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Anonymous Poster

DDC Controller Power

11/15/2007 5:07 PM

Some DDC controllers that use 24 VAC power publish a "Class II" rating which states that the transformer providing power cannot exceed 100 VA. Where can I find these guidelines? I think this is a UL rating. I've tried to google this but can't find it. I'm trying to understand why some controllers can be powered by over 100 VA and some cannot.

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hastingselectric
Power-User

Join Date: Oct 2007
Location: Hartwell Georgia N34* 56.770 / W83* 35.431
Posts: 222
Good Answers: 1
#1

Re: DDC Controller Power

11/17/2007 7:55 AM

The National Electrical Code Article 500, Hazardous (Classified) Locations, Classes I,II, and III, Division 1 and 2 covers this as far as installations go. It provides a FPN,(fine print note at the beginning of the article), which references NFPA 497 (National Fire Protection Association) and NFPA 499.

These references should help you find the answer you are looking for.

Good luck, James

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