28-F-60 Channel Balance

Thanks for posting. Yes, this is very likely an S380-29 Channel Balance. The only other possibility would be the S385-29, which is very similar except the depth of the bottom nylon shoe is different. See the illustration below to see what I mean. Measure the depth of your old balance's shoe just to confirm what matches best.

Comparison of the S380 and S385 balance shoes.

As far as the stamp option goes, the stamp on your old balance leads me to believe you need a stamp of 2860, which would support a window sash in the weight range of 32 through 35 pounds. The stamp option 2865 will work with sashes that weigh 35 through 39 pounds. You always want the window sash to fall within the proscribed weight range of whatever stamp option you go with, so if you're uncertain, weigh the window sash to be safe. 

Finally, I'm afraid I don't recognize the plastic piece you show; could you show us where it installs onto the window? That might give us a clue as to what you need. Many thanks. 

Thanks for verifying! Based on the shoe size, I think our S380-29 is going to be your best bet. The fact that the shoe is a hair smaller than 1" is normal, since the nylon tends to wear down over time.

The 18-018 top sash guide is frequently compatible with the S380-29, but there are dozens and dozens of other guides that can say the same. There's no way to guarantee the top sash guide based on the balance alone. You will need to remove the other and compare it to the dimensions and design of our part to verify. If it differs, you can submit a few photos here for me to review.

Lastly, for weight, that's a tricky question. You're right to be concerned as you want the strength option to be as close to precise as you can mange. These can be sensitive systems.

In these cases I like to try to cut to the heart of the matter. has your 28-F-60 option been working fine for all these years without issue? If so, I personally don't see the harm in sticking with it. 36 pounds is a little off from the maximum range of this stamp, but if it's been fine for this long then I see no reason to change.

Alternatively, if you've always found this window to be a little difficult or stiff to open, then this may be the reason why. In that scenario, using the 2865 option instead might be beneficial.

Hopefully that insight helps you come to a decision. I'm happy to answer anything else you may need, just let me know.