Difference between revisions of "Dimmers & Switchbanks"

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'''Dimmers & Switchbanks''' are both ways to control lighting levels, improving both utility and comfort.
+
[[image:Dimmer 4476-3.jpg|right|250px]]
 +
[[image:Switchbank_new_1083-6.jpg|right|250px]]
  
 +
'''Dimmers & Switchbanks''' are both ways to control lighting levels, improving both utility and comfort.
  
−
==Advantages of Control==
+
This article sets out the advantages of controlled lighting levels, and looks at the relative merits of different ways of achieving them. Some installation notes are also included.
 +
 
 +
 
 +
=Advantages of Lighting Level Control=
 
Controllable lighting brightness permits  
 
Controllable lighting brightness permits  
 +
* Relaxed lighting in the evening
 
* Bright lighting when its needed for a task
 
* Bright lighting when its needed for a task
−
* Relaxed lighting in the evening
+
* Improved safety by allowing lighting level to be selected which is appropriate for the task in hand.
−
* Low lighting at night.
+
* Better comfort and better visibility.
 +
* May reduce energy use
 +
 
 +
=Methods of Lighting Level Control=
 +
==Dimmer & dimmable lamp==
 +
[[image:Dimmer 4476-3.jpg|right|190px]]
 +
A '''Dimmer''' is an electronic control that reduces the power flowing through the lamps it controls, which in turn causes a continuously variable change in brightness to be achieved.
 +
 
 +
Depending on the lamp technology, the reduced brightness may also reduce the energy consumption. Note that a [[filament lamp]] will still use a significant proportion of its "full brightness" energy, even when dimmed.  
  
−
It makes for better comfort and better visibility.
+
Dimmers don't require any overlap in lighting areas to achieve their effect.
  
−
How it affects energy use and running cost depends on which method of control is used.
+
===Compatibility===
 +
Standard dimmers have restrictions on the types of lights they will run.
 +
* Fully compatible with mains filament bulbs
 +
* Fully compatible with mains [[halogen]]s.
 +
* Compatible with most electronic 12V halogen lighting transformers, but not all.
 +
* Not compatible with toroidal halogen lighting transformers.
 +
* Compatible only with [[CFL]]s specifically marked as dimmable
 +
* Compatible only with [[LED]]s specifically marked as dimmable
 +
* Not compatible with linear [[fluorescent]] unless fitted with special dimmable electronic ballast and compatible dimmer switch
 +
* Not compatible with [[discharge lighting]] (HID, sodium, mercury)
  
 +
Note that the dimming range for some dimmable LED and CFL lamps can be far narrower than for an incandescent lamp - typically the dimmest setting is quite a bit brighter than that of an incandescent lamp (this however does depend on the dimmer - ones specifically designed for LED use for example tend to achieve far better results.
  
−
==Summary==
+
Also note that unlike an incandescent lamp the colour temperature of LED and CLF lamps does not get significantly lower as they dim - so they can seem somewhat "cold" looking when dimmed.
−
* Dimmers make lighting less energy efficient when set to reduced brightness.
 
−
* Switchbanks are a good idea for new installs, and on average save many times their cost.
 
−
* Dimmers are the neat option for multi-bulb chandeliers.
 
−
* Dimmers are significantly easier and thus cheaper to retrofit than switchbanks, but normally result in higher run costs than a switchbank.
 
−
* Dimmers prevent use of CFL lamps.
 
  
−
==Dimmers==
+
===Reliability===
−
===Energy Efficiency===
+
Dimmers themselves aren't as reliable as switches, and failures do occur occasionally. 250w dimmers are rather less robust on the whole than 500w dimmers.  
−
A '''Dimmer''' reduces the power flowing through a filament lamp by a small amount, causing a large fall off of light output. As an example, 500w of halogen lighting consumes approx 300w while putting out the same amount of light as a 40w filament bulb.
 
