St Marys Student Accommodation
Brief: ADL Mechanical & Electrical Contractors Ltd have been contracted to provide the Design Development; Supply; Installation & Commissioning of the mechanical & plumbing installations of the new student accommodation at St Mary’s, Upper Byron Place, Bristol.
The St Mary’s site is part existing and part new, within a commanding position of Bristol. The overall site design is split into four main blocks A, B, C & D with blocks A & B joined. The overall site provides a total of 153 student bedrooms alongside impressive common student areas. The majority of common student areas are located at a basement level underneath Block A. Block A has been renovated/preserved from an existing building with Blocks B, C & D new constructions.
The scope of the mechanical works consists of:-
o Hot & Cold Water Services
o Above Ground Drainage
o Rainwater Installation
o Air Conditioning
o BMS Automatic Controls
o Dry Riser Installation
o Natural Gas Installation
Programme: 48 weeks total
Project Value: £1.3Million
Full Project Narrative
The heating system installed is an intrinsic part of the mechanical services.
Heating is generated via a central plant located in the basement of Block A. The heat generation is a mixture of natural gas fired boilers alongside a Combined Heat & Power (CHP) unit. The CHP unit is designed to run constantly, providing a base heating load, as such the CHP is connected to it’s own proprietary 1,000L buffer vessel. There are 4no. natural gas fired boilers mounted on a proprietary frame located in the centre of the plantroom. The boilers connect via a manufacturer’s plate heat exchanger to the main headers. The primary pipework from the boilers to the main headers is where the CHP connects into.
LTHW pipework is generally installed throughout the buildings using copper pipe with crimped fittings. To transfer LTHW between the buildings Rehau underground pre-insulated PEX pipework has been used along with proprietary fittings.
Block A & B is heated via radiators throughout the building served with LTHW copper pipework. Hot water is provided to Block A & B via calorifiers located within the Block A basement plantroom, served with LTHW from the main plant.
LTHW is provided to the Block C townhouses to serve a Heat Interface Unit (HIU) within each townhouse (8 no.). The HIU within each townhouse provides the hot water provision throughout each townhouse. Heating within the townhouses is provided by electric heaters installed by the electrical contractor.
LTHW is provided to Block D to serve hot water cylinders (3 no.), located at each level. Each cylinder provides hot water to their respective level.
The CHP unit and the boilers exhaust the combustion gases via flues routed to roof level via a dedicated riser.
The heating system is accompanied by a number of required additional plant items: Pressurisation Unit; Expansion Vessel; Dosing Pot; Air/Dirt Separator.
Cold Water Service
Given the number of outlets throughout the site, the cold water requirement is significant.
A new utility connection from the town main is provided to the cold water tankroom within the basement of Block A. The cold water storage tank has a nominal capacity of 15,000L.
To ensure sufficient pressure to all outlets a cold water booster set is installed within the tankroom located within the basement of Block A. The booster set is a twin pump unit in a duty/standby configuration serving the entire site. Blocks C & D are served via underground MDPE pipework.
Internal pipework throughout all blocks is installed using copper pipe with crimped fittings.
The incoming mains cold water is provided with an in-line physical water softener.
Located within the basement Block A tankroom is a CAT5 booster set which serves landscaping & bin store outlets throughout the site.
Hot Water Installation
Hot water is provided throughout the site with different systems utilised.
Block A & B are served via calorifiers located within the Block A basement plantroom. Each calorifier is 1,000L and is heated via the LTHW. Hot water is piped throughout via copper pipe with crimped fittings. A pumped hot water return is installed to ensure temperature at the outlets is achieved.
Block C hot water provision is via the localised HIUs in each townhouse. The HIUs are located centrally within each townhouse with copper pipe complete with crimped fittings to each outlet.
Block D hot water is provided via semi-localised cylinders. Each floor has a 250L cylinder heated via the LTHW. Hot water is piped throughout via copper pipe with crimped fittings. A pumped hot water return is installed to ensure temperature at the outlets is achieved.
Within the Block A basement common areas localised electric water heaters are utilised where required.
Above Ground Drainage
Above ground drainage has been installed to remove waste away from the water points throughout the building.
Traps are installed to all points to prevent odours spilling out from the wastes.
The drainage pipework to all levels above ground floor level is installed in U-PVC, with the drainage pipework at basement level within Block A transitioning to HDPE.
Internal rainwater has been installed within areas throughout the blocks. The rainwater has been installed in HDPE pipework & fittings.
Various ventilation systems are employed throughout the site.
The general principle for the accommodation areas is for fresh air introduced via natural means with trickle vents installed within the windows.
Within Block A each studio is provided with a central extract fan, with ductwork connected to air valves within the bathroom and living areas. The fan is designed to run at a constant trickle with an in-built humidstat, which when increased humidity levels are detected ramp the fan up to boost the extract rate.
Within Blocks B; C & D, each studio is provided with ceiling mounted extract fans within the bathrooms. The fans are connected to plastic ductwork routed to exhaust to external. The fans are designed to run at a constant trickle with the fans connected to the local lighting circuit, which when switched ramps the fan up to boost the extract rate.
Fans within all blocks terminate to external via circular façade mounted louvres with the exception of the top levels, where the terminations are via roof cowls.
Various localised extract systems are installed to cleaners rooms throughout all blocks.
Due to the shortage of natural ventilation within Block A basement, fresh air is introduced via heat recovery units. The heat recovery units are located within the ceiling spaces, typically within the spaces they are serving. The heat recovery units are connect via insulated ductwork to ceiling mounted grilles/diffusers. The heat recovery units intake/exhaust air via roof mounted cowls located within the flat roof area of the basement. Control of the heat recovery units is via localised controllers, which enable time schedules and also occupant override if necessary.
Refrigerant based air conditioning systems are installed to provide cooling to the Block A basement server room and cooling/heating to the Block A basement gym area.
The server room is installed with a wall mounted fan coil unit, with a localised controller. The condensing unit is located external to Block A at ground level.
The gym is installed with a ceiling mounted cassette fan coil unit with a localised controller. The condensing unit is located external to Block A at ground level.
BMS Automatic Controls
Given the size and complexity of the systems installed, a comprehensive Building Management System (BMS) is required.
The BMS system’s main panel is located within the Block A basement plantroom, with a secondary panel located within Block D. The BMS system utilises a Trend based platform to control & monitor the mechanical & plumbing plant & equipment.
To comply with Part L regulations and obtain the required BREEAM credits, a comprehensive metering system has been installed. The BMS system incorporates alarms to alert the building operators of out of limit values detected from the meters.
Along with controlling & monitoring the installations, the BMS systems incorporate a number of safety systems, which during certain conditions will shut down plant & equipment and close off the gas supply to the plantroom.
Dry Riser Installation
With the height of the separate blocks and their layouts, it has been necessary to install dry riser systems to Blocks A & D.
The dry riser system incorporates an inlet valve at a location determined by the architect to allow the fire brigade to connect with ease. Via galvanised steel pipe complete with victaulic fittings the inlet valves are connected to outlet landing valves, which are installed 1 no. per level within designated stairwells.
Natural Gas Installation
Natural gas is provided to the site via a new utility connection, with the utility gas meter located in a dedicated meter room adjacent the bin stores at the main site entrance.
From the utility gas meter, the gas pipework is routed underground via HDPE pipework to the new Block A basement plantroom. Within the plantroom steel pipework complete with welded/screwed fittings routes the gas to the boilers and the CHP unit.