21 " channel balance

A home owner from Thousand Oaks, Ca. says:
Hi, we need a replacement for a 21" channel balance.

I don't know the brand, but stamped on the piece is 'a 21-3' (that's the only marking I can find)

The channel width is 1/2" (actual 9/16")

The other balance seems to be functioning adequately, but is probably 20 years old. Would you advise getting a pair and replacing both?

Okay, I hope I uploaded the photo correctly.

Thank you in advance for your help.
User submitted a photo of a window balance.
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Tom from SWISCO responded:
Hey, thanks for posting. I've narrowed this down to two possible channel balance Series: either our Series 380 or our Series 385 balances.

Now, as you can see, there is only one difference between these two Series, and that is their bottom shoe. The Series 380 uses the 15-005 while the Series 385 uses the 15-004. I can't quite tell what you have based on your pictures, though. Please carefully compare their dimensions to your own hardware and see which is a better match.
15-004 and 15-005
A home owner from Thousand Oaks, Ca. says:
Greetings Tom!
Thank you very much for getting back to me.
Okay, this is a bit tricky, but from the dimensions you're showing me, I'm pretty certain that it's the 15-004 that we require (Series 385) and from what I am reading on your website, I think it best if we order a new pair.
One thing I'm not certain about is the correct sash weight range. I'm speculating that the proper one would be #2030 (as I mentioned before, the only stamp I can find is 'a 21-3'
These are pretty heavy duty casement windows, so please advise whatever you feel would be best and then I'll place the order. Again, many thanks!!
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Paul from SWISCO responded:
Before ordering, I would double check the length of the metal channel. If you have a stamp of 21-3, you should have a channel length of 22".

The best way to determine what stamp you need is to weigh the sash and compare it to the option weight range chart listed under whichever balance you decide to go with.
A home owner from Thousand Oaks, Ca. says:
Hi Paul... thanks for getting back to me.
I'm glad you pointed out the correct length measurement of the metal channel.
I had accidentally measured it on the wrong side!
So thanks to you and your staff, hopefully we've selected the correct item.
I just placed the order so everything should work out well.
I like the way your system works...very nice website and customer service!
Best regards,
Mark N.
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Paul from SWISCO responded:
Great! Glad we caught that, too. If you need anything else, please feel free to ask.
A home owner from Thousand Oaks, Ca. says:
Hi again, Paul.
Okay, we received what appear to be the correct channel balances but it might just be that the ones I ordered have too heavy tension on the springs.
What occurred when we re-installed the window was that the clips in the balances got pulled down to the ROUND hole beneath the SQUARE one in the channel!
I'm not sure what to make of this other than that the tension is too much.
So anyway, I do believe we're doing the installation correctly but I surmise that we need balances with a lower tension.
Whatever input you can give me would be very helpful.
(We ordered the 2130 weight option)
Thank you in advance for your help.
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Paul from SWISCO responded:
Hmm... usually a stamp of 21-3 corresponds to our 2130 option, so I would have chosen the same thing. It's possible the spring strength was not correct in the first place. What is the weight of the window sash? That will let us know for sure whether it's a problem with spring strength or something else.
A home owner from Thousand Oaks, Ca. says:
Hi again, Paul, and thank you so much for getting back to me so soon.
(Incidentally, and I believe I mentioned this before, thanks to your note, we did switch to the 22" channel, which was the correct length)
Anyway, I just weighed the window, and as best I can tell on our bathroom scale, it's about 20 pounds or very close to that.
So I think we should order balances that you think will work for that weight.
Interestingly, I just noticed when I removed the sash that on of the new balances had broken a string. Do you think that means we were doing the installation incorrectly?
Sigh, as you can see, this is not my specialty!

So please let me know which ones to order and we'll try again.
No worries on the first pair, I don't want to bother shipping back and forth...I just want to fix this darn window!!
Thanks again...
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Paul from SWISCO responded:
Well, with a sash weight of 20 pounds, I'd recommend our 2140 option off the bat. Two balances with this weight can support a sash weight range of 15 through 23 pounds, which comfortably covers yours. However, this implies that the original balances were too weak, rather than too strong. Do you think that might have been the problem?

Make sure to watch the video below to see how to properly install a window channel balance.
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