Spring replacement

A contractor from PA says:
Hello. I need to replace the springs I found on some of the sashes I'm working on. These mount with a screw slightly above the meeting rail in the jamb.

I should be able to use a Series 400 spiral balance but don't know what length to order. The total jamb height is 46" while the height of the lower sash is 24". So total possible travel for the lower sash is 22". I'm guessing 22" would work?

Also, is the tube mounted to the top of the jamb with just one screw or is there something else that needs to be installed with it too? I've seen small metal blocks next to the tubes at the tops of other windows that have tube balances which is why I ask.

Finally, is there a morning bracket that you would recommend since this is a retrofit? Thank you!
User submitted a photo of window hardware.
A contractor from PA says:
Last line should be mounting bracket, not morning bracket.
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Paul from SWISCO responded:
For older wood sashes like this, I recommend our Series 500 spiral balance. This has a 5/8" diameter tube. I also recommend using it with our 17-012 bracket. This style has been used since the 40's by wood window manufacturers. You would simply screw the balance at the top of the window track screw the bracket on the bottom of the sash. To charge the balance, you can either use our 75-004 or 75-005.

I have a little trick I like to use to determine balance length for this kind of window. Measure the height of the glass and add 3" for the bottom sash or 1" for the top sash.
A contractor from PA says:
Thanks Paul. I'll have to see if the groove is at least 5/8" wide for the Series 500 (vs 400). Would there be any issues if I installed a 3/8" tube in a groove that's 5/8" wide? Or should the tube be snug inside the channel?

For your measuring trick, would I measure the distance of between the bottom of the lower piece of glass and the top of the upper piece of glass? These are 6-lite sashes so there is a muntin dividing the panes of glass. (Each piece of glass is 10" tall and and I think the muntin is about 1/2" wide when deducting the glazing rabbets where the glass sit.) 10+10+1/2+3 = 23 1/2" In this case is it better to round up or down?

Also, do you recommend mounting the bracket (17-012) to the bottom of the sash by mortising the bracket into the bottom rail of the sash?

Thanks again.
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Paul from SWISCO responded:
I have replaced the balance you show with our Series 500 in the past without having to cut or rout out the groove. As for length, yes I would round up to the next whole number. Based on your measurements, I would recommend 22" for the top sash and 24" for the bottom sash. I have not found it necessary to route out the bottom of the sash for the 17-012 bracket. I used a flat head screw to install it.
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