Lamp load Vs. Transformer capacity

Discussion in 'Landscape Lighting' started by jbailey52, Jan 4, 2007.

  1. jbailey52

    jbailey52 LawnSite Bronze Member
    Posts: 1,089

    Can someone explain the difference with this? I believe It is pretty obvious... but I need to me re-assured.... kind of shocking that a 600 or 900 watt transformer cost so many hundreds of dollars, but can only handle 450 or 675 watts of lamps respectively.
     
  2. jbailey52

    jbailey52 LawnSite Bronze Member
    Posts: 1,089

    Forgot to add that in the booklets... it basically says Tranformer capacity, and 75% lamp load... does that mean you shouldnt go over 75% of the transformers capaxcity? Thanks in advance!
     
  3. Allure

    Allure LawnSite Senior Member
    Posts: 426

    you need to allow for resistance. wire loss (watts) can be as high as 20% so the lamp load should never exceed 80% of the transformers capacity.

    Also, you want a transformer with extra capacity to allow for adding extra fixtures in the future or for higher wattage lamps.
     
  4. jbailey52

    jbailey52 LawnSite Bronze Member
    Posts: 1,089

    Right.. I have taken all of this into consideration.. I just never saw a transformer actually list the 75% usage numbers before... Thanks
     
  5. jbailey52

    jbailey52 LawnSite Bronze Member
    Posts: 1,089

    Also... when a transformer says oversized terminals etc... room for 7 #10 wires... this means in each common correct? So technically althought it may be over doing it, you could have 7 in common one, 7 in common two, and seven in common 3 (in a 3 common 900 watt trans?)
     
  6. Allure

    Allure LawnSite Senior Member
    Posts: 426

    i believe they mean 7 wires in each tap. I was at a lighting class today. we were working with a 1500 watt multi tap transformer. the taps could accomodate 6-7 #10 wires. The commons could only handle 300 watts each so i can't see adding 7 wires to one common.

    Who makes the transformer? The one we worked with was from cast.
     
  7. jbailey52

    jbailey52 LawnSite Bronze Member
    Posts: 1,089

    Yep, cast.. I understand the 300 per common.. just wondering how many cables (if under 300 total watts) could be added to each tap...
     
  8. eskerlite

    eskerlite LawnSite Member
    Posts: 222

    6-7 10-2 cables.
    sean c.
     
  9. Allure

    Allure LawnSite Senior Member
    Posts: 426

    each common can accomodate 300 watts for the 1500 watt transformer. each tap can handle the total watts for the transformer (ie.1500).
     
  10. Az Gardener

    Az Gardener LawnSite Gold Member
    Posts: 3,899

    I think it varies from one manufacturer to the next. I believe the F/X rep told me their transformers, say a 600 is really like a 654 or something but they label it as a 600 because most installers are not up to speed on the more technical points. Just as we are discussing here. So to save repeating the same information on warranty calls they just made the switch. I may be wrong but I believe that is what I have heard.
     

Share This Page