How Temperature Affects Life
LFP cells perform best near 25°C; each 10°C rise roughly halves usable cycle life. Large cabin temperature spread also causes pack-to-pack SOC imbalance and faster aging.
Control Targets
- Cell temperature kept 20–35°C
- Max cabin ΔT ≤5°C
- Dew-point control to avoid condensation
| Temp | Life impact |
|---|---|
| 25°C | 100% baseline |
| 35°C | ~55% |
| 45°C | ~30% |
Air vs Liquid Cooling
Low-rate small systems can use air cooling; high-rate large systems prefer liquid cooling for better precision and consistency, linked to fire control.
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Airflow, placement and sealing
A unit that is correctly sized can still fail to hold setpoint because of how the air moves inside the cabinet. The evaporator takes in whatever air is beside it. If the warm air leaving the equipment rises into that intake, the refrigerant has no cold surface to evaporate against and the controller sees a cabinet that will not cool, whatever the rating on the box.
The three symptoms to look for are familiar: the setpoint is reached at the bottom of the cabinet but never near the top, the compressor runs continuously while the panel reads close to ambient, and the unit's own intake temperature is close to the ambient.
- Mount high, where the warm air rises
- Fit a baffle so air passes across the full height of the equipment rather than around it
- Direct the discharge across the load, not down into the floor of the cabinet
- Seal the perimeter between the unit and the cabinet wall; an IP-rated cabinet with an unsealed unit is not an IP-rated cabinet
- Keep the intake grille clean and unobstructed; flow resistance at the intake quietly costs capacity
Measure the temperature spread from the bottom to the top of the cabinet after a full working day. A spread above 8 °C points at the airflow rather than the capacity, and it is a cheaper fault to fix than a larger unit.
Maintenance intervals that fit the site
There is no single correct interval. There is only an interval that is written down, and a filter and condenser that can be reached without dismantling the panel. What a unit in a clean air-conditioned plant room needs and what a unit under a machining centre needs are two different schedules.
| Environment | Filter | Condenser | Drain |
|---|---|---|---|
| Clean indoor plant room | Quarterly | Twice a year | Monthly |
| Workshop with dust or swarf | Monthly | Quarterly | Monthly |
| Outdoor coastal | Quarterly | Every two months | Monthly |
| Desert, sand-laden air | Monthly | Every two months | Monthly |
| Wash-down or high humidity | Monthly | Quarterly | Weekly |
Two habits do most of the work. The first is recording the ambient at each visit, which converts next year's argument about whether the unit has degraded into a settled question. The second is never pressure-washing a dry, dusty coil from the front, which drives the dust into the fins instead of shifting it. Clean dry first, rinse gently, and let it dry before the unit runs again.
Fault diagnosis: symptom, likely cause, what to check
The failure that costs the most is the one that always looks like the compressor. In practice the compressor is rarely the first thing to fail. What fails first is airflow, then the drain, then the sensor, and the compressor is usually simply working against conditions that have quietly become impossible.
| Symptom | Most likely cause | Check first |
|---|---|---|
| Setpoint never reached, compressor runs flat out | Recirculation into its own intake | Intake temperature against ambient |
| Bottom of the cabinet cold, top no warmer than ambient | Air bypassing the equipment | Baffle position and discharge direction |
| Capacity fell without an obvious cause | Fouled condenser | Coil surface temperature and dust build-up |
| Trips in humid weather | Blocked condensate drain | Drain path, and whether it is graded to drain |
| Controller reads a wrong or frozen temperature | Sensor fault | Sensor resistance, then the wiring |
| Ices up inside | Low airflow, or a setpoint below the dew point | Filter condition and setpoint |
Log the duty cycle before any of this. A unit that logged 100 % through the previous summer had the answer to the question already written down, and nobody had read it.
What to ask before the order is placed
Five questions rarely change the price and frequently change whether the cabinet still works in year six. Ask them at quotation stage, when they are still questions, rather than after commissioning, when they become arguments.
- At what ambient temperature, and at what supply voltage, is the quoted capacity valid?
- What is the measured airflow in cubic metres per hour, and what clearance does the condenser need to be installed with?
- What is the control accuracy, and what does the unit do if its own sensor fails? A unit that assumes a safe reading turns a five-minute wiring fault into a burned panel.
- What is the compliance documentation, and does the test report actually exist for the unit being quoted — not for a sibling model?
- What is the lead time on a replacement unit, given where the cabinet physically is?
Those five answers, written down and signed off at quotation, are usually worth more to the project than a few percentage points of extra capacity.
Energy, duty cycle and the ten-year view
Over a ten-year life the energy is typically a larger share of the total cost than the unit itself. That changes which comparison is worth making: not "which is cheaper to buy" but "which will this cabinet consume over a decade", taken from the duty cycle the site will actually see rather than from a catalogue point that assumes continuous running.
- A correctly sized unit cycles. Most of its life is spent at part load, not at its rated point, and that is where a compressor is most efficient.
- Two units at about 60 % each usually beat one at 120 %: they share the duty, they run staggered, and a failure degrades the cooling rather than removing it.
- A fouled condenser is worth roughly a fifth of the capacity, and considerably more on an energy basis, because the compressor fights a warmer surface all year.
- Monitoring that reports duty cycle is usually justified within two seasons, first through the maintenance visits that get avoided.
The counter-argument is first cost, and it is not weak. But the honest comparison is ten-year against ten-year, with the energy figure derived from the site's actual duty rather than from a datasheet assumption that suits the supplier.
Service life, monitoring and lifecycle
Where a cabinet is critical, the interesting question is not whether the unit works but whether anyone finds out when it does not. The failure mode worth designing against is silent: the compressor stalls, the cabinet warms over several hours, and the trip happens when the equipment can no longer take the temperature.
The minimum is a temperature sensor in the cabinet with an alarm above the setpoint and a contact that somebody sees. The useful addition is fan status and duty cycle over a monitoring interface, which separates an airflow fault from a refrigerant fault in minutes rather than a day. Duty history is also the only honest record of whether the original sizing was right.
Service life is governed less by the compressor than by the fan, the filter and the drain, in that order. They are cheap, and they are the items worth putting in the maintenance budget at specification time, alongside the question of how long a replacement unit takes to reach the site.