Ask an air conditioning installer how the cooling load was calculated, how ventilation and heat reduction were considered, who will perform refrigerant work, what permissions are needed, and exactly what the quotation includes. Also ask about noise, drainage, electrical work, controls, commissioning, warranty, maintenance, records and response if performance falls short. Good answers should be specific to the property and documented.
Ask how the design was reached
A credible proposal should explain the inputs behind equipment selection. Ask for room-by-room loads, design conditions, occupancy, glazing, equipment heat and operating hours. If capacity was selected only from floor area, ask what important factors may have been omitted.
Discuss heat reduction before active cooling. Shading, lower-energy lighting, ventilation changes and equipment scheduling may reduce demand. Ask whether the proposed system provides outdoor air or merely recirculates room air, because cooling capacity is not a substitute for a ventilation strategy.
- What peak indoor and outdoor conditions did you design for?
- How did you allow for solar gain and occupancy?
- Why is this system type suitable for each zone?
- How will performance change at part load?
Verify competence and responsibilities
For stationary equipment containing or designed to contain regulated F gases, ask for evidence of relevant company certification and technician qualifications. Confirm who performs electrical, structural, roofing or fire-stopping work and what competence or registration applies to those tasks.
Insurance, risk assessments and method statements should match the project rather than exist as generic paperwork. Ask who is responsible for permits, landlord approval, planning checks and building-control liaison. The property owner or tenant should obtain independent confirmation where responsibility is uncertain.
Interrogate the quotation and installation details
The quotation should identify models, quantities, controls, pipe lengths, electrical supplies, isolators, condensate arrangements, access equipment, builders' work, finishes and waste removal. Clarify allowances and rates for changes before signing. Avoid comparing totals when scopes differ.
Ask where outdoor units will go and how noise, vibration, airflow, visual impact and future servicing have been addressed. Confirm where condensate terminates and how leaks or pump failures will be detected. Request drawings for complex or landlord-controlled premises.
- What is excluded from the fixed scope?
- Who makes good walls, ceilings and decoration?
- Can every filter, drain and valve be safely reached?
- What disruption and shutdowns should occupants expect?
Define proof of performance and aftercare
Ask what commissioning will measure and what documents will be handed over. Useful records include equipment schedules, test results, controls guidance, warranties, refrigerant information and as-installed routes. Agree how defects observed only during hot weather will be assessed.
Understand warranty conditions, maintenance needs, call-out hours and parts exclusions. Ask whether the installer can support applicable F-gas duties and whether a separate accredited TM44 inspection may be required when the building's combined systems exceed 12 kW.
Frequently asked questions
Should I choose the installer offering the largest system?
No. Larger is not automatically better. Oversizing can impair control and efficiency. Choose a justified design based on calculated loads, suitable zoning and credible operating assumptions.
How can I verify F-gas credentials?
Ask for the company certificate and technician qualification details, then verify them with the issuing certification body where possible. GOV.UK explains which qualifications and certifications are required.
Should a quote include planning permission?
Do not assume it does. The quotation should state who checks and obtains planning, landlord or other approvals. The applicant remains responsible for ensuring the necessary permissions are in place.
What should happen at handover?
The installer should commission the system, demonstrate controls and provide agreed records, warranties and maintenance information. Record any incomplete work and the date for resolution.
Is a long warranty enough evidence of quality?
No. Check what it covers, labour and travel terms, maintenance conditions, response arrangements and who supports it if the installing business changes.
Related guides
Sources and further reading
How this guide was prepared
This guide was written by the Local AC Installers Editorial Team. We compare official guidance, legislation and established consumer information, separate general information from project-specific advice, and show publication dates and sources. We do not accept installer accreditation claims at face value.