SWISCO - The Replacement Hardware Authority

coil balance strength

A handy person from Santa Cruz CA says:
Hi Swisco,

I have a sash with S-180 coil balances. The coils on both sides have broken. They look like they were cleanly cut. The stamp on the coil end is "5Y". Does this mean a 5 pound coil? What does the "Y" mean? The sash measures 21.5" x 21". I believe it is single strength insulated glass.

Using your formula of 2.25 lbs per sq. ft., I get 7.05 lbs. That would mean at most a 4 pound sash on each side.

Could the coils have broken because they were oversized? The windows were made by LBL and were originally installed in 2004. They operated without problem for 10 years.

Do I need 4 or 5 pound coils.

Thanks,
-Eric
Profile picture of Paul
Paul from SWISCO responded:
Good morning, Eric! Thanks for contacting us. I'm actually not sure what the Y means, but I suspect it's some kind of mark that denotes manufacturer. I don't think it should have any bearing on the strength of the spring. The 5 is what's most important.

If you had S180-5 coil springs work without issue for 10 years, I personally think you should stick with that. If it ain't broke, as they say, don't fix it!
A handy person from Santa Cruz CA says:
Hi Dave,

Thanks for your response. I have a few follow up questions.

There are 13 other single hung tilt-in windows in the house. They all have the same style of coil balance, though all but one of the sashes is larger than the one with the failed balances. None of the other sashes have failed balances. I checked them all.

This brings up the following questions about the balances in this sash.

1. Why would this be the only sash with failed balances?
2. Why would both balances in this sash break, while all the others are fine?
3. Both coils snapped super-cleanly, as if they were cut with a straight edge? Is this a typical failure?
4. What's the typical lifespan of a coil?

If you have any insights into these questions, I'd appreciate hearing them. I'm still wondering if the 5lbs balances were oversized and might have contributed to pre-mature failure.

Thanks,

-Eric
Profile picture of Paul
Paul from SWISCO responded:
The typical lifespan of a balance is about 5 to 10 years, depending on how often the window is used. The way your balance broke, and the timing, is pretty normal. Are the other windows as old as this one? Are they also used as often? If so, then you may want to keep an eye out for any wear or future breakage. No reason to jump on it quite yet, but keep it in mind.
A handy person from Santa Cruz CA says:
Hi Paul,

Thanks for the thorough response.

All of the windows were installed in 2004. The sash in question is probably operated more often as it's in a bathroom.

In addition to the failed balances, I'd like to order some replacement balances for the other windows, since you believe they're nearing their life end as well.

All but one of the other sashes are bigger than this one. Do you think I should order based on your formula 2.25 lbs/sq ft or upsize them like the sash in question appears to be? (That is, it has 5lb balances where your formula calls for a 4 lb balance.)

Also, the jambs have no cut outs to remove the balances. Any thoughts on notching cutouts in the jambs underneath the stops?

Thanks,

-Eric
Profile picture of Paul
Paul from SWISCO responded:
The formula is helpful, but it's really more of a guideline. Your best bet would be to read the stamp printed on the coil springs or to simply weigh the sash on a scale. I find those two methods to be a little less complex! Once you get the sash weight, you can divide that number between the number of coils it uses. For example, if you have four springs in a sash and the sash weighs 24 pounds, you would use four 6 pound springs. If you were to look at the coils for the same example sash, you may see that they are each stamped with "6."

As for cutting in the jamb, you could consider our 75-069 jamb spreaders. See the video below for information on how they work.
If you don't want to go that route, then when cutting space for the pivot shoe you have to keep two things in mind:

-For the pivot shoe that goes to the bottom sash, cut a hole at the top of the jamb.
-For the pivot shoe that goes to the top sash, cut a hole at the bottom of the jamb.

This will ensure that the pivot shoe does not fall through the hole during the window's normal operation.
Reply to Thread
Use this form to ask a follow-up question or to share your experience regarding this subject.
(your email address will be kept private and is only used to inform you when a response has been made)