Which coil do i get?

Hey Mikey. Yes, these do look like Series 190 Coil Balances, which connect with the 15-180 Pivot Shoe. To know what spring weights you need, please give me the exact weight of the window sash. I can then work out what weights you require.

Thanks, Mikey. That's actually pretty huge for this kind of window. The absolute strongest spring we can sell for this is our S190-940, which only carries 9 pounds per spring. Since you can only have two per side at the absolute maximum, that's only 36 pounds of support, which is too weak.

You may want to double check the weight. If it is exactly 40 pounds, then I'm afraid we cannot offer you a spring that can support its weight.

This type of balance is not designed to use two springs. There are only two screw holes on the shoe for them to install, and the clip (15-181) can only hold two. There wold be nowhere for a third spring to go.

If your balance assembly does have three springs per side then someone messed up somewhere. It's possible the original installers just kind of shoved whatever they had on hand in the window and hoped it would work. It happens all the time, to my frustration. That also doesn't change the fact that this is not how these balances are supposed to work. It's ultimately up to you but I would not advise using three springs per side.