Swisco 770 - 27C match up question

Question

Hello. I purchased 4 of your model 770 27C channel balances. They are not exactly the same as the broken ones I have. I chose the 27" length based on the measured length of my old ones. Note in the pics that the old ones are labeled "26C" but are in fact, 27" long. You will also note in the pics that the spring is anchored in a different location. I do not know who manufactured my windows as there are no identification marking anywhere to be found. I've installed two of the units I bought from you. I think the springs are a little bit too tight. When I unlock the window, it starts to slide up on its own. I can live with that if it is not going to cause premature wear or breakage. Did I order the wrong length? What is the standard mounting height in the window frame? Mine are anchored near the top.

Bob · Accepted Answer

Thanks for writing in. If your original balances were 27" long, then the S770-27 was absolutely the right length--that's first and foremost. Don't worry about the position of the spring inside the metal channel; this doesn't matter. It all comes down to the stamp option. Some older versions of the Series 770 use a different rating system for stamp options than what we use, which seems to be the issue here. A stamp option of 27C supports a sash in the weight range of 17 through 22 pounds. It sounds like this is too strong for your window, which is why the sash keeps drifting upward. The balances will indeed break faster because they're under greater tension, so it's in your best interest to get balances with the right stamp option.

For the S770-27, a stamp option of 27B supports a sash in the weight range of 11 through 17 pounds. I would obtain the exact weight of your window sash to see if it falls in this range instead.