Reference manual

What would be the best reference manual to find the age or tonage of a piece of equipment from the serial # or model #. I had a link to one but I have no idea where it went. Do you always put the age of each appliance in your reports?

Prestons Guide

I gave my Prestons away and use the Carson Dunlop Technical Guide

I know nothing about the Carrier Blue Book but understand it is available on Disk for considerable less money .

Roy Cooke

look in the model # for #'s divisible by 6 and 12.
this will often tell you the tonnage.

for example, if you find a 24 in the model #, it indicates a 2 ton, 36 for a 3 ton, 30 for a 2.5 ton, etc…

age is a whole nother can of worms.
preston’s is decent, but it’s not always helpful to me.
i find myself contacting the manufacturer once in a while.