what number of coil need to puchase

Hello there!

We appreciate you reaching out to us. It looks like you have an older version of the 15-180 pivot shoe which uses the S190 coil springs. I recommend you check the band of the spring for a weight code. If there aren't any, get back to me with the exact weight of the sash and I can calculate what you need.

You will also want to replace the coil balances and pivot shoes on both sides of the window as you don't wanna mix and match new and old hardware. 

Sure so what you would want to do is remove the window sash and then place it on a scale. A common bathroom scale will suffice!

Thanks for getting back to me! I recommend using (1) S190-940 9-pound coil spring on each side of the window which will total 18 pounds of overall support. We also sell the 15-186 single spring support and the 15-182 balance bushing. 

Let me know if you have any questions!

Awesome! You're very welcome, of course. We really appreciate the business, it means a lot.

Feel free to reach out if you had any other questions.