window coil balances

A home owner from Lexington, Kentucky says:
March 14, 2016
I need two coil blances probably of 152 series. No weight written on the spring except an F.

The marking F could be a 7 on the reverse side. Based on the color (brownish) I think it was a 152-7.

My window lower sash weight is 14.5-15 lbs. Should I use coil balance 152-7 or 152-8?

The old 152-7 were broken. So I am thinking to use 152-8 which may be stronger and still in the upper range. Usually you recommend rounding up after sash weight is divided by 2 so 152-8 would be the correct part based on that calculation.

What are the part numbers for the upper support for 152-7 or 152-8?

Thanks a lot.
User submitted photos of a window balance.
Profile picture of Paul
Paul from SWISCO responded:
March 16, 2016
For a 14.5-15 pound sash, I would recommend our S152-8.
8 lb Series 152 Coil Balance
8 lb Series 152 Coil Balance
S152-8
$4.90
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