  
−
Use of dimmers reduces energy use by a fairly limited amount compared to running the bulbs at full brightness, but either replacing the bulbs with more suitably rated ones or use of a switchbank reduces energy use much more.
+
Filament bulbs occasionally consume a heavy current surge on failure, due to arc-over. Such a current surge has a high chance of destroying a dimmer. These surges are more likely to occur with
 +
* small form factor mains filament bulbs (especially [[Halogen Lighting|mains halogen]])
 +
* short [[Cables|cable]] runs.
  
−
Use of dimmers is thus an energy wasteful way to reduce light output. The energy wasted is not dissipated in the dimmer, but in the bulbs.
+
Some dimmers include "soft start" facilities. These may enhance the life span of halogen lamps in particular.  
  
−
===Run Cost===
+
12v bulbs and non-filament type lamps don't suffer from this.
−
Run cost depends entirely on what lighting is used at what setting for how long, so is a very variable figure.
 
  
−
To get some idea of how dimmers cost money to run, we will compare a 40w filament lamp on full brightness to 500w of halogen lighting dimmed to the same light output.
+
Dimmers should not be loaded past their max rating, this elevates failure rate greatly. Note also that many dimmers also have a minimum load required for correct operation - this can be a problem with some LED loads due to their low current draw.  
  
−
If your use is different, your figures will be different.
+
===Wiring Arrangements===
 +
A dimmer usually replaces an existing switch, with no added complication. (although note that remote control dimmer switches may not work with low energy lamps unless a bleed resistor is also fitted to allow a small current to flow through the lamp when "off")
  
 +
The exception to this is when [[2 Way Switching|two way]] operation is required. If you wish to control brightness from both switch positions then a special master / slave dimmer switch will be required. Conventional dimmers will allow [[2 Way Switching|two way switching]], but not two way brightness control.
  
−
====40w Filament Bulb====
+
==Switchbank==
−
A 40w filament lamp uses 40w. At 10p/unit that's 0.4p/hr.
+
[[image:Switchbank_new_1083-6.jpg|right|190px]][[image:GEC-grid-1.jpg|right|180px]][[image:GEC-grid-2.jpg|right|180px]][[image:GEC-grid-3.jpg|right|180px]] [[image:MK-grid-1.jpg|right|180px]] [[image:MK-Grid-2.jpg|right|180px]]
  
−
With 2 hrs/day of undimmed use, that costs 0.4p x 2 x 365 = £2.92 per year.
 
  
−
====Dimmed halogens====
+
A '''Switchbank''' is a bank of 2 or more switches, where each switch controls some of the lights in a room. More than one [[lighting]] level is thus achieved depending on the number and combination of lights turned on.
−
500w of halogens dimmed to equivalent the output of a 40w filament bulbs uses 300w.
 
  
−
At 10p/unit that's 3p/hr.
+
To operate well, switchbanks require lights to have overlapping lighting areas; so a long room with only two lights, one at each end, may not be an ideal candidate for a switchbank. Uneven lighting can be an issue when fitting switchbanks to an installation with a minimum number of lights, as was common practice in the 1970s and before.
  
−
With 2 hrs/day of dimmed use, cost = 3p x 2 x 365 = £21.90 per year.
+
When using a switchbank with multiple downlighters, there are various ways to distribute the lights among the switches. Groups of lights on each switch and alternate lights on each switch are both popular options. What works best depends on the room and lighting layout.
  
−
Over 25 year product life, extra electricity cost use dimmed high power lighting in place of a more appropriately sized lamp = (21.90 - 2.92) x 25 = '''£474''' This is just for one lamp.
+
2 or 3 switches are often enough for most rooms. More switches make for more possible lighting patterns or levels if desired.
  
−
===Safety===
+
===Compatibility===
−
The ability to use cool running CFLs on switchbanks and inability to use these with dimmers probably accounts for a slight safety difference. In 2001 there were 69,000 house fires in UK. How many of these were caused by hot filament bulbs in fixed fittings is not known, and what percentage of dimmer users would use CFLs if they had a switchbank instead is also not known.
+
Switchbanks are compatible with all types of [[lighting]].
  
