Chiller Not Reaching Setpoint Temperature: Causes and Fixes

When a chiller can't reach its water setpoint, the cause is usually one of four: cooling capacity is insufficient for the plant's actual heat load, the condenser is dirty so the compressor runs at reduced efficiency, refrigerant charge is low due to a leak, or water flow through the system is insufficient or poorly distributed across multiple machines.

TL;DR — check these first:

• Compare the plant's actual heat load against the chiller's rated capacity
• Check and clean the condenser (air- or water-cooled) for dust, fibers or scale
• Check refrigerant pressure and for signs of a leak
• Check water flow and distribution across machines, especially on a central system
• If free cooling is installed, confirm it engages correctly at lower ambient temperatures

Is insufficient capacity the cause?

If the plant's actual heat load (from machines, hydraulics, molds) exceeds the chiller's rated capacity, the unit simply can't keep up with demand regardless of its condition.

How to confirm: Compare the summed heat load of all consumers (the material being processed, plus hydraulics and periphery) against the chiller's rated capacity; the problem appears or worsens when a new machine is added to the same system.

Fix: Recalculate the plant's heat balance and compare it to actual capacity; if load genuinely exceeds it, an added unit or a larger replacement is needed.

Is a dirty condenser the cause?

The condenser (air- or water-cooled) transfers heat from the refrigeration circuit to the surroundings; if it's coated in dust, fibers or scale, heat transfer drops and the compressor runs at reduced efficiency regardless of the unit's rated capacity.

How to confirm: Condensing pressure (high side of the refrigeration circuit) reads higher than normal for the given ambient temperature; a visual check of the condenser fins shows buildup.

Fix: Regular condenser cleaning per the manufacturer's instructions (typically seasonal, more often in dusty environments); for water-cooled condensers, check and clean for scale.

Is low refrigerant charge causing the problem?

A refrigerant leak reduces cooling capacity gradually, since the system runs with less working fluid than it was designed for.

How to confirm: Low evaporating pressure (low side of the circuit) relative to normal for the operating conditions; the compressor runs longer to reach the same temperature; visible oil traces at fittings (a sign of leakage).

Fix: Find and repair the leak, then recharge refrigerant per the manufacturer's specification — topping up without finding the leak is a temporary fix that recurs.

Is water flow or distribution the cause?

On central systems with multiple machines, insufficient total flow or poor distribution (one machine "steals" flow from others) means some machines receive water at a higher temperature than the chiller is actually delivering.

How to confirm: Water temperature at the chiller outlet is fine, but individual machines still show a mold-temperature problem; the issue depends on the machine's position within the distribution system.

Fix: Check and balance flow across system branches; check pumps have adequate capacity for the total number of connected machines; consider two temperature circuits (colder for molds, warmer for hydraulics and periphery) for further savings and stability.

Cause overview

Perotec Systems supplies and services industrial chillers and cooling systems tailored to process requirements, for the regional market. Browse the full chillers range or read Sizing Industrial Cooling: Chillers and Free Cooling. Contact us with your plant data — we size the heat balance free of charge.