Need help choosing the right coil springs

Handy Person from Kerhonkson, NY

Jun 19, 2025 5:25 pm

Hi,
I took out the parts from my window, and they have patent number 5.353.548 on them, which I saw on another post are your parts 15-086 and 15-087. The markings on the springs are:
4 38W
7 30W
The windows itself weighs 21 pounds.
Can you help me with what springs I need? I've attached pictures.
Thank you,
Ralph

3 user uploaded images

4 Replies

Bob from SWISCO

Jun 19, 2025 9:36 pm

Thanks for posting. Yes, this looks like a 15-087 Pivot Shoe and 15-086 Tandem Housing. These parts work with Series 180 Coil Balance springs. A spring stamped '4' can be replaced with the S180-04 4 pound spring. A spring stamped '7' can be replaced with the S180-07 7 pound spring. Let me know if you have further questions.

Series 180 coil balance diagram

Handy Person from Kerhonkson, NY

Jun 20, 2025 6:36 pm

Hi, Thanks for getting back to me. I was confused because the guidance says the springs should total up to the weight of the windows, which is about 21 1/2 pounds. 4 plus 7 is only 11, so I assume its the total of the springs on both sides that should equal the weight of the window, which makes more sense.

Bob from SWISCO

Jun 20, 2025 11:57 pm

Yes, with coil springs you want the spring weights on one side of the sash to equal half the total weight of the sash, so that way the overall support comes out to the total weight. In this case, 11 pounds of support on each side comes to 22 pounds, which works just fine (you just have to be within 1 pound of the actual total weight). Let me know if you have further questions.