IMI Cornelius – CellarKing Systems

Cellar over-cooling (too cold) (Cellar dips well below setpoint, e.g. <8°C, risking cask ale)

– Likely a thermostat failure in the closed position. On older CellarKing, a mechanical thermostat controls compressor. If its sensor bulb lost charge or contacts welded, the compressor may run nonstop. Check the thermostat: turn its knob warmer and cooler – if it never clicks off even when cellar is clearly cold, it’s faulty. – Also consider if any heater in the cellar (for ale) is not working – though usually if too cold, it’s the cooling not stopping. – If the thermostat seems fine (clicks on/off at some point), perhaps it’s mis-calibrated or placed poorly. Is the sensing bulb in the return air flow? If it got dislodged and touching a cold surface, it will “think” the cellar is colder than it is and maybe short-cycle, but over-cooling typically means it never turns off. – Rule out a wiring misconfiguration: on some systems, if wired for remote on/off control by the brewery, bypassing that incorrectly could force constant run. Ensure any remote stop circuit is properly closed (or if brewery panel was removed, that the wires are joined to allow control).

– Replace the thermostat: A direct replacement might be hard to find, but you can use a universal electronic controller or a robust mechanical one set to 12°C cut-out, 2°C diff. Electronic retrofit (digital stat + probe) can be mounted easily and will be more accurate. This stops the overcooling and usually improves temperature stability. – In interim, you can set up a simple plug-in controller (some pubs use plug-in fridge controllers) to cycle the unit until proper fix. But permanent fix is best for reliability. – If a heater was supposed to kick in at low temp (to keep at 12°C), fix that heater or its control too. Some CellarKing setups had a heater plate for casks – ensure it’s powered and controlled by a thermostat. Replace its thermal fuse or stat if needed. – Educate staff not to fiddle with the stat beyond the recommended range; sometimes these were hidden to prevent tampering. A digital stat can be password-protected to avoid someone cranking it to “max cool” and freezing the cellar.

Frequent cycling / short run (Unit turns on for brief periods, maybe every few minutes, not a long steady run)

– Could be pressure control cycling: Some older units use a pressure control to cycle the compressor (especially if set up as a pump-down system with a solenoid). If a liquid line solenoid closes at setpoint, the compressor will pump down and cut off on LP, then restart when pressure rises. That’s normal – but if it’s too frequent, maybe the LP control differential is too narrow or the refrigerant is slightly low causing rapid pressure rise after off. Check the pump-down cycle time; ideally, compressor off cycles should be few minutes at least. – If no pump-down, then the thermostat differential might be too small or sensitive. A mechanical stat on its edge of range can rapidly cycle (hunting around a narrow band). Observe if it’s the thermostat clicking on/off quickly. – Another cause: compressor internal overload – if the compressor runs for a short time then stops (and you hear no click from stat or LP/HP), it might be overheating and tripping internally. This would have a distinct pattern (runs maybe 30-90 seconds, off a few minutes, repeat). Feel the compressor – if extremely hot and off, likely internal overload. – Also, electrical supply issues: low voltage can cause the motor to overload and cut out. Check voltage at compressor terminals during start and run. If it dips significantly, that’s a supply problem (maybe undersized wiring or other heavy loads).

– Adjust differential: If pump-down cycling is too quick, increase the LP control’s differential (or the thermostat’s differential). For example, set the LP cut-in a bit higher so compressor stays off longer before restarting. On a thermostat, maybe a 4°F (2°C) diff if possible. – Thermostat upgrade: Installing a modern controller with an inbuilt time delay (3-5min anti-short-cycle) will virtually eliminate rapid cycling due to control issues. Many digital controllers have this safety time built in. This protects the compressor as well. – Charge and TXV: Ensure proper refrigerant charge so that when the unit cycles off, the pressure doesn’t rise too fast (which can happen if there’s non-condensables or overcharge). Proper charge + a sound TXV will stabilize off-cycle pressures. – Compressor cooling: If internal overload is tripping, address why compressor is overheating. Check condenser – a partially clogged condenser can cause high head and overheating even if HP isn’t tripping. Clean condenser, confirm fan. Check suction superheat – if too low, floodback can also cause overload (but usually it’s high heat). If voltage is low, perhaps run a dedicated circuit or buck/boost transformer if needed. In worst case, if the compressor windings are deteriorating (drawing high amps from age), you may need to replace the compressor or the entire condensing unit. – Prevent rapid restart: If the unit lacks one, add a delay timer or relay such that once it turns off, it can’t start for, say, 3 minutes. This can be a simple plug-in time delay relay in series with the compressor contactor coil. This modification will save the compressor from short-cycle stress.

Major refrigerant leak or compressor failure

– With older CellarKings, you might encounter the system not holding any charge (oily residue around joints) or a seized compressor. Evaluate if repair is feasible: parts availability (e.g., R22 compressor replacements) and cost relative to new. – If the compressor is not running at all (hums/buzzes and trips breaker) and you confirm it’s the compressor fault (windings shorted or open), that’s a failure. Also consider age: if it’s, say, 25 years old, replacement might be more economical in long run. – For leaks, common spots: flare connections (if any), evaporator U-bends, or condenser hairpins, especially if vibration mountings got loose. Do a pressure test with nitrogen to locate. – If the unit used R22 originally, by law you can’t refill with R22 now. It would need a retrofit gas or conversion. Many R22 cellar units were retrofitted to R407C or R404A blends. Determine what’s in it now via labels or test – sometimes they had a sticker after retrofit.

– Repair vs Replace: If compressor failed, weigh replacement cost (new compressor plus new gas, new oil, filter, labor) versus a new packaged cooler. In some cases, breweries have replaced entire systems proactively. However, if budget is a concern and the rest of unit is fine, you can change the compressor. Use a modern equivalent (e.g., an R407F or R448A compatible compressor) and change expansion device and oil accordingly. Essentially, perform a retrofit. – For a retrofit refrigerant: R407F or MO99 are options for ex-R22 systems. Adjust the TXV or replace the capillary if needed to match new refrigerant performance (or get a new TXV bulb charge for that refrigerant). After retrofit, label the unit clearly with the new gas. – Leak fix: Braze any leaks. If the evaporator is full of pinhole leaks (e.g., from corrosion), replacement might be needed; a skilled tech could sometimes isolate a leaking circuit if it has multiple passes, but often not worth it – better to replace coil or entire evap unit. – Follow best practices: install a new filter-drier, triple evacuate, charge with correct weight (if known) or to performance if not. Add fluorescent dye for future leak detection if you suspect tiny leaks remain. – After major repair, definitely do a full run test: measure pressures, verify control cut-in/out, check that fans start, etc. It’s essentially recommissioning the system. – Consider adding some modern touches to an old system you repaired: e.g., put in a high-pressure cut-out if it didn’t have one, or a sight glass with moisture indicator to monitor refrigerant health, etc. Small upgrades can protect your big repair investment.