The beer’s pouring warm. The glycol chiller is running but the temperature on the tank or at the font keeps climbing. In a brewery, the fermenter won’t hold temperature. In a process cooling application, the production line is out of spec. The chiller sounds like it’s working — compressor running, pump on — but the glycol just isn’t cold enough. Here’s what’s going on.
Glycol cooling systems are straightforward in principle: a chiller cools a glycol-water mix, a pump circulates it through the load, and it comes back warm to be cooled again. When the system can’t maintain temperature, the fault is either in the chiller, the circulation, or the glycol itself.
Low Glycol Level
The first thing to check and the most common cause. Glycol systems lose fluid over time — from small leaks at fittings, pump seals, or hose connections, and occasionally from evaporation in open or poorly sealed reservoir tanks. When the level drops too low, the pump starts drawing air, circulation becomes erratic, and cooling capacity falls off a cliff.
Check the reservoir tank. If the glycol level is below the minimum mark — or below the pump inlet — top it up with the correct glycol-water mix. Don’t just add water. Diluting the glycol concentration changes the freeze point and thermal properties of the entire system. And if the level dropped quickly, find the leak before topping up — otherwise you’ll be doing this again next week.
Incorrect Glycol Concentration
Glycol concentration matters more than most people realise. Too little glycol in the mix and the fluid can freeze inside the chiller’s evaporator when the system pulls down to low temperatures. Too much glycol and the thermal capacity drops — the fluid can’t absorb and carry heat as efficiently, which means the system struggles to cool the load even though the chiller is working hard.
For most beer and beverage applications, propylene glycol concentration should be between 30% and 40% by volume, giving a freeze point well below the operating temperature while maintaining good heat transfer. A refractometer check takes two minutes and tells you exactly where the concentration sits. This should be checked annually at minimum.
Failed Circulation Pump
The chiller can be making ice-cold glycol, but if the circulation pump has failed or is running at reduced capacity, that cold glycol never reaches the load. A pump impeller can wear, a motor winding can partially fail (pump runs but slowly), or the pump can seize entirely.
Check the pump — is it running? Is it vibrating normally? Feel the glycol lines either side of the pump. The supply line should be noticeably colder than the return. If both lines are the same temperature, the glycol isn’t flowing properly. A pump swap is a routine repair that gets the system back online quickly.
Dirty Condenser Coil
The chiller rejects its heat through a condenser coil — either air-cooled or water-cooled. An air-cooled condenser that’s clogged with dust, fluff, or debris can’t reject heat efficiently. The compressor runs hotter, head pressure climbs, and cooling capacity drops. In severe cases, the high-pressure safety switch trips and the compressor shuts down altogether.
Look at the condenser coil. If you can’t see through it, it needs cleaning. In a cellar environment with dust and cardboard fibres in the air, condensers can block up surprisingly fast. A thorough clean with a coil brush and compressed air — working from the clean side out — will often restore full cooling capacity immediately.
Compressor Weak or Failed
If the condenser is clean, the glycol level and concentration are correct, and the pump is circulating, the compressor itself might be the problem. Compressors lose efficiency as they age — valves wear, seals degrade, and the unit can no longer compress refrigerant to the pressures needed for proper heat exchange.
A suction and discharge pressure test will show immediately whether the compressor is pulling its weight. Low discharge pressure and high suction pressure together indicate a weak compressor. At that point, it’s a compressor replacement or a new chiller unit depending on the age and value of the equipment.
Glycol Lines Not Insulated
Glycol circulates at temperatures well below the ambient air in a cellar or plant room. If the glycol pipework isn’t insulated — or the insulation has deteriorated — the fluid picks up heat from the surrounding air on its way to the load. On a long pipe run, the heat gain can be significant enough to raise the delivered glycol temperature above what the load requires.
Check the insulation on all glycol lines, particularly in warmer areas like above ceilings, through risers, or past hot water pipes. Any bare copper or steel pipework carrying cold glycol is a heat gain problem and a condensation risk. Proper closed-cell insulation solves both issues.
Blocked Strainer in the Glycol Circuit
Most glycol circuits have a strainer or filter to catch debris. Over time, these block with sediment, pipe scale, or degraded glycol residue — especially in older systems. A blocked strainer restricts flow just like a failed pump would, and the symptoms are identical: the chiller cools the glycol in the tank but it doesn’t reach the load effectively.
Check and clean the strainer. On systems that haven’t been maintained, the strainer can be almost completely blocked. While it’s out, inspect the condition of the glycol itself — if it’s dark brown or smells off, the glycol has degraded and the entire system needs flushing and refilling.
Call ADK
Glycol chiller systems serve breweries, pubs, wine cellars, bakeries, and industrial process cooling across London. When they underperform, the consequences are immediate — warm beer, failed batches, out-of-spec production. ADK engineers diagnose and repair glycol chiller systems on site, from pump replacements and condenser cleans to full compressor swaps and glycol system recommissions. Call us and we’ll get your temperatures back where they should be.