Constant force coil is broken

A quick learner from Raleigh NC says:
Hi,

I have several windows in which the all constant force springs are broken. The windows are tilIt double glass about 30x28 inches and there only seems to be a single coil per side. Unfortunately I can't find any markings to indicate how many pounds the coil should balance.

Can you recommend coil spring replacements?

Thanks
Bill
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A quick learner from Raleigh NC says:
Follow-up info:
the window weighs about 17lbs and I think the coil has the number 8 stamped on it. So I'm thinking I need some 8lb coil spring replacements.
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Casey from SWISCO responded:

Hello,

Take a look at our 15-180 balance shoe, which holds the S190 balance shoe. I agree that one S190-840 coil on each side of the window would support the weight of your sash. Thanks for posting! 

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