Water in Your System?

Author:  Chris Savage

Water in Your System?

Do you have water in your ammonia refrigeration system?  How would you know if you have water in your system?  How would water get in your system?  Why does it matter if you have water in your system?  What do you do about water in your system?

Have you ever been asked any of these questions about your system or asked yourself any of these questions?  It doesn’t come up very often but it is certainly something you should be aware of as the operator or someone responsible for the performance of an ammonia refrigeration system.  After all, water in your system affects both system performance and efficiency.

If you have any of these questions the first thing that we at Carlson & Stewart Refrigeration would do is point you at the IIAR Bulletin No. 108 – Water Contamination in Ammonia Refrigeration Systems.  This is a great source of information and can provide much more detail than I can in this brief blog.

Let’s see what we can do to give you some quick insight and maybe encourage you to dig a little deeper into your system to make sure water isn’t an issue for you.

First of all, why does it matter if you have water in your system?  It matters because it negatively affects system efficiency, how much it costs to operate a given system at a given capacity.  As the concentration of water increases, the saturation point increases.  At 10% water by volume, the saturation point increases by about 3°F at most pressures.  As the concentration increases the saturation point increases at a faster rate.  This increase in saturation pressure means that you will need to lower your system pressure to maintain system capacity.  IIAR Bulletin 108 tells us that for every 1°F that system pressure is lowered reduces high stage compressor capacity by 2.5% and booster capacity by 3%.  Which means that you are going to need to run more compressor(s) to get the same capacity. 

Performance is also affected by the changing saturation point.  An evaporator that has a rated capacity based on a 10°F temperature difference will lose 10% of its capacity for every degree that saturation point increases.

So how would you know if you have water in your system?  This is a really good question.  There are a couple of ways to go about it.  First of all you can look for physical signs that might indicate you have water.

  • Are you seeing any internal corrosion?  When you open up your compressor for inspection do you see any rust/corrosion. 
  • When you drain oil, do you see any water?  This is not always easy to see but if you let your drained oil sit for a bit, the water and oil will separate.

You might also become aware of degrading performance in different evaporators within the system that you can’t otherwise explain.  This may be a difficult one because it will be a gradual degradation over an extended period of time.

And, of course, you can always test your ammonia for water.  Did you know that?  It is actually not that difficult of a test but it does require removal of a small sample of liquid ammonia from the system.  So you do need to know what you are doing to make sure that you and everyone around you is safe during the process.  If this is something that makes you a little nervous, not a problem.  Carlson & Stewart would be happy to help.  This simple test can also give you an idea of how much (percentage by volume) water is in your system. 

Well, that is probably enough for today.  Hopefully we’ve given you something to think about.  Give us a call if you would like to learn more.  Perhaps in a future blog we can talk about what to do if you do have water in your system.