Window sash springs

Hello! Thanks for reaching out to us. I'm afraid that it's not possible to identify replacement balances without seeing the originals as a reference. All I can say for sure is that these are non-tilt window channel balances, based on the window design, but that's it. There are an absolute ton of different varieties of this type, which you can see here, and they are not interchangeable. 

Is there an identical window in the house that still has its balances? If so, we can use that as a reference to make a recommendation. The video below will also clarify exactly what data we need, at minimum, to help.

Thanks! Is this window identical in terms of size and weight, as well? If so, this balance is a great reference. Based on what I see here, you have either our S380-26 or S385-26, depending on the depth of the bottom shoe. That's the only difference between them. I recommend measuring your shoe and referring to our dimensions to confirm the best match.

Comparison of the S378, S380 and S385 balance shoes.

Length is extremely important, yes, as is the calibration of the spring (indicated by the stamp). If either detail is off by even a little on your replacement balances, then they won't work. Worst case scenario, they could even damage the window. These have to be exact. You can't just put anything in there.

If the window you need to repair is missing its balances then that complicates matters. What I need is the height of the visible glass for the sash in question. Just the glass; don't measure the frame or anything. I don't need the overall size and knowing it won't be helpful. The visible glass height will allow me to determine the correct balance length. I also need the exact weight of the sash down to the ounce, so that I can determine its calibration.

Lastly, can you at least confirm that the window missing its balances is the same make as the one that still has them? 

Well, the window won't work if the balances aren't weighted properly. If they're too light, the window will drift down after you open it. If they're too strong, they'll be much harder to close and could even drift open on their own. Like I said before, you can't just put anything in there. These are very precise applications.

With a visible glass height of 20-1/8", you could reasonably use a 21" long balance. This isn't a guarantee but it's probably going to be the best estimate you can hope for. Your next step should be to verify the Series, as outlined in my response yesterday, and then get the weight of the sash. We have a chart on both the S380-21 and S380-21 store page that tells you how much weight each option supports. All you need to do is weigh the sash and refer to that chart.

This is of course only assuming that the window that's missing its balances is identical to the one that still has them, other than size. That's what I'm basing this entire process off of. If it's a different make entirely then there's a strong chance that the Series 380 and Series 385 are both totally wrong. 

No, there's no need to weigh the window that still has balances. The only reference that window gives us is for the Series. To be honest, that's the only clue we have as to the Series. 

With a weight of 18 pounds, 10 oz, you can use the 2040 stamp option for an S380-21 balance. This stamp carries 15 through 23 pounds so it should be perfectly sufficient.

That would be my recommendation, but please understand that it is only an educated guess. There is no guarantee that it will work, but I think we've done enough homework to lend it a high degree of confidence. If you wanted peace of mind, you can see our return policy here.

Thanks for clarifying about the shoe. It sounds to me like it just wore down a little from frequent use. It happens all the time. It was almost certainly the 1-3/32" size originally, so that'd be our Series 385, not the Series 380 as I originally surmised.

To recap, we're looking at the S385-21 with a 2040 stamp for the missing balances, and then the S385-26 with a 2520 stamp for the balances you still have.

Sounds good! I was happy to help, of course. Feel free to reach out if you had any other questions or concerns.