I have a 25 inch long balance.

I agree, our Series 770 looks like a good base for this, other than the clip. What we can do is make this balance for you but with a 62-105 hook at the end of the cord to match your original, though this would have to be a custom order. Does that interest you?

If so, please tell me the stamp printed on the metal channel and how many balances in total you were interested in buying. I can then email you a purchase link and price quote that will let you add these custom parts to your cart.

Well, your old stamp of 2440 tells me that the old balances were designed to hold 22 through 25 pound loads. If your sash is 24 pounds then that is right on the money, so spring strength isn't the issue.

Odds are the problem was just with age. Balances have a lifespan of around 10-15 years, depending on frequency of use.

I'm happy to email you a price quote, but I will still need quantity. Our Series 770 uses a different rating system than your original, so it will have the 25D stamp on it, not 2440. The weight it can hold is the same, so don't worry about that, it's just a different stamp.

Sure, so that'd be 4 balances altogether. I'll email that purchase link to you right now.

Please let me know if I can be of any further assistance.

I'm sorry to hear that you're having trouble. That definitely sounds like you're having an issue with spring strength.

As mentioned before, the balance we sold you is calibrated to hold 22 through 25 pounds. Based on your description of the problem, it sounds like this is way too strong. Can you triple check the weight of the sash to ensure that it's 24 pounds? 

That's pretty odd, then. Let's try to narrow it down a little further. When you go to close the window, is it difficult to close the minute you apply pressure, or does it close normally at first but then hang up on the last few inches?

I've been discussing this issue with my senior colleague, and based on the issue described and the data given, the only conclusion that we can draw is that the spring isn't strong enough to carry the weight of the sash. That shouldn't be possible, though, since these have the 25D calibration. 

Did you have this issue with the other two balances that you purchased, or are they working fine? Can you also confirm that all four balances have the 25D stamp option? 

Right now what I want to do is send you new balances to make up for the clearly defective hardware, but I just want to be sure that whatever we send you is going to work. The last thing I want to do is send you a new batch that have the same exact problem. I just don't know what that problem is at this stage. Based on everything you've told me so far, there's no reason why these shouldn't be working.

The 25D stamp is rated to hold precisely 22 through 25 pounds; this rating is based on two balances per sash, so you don't double it. To put it another way, two 25D balances do not support 50 pounds. They strictly support 22 through 25. Balances are always meant to work in pairs and the listed support strengths reflect this.

I'm afraid at this point we are at a loss. Based on all the data given, there is no reason why these balances shouldn't be working for you. I agree that the issue seems like a problem with spring strength, but you tested the gauge of the spring yourself. These balances should be a perfect fit for your sash weight. The only logical conclusion that I can draw given the information at hand is that your sash is much lighter than 24 pounds. That is where all the math is pointing right now.

The only recommendation I can give you is to return the balances you purchased from us for a refund. You can see our return policy here. After that, you have two potential options:

1. You can opt for the 26C stamp balance, which is weaker than the 25D. Note, however, that these are only rated to carry 17 through 22 pounds (as a pair). Assuming that the 25D is too strong then the weaker spring would be the way to go. Just note that that support strength is much lighter than the sash weight given.
2.  You could consider contacting the original manufacturer of the window for assistance. It is possible that this window requires special allowances that we are not aware of.

I am sorry that we cannot offer another solution to this. 

You do, I'm afraid. Like I mentioned in my last post, two 25D balances only support 22 through 25 pounds. They do not support 50 pounds. It's important to understand that a balance rated for 50 pounds would have an extraordinarily powerful spring. These are pretty uncommon and have to be custom built from scratch on a case-by-case basis. This isn't something that the manufacturer would accidentally put in the wrong balance or anything.

All channel balances are calibrated as a pair. These are not springs that are meant to work on an individual basis, and you do not add their tension together.

I will reiterate to get to the heart of the matter: if your sash is 24 pounds, then the 25D stamp should work without issue. If it doesn't, then the only conclusion I can draw is that your sash is not 24 pounds.