−
A well known failure mechanism of dimmers is arcing of the potentiometer. This happens more often than switch arcing. Whether this has any significant effect on safety is not known.
+
===Reliability===
 +
Switchbanks are as reliable as any other light switch arrangement. If more lights are fitted at the same time, that translates to more routine bulb replacements.  
  
−
What sort of magnitude these differences make is an unknown.
+
===Installation Tips===
 +
Single sized standard light switches come with up to 4 switches, plenty for most rooms.
  
 +
====More Switches====
  
−
===Reliability===
+
Large and specialist lighting installs may require more switches. Standard double faceplates come with upto 6 switches. To get even more switches requires either a '''gridswitch''', additional faceplates, or a custom switch assembly made from a blanking plate. The '''gridswitch''' is the usual choice, and can incorporate dimmers and indicators etc as well as switches.
−
A dimmer is a single failure point, and dimmers have variable reliability. 250w dimmers seem on the whole to be less robust in this respect.
 
  
−
Dimmers have limited power ratings, so extension of the lighting circuit or fitting of higher power bulbs may cause overload.
+
Each additional switch doubles the number of available lighting patterns, hence 3 and 4 gang switchbanks are normally plenty.
 +
* A 2 gang switch gives 3 lighting levels, if the lights are of different wattage
 +
* A 3 gang switch gives 7 lighting patterns/levels
 +
* A 4 gang switch gives 15 lighting combinations & levels!
  
−
If dimmers are used over their ratings, early failure is likely.
+
Shown at right, an 8-gang GEC metalclad gridswitch with 8 intermediate switches. This would have 32 strapping wires connected to the switches, plus CPCs and any neutrals passing through the box.
  
 +
===Wiring Arrangements===
 +
====Loop-in====
 +
[[House Wiring for Beginners|Loop-in]] is the most common lighting circuit arrangement. Power is daisy-chained from each lighting fitting to the next, and a separate switch wire connects a switch to each fitting. This is simple and easy to implement for [[House Wiring for Beginners|general lighting wiring]], but is not compatible as it stands with switchbanks. To retrofit switchbanks into such a system would require additional wiring, complicating the wiring layout.
  
−
===Compatibility===
+
====Switch loop through====
−
Standard dimmers are compatible with mains filament bulbs & mains halogens.
+
The other method in use for domestic lighting is to run the power feed to the switch first rather than the lighting (so power feed to the next room is taken from the switch position and not from a light fitting). From the switch, a [[Cables|cable]] with neutral, earth & switched live is run to the lighting. A minority of house lighting is wired this way.
  
−
Other types of lighting require a ballast or power supply that is specifically designed to be dimmable, plus a dimmer designed to work with them.
+
When more than one [[Cables|cable]] is run from the light switch to more than one light fitting, a switchbank can be retrofitted without adding any further wiring. However in most retrofit cases such wiring is not already present. Hence switchbanks are more often fitted at new installation and [[Rewiring Tips|rewire times]] rather than retrofitted.
  
−
Dimmable fluorescent lighting ballasts are available. Dimming these does reduce the energy efficiency of fluorescent lamps to some extent, but nowhere near as much as with filament lamps.
+
==Combined dimmer & switchbank==
 +
Another option is to combine both techniques. There are a few possible ways to do this:
 +
# Dimmer followed by switchbank
 +
# Multiple dimmers
 +
# A switch for some lights, and a dimmer for the other lights
  
−
CFLs and dimmers are not compatible.
+
This gives some the advantages of a switchbank while retaining the continuously variable nature of the dimmer.
  
−
Dimmers have one significant advantage, which is that they can easily replace a single lightswitch in an existing installation, with no need for any extra wire to be put in. However, depending on how much power and time dimmed lighting is used, retrofitting a switchbank and adding any extra wire needed can work out cheaper, as well as being more energy efficient.
 
  
−
==Switchbanks==
+
==Switch dimmable low energy lamps==
−
A '''Switchbank''' is a bank of 2 or more switches. If each switch controls 1 or some of the lights in a room, lighting level can be controlled by which lights are turned on.
+
Lamps are available that will select more than one brightness level, controlled by operating an ordinary lightswitch a number of times in sequence. These allow dimming with no wiring changes.
  
