Glastonbury Library

Working under Futures for Somerset, F P Hurley were employed by Somerset County Council to provide a new photovoltaic and heat pump installation to Glastonbury Library as part of the Council’s wider decarbonisation scheme.

PV Installation

The installation of the PV system was part of a wider scheme of decarbonisation works at Glastonbury Library. The system consists of 138 No. 495W JA Solar panels giving a total rated power of 68.31kW, connected to the electrical network via 2 No. Growatt inverters.

This generated power is used to provide sustainable energy to Glastonbury Library, including powering the 3 No. 45kW Mitsubishi CAHV Air Source Heat Pumps, which were also installed by F P Hurley as part of the works, with any excess generation feeding back into the grid.

These panels are mounted to the roof via a fixing system suitable for the particular makeup of the roof, in this case a traditional slate roof, which presented difficulties regarding safe access. In order to complete these works in a safe and efficient manner a fixed scaffold was erected for the duration of the works.

This project was one of many similar schemes carried out by F P Hurley for a total value of £2.2m.

Heat Pump Installation

The 3 existing gas boilers were inefficient and approximately 35 years old and therefore had exceeded their life expectancy. They were removed and replaced with 2 No. Mitsubishi Air Source Heat Pump Units (ASHP) to meet the required heating load for the building. The ASHP specified for this building were Mitsubishi CAHV-P500YB units with a total deliverable capacity of 80kW. The units were supported on paving slabs with a 200mm pea gravel boarder to act as a soak away for condense water. The heat pumps sat on flexi feet mounting blocks to prevent any vibration into the building.

Pre-insulated pipework with glycol mixed water was connected to the internal cylinder. Flexible hoses were used to connect the Mitsubishi Ecodan unit to the primary pipe work. Isolation valves and a flushing bypass circuit were installed to each ASHP unit.

The heat pump condensers have a SCOP of 3.54 at 35C flow and operate using R407C refrigerant which has a GWP of 19.5.

Two secondary LTHW circuits were connected into a common LTHW low loss header. Each of the secondary LTHW circuits is complete with duty / standby pump, control valves, sensors and gauges where required.

The secondary LTHW circuits installed are as follows:

• Circuit 1: Variable temperature (weather compensated) circuit serving the space heating systems such as radiators.
• Circuit 2: Constant temperature circuit serving LTHW coils (e.g. fan convectors).

The heat pump system is designed to allow independent occupant thermal control, in all separate rooms / areas (including floors) within the building. The system is separated into zones to allow separate occupant control over each area.

The LTHW low loss header is provided with 2  spare connections to facilitate connection for future adaptability. The LTHW systems is unvented, complete with expansion vessels and pressurisation unit to maintain LTHW system pressure between safe working limits all in accordance with the manufacturer’s recommendations.

A quick fill cold water connection is provided to the LTHW systems complete with isolation valves, double check valve and flexible connection.

An in-line steel microbubble deaerator / dirt separator was provided on the LTHW primary flow to remove air from the LTHW system and to prevent the build-up of silt or debris in the boilers.

A welded steel dosing pot unit complete with tundish, air vent, inlet, outlet and drain valves was provided

The LTHW system has had all the necessary water treatment chemicals provided to inhibit the growth of microbiological organisms, limit the build-up of solids and scale and prevent corrosion.

Mitsubishi PAC-FS01-E flow sensors have been provided in the return pipe work to each air source heat pump unit.