Spring weight stamped as 4Y

A landlord from vermont says:
October 28, 2018
I believe that I will need the tandem set up using 15-087 and 15-086. The spring has a stamp of 4Y, is this a 4 lb spring?
When I install the the two coil housing, I assume that I hook them together and then pull the spring out and run one on top of the other up to the clip.
Thanks you.
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Paul from SWISCO responded:
November 6, 2018

You are correct in choosing the 15-086 coil housing and 15-087 coil housing pivot. You are also correct in needing a 4 lb. sash for your coil spring. For that, see our S180-4. You will run one spring over the other and hook both of them to the 16-024 clip. Review all the parts and let us know if you have any further questions.
4 lbs Series 180 Coil Balance
4 lbs Series 180 Coil Balance
S180-04
$4.20
Coil Housing Pivot
Coil Housing Pivot
15-087
$5.97
Mounting Bracket
Mounting Bracket
16-024
$0.66
Tandem Coil Housing
Tandem Coil Housing
15-086
$1.68
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