−
The more switches are used, the finer the control possible.
+
===Compatibility===
 +
As only the bulb is changed to get this feature, the fitting remains compatible with all lighting types. These are not usually compatible with conventional dimmer switches.
  
 +
==Home automation dimmers==
 +
Dimmer systems are available for integration with home automation systems. These are typically controlled by either proprietary RF signalling, or more commonly, by WiFi. These allow brightness (ans in some cases colour) to be controlled from an "App" on a smart phone or tablet. With home automation systems wither the lamp socket itself can be "smart" or you can opt for "smart" bulbs.
  
−
===Sizes===
 
−
Standard faceplates the size of a single lightswitch come with upto 3 switches. Standard double faceplates come with upto 4 switches. More switches requires a larger faceplate.
 
  
−
It is not difficult to make a standard size faceplate using more switches if this is desired. However a 4 gang switchbank is normally plenty.
+
==Boost & dim==
 +
An 18v transformer can be used to provide 3 settings of boost, normal and dim for filament lamps. The result is significantly better energy efficiency that just a dimmer. The transformer is wired to give 222v, 240v or 258v.
  
−
===Energy Efficiency===
+
Its also possible to implement 2 brightness settings by using a bridge rectifier and capacitor, to give normal and boosted rms voltage.
−
All lights used operate at full normal efficiency. Lighting controlled by a switchbank is thus much more energy efficient than when using dimmers (at below full brightness setting).
 
  
−
Greater energy efficiency means less heat, and this is welcome on hot summer days.
+
Full discussion: [[Filament_lamp#Bulb_Boosting|Bulb Boosting]] & [[Filament_lamp#Switchable_Boost|Switchable Boost]]
  
 +
===Compatibility===
 +
Compatibility depends on the method chosen. See [[Filament_lamp#Compatibility|Compatibility]]
  
−
===Run Cost===
 
−
Lighting run cost is directly proportional to the total power of light bulbs switched on. When less than the maximum lighting brightness is being used, this is a much lower cost option than a dimmer.
 
  
−
Fitting a 2 gang switch in place of a single switch can cost an extre £1, and the extra cable might cost £1, or more with a long run. Typically this the minimal extra install costs is paid back many times over in the life of the installation.
+
==Dimmable fluorescent==
 +
A dimmable fluorescent ballast enables dimming fluorescent tubes over a wide range. A dimmer control compatible with the ballast must be used.
  
−
A switchbank can also be used to mix or choose between filament lighting and CFL. For example, someone that is not keen on CFL might use CFL just for background light, with filament as the main lighting.
+
How to make a fluorescent fitting [[Fluorescent Lighting#Fitting Types & Installation Methods|unseen]]
 +
How to ensure good [[Fluorescent Lighting#The Many Different Whites|light quality]]
  
 +
=Fitting=
 +
==Dimmer==
 +
Dimmers just replace a lightswitch in an existing installation, with no need for any extra wiring to be installed. Retrofitting is easy, and the cost minimal.
  
−
===Safety===
+
==Switchbank==
−
A switchbank enables very low power night lighting to be used without the need for a plug in light. Total run cost for a 3w cfl lamp used 8 hours a night is under £2 per year.
+
If 2 or more light fittings have their own [[cable]]s running to the switch, then a switchbank can be fitted very easily. Its just a case of replacing the old switch.
  
−
Nightlights can of course be used in plug-in lights without a switchbank, but a fixed fitting is neater and slightly safer.
+
But more often there are no separate cables, and extra [[Cables|cable]] needs to be run to retrofit a switchbank. This heavily limits their retrofit use in practice.
  
−
A nightlight reduces night time accidents, and is good for kids afraid of the dark.
+
Retrofit cost is trivial in the first case, but requires additional new cable(s) in the 2nd case.  
  
−
A switchbank also enables use of CFLs, which are a lower fire risk than hot filament lamps.
+
The extra cost of fitting a switchbank when building new is trivial.  
  
