we wanted a more white light. In the bedroom a more warm subdued colour  However, the reading spot lamps over the bed to be a bit whiter.  LED's are available in Very Warm White, Warm White, White and Blue-White.  The colour of light is measured on the Kelvin Scale. We settled on using two different types of leds the main variation was in the construction.

Thinking about what I wanted to do. I decided that I wanted the cheap and cheerful type of LED's. The major flaw with the cheaper bulbs is the lack of a built in voltage regulator. So as well as selecting the type of LED I also purchased an in-line 12 volt regulator. All the lighting circuits on the boat pass through the regulator. The function of the regulator is stop the LED's from seeing larger voltages when the battery system is charging, which can sometimes go as high as 15 volts.

The device is similar to this one.

So one year later, the feedback is that our lighting has worked flawlessly. The lighting rail voltage is stable at 12 whatever the battery voltage might be. With all the lights turned on our power consumption is 3.9 amps or 37 watts. Which is a significant saving over the original 56.2 Amperes (674 watts) of consumption.

Types and colour range of leds as well as price have changed in the last year. The items were all purchased on ebay came from china and totalled less than £60. I also changed the tunnel light to an led type. One of the larger 12 volt kind as used by off road vehicles.

This works very well, I have left the original brass tunnel light in place and it is used for polishing and as a backup device only. Now, I need a good replacement for our shoreline fridge which is the biggest draw on the battery bank, but one which is just as efficient as the leds.

No comments:

Post a Comment

Please put your name to your comment. Comments without a name may automatically be treated as spam and might not be included.

If you do not wish your comment to be published say so in your comment. If you have a tip or sensitive information you’d prefer to share anonymously, you may do so. I will delete the comment after reading.