PPM schedule for chillers and AHUs
Build a PPM schedule for chillers and AHUs by listing each asset, taking tasks from the manufacturer's manual and a maintenance specification library such as SFG20, grouping them into daily, weekly, monthly, quarterly and annual tiers, adjusting intervals for site conditions, and assigning each task to a trade with a recorded completion.
What is a PPM schedule?
PPM means planned preventive maintenance. A PPM schedule lists every maintenance task for an asset, how often it is done, who does it and what is recorded. For a maintenance contractor it is also the basis for pricing the contract and proving service delivery.
Where the tasks come from
Do not invent task lists. Three sources cover most needs:
- The manufacturer's manual. It states recommended checks and service intervals for that exact model. Warranty conditions often depend on following it.
- A maintenance specification library. SFG20, owned by BESA, is a widely used library of maintenance specifications in the UK building services industry, with task lists by asset type. Other libraries and client specifications apply in other regions.
- The contract. The client's service level terms may require a higher frequency than the manual.
Intervals vary by manufacturer, system type, operating hours, environment and local regulation, so the tiers below are a structure to fill from your sources, not a set of fixed intervals.
Chillers: typical task tiers
| Tier | Typical tasks |
|---|---|
| Daily or weekly | Log operating readings such as temperatures, pressures and motor current. Check for alarms, unusual noise, vibration and leaks. |
| Monthly | Inspect for refrigerant or oil leaks, check controls and safety devices, inspect electrical connections visually. |
| Quarterly | Check condenser and evaporator performance trends, inspect water treatment and flow, check the condition of strainers. |
| Annual or longer | Service the compressor as the manual directs, test safety and protection devices, clean or inspect condenser and evaporator tubes, review oil and refrigerant condition. |
AHUs: typical task tiers
| Tier | Typical tasks |
|---|---|
| Monthly | Inspect filters and change when dirty or when pressure drop is high. Check belts, fan operation and unusual noise. |
| Quarterly | Check belt tension and wear, inspect and clean drain pans and drains, check damper and actuator movement. |
| Six-monthly or annual | Clean coils, inspect fan bearings and motor, check electrical connections, verify controls and sensors, check airflow. |
In dusty regions filters can load much faster than a manual assumes. Set the interval by measured condition and record the reason for any change.
Example of a task entry
A well-formed PPM task has a name, an asset, an interval, a trade, an estimated time and a checklist. For instance: "AHU L05, filter inspection, monthly, HVAC technician, checklist: filter condition, pressure drop reading, belt condition, unusual noise." The estimated time and trade matter if you price the contract from the schedule, because they turn the schedule into labour hours.
Pricing from the schedule
A contractor can turn the schedule into a price. Count the tasks per year for each asset, multiply by the estimated time and the trade, add travel and supervision, then add spares, consumables, overhead and margin. The same schedule then becomes the delivery plan, so the contract is priced and run from one source.
Record the right things
A completed tick is weak evidence. For each visit capture:
- The date, the technician and the asset.
- Readings taken, such as pressures, temperatures, current or filter pressure drop.
- Findings and any follow-up work order raised.
- Parts used.
Readings over time show a chiller drifting before it trips. They also settle disputes about whether a service happened.
Common mistakes
- Copying a generic task list without checking the model's manual.
- Setting intervals once and never reviewing them against failures.
- Scheduling by calendar only, with no allowance for access, permits or isolations.
- Letting overdue tasks pile up without a weekly review.
How JobNext handles PPM
JobNext's Hard FM module holds an asset register with criticality and warranty, PPM plans and schedules, and work orders with approvals. The dashboard shows what is due this week and what is overdue, and technicians capture service on mobile with QR tags. The platform can also draft PPM plans with AI assistance for assets that have none, which a person approves. A logged service can post a material issue and a BOQ measurement through to billing.
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Frequently asked questions
What does PPM mean in facilities management?
How often should a chiller be serviced?
How often should AHU filters be changed?
What is SFG20?
What should be recorded at each PPM visit?
Can JobNext generate PPM plans?
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