Low Voltage Transformer and LED

[Little Bill]

I know that dimmers for LED are different than for incandescent bulbs. Example: 600W max dimmer for incandescent, 150W max for LED.
My question is would the same difference be for a transformer, 120V to 17V, for landscape lighting. In other words, would you size the transformer the same for low voltage incandescent bulbs vs low voltage LED bulbs?

Customer wants 10-12 LED lights that are rated at 1.5W. These can run on 9V to 17V. The run from the transformer to the lights will be approx 25'-30'.

 

[winnie]

I'm guessing here, but if this was a transformer providing low voltage AC, then you would need to oversize somewhat because of harmonics. If the LEDs were supplied with low voltage DC, then no oversizing would be needed.

 

[Little Bill]

I'm guessing here, but if this was a transformer providing low voltage AC, then you would need to oversize somewhat because of harmonics. If the LEDs were supplied with low voltage DC, then no oversizing would be needed.

Apparently the lights have an on board driver as the specs say they can be fed with AC or DC.

 

[Little Bill]

Determine current draw of each lamp, consider which secondary voltage tap specific lamps will be on, and multiply, then allow for at least 20% head room. More if you think client could add/request additional lamps later. Rule of thumb is not to exceed 80% of trans listing.
But for 12 led bulbs rated 1.5w each I would guess a 60w (?) transformer would be the smallest you could buy which would offer roughly 5a on the secondary. If clients haven't seen or mocked up the lights at night they might be disappointed with the brightness in some locations (up lit trees etc) unless this is some ultra low key under step or path light. I mention this because the MR16 'style' led's that can throw some light are typically around 3.5 / 5 / 7 watts each. So take their 1.5watt request and tell them you want to add in some future capacity unless they've already bought the parts & they are on site.
fwiw - Landscapers do most of the installs these days, and every job I visit I'll open up the trans and never fail to discover everything on one tap of the two or three secondary taps provided with like 50+ lamps on over 100ft of 14/2 lo vo. When the trans says (example) 600w it's usually two 300w secondaries.

I haven't seen the lights other than on their website. I think they are just LED and not an actual LED bulb. The customer wants these on an outdoor fireplace. He plans on putting them right under the mantle.

 

[TwistLock]

yeah, I deleted that when your post appeared, after I posted, saying you could use a DC driver making mine irrelevant.