Casey from SWISCO responded:
November 9, 2010
You should check the balance you are replacing for any markings numbers and/or letters. The stamp options refer to different strengths.
15" Series 770 with stamp option 15B will carry a window sash weight range of 7 through 10 pounds 15C will carry 10 through 16 pounds 15D will carry 16 through 19 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. |