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52 Installation and trouble shooting low voltage d.c. lighting
DC lighting installation guide for Thin-Lite, Light It Technologies and
Iota Engineering products.

This page is designed to help you in your low voltage d.c. lighting
installation or retro-fit as well as helping in troubleshooting your
existing system.

Before you start your installation project, lay it out on paper. From
past experience this will help insure that it is done right the first time.

A very important thing to keep in mind is: low voltage (lower than
the rated voltage) will reduce the life span of a low voltage
d.c. fluorescent light fixture. The electronics in a dc fluorescent
light is actually an inverter/ballast. It takes low voltage d.c., inverts it
into alternating current - then steps it up to a high voltage/high
frequency to fire and run the fluorescent tube. From this point on we
will refer to the inverter/ballast as simply a ballast.

Let's do some math. For example, a 12 volt d.c. ballast driving a 12 watt
fluorescent tube will consume a little over one amp. Volts times Amps
equals watts. Volts are the pressure, amps are the the quantity and a
watt is the power of the work being done. If the incoming voltage is too
low, the ballast will make it up in amperage. Amperage also equates
to heat in the electronics. This reduces the operating life of the ballast.

Please note, a ballast can draw from 100 percent to over 200 percent of
the rated amperage on start up. The factors that can affect this are:
low supply voltage, a cold fluorescent tube or an old fluorescent tube.

Here are a couple examples of what can go wrong with poor planning
of a system:

First Example:

In December of 2008 we received a call from a customer in New York.
They need some 24 volt / 32 watt ballasts shipped next day air. The
customer did not say what they needed them for, just that they needed
them. Well, they got them as planned
About a week later I received a call from the customer saying that all
of the ballasts had self-destructed. Here is the picture after I grilled
them. Each 32 watt ballast was connected to a 36 watt fluorescent
tube - it will work but the tube would not be driven to full brightness.
Next, each ballast had its own 10 ga wire going to the same switch.
The 10 ga. wire is okay but having eight of these ballasts connected
to the same switch is a recipe for failure. Please note that these lights
were in an outbuilding near a runway and in the snow. It gets better,
the batteries supplying the ballasts were in another building over
fifty feet away. The wire run, using 8 ga. wire, would have been a
minimum of seventy feet. When the switch was turned on, all of the
lights tried to fire at the same time, the voltage dropped dramatically
which caused the ballast to over-amp and smoke.

Second Example:

Last year (2009) we received a phone call from a repair shop in the
San Francisco Bay area. They had a mobile disaster command post,
a full size bus, in for repair. The vehicle had twenty-four 12 volt / 30
watt fluorescent light fixtures. The command post conversion was about
six months old and all but a few of the light fixtures had failed. Each
light had its own switch but the people using the vehicle left all of the
switches on for convenience. There was a master switch inside the
doorway and on entering or leaving the vehicle they would flip the
switch. All of the non-essential gear such as lights and radios drew
power through this switch. There was one circuit for all of the lights.
Let's see, twenty-four 30 watt fluorescent lights (not counting the
other 12 volt loads) coming on at the same time - that sounds like
a minimum of 60 amps on startup. It is surprising that the lights acutally
came on in the first place. This was another installation that was
doomed to failure because of poor planning.

Third Example:

Last year we received a call from the owner of a forty-foot house boat.
The batteries were on one end and there was a single 12 ga. lighting
circuit supplying power for several 1056 tail light bulb fixtures. He
wanted to replace these lights with fluorescents for more light and
efficiency. The electrical system was 12 volts and there was no way
to replace the existing wire with a larger size. The bottom line was
that this installation could not be retro-fitted with fluorescent lights. It
could have been upgraded with LED lighting but the cost would have
been prohibitive due to the amount of area to illuminate.

Fourth Example:

Several years ago one of our customers who lives off-grid with a 12
volt photovoltaic system wanted to replace their incandescent lights
with 12 volt compact fluorescent lights. With very little sunlight during
the winters in Michigan, they were often running low on battery power
and had to use propane wall lighting. He replaced the incandescent
lights and everything was fine until the following winter. They had one
lighting ciurcuit which supplied three bedrooms in a line. In the
farthest bedroom the compact fluorescent lights started failing, then
the ones in the middle room. The bedroom closest to the battery bank
had no problems. Because of the difficulty in rewiring a circuit for
each room, they went back to low voltage incandescent lights for the
end bedroom. They also used 12 volt LED lights in all of their reading
lamps which worked out fine.

These stories are brought up to give you an idea of what kind of planning
is needed for a successful low voltage d.c. lighting system. When done
right they perform well for years.

One of our 12 volt dc. outdoor lighting systems has a Thin-Lite mod. 153
light which has always had a 40 watt tube in it as well as a McLean 30 watt
fixture. I installed these around 1985 and they work just fine today. These
are used once or twice a day, always have the proper voltage and when
a tube starts to go bad, it gets replaced.

A note on recreational vehicle lighting systems.

