That seems a little low, for sure. What kind of BX cable was it? 2 conductor with a bare ground wire? What is the wire size? (no. 14 is pretty common--its 0.064" diameter, which is just about exactly 1/16" in diameter. Is the metal jacket aluminum or steel? If aluminum, its worth some money, too. I would expect a recovery in the 30% range. Is it a specialty BX that maybe has Ethernet cable or some kind of very small control cable? If that is the case your recovery would be very low.
Did you do a decent sample size? It depends on your scale--if it only reads to a 1/2 lb, you will need a big sample to get any accuracy. When I did samples like this, I used a scale good to 1/100lb (0.01lb) and used samples about 18" long.
Just to confirm the % recovery method:
(% copper recovery) = (wt. of bare copper wire from sample) divided by (total sample weight)
(% aluminum recovery) = (wt of bare aluminum jacket from sample) divided by (total sample weight)
(% insulation recovery) = (wt of insulation, paper, etc from sample) divided by (total sample weight)
The percentage of copper + aluminum + insulation should add up to 100%.
Another detail to consider is who you sell it to. A yard with a granulator that can separate aluminum from copper will eat this stuff up very easily and, in theory at least, should be paying you the best for your product. YMMV.
Hope this helps!
Jon.
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