C7 Low Voltage Landscape & Outdoor Lighting Systems

Question 1

A low voltage landscape lighting transformer is rated at 150 watts.
The designer wants to run two cable runs from it.
Best practice limits each run to what maximum percentage of the transformer's total wattage?

Accepted Answer

Each run should not exceed 50% of the transformer rating

Answer

100% on one run, 0% on the other

Answer

No more than 80% of transformer rating per run

Answer

Wattage per run is unlimited as long as total does not exceed the rating

Question 2

When calculating voltage drop for a low voltage (12V) landscape lighting cable run, why is voltage drop especially critical compared to 120V circuits?

Accepted Answer

A small absolute voltage drop represents a much larger percentage of the total 12V supply, causing noticeable dimming

Answer

12V systems are not subject to voltage drop since they are low voltage

Answer

Voltage drop causes overheating on 12V systems but not on 120V systems

Answer

12V landscape lights are designed to operate at any voltage between 5V and 15V without effect

Question 3

What is the maximum burial depth required by the NEC for a low voltage (12V) landscape lighting cable that is NOT in conduit?

Accepted Answer

6 inches

Answer

No burial required — surface-laid is permitted

Answer

12 inches

Answer

24 inches

Question 4

A landscape lighting design calls for ten 5-watt LED path lights on a single run from a 12V transformer, using 12 AWG cable over a 100-foot run. What is the approximate total load on this run?

Accepted Answer

50 watts

Answer

5 watts

Answer

25 watts

Answer

100 watts

Question 5

A low voltage landscape lighting transformer connected to a 120V GFCI-protected outlet must be installed outdoors. What NEC requirement applies to the outlet supplying it?

Accepted Answer

The outlet must be GFCI-protected and have a weatherproof cover rated for 'in-use' (while-in-use) protection

Answer

The outlet must be a twist-lock type rated for outdoor use

Answer

A dedicated 20-amp circuit is required for any landscape lighting transformer

Answer

Outdoor outlets do not require weatherproof covers if the transformer plug is rated for outdoor use

Question 6

When connecting multiple cable runs to a multi-tap landscape lighting transformer, which tap should be used for the longest cable run?

Accepted Answer

The highest voltage tap (e.g., 14V or 15V) to compensate for voltage drop over the longer distance

Answer

The lowest voltage tap (e.g., 11V) to reduce energy consumption

Answer

All runs should use the 12V tap regardless of distance

Answer

The tap selection does not matter because LED fixtures self-regulate voltage