Many motor homes will have a single wall switch which operates
several 12 volt d.c. fluorescent lights. The wall switch is usually designed
for a.c. (alternating current) operation and will not stand up to long
term use with direct current. As the switch is used, the contacts start
to burn and crater. This increases the resistance which lowers the
voltage going to the lights. It is not unusual to get a call from a customer
with a several year old RV where a few of the ceiling lights have
failed within days of each other.               

Trouble shooting you system.

When you start to have problems with your system the first thing to
do is to check the voltage at the fixture itself. Check the voltage
while all of the lights are running. If you do a voltage test with no
load on it you can get a good voltage reading - usually the
same as if you checked it at the battery.
If the battery is low, or the wiring is too light, or the switch has high
resistance in it, or the connections are not tight - it will show up under
load.  

 
The wrong way to wire a low voltage d.c. lighting system.
low voltage d.c. lighting wiring the wrong way
 
The right way to wire a low voltage dc lighting system.

dc lighting wiring right way

 
The following chart gives wire size recommendations
based on the amp draw on the circuit and the distances
the lights are away from the battery(s). This is for a
12 volt system.

For a 24 volt system you can use the next smaller wire
size than shown for 12 volt.

For a 48 volt system you can use two smaller wire sizes
than shown for 12 volt.

Amps
14 ga.
12 ga.
10 ga.
8 ga.
6 ga.
4 ga.
2 ga.
1/0 ga.
2/0 ga.
4/0 ga.
1
90
140
230
360
580
912
1440
2
45
70
115
180
290
456
720
1160
1440
2120
4
20
35
55
90
145
228
360
580
720
1160
6
15
24
35
60
95
150
240
386
486
760
8
11
17
30
45
71
114
180
290
360
580
10
9
14
24
36
57
91
145
230
290
460
15
6
9
14
24
38
60
96
153
192
300
20
4
7
11
18
29
45
72
115
145
232
25
3.6
5.6
9
14
23
36
58
92
116
184
30
3
4.8
7
12
19
30
48
77
97
154
40
5.6
9
14
23
36
58
72
112
50
4.6
7.2
11
18
29
46
58
92
100
5.8
9.2
14.4
23
29
46
150
9.6
15.4
19.4
30
200
7.2
11.6
14.6
22

 
Knowing what the amp draw for a low voltage d.c. light fixture is very important
is setting up, or trouble-shooting, a lighting system.
Basically you take the wattage of the light, divide it by the voltage and add
about twenty percent for fudge factor.
This will give you an approximate amperage draw while the light is running.

Starting up a dc fluorescent light requires a higher amp draw than when it
is running.  
The starting amp draw can be 1-1/2 to 3 times the running amperage.

This is affected by the following:

Temperature of the fixture, the colder the tubes, the harder it is to fire
them.
Condition of the tubes, as the ends darken it takes more power to
ionize the gas and fire the tube.
Battery voltage, as the battery voltage drops the draws more amps
to fire the tube.

 

Above is an old, nasty looking Thin-Lite (REC) model OEM-153 light fixture.
I installed this back around 1985 under a covered outdoor area.
It runs off of a gel cell battery that is charged by a 70 watt solar array.
I do not know how many tubes it has had since then but the ballast is
the original one.
This light gets turned on almost every morning for one to three hours,
depending on the time of year.
It is used in the evenings a few times a week.
The battery is always kept at the highest state of charge possible, the wiring
is heavy enough for this fixture and the connections are tight.
I figure the long life of this fixture is due to the above factors along with
a limited number of on/off cycles.    









