An annual chiller service should establish the condition of the complete chilled-water system, not just confirm that the compressor starts. Pumps, strainers, condensers, loop pressure, water flow, fan coils, drains, controls and electrical connections all affect the plant's operation.
The annual visit also sits within a wider planned maintenance schedule. Dometic specifies daily, monthly and quarterly checks alongside annual work, so the service should review the vessel's records and deal with trends rather than treat the plant as an isolated snapshot.
Start with records and operating data
The service should begin with start-up data and a review of the chiller log. Dometic advises recording what was done, where, by whom, when and why for all maintenance and service.
Before the engineer attends, crew should assemble the trend logs, fault history and manufacturer manuals. Useful entries include start-up pressures, temperatures, water-flow readings, alarms, filter and strainer work, and parts used. This gives the engineer evidence of recurring pressure loss, declining flow or repeated alarms that may not be present during a short test.
The exact schedule must follow the installed manufacturer's manual. Requirements for Dometic chilled-water equipment, Heinen & Hopman systems and Frigomar marine air conditioning should not be treated as interchangeable.
A practical service record should connect each observation to an action:
| Area | Reading or evidence | Service response |
|---|---|---|
| Start-up | Pressures, temperatures, flow and alarms | Record in the dated log |
| Seawater strainer | Debris present | Isolate safely, clean and reassemble |
| Chilled-water strainer | Pressure drop rises 2 to 5 psi above clean baseline | Clean the strainer |
| Cold loop | Return pressure repeatedly falls | Locate and correct the leak |
| Condensate drain | Does not drain completely within 30 seconds after pouring a quart | Check for blockage |
| Condenser | Internal marine growth | Assess cleaning from documented condition |
Seawater circuit and condenser checks
Dometic's schedule calls for daily inspection of the seawater strainer and removal of debris. Crew must follow the vessel's safe isolation procedure, and the seawater pump must never run with the strainer removed. After reassembly, confirm a steady overboard discharge.
The annual service should measure and record seawater flow after the strainer has been cleaned and before making adjustments. A recorded figure can then be compared with the equipment specification and future service readings.
For shell-and-tube condensers, a head-pressure reading does not replace internal inspection. Dometic requires the tubes to be inspected visually for marine growth. Heinen & Hopman recommends inspecting a seawater-cooled condenser at least four times per year and checking the sea-water and chilled-water pumps for corrosion or malfunction before a warm-water season.
Chemical cleaning is not automatically part of an annual service. Dometic says condenser coil cleaning is not routine and requires documented symptoms such as rising head pressure or amperage together with declining capacity. Chemical cleaning should be handled by an engineer and carried out according to the exact equipment manual.
Chilled-water loop, strainers and pumps
Annual pump work includes cleaning the outside of the motor and pump, keeping the motor's air passages open, and checking the pump housing and impeller shroud for wear or corrosion. Dometic states that worn or pitted impellers reduce water flow and should be replaced.
Both circulating-water and seawater flow should be measured and recorded annually. Strainers should be cleaned before those readings are taken, otherwise the figures will not represent maintained flow through the system.
Chilled-water strainer cleaning should be based on differential pressure, not an arbitrary annual date. Establish the clean pressure-drop baseline and clean the strainer when the differential rises 2 to 5 psi above it, as specified by Dometic.
Dometic also calls for a quarterly check of cold-loop return pressure at the circulation-pump inlet. For most boats, its stated range is 12 to 20 psig. Recurring pressure loss indicates a leak that must be located and corrected rather than repeatedly masked by restoring pressure.
Some systems have a chilled-water filtration unit. Heinen & Hopman describes equipment capable of removing particles as small as 5 micrometres, controlling pH, restricting bacterial growth and separating air bubbles. Where such a unit is fitted, its own manufacturer's instructions govern maintenance.
Fan coils, drains, controls and electrical condition
Return-air filters need attention more frequently than the annual visit. Dometic calls for inspection and cleaning or replacement at least monthly, according to filter type, because dirty filters reduce airflow and capacity.
Condensate drains also require a functional test. Every three months, Dometic specifies pouring a quart of clean water into the airhandler or chiller drain pan. If it has not drained completely within 30 seconds, the outlet should be checked for blockage.
