Archive for March, 2010

All About Transformers

March 5th, 2010

  TA Series 12v Transformer Painted

Our goal is to provide a simple, cost-effective, and informative format for purchasing low voltage landscape lighting transformers. Be sure to check out our line of L.E.D. transformers and bulbs.

Our transformers are priced at wholesale (available to all) and ready for shipping within 24 hours (except for weekends/holidays). All transformers have a warranty, are easy to install, and have instructions for mounting & wiring. As with any such device, follow all safety instructions.

Torodial Cores Transformers:

  • Run quieter than magnetic core transformers
  • Run cooler
  • More energy efficient: only draws what it uses
  • Longer lasting: best on the market

Benefits:

  • TR Series large terminal allow you to use up to #6 wire for home runs
  • Stainless steel will not rust or corrode
  • Multiple taps allow for longer runs without voltage drop
  • Plugs into a GFCI outlet
  • Timer fits inside the enclosure
  • Easy pluggable photocell ready (side knockouts)
  • Removable door and bottom panels for easy access

 

Lamp Voltages, Output and Input Amperage

March 5th, 2010
  • Use a voltmeter to check the voltage at each fixture (10.8v – 12v)
  • Use a clamp meter to check output on the low voltage cable at the transformer to make sure you have not exceed 25 amps per circuit (your breaker will likely trip if you have)
  • Use a clamp amp meter to measure the input current not to exceed the max input current rating. Each transformer is marked with the appropriate input current
  • Be sure to put the door on and latch it

These instructions are included with each purchase (located inside the transformer box).

These guidelines are used for illustration purposes and manufacturer Installation & Instruction Manuals should be used for actual installation.

Connecting Cables to Transformer

March 5th, 2010

Connecting the Cables to the Transformer:

Whenever working with transformers, keep in mind the output exceeds 12 volts and you want to be cautious during installation. Exceeding 12 volts at the fixture will cause the lamp to burn at a higher rate. This will cause the light bulbs to prematurely burn out. You will need to us an Amp / Probe Volt Meter to ensure accurate voltage readings at the fixture (you may be able to rent the tool versus purchasing).

  • Remove the stainless steel transformer door (room to work)
  • Be sure to run the wire through the holes (knockouts) on the bottom panel
  • One side of the wire (smooth or ridged) connects to the common (COM). Don’t forget, you can have up to 300 watts on the common.
  • The other side connects to the voltage tap
  • Make sure all screws are secure
  • Turn off circuit breakers before you plug in the unit; after you plug it in, turn on one circuit breaker at a time to be sure there are no shorts

These guidelines are used for illustration purposes and manufacturer Installation & Instruction Manuals should be used for actual installation.

Voltage Drop: Illustration

March 5th, 2010

Maximum Wattage:

12/2 has a maximum of 192 watts or 16 amps per run (line)

10/2 has a maximum of 288 watts or 24 amps per run (line)

8/2 has a maximum of 384 watts or 32 amps per run (line)

Illustration: Using the previous example of 800 watts

If you use 12/2 wire, you will require 5 runs

If you use 10/2 wire, you will require 3 runs

If you use 8/2 wire, you will require 2 runs

Measure the distance from the transformer to the very first fixture on each run. You do this to calculate the voltage loss. Use this formula:

Cable Voltage Drop = (Wire Run length x Total watts on the run/ Constant) x 2

12/2 wire cable has a constant of 7500

10/2 wire cable has a constant of 11920

8/2 wire cable has a constant of 18960

These guidelines are used for illustration purposes and manufacturer Installation & Instruction Manuals should be used for actual installation.

Illustration:

Your 900 watt transformer is mounted on the outside of your garage. You are installing 40 fixtures at 20 watts each (800 watts). 12/2 direct burial wire was easy to find at your local hardware store so you decide that is the way to go. You’ve done your homework prior to installing your low voltage landscape lighting system and have rightfully decided on 6 wire runs; making sure not to exceed 192 watts on any given run or 300 watts for each of the 3 COMs.

  • Run 1 has 180 watts (9 lights) – courtyard
  • Run 2 has  140 watts (7 lights) – front walkway/driveway
  • Run 3 has  140 watts (7 lights) – front left side trees/house
  • Run 4 has 140 watts (7 lights) – front right side trees/house
  • Run 5 has 120 watts (6 lights) – plants beds, shrubs
  • Run 6 has  80 watts (4 lights) – Steps

Run 1: First fixture is 25 feet away from the transformer. Use the cable voltage drop formula above.

25 x (180/7500) x 2

25 x (.024) x 2 = 1.2 v. drop

Run 5: First Fixture is 150 feet away from the transformer. Use the cable voltage drop formula above.

150 x (120/7500) x 2

150 x (.016) x 2 = 4.8 voltage drop

You’ll need this information when making connections to the appropriate tap on the transformer.

Voltage range is 10.8v to 12v at each fixture.

If you set Run 1 on the 12v tap, you will have a reading of 10.8 volts (12v – 1.2v drop). Great for the first fixture, however that last fixture on that run will fall below 10.8. Use a volt meter for a reading.

Run 2 on the other hand have a voltage drop of 4.8v. Set on 12v, you will have a reading of 7.2v at the first fixture. To get back to the 10.8 – 12v range, you will have to use voltage taps between 16v – 17v tap.

This is a great illustration for using multi-tap transformers versus the standard 12 volt single tap found in many hardware stores.

These guidelines are used for illustration purposes and manufacturer Installation & Instruction Manuals should be used for actual installation.

Voltage Drop

March 5th, 2010

Measure the distance from the transformer to the very first fixture on each run. You do this to calculate the voltage loss. Use this formula:

Cable Voltage Drop = (Wire Run length x Total watts on the run/ Constant) x 2

12/2 wire cable has a constant of 7500

10/2 wire cable has a constant of 11920

8/2 wire cable has a constant of 18960

These guidelines are used for illustration purposes and manufacturer Installation & Instruction Manuals should be used for actual installation.

Direct Burial Landscape Wire

March 5th, 2010

Maximum Wattage:

12/2 has a maximum of 192 watts or 16 amps per run (line)

10/2 has a maximum of 288 watts or 24 amps per run (line)

8/2 has a maximum of 384 watts or 32 amps per run (line)

Landscape Lighting Industry Standards (subject to change)

Calculate the Load

March 5th, 2010

These multiple tap landscape lighting transformers have built in secondary circuit breakers connected to the commons (COM). Each circuit or COM can handle up to 25 Amp or roughly 300 watts each. If a circuit exceeds 25 Amps you will likely overload the circuit and trip the breaker.

To illustrate:

A) 300W transformer has one COM and can handle up to 300 watts

B) 600W transformer has two COMs and each COM can handle 300 Watt (2×300=600)

C) 900W transformer has three COMs and each COM can handle 300W (3×300 = 900)

Now:

  • Add up your fixture’s total wattage and divide into 300 Watts (25amp) maximum per circuit
    • 40 fixtures @ 20 watts each = 800 watts. Requires 2.6 circuits or 900 watt (3 circuit) transformer
    • Select your cable/wire

Mounting Transformers

March 2nd, 2010

These guidelines are used for illustration purposes; manufacturer Installation & Instruction Manuals should be used for actual installation.You must always follow National Electric Code and local codes when installing these transformers to maintain the manufacturer warranty and to avoid any damage to the transformer or any serious injury.

  • Transformers have a 6′ cord so be sure to consider this when selecting a location
  • Must plug in to a 120 volt AC Power Source or GFCI Outlet
  • Mount at least 1.5 feet above grade level
  • Use wall anchors appropriate for the surface