Need replacement spiral balance rod

A home owner from Princeton NJ says:
Hi,

We have these two double sash wooden windows as seen in the first photo. The two lower sashes (the only ones we're concerned with) each use 2 spiral balance rods, which have become defective. We'd like to replace them but need to get new spiral balance rods.

The lower sashes are 32"W x 27 3/4"H. and the full height of the window is 54".

The remaining photos show 1) a removed spiral balance rod, 2) a close-up of the top of the rod, 3) a close-up of the bottom of the rod and bracket, and 4) a view of a rod properly attached at the top.

The tube is 27" long and 9/16" in diameter. I don't see any colored tip. The bracket is 2 1/2" long and 3/8" wide.

What do you recommend as a replacement spiral balance rod and related hardware for these windows?

Thanks very much.
Dennis
User submitted photos of a window balance.
Profile picture of Paul
Paul from SWISCO responded:
Thanks for posting, Dennis. I recognize this balance. It's a very old type not used anymore. I believe that our Series 500 spiral balance can be used as a replacement, in addition to our 17-012 bracket. This setup has been used in wood windows since the 40's. Check out these suggestions and let me know what you think.
A home owner from Princeton NJ says:
Thanks Paul. I had a feeling you would recommend the Series 500, but wanted to wait until you replied before ordering.

BTW, I ordered the red tip because I was not sure of the sash weight and assumed that a 32" x 27 3/4" sash should weigh between 7 and 29 lbs.

Does that seem like a reasonable assumption?

Thanks,
Dennis

Profile picture of Paul
Paul from SWISCO responded:
It's hard to say for sure. The Red Tip is usually a safe bet for these old windows, but there's no saying if yours is heavier than normal. You may want to put a scale on the sill and gently lower the sash on it to get a ballpark. It's not ideal, of course, but it'll at least give you a better idea.
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