sash balance replacement

A home owner from Charlotte says:
I have non tilt double sash wood windows that are in good shape, albeit 30 yrs old. I need to replace the old balance springs but thought a spiral balance replacement would do the trick. Both upper and lower sash have an overall length of 38 inches and weigh about 21 lbs. The groove in the side of the sash is 5/8". In looking at your site, I thought the Series 500 with a foot bracket might work. Could you suggest an appropriate spiral balance length. I figure the lower sash balance would need to be maximum length, the upper could be shorter?

Thanks for assist,


Am I on the right track
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Tom from SWISCO responded:
Thanks for posting, Jack. Did you have spiral balances installed originally? If not, please double check to make sure you have enough room to install one. If so, our Series 500 is a good choice. It has been used on wood windows for decades.

As for the length, please give me the width and height of the visible glass on each sash you are looking to replace. Knowing the size of the visible glass will help us determine what length you need. Please also give me the weight of each sash so that we can recommend the appropriate tip color.
A home owner from charlotte, nc says:
1st window glass dimensions:L33 3/4"by W27 5/8,approx wt 28 lbs.

2nd window: L30 3/4 by W27 5/8, approx wt 25lbs.
These wts are based on a calculated method found on a website. Maybe you have a method based on dimensions and double pane glass.

The window has a tube spring currently.
User submitted photos of window hardware.
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Paul from SWISCO responded:
Hey, Jack. Thanks for your patience in this matter. For a glass height of 27-5/8", I recommend our use S500-29 for the top sash and S500-31 for the bottom sash. For sashes up to 30 pounds, use the red tip. You will also need our 17-012 bottom balance brackets to attach to the sash and a charging tool like our 75-004 or 75-005. Let me know if you have any other questions!
A quick learner from Charlotte says:
There are two different sized windows:

Window 1: height of glass 33 3/4, width 27 5/8 (both upper and lower sash.

Window 2: height of glass 30 3/4, width 27 5/8 (both upper and lower sash.

Please recommend based on these dimensions.


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Paul from SWISCO responded:
Thanks! For Window 1, I recommend a 35" long balance and for Window 2, I recommend a 32" long balance.
A home owner from charlotte says:
Hopefully, last time. Each of window #1 and #2 have an upper and lower sash of the same dimension. Could you spec the the balances for each window for both lower and upper. I expect the upper sash balance would be shorter than that for the lower sash balance.

Thanks again
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Paul from SWISCO responded:
Sure!, for Window 1, the top sash will take a 35" long balance and the bottom sash will take a 37" long balance. For Window 2, the top sash will be 32" long and the bottom will be 34" long.
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