"No Need to Derate" What does it really mean?

Re: "No Need to Derate" What does it really mean?

Found the phrase "No Need to Derate" listed for a MorningStar PWM controller on one vendor's site... And seems to be a phrase from MorningStar themselves:

http://www.google.com/search?q="No+Need+to+Derate"+site:www.morningstarcorp.com

I would guess this gets back to some definitions of how NEC rates electrical circuits and solar power systems...

Normally, you can only run a wire/circuit breaker at 80% of rated capacity.

• 15 amp circuit * 0.8 = 12 amp maximum
• 20 amp circuit * 0.8 = 16 amp maximum

etc...

Also, NEC calls for "double derating" of solar panels (i.e, 0.8 * 0.8 maximum load or take the maximum Isc*1.25*1.25=1.56x; and the controller must be rated 1.56x larger than the solar array itself).

A bit of this comes from the fact that many solar products are not UL approved and the NEC is trying to fix problems by adding more "derating factors" to hardware.

NEC, from my point of view, should not be requiring deratings on solar equipment--that is the job of the manufacturer to design the product to work at "rated" loads. And, if UL approved, the controller should have been reviewed/tested/qualified by UL/NRTL's to operate at the name plate rating.

You can see if everyone keeps adding their own derating factors--you end up needing to get a ~60% large controller. And it makes the vendor's ratings sort of redeculous (i.e., the 30 amp solar charge controller can only be operated at 19.2 amps.

I would not call it a pitch--Hopefully, it is an accurate representation of the capabilities of the equipment being sold (yea--probably a bit much to hope for that).

-Bill