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 1 Site Search - Quick Index   |    2 The Realities of Purchasing On-Line   |    3 Why Do Business With Us?   |    4 Distributor of IOTA Engineering, Quick Cable and Anderson SB products   |    5 Photovoltaics,Batteries, Cable and Wire   |    6 Lumen Outputs of Compact Fluorescent and Incandescent Lights   |    7 48 volt D.C. fluorescent lights   |    8 DC Lights   |    9 DC Fluorescent Lights   |   10 DC Fluorescent Outdoor Floodlights   |   11 DC Compact Fluorescent Screw-in Ballasts & Tubes   |   12 DC Compact Fluorescent Screw-in One Piece Lights   |   13 DC Indoor Flood, Ceiling and Cabinet Fluorescent Lights   |   14 Portable & Emergency Fluorescent Light by Flexcharge   |   15 DC Fluorescent Inverter Ballasts by IOTA Engineering and Montana Light     |   16 Charge Controller Musings   |   17 Bogart Engineering SC-2030 Solar Charge Controller   |   18 Light Bulb Socket Adapters   |   19 Thinlite Indoor Fluorescent Lights   |   19 A - LED Lighting by Thin-Lite   |   20 Thinlite Outdoor Lights   |   21 Thinlite Replacement Ballasts   |   22 Thinlite Replacement Lens - Diffusers   |   23 Thinlite DC Lighting Products   |   24 DC Lighting   |   Glossary of Alternative Energy Terms   |   25 Parallel and Series Battery Bank Information   |   26 What we sell and why.   |   27 Amps Volts and Watts   |   CHARGE CONTROLLERS   |   28 Emergency and Disaster Preparedness Notes   |   29 Photovoltaic Module & System Wiring - Setting Up A PV System   |   30 Wind - Hydro - Solar Charge Controllers by Flexcharge   |   31 Water and Air Heating Diversion Loads for Charge Controllers   |   32 Maximum Power Point Tracking Charge Controllers   |   33 Solar Converters, Inc. Charge & Lighting Controllers   |   34 SES Flexcharge Charge Controllers   |   35 Thin-Lite ballast replacement installation guide   |   36 Solar Converters Special Solar and Battery Charging Equipment   |   37 TriMetric Battery System Monitors and Deltec Co. shunts   |   38 Timers,Linear Current Boosters,Photoswitch,Voltage Controlled Switches   |   39 Battery Desulphator   |   40 Solar Converters, Inc. Products   |   41 Flexcharge Products   |   42 DC Circuit Breakers   |   43 Thin-Lite products we stock     |   44 DC Fuse & Circuit Breaker Types & Installation   |   45 UL Listed DC Breakers up to 125 volts   |   46 IOTA Engineering IQ4 Smart Charge Controller Owners Manual   |   47 Our own alternative energy systems   |   48 DC Fuses, Holders & Fuse Blocks   |   49 Class T- DC Fuses & Fuse Blocks   |   50 ANN - ANL - CNL DC Fuses & Fuse Blocks   |   51 Inverter Cable and Overcurrent Protection Guide   |   52 Installation and trouble shooting low voltage d.c. lighting   |   53 Diodes - Blocking & Bypass, What do they do?   |   54 Low Voltage D.C. Lighting Tips   |   55 Your On-Line Privacy   |   56 Electric Vehicle and Alternative Energy Battery Disconnects   |   57 Power Distribution & Splicer Blocks   |   58 Cable and Butt Splices & Connectors   |   BATTERY POST & TERMINAL CONNECTIONS,  ADAPTERS AND BATTERY ACCESSORIES   |   59 Battery Post Marine Conversions & Terminal Extensions   |   60 Battery Post Connectors Conversions Adapters Repair   |   61 Battery Terminal - Cable Lug Covers & Protectors   |   62 Heat Shrink Tubing & Cable Lugs by QuickCable       |   63 Compression Connectors - Lugs   |   64 Heavy Duty Cast Copper Connectors - Lugs   |   65 Copper Connectors - Lugs by Quick Cable - MAX   |   66 Magna Lug Heavy Duty & Fusion Lugs by QuickCable   |   67 Anderson SB Connector quick connects   |   68 Anderson SB Connector Accessories   |   69 Anderson SB Connector Parts   |   70 Thin-Lite LED and Fluorescent Comparisons   |   71 Overview of Our Photovoltaic Systems   |   72 Iota Engineering Battery Chargers / Converters     |   73 SAE Connectors, Plugs, Sockets & Cords   |   74 Electric Vehicle Power Supplies Converters by IOTA Engineering   |   75 DC to DC Voltage Converters & Dimmers by Solar Converters   |   76 Universal Generator Starter switch by Solar Converters   |   77 Stranded vs Solid Wire in low voltage systems   |   78 IOTA Engineering Power and Lighting products   |   79 QuickCable Tools, Cable Crimper,  Cutter & Stripper   |   80 Wire & Cable Gauges and Information   |   81 TriMetric 2030 and SC-2030 Wiring Layout   |   82 DC to DC Voltage Converters   |   83 PowerMax Transfer Switch & TriMetric 2020 Features   |   84 IOTA Engineering DLS Battery Charger Features   |   85 Lighting Systems   |   86 Practical Alternative Energy Applications   |   87 Portable  and Emergency Power Systems   |   88 Custom Cables   |   89 Our Customers Systems   |   90 Resources for Disaster & Emergency Preparedness   |   91 PowerMax Transfer Switch Views and Schematics   |   93   |   94 Battery Wiring Diagrams   |   95 Battery Condition and State of Charge Charts   |   96 Order Form   |   97 Backup Power?   |   98 Energy Expectations   |   99 Power Needs Worksheet   |   100 Efficiency   |   101 Wire Loss Chart   |   102 Solar Insolation Map / Chart   |   103 Utility Inter-tie   |   104 About Us   |   105 Statement of Policy & Warranty/Returns   |   Contact Us   |   MPPT Charge Controllers - FAQ   |   Battery Equalizer/DC Autotransformers - FAQ   |   Constant Voltage Pump Drivers  - FAQ   |   Linear Current Boosters - FAQ   |   Information   |   1   |   2   |   3   |   4   |   5   |   6   |   7   |   NEWS-info links   |   Home Power Articles   |   R   |   P   |   A   |   B   |   C   |   D