A constant-pressure water make-up system keeps HVAC and process loops topped up as water expands and contracts. Selection is a balance of expansion volume, replenish rate and stable pressure – not just a pump size.
The Operating Reality
The system sits on a closed heating or chilled-water loop with a pressure tank, a make-up pump and control that holds the loop set-point as temperature swings move the water volume.
Why It Matters
Under-sized tank volume forces the pump to short-cycle; wrong head lets pressure sag at peak draw; no integration with dosing leaves the loop diluting inhibitor on every top-up. The points below keep make-up stable and compatible with water treatment.
Key Selection Points
- Tank volume should absorb the loop’s expansion/contraction band so the make-up pump runs in long cycles, not short bursts.
- Pump head must hold set-point at the loop’s peak make-up demand, not just at steady state.
- Start/stop pressure set-points should be set with margin so normal thermal movement does not trigger repeated pump starts.
- Integration with dosing: because every litre of make-up dilutes inhibitor, the make-up signal should drive or align with the dosing controller.
- Make-up metering lets the plant quantify top-up and catch leaks early, before they dilute chemistry or lose pressure.
Selection Checklist
- Calculate expansion volume from loop water content and the operating temperature swing.
- Size the pressure tank to cover that band with comfortable pump cycle time.
- Set pump head for peak make-up demand, not steady-state pressure.
- Align make-up start/stop set-points with dosing so top-up does not dilute inhibitor unprotected.
- Add make-up metering to quantify top-up and detect leaks early.
Related Products
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FAQ
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