Formula & worked example
Ve=Vs(ρcold/ρhot−1); Vtank=Ve/[1−Pfill,abs/Prelief,abs].
A 1,000 L glycol loop dropping from 1040 to 1010 kg/m³ expands about 29.7 L before pressure acceptance.
HVAC engineering calculator · Updated Sep 17, 2026
Glycol Expansion Calculator — Closed-Loop Expansion & Tank Acceptance
Estimate glycol-loop thermal expansion and ideal diaphragm-tank volume from system volume, cold/hot fluid density, fill pressure, relief pressure and design margin.
Inputs
Live result
Fluid expansion 29.70297 L
Expansion fraction 2.970297%
Pressure acceptance 37.376191%
Ideal tank volume 79.470297 L
Tank with margin 87.417327 L
Assumptions & limits
- Use glycol-mixture densities at actual cold/hot temperatures.
- Manufacturer precharge and code sizing govern final tank selection.
Frequently asked questions
What does this Glycol Expansion Calculator calculate?
Estimate glycol-loop thermal expansion and ideal diaphragm-tank volume from system volume, cold/hot fluid density, fill pressure, relief pressure and design margin.
Is this suitable for final equipment selection?
Use it as an auditable engineering cross-check. Final selections should use measured design conditions, manufacturer data, applicable standards and local code.
Why does MAXScanner expose the assumptions?
HVAC shortcuts can hide density, pressure, concentration and effectiveness assumptions. Exposing them makes the result easier to verify and revise.