Casey from SWISCO responded:
June 2, 2011
If you are sure you have the Series 770 channel balance you would need the S770-30 with the option 30C.
If you want to double check that you have the right replacement balance series picked out... send us photos of both the top and bottom of your existing balance. We will take a look at your pictures and try to confirm which balance series you need. |
Casey from SWISCO responded:
May 29, 2012
Thanks for posting! The stamp located on your channel balance indicates its strength; or, how much weight it can support. Keep in mind, however, that the stamp options for each balance differ depending on what Series balance you have, as well as its length.
For the S770-30, a 30B will carry a window sash weight range of 13 through and including 19 pounds; an option of 30C will carry 19 through and including 24 pounds; and finally 30D will carry 24 through and including 29 pounds. This information is based on 2 balances per sash. Balances are designed assuming friction in the jamb weather-strip will carry a portion of the sash weight. Suggested sash weights are approximate |