Glycol Pressure Drop Corrections for Hydronic Systems (Part 2)

Norm Hall
 / 
July 25, 2022
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Last week the article covered pressure drop correction calculations. Today we offer you some handy charts to use for second glycol correction pressure drop.

 

Pressure Drop Corrections for Glycol/Water Solutions
Percent Propylene GlycolPercent Ethylene Glycol
Average Temperature30%40%50%30%40%50%
35F1.561.782.001.371.471.60
45F1.461.631.901.301.391.51
50F1.411.561.801.271.361.47
80F1.201.291.451.111.181.27
100F1.101.191.301.041.101.17
130F1.011.071.150.961.011.06
150F0.961.011.070.920.961.01
170F0.930.971.020.890.920.96

Glycol Pressure Drop Correction Example

Let’s assume we have a primary variable chilled water system with a 40% Dowfrost fluid. The system is designed for a 45⁰F average temperature. The engineer’s calculations would be more detailed, but this will get the point across as an example.

 

ITEMWATER BASED PD (FEET)GLYCOL BASED PD (FEET)
Chiller28
Mechanical room equipment10
Distribution piping33
Pipe fittings (25%)8
Farthest (controlling) AHU16
Control valve12
AHU piping and valves4
Totals6744
Glycol correction factor1.631.0
Correction head10944
Total before safety153
Pump head with 15% safety factor176

 

You can see the correction factors add up quickly. Not something you want to miss. We hope this short R. L. Deppmann Monday Morning Minutes will help you in your determination of glycol based system pump head.

 

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