Charing Cross Hospital were undergoing a carbon reduction initiative to displace steam and chilled water systems with new air source heat pumps. The scheme comprised the installation of four main heat pumps installed on the roof of the Oncology / Radiotherapy building, and a series of satellite heat pumps and supporting circulation pumps installed in the Tower and Laboratory Block buildings. The scheme required a substantial amount of electrical power to support the heating and hot water equipment, with the maximum demand in the region of 2,450kW.
The existing high voltage and low voltage electrical infrastructure at Charing Cross Hospital did not have adequate spare capacity to provide power for the magnitude of the proposed loads. Therefore, it was necessary to modify the existing electrical infrastructure and construct a new ground floor two-storey substation and roof substation to support the increase in load and allow for future expansion of the Hospital site. To enable the new substations to be integrated onto the Hospitals high voltage network, it was necessary to undertake modifications to two existing radial transformer feeders, to form a new open ring network from which the new substations can were connected to. Playfords were engaged to construct two new substations at Charing Cross Hospital. Substation SS7 – at ground level in between the Laboratory Block building and the Oncology building, consists of a reinforced concrete base carrying cavity brick walls, constructed to house four ring main units and close-coupled 2MVA transformers.
The substation building and cladded to house four low voltage switchboards and associated ancillary equipment such as DC systems, BMS marshalling boxes and outstations, small power, and lighting distribution boards etc. Access was provided by steel staircases, and the sub-stations were fitted with Sunray Doors. The surrounding external walkway and access / egress points were all fitted with new general and emergency lighting.
The new Substation SS7 low voltage switchboards are configured to accept the outputs of new transformers and provide points of connection for the mechanical services which were installed under a separate contract by others. The low voltage switchboards are separated by normally open bus-couplers, configured to automatically close upon receipt of a mains failure signal. However, to address the necessity to provide emergency standby power in the event of a catastrophic failure, new mobile generator connection points were incorporated within the switchboards to support disaster recovery. In addition to the works associated with Substation SS7, a new substation – namely Substation SS8 – on the roof of the Tower Block building was installed. The roof substation consisted of an RMU connected to a new HV ring for future use. In addition to the Substation SS7 and Substation SS8 infrastructure, Playfords installed a sub distribution low voltage switchboard on the 12th floor of the Tower Block building to provide points of connection for hot water and heating equipment installed under a separate contract by others.