 +
A switchbank can also be used to mix or choose between filament and other lighting. One example of this would be concealed [[Fluorescent Lighting|fluorescent uplighting]] with [[Halogen Lighting|halogen]] spots for task and feature lighting.
  
−
===Reliability===
 
−
Switches are an order of magnitude more reliable than dimmers.
 
  
−
A switchbank is a redundant array from a reliability viewpoint, meaning that if one element fails, the system as a whole still continues to work.
+
=Bulb Life=
 +
Switchbanks have no effect on lamp life.
  
−
These 2 points make a switchbank very much more reliable than a dimmer.
+
Dimmers usually soft start lamps. This extends mains [[halogen]] lamp life to some extent, but may make less difference with all other types of lamp.  
  
 +
Switch dimmed [[cfls]] and dimmed linear [[fluorescent]] tubes last far longer than filament lamps. Dimming them has little effect on lamp life. Linear fluorescent tubes on electronic ballasts see around 20,000 hour life average.
  
−
===Compatibility===
+
Boost dimming reduces filament lamp life when on max setting.
−
Switchbanks are compatible with all types of domestic lighting.
 
  
−
Switchbanks have a power rating equal to that of nearly all domestic lighting circuits, so need to limit lightbulb power or upgrade the switches does not occur.
 
  
−
To operate well, switchbanks require lights to have overlapping lighting areas.
+
=Energy Efficiency & Running Cost=
 +
While it is often assumed that fitting a dimmer will reduce energy use, the reality may be more complex. If you elect to use a more powerful filament lamp than you otherwise would have, running costs may actually increase.
  
−
Switchbanks have one compatiblity limitation, which is that replacing a single switch in an existing installation will often require an extra wire to be run from switchabnk to light fitting. This is not always the case, but frequently is.
+
If frequently using less than maximum brightness illumination, the energy saving potential of a switchbank is much greater.
  
 +
For users who normally always run their lamps at maximum brightness illumination, neither option will save significant energy or cost.
  
−
==Dimmable CFLs==
 
−
These exist but are very hard to find in the UK. They typically have 2 or 3 brightness levels rather than being continuously dimmable.
 
  
 +
=Summary=
 +
* Switchbanks are a good idea for new installs.
 +
* Dimmers are the neat option for multi-bulb chandeliers.
 +
* Dimmers are significantly easier and thus cheaper to retrofit than switchbanks.
 +
* Dimmers give the greatest amount of lighting level control
  
−
==See Also==
 
−
[[Special:Allpages|Wiki Contents]]
 
  
−
[[Special:Categories|Wiki Subject Categories]]
+
=See Also=
 +
* [[Special:Allpages|Wiki Contents]]
 +
* [[Special:Categories|Wiki Subject Categories]]
  
  

Revision as of 09:55, 12 July 2019

Dimmer 4476-3.jpg
Switchbank new 1083-6.jpg

Dimmers & Switchbanks are both ways to control lighting levels, improving both utility and comfort.

This article sets out the advantages of controlled lighting levels, and looks at the relative merits of different ways of achieving them. Some installation notes are also included.


Advantages of Lighting Level Control

Controllable lighting brightness permits

  • Relaxed lighting in the evening
  • Bright lighting when its needed for a task
  • Improved safety by allowing lighting level to be selected which is appropriate for the task in hand.
  • Better comfort and better visibility.
  • May reduce energy use

Methods of Lighting Level Control

Dimmer & dimmable lamp

Dimmer 4476-3.jpg

A Dimmer is an electronic control that reduces the power flowing through the lamps it controls, which in turn causes a continuously variable change in brightness to be achieved.

Depending on the lamp technology, the reduced brightness may also reduce the energy consumption. Note that a filament lamp will still use a significant proportion of its "full brightness" energy, even when dimmed.

Dimmers don't require any overlap in lighting areas to achieve their effect.

Compatibility

Standard dimmers have restrictions on the types of lights they will run.

