Paul from SWISCO responded:
September 26, 2017
I see you have the old discontinued Series 151 coil spring set up. It has since been replaced with our Series 150 coil balance system along with our 15-140 coil balance shoe. There is a number that will be stamped near the end of the cut out hook of the old springs to indicate the spring weight.If there are no numbers, you will have to weigh your window sash and divide it by 2 for each coil on each side.
|