Key Takeaways
- Modern oil-based sealants differ from older polymer formulas: Unlike problematic polymer sealants that react with moisture and cause blockages, newer oil-based products like AC Smart Seal remain inert and non-reactive
- Proper diagnosis must come first: Always perform thorough leak detection with electronic detectors and soap verification before considering any sealant application
- Sealants work for specific scenarios only: Best suited for small, unrepairable leaks in aging evaporators with formicary corrosion where traditional repair isn’t cost-effective
- Real-world testing shows success: Four years of field testing across 10-15 applications resulted in zero compressor failures or metering device blockages when used correctly
Confession
I have a confession to make. Yes, I use internal HVAC sealants.
I guess you’re going to have to keep reading to understand why.
Internal sealants in the HVAC/R industry have been given a bad rap, rightfully so, as the older polymer-based sealants would react to moisture and air and be the cause of potential system blockages.
There were also technicians that would ignore the process of a proper leak detection procedure and add a can of sealant without much of a diagnosis. This actually still happens quite often, but I’m here to help with a little education.
Service call on a frozen coil:
The Right Approach
Before we get into using a leak sealant product, we need to understand a few things first:
- Is there a leak?
- Where is the leak?
- Is it repairable in a cost-effective way?
If a technician first discovers the system is short of refrigerant, adding leak sealant and walking away is not acceptable.
The technician should perform a leak inspection. My suggestion is with an electronic leak detector and then with soap to verify its presence. Most leak detectors can pick up a very low leak rate, so in some cases, bubbles may not appear.
In the right circumstance, dye can be used. As I stated, in the right circumstance it is actually very effective, especially in thicker evaporator coils that contain 5 rows or more. Understanding how refrigerant works in your system helps explain why even small leaks can significantly impact performance.
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Product Testing
This is where I’m going to be biased, only because I have tested this product in many different applications, ranging from walk-in boxes to reach-ins to a Liebert unit inside of a small data center.
December of 2017 was the first time I used AC Smart Seal.
Since then, I’ve used it 10-15 times. All units were well out of warranty and had leaking evaporators.
I can report that not one system has had a failed compressor or blocked metering device.
The simple reason is that the product is an oil-based formula, not polymer-based.
Furthermore, as per the manufacturer, it doesn’t react to air or moisture. In fact, it’s inert and non-reactive.
It acts mechanically – as refrigerant is forced from the leak site, the oil-based sealant is dragged along with it, for lack of a better phrase, and the elastic molecules begin to aggregate, creating a seal. This is particularly important in systems with bi-flow TXVs where maintaining proper refrigerant flow is critical.
Does it work in every situation? No!
The leak needs to be small enough for it to work.
If you notice a large leak on a braze joint, repair it.
If you’re dealing with a seasonal mystery leak or find a corroded evaporator coil contributing to your problem, an internal leak sealant could be a candidate.
It will give you a runway of operation until a more suited repair can be made or scheduled, depending on the nature of the application.
Listen to an old-school episode of the HVAC Know It All Podcast discussing internal sealants:
Case Study
Early in 2021, I found a frozen evaporator coil on a Liebert unit.
I allowed it to thaw and determined the system was short on refrigerant charge – we had a leak.
The system had dye previously added many years prior, and my leak detector was sensing a leak in and around the evaporator.
Due to the size of the coil and the location of the leak, soap wasn’t going to work to pinpoint the location.
I used a black light and discovered a very small leak. Again, due to location, not exactly fixable in a cost-effective way.
Because of the age of the machine, I talked about replacement with the customer, but in the meantime, they were on board with trying out a sealant.
I educated the customer on my past experience with AC Smart Seal, and they had nothing to lose at this point. This type of proactive approach aligns with strategic maintenance scheduling that can prevent emergency situations.
Diagnosis to determine the system was low on refrigerant charge
Addition of AC Smart Seal
System operation after the addition of refrigerant charge and TX valve adjustment
In Conclusion
The purists may not agree, but these tests that I have conducted over the last four years in various applications have revealed zero system failures and, in the above case, showed no detection of a refrigerant leak post-use of the sealant.
Verification of a leak and finding the leak are essential to the process, and education of and testing the product is a must.
Next, the application must fit. In this case, a very small “unrepairable” type leak was the perfect candidate.
While internal sealants remain controversial in our industry, modern oil-based formulations have proven their value in specific applications. The key is proper diagnosis, customer education, and understanding when this solution is appropriate versus when traditional repairs or replacement are necessary. As with any tool in our arsenal, it’s not about whether to use it, but knowing when and how to use it effectively.
