Low Voltage Transformer Sizing

Reply

  #1  
Old 09-12-20, 04:22 PM
C
Member
Thread Starter
Join Date: Aug 2006
Location: USA
Posts: 74
Received 0 Votes on 0 Posts
Low Voltage Transformer Sizing

I have low voltage lighting in our back yard and after adding some new lighting, the lights at the end of my run are not being powered (there's less than 10V at the end).

I'm using a 300W Transformer (Malibu ML300RTW) and 12G line with about 200 feet total. The line starts at the transformer and runs around our yard with lights spaced about 10 feet apart. I'm not able to connect the transformer to the middle of the 200 foot run unfortunately.

I have 10 LED bollards (2W each) and 5 LED spotlights (4W each). I added 4 sets of LED string lights at 9W each and that's when I overloaded the line.

The lights up to about 150 feet have sufficient voltage, but the lights on the last 50 feet are dim and the last 2 lights won't come on.

Can I replace the 300W transformer with a 400W or 450W transformer to fix this?
 
  #2  
Old 09-12-20, 05:09 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 61,398
Received 1,399 Votes on 1,296 Posts
Unfortunately replacing the transformer with a larger one will not help.

You only have 75 watts of load on the line. You didn't overload anything. Actually.... even though there is a lot of wire..... there shouldn't be that much drop at the end. It sounds to me like you may have a bad splice.

Some transformers have multiple or changeable voltage outputs. Increasing the voltage slightly could help.
 
  #3  
Old 09-20-20, 06:21 PM
C
Member
Thread Starter
Join Date: Aug 2006
Location: USA
Posts: 74
Received 0 Votes on 0 Posts
I am going to switch to a multi-tap transformer to see if a 13V or 14V feed will improve this situation.

Do I need to “protect” the lights at the first part of the string?
 
  #4  
Old 09-20-20, 07:03 PM
Z
Forum Topic Moderator
Join Date: Sep 2005
Location: USA
Posts: 5,660
Received 173 Votes on 154 Posts
The lights towards the end of a long run will always be dimmer. Unfortunately, at 12v, voltage drop quickly becomes an issue over about 150'.

There are a few options:
1) Some people recommend a loop, basically another 12ga wire coming 'back' from the furthest light and connected back to the transformer (observing polarity so you don't have a short). It's sort of a way to parallel the conductors to get more voltage at the far end. (I've never tried this myself, so I can't say for sure how much it helps)

2) Connect to a higher voltage output as Pete mentioned. You can either use the lower 12v output for the lights 50-100' or closer, and the higher voltage for the further away lights. Or connect them all to the higher voltage. Back in the days of incandescent bulbs, that would mean the closer ones would burn brighter and burn out more quickly. I assume with LED lights, since they have voltage regulators on them anyway, the higher voltage won't bother them. (Pete, can you confirm?)
 
  #5  
Old 09-21-20, 09:47 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 61,398
Received 1,399 Votes on 1,296 Posts
The LED lights will work fine at the higher voltage.
 
Zorfdt voted this post useful.
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: