Not sure what my sash weight is

A handy person from San Francisco says:
March 29, 2017
Hi Experts!

I'm pretty sure that my replacement window balance is the S350-28, however, I don't know what the weight of the sash is. My old window balance doesn't have any markings on it to check. Do you have any suggestions for where to start? I did try to lift the window up before without the balances and it was probably in the 20-40lbs range, but I'm not sure. Does that seem reasonable? It's a double pane window approx 23.5"x 47" total size of top and bottom.

Looking forward to your advice!

Irving
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Tom from SWISCO responded:
March 29, 2017
Thanks for posting! If your old balance has no stamp to use as reference, you'll need to remove the sash from the frame and place it on a scale to get the exact weight. I'm afraid that's the only course of action left. I do not recommend estimating the weight, since these are pretty delicate systems. You don't want the spring to be too weak or too strong.
A quick learner from California says:
March 29, 2017
Ok, thanks!
28" Series 350 Channel Balance
28" Series 350 Channel Balance
S350-28
$10.97
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