The annual schedule includes inspection of airhandler valves and sensors, but control or sensor calibration belongs with an engineer. Alarm history should form part of this work because a recurring safety fault requires diagnosis even if the unit restarts.
Electrical checks require isolation of the main power supply before connections, components or wiring are touched. Dometic's quarterly guidance includes tightening loose connections and looking for burn marks or frayed wires, as heat and vibration can loosen connections.
Periodic voltage measurement is also part of Dometic's electrical service guidance. It says pumps and fans typically permit voltage within ±10% of nominal, while compressors typically permit ±5%. Any reading outside the component tolerance, or evidence of arcing, burnt insulation or heat damage, requires an engineer.
Refrigerant should be assessed, but an annual service does not mean an automatic top-up. Dometic says the factory charge is adequate for the life of the system and that a low charge indicates a leak. The leak should be found and repaired before normal operation resumes, with refrigerant handling left to an engineer.
What crew can check safely
Crew checks support the annual service by giving the engineer a reliable history. They should remain within the vessel's isolation procedures and stop where electrical, refrigerant or chemical work begins.
- Keep a dated log. Record start-up pressures, temperatures, flow readings, alarms, filter and strainer maintenance, and parts used.
- Inspect the seawater strainer. Follow the vessel's safe isolation procedure, remove debris and confirm steady overboard discharge after reassembly. Never operate the seawater pump while the strainer is removed.
- Maintain return-air filters. Inspect and clean or replace them at least monthly, according to filter type.
- Exercise laid-up equipment. Dometic recommends operating chillers and airhandlers for 30 to 60 minutes once a month and cycling reverse mode. Monitor alarms and leaks while the plant runs.
- Record quarterly observations. Log cold-loop pressure, perform the clean-water condensate-pan test and visually inspect accessible connections for corrosion or heat damage. Do not touch electrical connections without isolating main power.
- Prepare for the service visit. Assemble trend logs, fault history and manufacturer manuals. Do not request a refrigerant top-up unless a leak has been diagnosed.
When to call an engineer
Stop routine crew checks and arrange technical attendance when the fault requires opening equipment, electrical work, calibration or controlled substances.
- Repeated pressure loss or leakage. Call when loop pressure repeatedly falls, or when a water or refrigerant leak is suspected.
- Low water flow. Arrange diagnosis if measured flow is below the equipment specification or a safety fault continues to recur.
- Electrical damage. Heat damage, arcing, burnt insulation, frayed wiring or voltage outside the component tolerance requires isolated, professional investigation.
- Condenser or pump damage. An engineer should open and inspect a shell-and-tube condenser, assess whether a coil needs cleaning, and investigate corrosion found on a pump impeller or housing.
- Controlled technical work. Refrigerant handling, high-voltage work, chemical cleaning, pressure testing and control or sensor calibration are engineering tasks.
Blueward Marine provides yacht air-conditioning and HVAC service in Mallorca, including chilled-water plant inspection and repair. Submit the fault, records and photographs through the online service booking form, or call the 24/7 emergency line on +34 971 251 374.
Frequently asked questions
Does annual yacht chiller service include adding refrigerant?
Not routinely. Dometic says the factory refrigerant charge is adequate for the system's life. If the charge is low, that indicates a leak, which should be located and repaired before normal operation resumes. Refrigerant handling should be left to an engineer rather than treated as an automatic seasonal top-up.
Which checks are annual on a chilled-water chiller system?
Dometic's annual work includes checking pump condition and measuring and recording circulating-water and seawater flow after cleaning the strainers. The wider maintenance programme also contains daily strainer checks, monthly filter service and quarterly pressure, drain and electrical inspections. Follow the manual for the exact installed model.
When should a chilled-water strainer be cleaned?
Use differential pressure rather than cleaning it solely by date. Establish the pressure drop with the strainer clean, then monitor it. Dometic specifies cleaning when that drop rises 2 to 5 psi above the clean baseline. Record the reading and service date so later checks have a reliable comparison.
Sources and further reading
These references informed this guide. Follow the procedures and limits for the equipment installed on board.