No OCPD required for 24v power supply with "internal protection"??

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CanaanP

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Sorry if this is not suited for the general forum, but we have an installation that is 380VAC 4W, 50Hz. A vendor has a panel fed with a 400A main breaker and tapped off of the internal bus bar is 14AWG wire feeding a .95A three phase power 24VDC supply. The power supply recently let its factory smoke out and because of its negative attention seeking behavior, it is now my first opportunity to even look at this panel and electrical design. I was dumbfounded to see 14 gauge wiring coming off of a 400A bus. The vendor claims that the power supply has internal line side non-replaceable fuses, therefore a breaker upstream is not required. I guess my concern here is that one would be relying on the integrity of those internal fuses to protect the extremely under sized wire for that potential current flow. Does anyone have any experience with "internally protected" devices?

TIA
 
Jraef

Jraef

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If the conductors feeding the power supply line terminals do not exit the panel, they fall under "tap rules" (at least here in North America).

Now that said; "internal non-replaceable fuses"? Doubtful. Sounds more like a "say what we have to in order to not have to do anything more" excuse. Got a brand name and model for the power supply?
 
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CanaanP

Member
The power supply is Mean Well DRT-240-24. This is the block diagram from the datasheet:
image002.jpg

The terminals for landing the line side wiring have been burnt up:
2019-06-21 11_00_39-Window.jpg
2019-06-21 11_01_11-Window.jpg

Regardless of the internal protection (or lack thereof), would the ground have to be sized to carry away the maximum deliverable current?

Thanks
 
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