Condenser Sub Cooling Control

[Red Man]

16C is not the same as 16K. While both are SI measurements and both change the same incremental step, they are not the same. It’s like when we use 15F....it isn’t the same as 15F (below water freeze point). 16K is approximately equal to 30F if I did the math correctly...which is likely to still be too high.

When talking about superheat 16K and 16C are the same. Kelvin and Celsius both use the same scale, they just have different starting points. They both equal 28.8 degrees superheat in Fahrenheit.

[jayguy]

When talking about superheat 16K and 16C are the same. Kelvin and Celsius both use the same scale, they just have different starting points. They both equal 28.8 degrees superheat in Fahrenheit.

Of course, they are the same from a differential standpoint. But I have seen several posts around here that talk about actual temperatures in C but differential in K. The posters were typically not USA based. Not sure if that is a standard measurement description or a personal one.

[Red Man]

Of course, they are the same from a differential standpoint. But I have seen several posts around here that talk about actual temperatures in C but differential in K. The posters were typically not USA based. Not sure if that is a standard measurement description or a personal one.

[heatingman]

Because adding 32 compensates for the different starting point in Celsius vs Fahrenheit. Multiplying by 9/5 accounts for the difference in the scale. Since superheat is simply a difference between two temperatures, we don’t add 32. Here’s an example...10 degree Celsius SST (50 Fahrenheit). We measure 20 degrees Celsius at the compressor (68 degrees Fahrenheit). That’s 10 degrees Celsius superheat (18 degrees Fahrenheit). Ten times 9/5 equals 18, that is our superheat in Fahrenheit. If we add 32 to that number we get 50 degrees which is not accurate.

I learned this by working on some low temp stuff where the controllers read out in Celsius. I was using the values for SST and pipe temp in the controller and trying to convert superheat to Fahrenheit by multiplying by 9/5 and adding 32. When the numbers didn’t seem right I figured out you can’t add that 32 when your just looking for a temperature difference.

Makes logical sense.

I would have learned the hard way like you did.


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[icemeister]

If you want to get really nit-picky, temperature in Kelvin isn't expressed in degrees at all, even though a Kelvin unit or "degree" is equal to a Celsius "degree". According to the National Institute of Standards (NIST) it should be expressed simply as K, not °K.

So a temperature difference ΔT of 30°C - 20°C would be expressed correctly as 10K.

Carry on.