Jim,

I had always heard it as 'lower than 60 degrees for the previous 24 hours'.

That would mean it could have been 60 or above during the previous day and it would still be okay to turn it on.

Was that old way of saying it correct, or is it 'if it is *now* less than 60 degrees, do not operate it (unless, of course, it is a heat pump).

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Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )