Ask how the new system is tested and what control setup is included.
Confirm who handles installation questions, equipment registration and future service.
Keep the written proposal and equipment documentation together so you can refer back to what was agreed.
Agree on startup tests before work begins
Ask what startup tests will be performed and which readings you receive. Depending on the system, the useful record may include temperature change, static pressure, airflow setup, refrigerant charging method, combustion or venting checks, condensate testing and thermostat configuration.
Separate the manufacturer parts warranty from the contractor labor warranty. Record who registers the equipment, the registration deadline, exclusions, required maintenance, diagnostic or travel charges, and the number to use for installation-related service.
Keep the signed scope, approved changes, model and serial numbers, startup results, registration confirmation and final invoice together.