3040 window sash balances

Question

Need 2 replacement sash balances for a 3040 single-hung metal window.
markings are : 3040P
length of metal only: 31 inches
strings are broken and springs are missing?

Casey · Accepted Answer

Hello,

It looks like you have either our S351-31, with a 15-002 bottom attachment, or S390-31, with a 15-001 bottom attachment. Take a look at the image below to determine which balance you'll need. Note that the bottom fitting of the balance shown in your photos is broken, so you'll need to find an intact balance from the other side or an identical window to measure. You'll also need a 3040 spring strength option for your replacement balances. Thank you!

Comparison of the S351 and S390 balance shoes.