HVAC and Boiler System Maintenance at British Consulate-General San Francisco Official Residence

We require a company to provide HVAC and boiler system maintenance at a residential property at 12 Presidio Terrace in San Francisco. The boiler system provides heating and hot water in this five bedroom, five bathroom, three story home. Due to the complexity of the system, we would like preventative maintenance visits initially every six months for the first year of the contract, to be reviewed at the end of the first annual period. The successful bidder should also be available for emergency call outs within 24 hours of initial notification. Please describe how you will meet these minimum requirements.