  • Fully compatible with mains filament bulbs
  • Fully compatible with mains halogens.
  • Compatible with most electronic 12V halogen lighting transformers, but not all.
  • Not compatible with toroidal halogen lighting transformers.
  • Compatible only with CFLs specifically marked as dimmable
  • Compatible only with LEDs specifically marked as dimmable
  • Not compatible with linear fluorescent unless fitted with special dimmable electronic ballast and compatible dimmer switch
  • Not compatible with discharge lighting (HID, sodium, mercury)

Note that the dimming range for some dimmable LED and CFL lamps can be far narrower than for an incandescent lamp - typically the dimmest setting is quite a bit brighter than that of an incandescent lamp (this however does depend on the dimmer - ones specifically designed for LED use for example tend to achieve far better results.

Also note that unlike an incandescent lamp the colour temperature of LED and CLF lamps does not get significantly lower as they dim - so they can seem somewhat "cold" looking when dimmed.

Reliability

Dimmers themselves aren't as reliable as switches, and failures do occur occasionally. 250w dimmers are rather less robust on the whole than 500w dimmers.

Filament bulbs occasionally consume a heavy current surge on failure, due to arc-over. Such a current surge has a high chance of destroying a dimmer. These surges are more likely to occur with

Some dimmers include "soft start" facilities. These may enhance the life span of halogen lamps in particular.

12v bulbs and non-filament type lamps don't suffer from this.

Dimmers should not be loaded past their max rating, this elevates failure rate greatly. Note also that many dimmers also have a minimum load required for correct operation - this can be a problem with some LED loads due to their low current draw.

Wiring Arrangements

A dimmer usually replaces an existing switch, with no added complication. (although note that remote control dimmer switches may not work with low energy lamps unless a bleed resistor is also fitted to allow a small current to flow through the lamp when "off")

The exception to this is when two way operation is required. If you wish to control brightness from both switch positions then a special master / slave dimmer switch will be required. Conventional dimmers will allow two way switching, but not two way brightness control.

Switchbank

Switchbank new 1083-6.jpg
GEC-grid-1.jpg
GEC-grid-2.jpg
GEC-grid-3.jpg
MK-grid-1.jpg
MK-Grid-2.jpg


A Switchbank is a bank of 2 or more switches, where each switch controls some of the lights in a room. More than one lighting level is thus achieved depending on the number and combination of lights turned on.

To operate well, switchbanks require lights to have overlapping lighting areas; so a long room with only two lights, one at each end, may not be an ideal candidate for a switchbank. Uneven lighting can be an issue when fitting switchbanks to an installation with a minimum number of lights, as was common practice in the 1970s and before.

When using a switchbank with multiple downlighters, there are various ways to distribute the lights among the switches. Groups of lights on each switch and alternate lights on each switch are both popular options. What works best depends on the room and lighting layout.

2 or 3 switches are often enough for most rooms. More switches make for more possible lighting patterns or levels if desired.

Compatibility

Switchbanks are compatible with all types of lighting.

Reliability

Switchbanks are as reliable as any other light switch arrangement. If more lights are fitted at the same time, that translates to more routine bulb replacements.

Installation Tips

Single sized standard light switches come with up to 4 switches, plenty for most rooms.

More Switches

Large and specialist lighting installs may require more switches. Standard double faceplates come with upto 6 switches. To get even more switches requires either a gridswitch, additional faceplates, or a custom switch assembly made from a blanking plate. The gridswitch is the usual choice, and can incorporate dimmers and indicators etc as well as switches.

Each additional switch doubles the number of available lighting patterns, hence 3 and 4 gang switchbanks are normally plenty.

  • A 2 gang switch gives 3 lighting levels, if the lights are of different wattage
  • A 3 gang switch gives 7 lighting patterns/levels
  • A 4 gang switch gives 15 lighting combinations & levels!

Shown at right, an 8-gang GEC metalclad gridswitch with 8 intermediate switches. This would have 32 strapping wires connected to the switches, plus CPCs and any neutrals passing through the box.

Wiring Arrangements

Loop-in

Loop-in is the most common lighting circuit arrangement. Power is daisy-chained from each lighting fitting to the next, and a separate switch wire connects a switch to each fitting. This is simple and easy to implement for general lighting wiring, but is not compatible as it stands with switchbanks. To retrofit switchbanks into such a system would require additional wiring, complicating the wiring layout.

