S380-30 correct tension?

A handy person from Dade City, Fl USA says:
I recently purchase a window balances from your company, order #345697.

The shape and size are identical to what I need, yet the amount of tension is not sufficient for our window. In order #345697 I chose option 2910. The window balance I need is 2906, which is stamped on the balance that came with the window. To possibly help identify the balance that I need to order there are two other markings on the orginal balance that might help, which are 1. DL 2. BS1.

I did not include a picture because the balance I need is identical in shape and size to the one I ordered. Only difference appears to be the spring tension.

Please advise. Many thanks, LeRoy
Profile picture of Paul
Paul from SWISCO responded:
Thanks for posting. I'm sorry to hear that the balances didn't work for you. Could you give me the weight of your sash? That would help us find the best option for you.
A quick learner from Dade City, Fl USA says:
Paul - the weight of the sash is 37 lbs.

Please advise. Many thanks, LeRoy
Profile picture of Paul
Paul from SWISCO responded:
Thank you. Please take a look at our S380-30 with a 2965 stamp option. A balance pair with this stamp can carry a window sash weight range of 35 through and including 39 pounds.

This 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.
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 4-7 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 856-317-6263 or at help@swisco.com.