Replacement Channel Balances

A handy person from Wonder Lake , IL says:
My typical double hung window channel balances are stamped labeled 28HDB, for the lower unit, and 28HD for the upper unit. The upper unit balance being 1" shorter than the lower balance so that the channel length does not interfere with the window lug before completely closing. The 28HDB length is 30". Since we usually operate the lower units only, the upper unit balances are in good working order.

Currently, I will only need 10 of the complete 28HDB balances including the knife lock shoe. The lower window unit wieghs 18 lbs. With all of my description in mind, which balance would I require?

Oh, and by the way, I wish to congratulate you on a website that has the most ease of navigation which allows for locating product data very quickly. I have had a tough time with other outlets. Yours, well, I just wanted to say thanks. I have bookmarked your site and will be revisiting it in the future.

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Tom from SWISCO responded:
Thank you! I'm very happy our website has been helpful for you. We are of course always happy to be as helpful as possible. Hopefully, I can help you now, as well.

To start with, I see you were looking at our S751-28, but you mention that your length is 30". Can you confirm? Make sure you're only measuring the metal channel.

You can also ignore the "B" portion of your stamp. I believe that's just a manufacturer mark, likely to indicate that it's for the bottom sash. I'm confident recommending our 28HD stamp, but if you wanted to be 100% sure you can weigh your sash on a scale.
A quick learner from Wonder Lake, IL says:
I am absolutely positive regarding the 30" length. These at Norco window units. I actually read a previous post from another customer that had the same windows and he also had a difference in total length of his existing balances as compared to your balance lengths. I don't believe it will make that much difference, I hope. And, as I stated in the previous post, the weight of my window unit is 18 pounds. If your are certain that the S751-28 will suffice, then I will go ahead and order that.

Please respond.

Thank you.
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Tom from SWISCO responded:
Hmm... this is not a typical situation. If your stamp reads "28," then the length of the metal channel should be 29" long. I don't know why the manufacturer would mark them "28HD" on a 30" long balance. However, if you're certain they are 30" long, and if your sash weight is 18 pounds, I would recommend the 29R stamp.
A quick learner from Wonder Lake, IL says:
There was an option shown on the website for the 30" balance. The option was the 29HD and that is what I shall order.

Also, I want to know if Swisco carries vinyl jamb liners. I need to replace one where the balance knife ripped through it.

Thank you for your assistance.
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Dave Sr. from SWISCO responded:
I'm afraid we do not sell jamb liners, but a local mill work may be able to help you.
How to install a ribbed tilt channel balance with knife lock shoe
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