Switch loop through

The other method in use for domestic lighting is to run the power feed to the switch first rather than the lighting (so power feed to the next room is taken from the switch position and not from a light fitting). From the switch, a cable with neutral, earth & switched live is run to the lighting. A minority of house lighting is wired this way.

When more than one cable is run from the light switch to more than one light fitting, a switchbank can be retrofitted without adding any further wiring. However in most retrofit cases such wiring is not already present. Hence switchbanks are more often fitted at new installation and rewire times rather than retrofitted.

Combined dimmer & switchbank

Another option is to combine both techniques. There are a few possible ways to do this:

  1. Dimmer followed by switchbank
  2. Multiple dimmers
  3. A switch for some lights, and a dimmer for the other lights

This gives some the advantages of a switchbank while retaining the continuously variable nature of the dimmer.


Switch dimmable low energy lamps

Lamps are available that will select more than one brightness level, controlled by operating an ordinary lightswitch a number of times in sequence. These allow dimming with no wiring changes.

Compatibility

As only the bulb is changed to get this feature, the fitting remains compatible with all lighting types. These are not usually compatible with conventional dimmer switches.

Home automation dimmers

Dimmer systems are available for integration with home automation systems. These are typically controlled by either proprietary RF signalling, or more commonly, by WiFi. These allow brightness (ans in some cases colour) to be controlled from an "App" on a smart phone or tablet. With home automation systems wither the lamp socket itself can be "smart" or you can opt for "smart" bulbs.


Boost & dim

An 18v transformer can be used to provide 3 settings of boost, normal and dim for filament lamps. The result is significantly better energy efficiency that just a dimmer. The transformer is wired to give 222v, 240v or 258v.

Its also possible to implement 2 brightness settings by using a bridge rectifier and capacitor, to give normal and boosted rms voltage.

Full discussion: Bulb Boosting & Switchable Boost

Compatibility

Compatibility depends on the method chosen. See Compatibility


Dimmable fluorescent

A dimmable fluorescent ballast enables dimming fluorescent tubes over a wide range. A dimmer control compatible with the ballast must be used.

How to make a fluorescent fitting unseen How to ensure good light quality

Fitting

Dimmer

Dimmers just replace a lightswitch in an existing installation, with no need for any extra wiring to be installed. Retrofitting is easy, and the cost minimal.

Switchbank

If 2 or more light fittings have their own cables running to the switch, then a switchbank can be fitted very easily. Its just a case of replacing the old switch.

But more often there are no separate cables, and extra cable needs to be run to retrofit a switchbank. This heavily limits their retrofit use in practice.

Retrofit cost is trivial in the first case, but requires additional new cable(s) in the 2nd case.

The extra cost of fitting a switchbank when building new is trivial.

A switchbank can also be used to mix or choose between filament and other lighting. One example of this would be concealed fluorescent uplighting with halogen spots for task and feature lighting.


Bulb Life

Switchbanks have no effect on lamp life.

Dimmers usually soft start lamps. This extends mains halogen lamp life to some extent, but may make less difference with all other types of lamp.

Switch dimmed cfls and dimmed linear fluorescent tubes last far longer than filament lamps. Dimming them has little effect on lamp life. Linear fluorescent tubes on electronic ballasts see around 20,000 hour life average.

Boost dimming reduces filament lamp life when on max setting.


Energy Efficiency & Running Cost

While it is often assumed that fitting a dimmer will reduce energy use, the reality may be more complex. If you elect to use a more powerful filament lamp than you otherwise would have, running costs may actually increase.

If frequently using less than maximum brightness illumination, the energy saving potential of a switchbank is much greater.

For users who normally always run their lamps at maximum brightness illumination, neither option will save significant energy or cost.


Summary

  • Switchbanks are a good idea for new installs.
  • Dimmers are the neat option for multi-bulb chandeliers.
  • Dimmers are significantly easier and thus cheaper to retrofit than switchbanks.
  • Dimmers give the greatest amount of lighting level control


See Also

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