HVAC Buffer Tank Design and Sizing Fundamentals

A: A hits the basic energy balance: 100 kW × 360 s ≈ 36 MJ, divided by 4.2 kJ/kg·K × 5 K gives ~1,700 kg, so ~1.7 m³. B drops the run-time requirement; ramp-up isn't the constraint. C double-counts a safety margin without a reasoned basis. D confuses hydraulic volume with thermal mass; pump casing volume is noise.

A: A and B are exactly why the PRV exists; isolation removes that protection. D is a downstream effect of A if pressure keeps climbing. C needs a pressure drop, not a rise; an isolated, heated tank goes the other way.

A: A follows the chain: 250 kW × 600 s = 150 MJ; divide by 4.18 kJ/kg·K × 4 K gives ~9,000 kg. B quietly drops run-time. C misplaces a decimal when converting MJ to kJ. D invents a fouling factor; fouling hits heat transfer, not stored energy.

A: A is the classic response; you've added lag right where the sensor lives. B sounds nice but volume doesn't change pump curve. C mixes up return-side buffering behaviour. D can happen later, but it's not the first-order effect.