Cellar Cooling: the one system in a pub that never switches off

What a cellar cooler is actually doing

A cellar cooling system is a refrigeration system that holds a room at a steady temperature well below normal room conditions — commonly in the region of 11–13°C, though the right figure is the one your brewery or supplier specifies for the products you sell, and cask ale, keg and bottled products do not all want the same thing.

The reason it is a harder problem than it looks is the duty profile. Unlike comfort cooling, which works hard for a few months and idles for the rest, a cellar cooler runs every hour of every day. That has three consequences: the annual energy cost is much higher than the plant size suggests, component wear accumulates continuously, and a failure is a stock-loss event rather than a comfort complaint. A cellar that drifts up over a warm bank holiday weekend can cost more in unsaleable product than the plant is worth.

Sizing: it is the deliveries, not the steady state

This is the mistake that produces most underperforming cellars. It is straightforward to calculate the steady-state heat gain through the cellar walls and ceiling and size a unit to match it. That system will hold temperature perfectly — right up until a delivery arrives.

A drop of casks and kegs at ambient temperature introduces a substantial slug of heat that has to be pulled down within a working timescale. A system sized only for steady-state load will take far too long to recover, and in a busy venue with frequent deliveries it may never fully catch up during the summer. Proper sizing therefore accounts for the pull-down load: the delivery volume, its arrival temperature, and the recovery time you need.

The other factors that move the number are cellar volume, the quality of the insulation — many pub cellars are old, below ground, and insulated to no particular standard — the door discipline, since a cellar door propped open during a delivery is an open heat path, and whether there is other heat-generating equipment in the space. Ancillary loads are easy to overlook: gas bottles, pumps, lighting left on, and in some cellars the boiler.

Where the heat goes — the fault that causes most callouts

A cellar cooler removes heat from the cellar and must reject it somewhere else. In a huge number of installations, that "somewhere else" is a small enclosed back-of-house space, a corridor, or a cupboard with a grille.

The result is a slow, self-defeating cycle. The condenser warms the space it sits in, the ambient around it rises, the system's efficiency falls, it runs longer to achieve the same cooling, which rejects more heat into the same space, and so on. On a hot day the system can end up running continuously and still losing ground on the cellar temperature — and the engineer called out finds nothing mechanically wrong, because there is nothing mechanically wrong.

The fixes are about heat paths rather than equipment. Reject the heat outside using a remote condenser. If it must be rejected internally, ventilate that space properly with adequate free area, and treat "the door is usually open" as a design assumption that will not hold. Where the layout permits, some venues reclaim the rejected heat usefully — into hot water or an adjacent space that wants warming — which turns a problem into a small saving.

Two siting details worth getting right at installation: keep the condenser out of direct summer sun and away from other equipment's hot exhaust, and consider noise. Cellar plant frequently sits close to neighbouring residential property and runs through the night, which puts it squarely in the territory of a BS 4142 assessment — far cheaper to design around than to retrofit after a complaint.

Running cost, and why efficiency pays here first

Because a cellar cooler runs continuously, an efficiency improvement here delivers roughly three times the annual saving of the same percentage improvement on a comfort cooling system that only runs in summer. If you are looking for the first place to spend an energy budget in a licensed premises, this is usually it.

What actually moves the number:

• Insulation. Frequently the cheapest and most effective intervention. Cellar ceilings and the wall to a heated space are common weak points, and older cellars often have none at all.
• Door discipline and door condition. Strip curtains, self-closers, and a door that actually seals. Unglamorous, and it works.
• Correct condenser siting. As above — the difference between rejecting heat outdoors and into a cupboard is a large, permanent efficiency difference.
• Modern controls. Sensible differentials that avoid short-cycling, and defrost strategies that are demand-based rather than timed.
• Condenser cleanliness. A cellar condenser in a back-of-house area collects dust and grease quickly, and a fouled coil directly raises running cost.

Because this is an all-electric load running around the clock, it also happens to be one of the better matches for on-site generation — the consumption profile is flat rather than peaky, which improves self-consumption. Our sister site covers commercial solar installation if that is worth exploring, and a commercial energy audit will establish the baseline first.

Maintenance and compliance

Continuous duty justifies a more frequent service interval than comfort cooling — quarterly is a reasonable baseline, and the environment argues for it too, since back-of-house areas foul condensers faster than a clean plant deck. A visit should cover condenser and evaporator cleaning, refrigerant charge assessment, defrost operation, drainage and drip trays, door seals, fan and bearing condition, and verification that the controller is holding the temperature you think it is.

On compliance: cellar cooling systems contain fluorinated refrigerant, so the F-Gas regime applies in the same way as it does to air conditioning — leak checking at intervals set by the charge in tonnes of CO₂ equivalent, record-keeping, and work carried out by certified engineers. The duty sits with the operator. This is regularly missed in hospitality, where cellar plant is thought of as "the beer cooler" rather than as refrigeration equipment with a legal regime attached. See our F-Gas guide and servicing page.

Note that cellar cooling is refrigeration rather than air conditioning, so it does not itself count toward the TM44 threshold — but any comfort air conditioning in the bar, restaurant or function rooms does, and in a hospitality venue that total commonly exceeds 12 kW.

Frequently asked questions

What temperature should a beer cellar be?

Commonly in the region of 11–13°C, but the correct figure is the one your brewery or supplier specifies for the products you stock, since cask ale, keg and bottled products do not all have the same requirement. What matters as much as the setpoint is holding it steadily, including after a delivery.

Why does my cellar warm up after a delivery?

Because the system was probably sized for steady-state heat gain rather than for the pull-down load. A delivery of casks and kegs at ambient temperature introduces a large slug of heat that has to be removed within a working timescale, and a unit sized only to hold temperature will recover far too slowly — sometimes never fully catching up during a busy summer.

Why is my cellar cooling running constantly and still not coping?

The most common cause is heat rejection into an enclosed space. If the condenser sits in a small back-of-house room or cupboard, it warms the air around itself, efficiency drops, it runs longer, and it rejects still more heat into the same space. An engineer will often find nothing mechanically wrong, because the problem is the heat path rather than the plant.

How much does cellar cooling cost to run?

More than most licensees expect, because it runs continuously all year while other cooling is seasonal — on many licensed premises it is the single largest electrical load. The main levers on running cost are insulation, door discipline, correct condenser siting, condenser cleanliness and modern controls, and improvements here pay back faster than on seasonal plant.

Does cellar cooling fall under F-Gas regulations?

Yes. Cellar cooling systems contain fluorinated refrigerant, so leak checking at intervals set by the charge in tonnes of CO2 equivalent, record-keeping, and the use of certified engineers all apply, with the duty resting on the operator. This is often missed in hospitality because the plant is thought of as a beer cooler rather than as refrigeration equipment.

We design, install and maintain cellar cooling for pubs, bars, hotels and hospitality venues across the UK. See restaurant and kitchen ventilation for front and back of house, servicing and F-Gas for the maintenance regime, and commercial air conditioning for comfort cooling in the trading areas. Or request a quote.