Replacement of Broken Constant Balance Springs

A quick learner from Chesterfield, VA says:
October 18, 2016
I have a double hung window with a broken coil spring. There are two springs on each side of the sash. Springs fit into 1 1/4" pockets and attach directly to the back locking shoes. The bottom coil in the picture has a cutout 1 5/8" from the end and is marked 5.5# 35". The other coil only has a 3 stamped on it and the cutout on it is only back 1/2" from the end. The window is 31" high and weighs about 18#'s. The width of the coils is 1/2". I was wondering if I could use a Universal 1 1/4" pocket size coil 96BU1 and 96BU3 (9#'s), but the catalog doesn't show their length. Thanks!
User submitted photos of a window balance.
Profile picture of Tom
Tom from SWISCO responded:
October 21, 2016
Thanks for posting. I don't recognize the universal coil number you gave us, but I based on your information and pictures I'd recommend our Series 160 coil spring. This matches your style and is 1/2" thick.

One thing I'm not sure about is which option is best. Your stamp of 5.5 indicates our S160-5, which can carry 5.5 pounds per spring. That means four of these together (two on each side) can carry 22 pounds. However you mention that your sash is 18 pounds, which makes me think our S160-4 would be better. This can carry 4.5 pounds per spring. I would double check the exact weight of your sash just to confirm.
4.5 lbs Series 160 Coil Balance
4.5 lbs Series 160 Coil Balance
S160-04
$4.50
5.5 lbs Series 160 Coil Balance
5.5 lbs Series 160 Coil Balance
S160-05
$4.63
How to replace a window coil balance
How to replace a window coil balance
VIDEO
WATCH >
How to Replace a Triple Coil Balance System
How to Replace a Triple Coil Balance System
VIDEO
WATCH >
Removing a Triple Coil Window Balance
Removing a Triple Coil Window Balance
GUIDE
READ >
Reply to Thread
Use this form to ask a follow-up question or to share your experience regarding this subject.
(your email address will be kept private and is only used to inform you when a response has been made)
Current wait time is 3-4 business days
We promise that one of our experts will personally get back to you as soon as they are able. Thank you very much for your patience and understanding. If your inquiry is time-sensitive, please feel free to reach us at (888) 991-1929 or at help@swisco.com.