Transformator output loads

[pihta]

Joey,

We got situation where we dont know what to do without knowledge about internal construction of your transformers. We have some project where at 840W transformer 414 watts (including voltage drop corrections) of 535W total is connected to 14V output. 414W to only 14V output, almost half of transformer capacity. Is it okay for transformer or not? How many toroids of smth is inside - would it burn and so on. Its 29Amps!

[JoeyD]

29 Secondary amps is able to put on one tap, you will be fine. ETL has de rated our taps to 30 amps on any secondary tap but up until they did that we told people they could load up to 50amps or 600 watts in a 12v unit on any one secondary tap due to the wire we use.

Our units are one true single core on the inside so no worries of balancing the load. You will be fine doing what your doing.

For the sake of not causing confusion the NEC states no more than 25amps on any secondary RUN but this does not affect the secondary tap of the transformer. That rule pertains tot he actual run from the transformer to the lights.

[pihta]

Thanks a lot, Joey!

So as I understand we can connect runs as we want to in any combinations!

[JoeyD]

yep! multiple runs to one tap is fine. We give you multiple common taps for ease of wiring not becuase there are multiple cores like other units out there. We make true single core units!!!

[steveparrott]

For the sake of not causing confusion the NEC states no more than 25amps on any secondary RUN but this does not affect the secondary tap of the transformer. That rule pertains tot he actual run from the transformer to the lights.

Joey, are you sure about that? This is the code:

411.2 Lighting Systems Operating at 30 Volts or Less. A lighting system consisting of an isolating power supply operating at 30 volts (42.4 volts peak) or less under any load condition, with one or more secondary circuits, each limited to 25 amperes maximum, supplying luminaires (lighting fixtures) and associated equipment identified for the use.

I've always understood that it is the circuit that's limited to 25A, (implying a single secondary tap) not individual runs. I could be wrong.

[JoeyD]

I believe the circuit is represented by the load carrying home run. You may be right however? I will have to verify. I know ETL and UL do not make the rules but we were limited to 30v per secondary by them on our labels. We used to tell guys our units could and still can hold up to 50 amps per tap per the wire rating of the wire we use off the cores. Obviously we have never had issue.

I will verify.

Thanks Steve.

[JoeyD]

After some digging and discussion with our in house engineer and product testing manager it is believed that the NEC is refering to the load carrying cable / home run as the circuit.

Example: You would need atleast 5 commons to load an 1120 or 1200w unit if this were the case. 4 homeruns pulling 20 amps and the 5th pulling 13 amps. That’s why I believe they are talking about the homerun cable.

Again I will try and verify for you. But I did confirm that we are rated per NEC on all of our units at a max of 30 amps per secondary tap.