trying to determine between 390 and 351

Question

I am trying to determine if I have the 390 or 351 type ballast.  The actual measurement of the shoe is 1-1/16".  Which one should I go with?  I assume the 15  4  marking means 15# 4 ounces for the spring.

Casey · Accepted Answer

Hello,

As long as the depth of the bottom shoe measures over 1", you should be able to use the S390-16 channel balance with a 1540 strength option since the bottom fitting can wear down a bit over time from rubbing on the window jamb. Thank you!