window channel replacement

Thanks for writing in. Confirm that the upper sash is the same size as the lower sash, just to make sure that you can use the same-sized balances. You'll need to remove the balances from the upper sash and confirm a few things. We need to know the length of the metal channels, not including the nylon fittings at either end. We also need a picture of the top nylon fitting. From there, we'll try and narrow down what you need. Many thanks.

Hey there, hopefully I can help. Knowing the size of your den sash, in relation to the balance, is definitely helpful, but I don't want to bet on that just yet. There is another way to determine the length of this kind of balance that I personally find more reliable.

What you want to do is measure the visible height of the glass for the sash the missing balances supported and then add 1. That's more or less how window manufacturers do it. For example, if you measured the visible glass for your den window sash, I think you'd find that it's 24". 

Then again, this method is mostly used for vinyl windows, not wood windows. Truth be told, it's not common to see your kind of balance on a wood window. The installers may have used another method but let's test out mine first and see what you get.

Assuming I'm right, you just add 1" to the visible glass to get the length you need. Then you'd pick either our Series 390 or Series 351, depending on the depth of your bottom nylon shoe. I can't tell which from your photos but it's definitely one of these. Finally, you'll have to get the exact weight of the sash to determine the proper spring calibration.

Awesome! In that case, I would go with our S390-16 with a 1550 stamp option. I think that's your best bet for this window.