Series 751 Channel Balance Option

A contractor from Albany, NY says:
Hi,
I have to replace the channel balances in a 30 year old,double-hung window with wood sash and double glazing. There is no manufacturer name on the window.

The balance are ribbed type with a shoe that looks like your 15-014 shoe. The only mark on the balance is "20" stamped on the face of the rib.

The metal part of the balance measures 21 1/8" long. Each sash weighs 17 1/2 pounds. Should I order the 21" Series 751? Also, please tell me which option I shoud order.

Thanks,
SBell
A customer submitted photo of channel balance attachments.
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Paul from SWISCO responded:
Thanks for contacting us! I agree, I think that our S751-21 channel balance is a good match to your own hardware. You may also want to look at our 19-029 short S-clip. However, I can't really say what option you need. If at all possible, please take our your window sash and place it on a scale to weigh it. Any common bathroom scale will do. Once you have its weight, let me know, and I can recommend the most appropriate channel balance.
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Paul from SWISCO responded:
Thanks for getting back to us. I think you should go with the 20HD stamp option. This can carry a window sash weight of 17 through, and including, 20 pounds.

Please keep in mind that the weight range information is based on 2 balances per sash. Balances are designed assuming friction in the jamb weather-strip will carry a portion of the sash weight. Suggested sash weights are approximate.
A contractor from Albany, NY says:
Hi Paul,

Each sash weighs 17 1/2 pounds. Please tell me which option I should order in the S751 21" ribbed type channel for a tilt window.

Thanks,
SBell
How to install a ribbed tilt channel balance with knife lock shoe
How to install a ribbed tilt channel balance with knife lock shoe
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