Mechanical
engineering
specification
Essential elements
Version 2.0
Resources Directorate
Mechanical engineering specification
Essential elements
Introduction
3
Cold water/pressurised water
3
Hot water
3
Hot and cold water (self-contained specification)
3
Pressurised water/natural gas/fuel oil storage/distribution
3
Natural gas/special purpose fixtures/furnishings/equipment
3
Gas/oil fired boilers
4
Alternative fuel boilers
4
Low temperature hot water heating
4
General ventilation
5
Toilet ventilation
6
Air conditioning units
6
Central control/building management
6
Testing and commissioning
7
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Introduction
1.
For incorporation into project design briefs and employers requirements
for design and build projects.
S10/S13 - Cold water/pressurised water
2.
Backflow prevention - reduced pressure zone backflow prevention
devices are not to be specified unless previously agreed as the only
course of action for category four liquid contamination. Preferable
solutions will include suitable break tanks and booster sets if required
for high pressure cold water applications.
S11 - Hot water
3.
Centrally based HWS production - where centrally based HWS
production is a prudent option, the method of hot water production
should be capable of being isolated completely from the heating system
distribution. Use of the same heating plant may be cost or ecologically
effective to provide the primary heat for the system, particularly in the
case of biomass boiler installations.
S12 - Hot and cold water (self-contained
specification)
4.
Hot water - local production of hot water should be considered when
serving toilet and kitchen accommodation facilities. Long runs of either
primary or secondary hot water circulation pipe work having high
standing losses are to be avoided wherever practicable in favour of local
direct water heaters. All remote water heaters (whether gas or
electrical) shall be linked to the timed outputs from the building
management system, with over rides being provided on control
extension switches or timetables.
S13/S32/S41 - Pressurised water/natural gas/fuel
oil storage/distribution
5.
Metering - new extensions to existing buildings shall be capable of being
separately metered for energy and water consumption. Metering shall
be capable of transmitting the metered information to the building
management system.
S32/N20 - Natural gas/special purpose
fixtures/furnishings/equipment
6.
Gas safety systems - gas safety systems shall be installed in all general
science, domestic science, craft or art rooms which utilise either
propane or natural gas in their curriculum. The gas safety systems
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shall comprise a control panel for each individual room thus served and
emergency control knockoff buttons are to be provided at all exits and
at the teaching station.
7.
Laboratory piped service - all laboratory piped service fittings
(especially gas lab taps), are to have secure metal fixing bases with a
locking base screwed to the worktop to prevent the fitting from being
forcibly twisted in the material of the worktop, rather than relying on a
manually or machine formed hole in the worktops.
T10 - Gas/oil fired boilers
8.
Natural gas boilers - natural gas boilers are to be of a fully modulating
and condensing type wherever practicable. Boiler controls in all cases
shall allow for total control of the boiler functions and temperature
control by building management interfaces and connections. Domestic
type boilers with integral controllers are not to be used.
T16 - Alternative fuel boilers
9.
Biomass boilers - on new or suitable refurbishment projects, the use of
biomass boilers is to be considered. The biomass boilers must be
backed up by a suitable alternative source such as noted above and
have fully interlocked control systems to ensure the safety and full
integrity of the systems when changing from one fuel type to another.
T31 - Low temperature hot water heating
10. Zoning - the zoning of new or refurbished buildings is to be considered
carefully in relation to the orientation, construction and usage of the
building. Alternative types of heat emitter shall always be provided with
separate piped circuits, due to the differing control parameters required
for each. Typical categories of separate circuit would be:
• Radiators
• Fan convectors
• Under floor or radiant heating
• Air handling plant (see section V10 – general ventilation)
11. Radiators - radiators to junior and infant accommodation shall be of the
low surface temperature type and shall incorporate matched
thermostatic valves set within the casing, with lockable settings
available on the control device. Sensors for the thermostatic valves are
generally to be located at low level in the return air grilles of such units.
All heating flow and return pipe work hidden within these casings is to
be either physically isolated or thoroughly insulated from the sensors to
prevent false temperatures shutting down the thermostatic valves in
error.
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12. Fan convectors - fan convectors shall, wherever practicable, have a
reverse air flow pattern with return air being brought into the unit at
high level and the supply air being provided at low level. Units shall be
sized to provide the required output at the lowest speed setting to
minimise motor and fan noise. Noise characteristics shall be in
accordance with the requirements of the CIBSE guide for the areas to
be heated.
13. Pumps - the use of electronically speed controlled pumps will only be
considered where the unit has a facility for manual speed control over
ride in the case of the electronic control element failing. Boiler
circulation pumps shall be of the twin head, single case type wherever
practicable with automatic changeover on a duty standby basis from the
main control panel. Twin head pumps shall be fitted on all critical
circuits, which shall be determined in discussion with the client. Single
head pumps may be considered for individual smaller heating circulation
where the type of pump is readily available and/or the temporary loss
of the circuit may be deemed an acceptable risk after discussion with
the client.
14. Heating circuits - all heating circuits shall have easily accessible and
frequent points of isolation, draining and air venting. All low level runs
of pipe work shall have drain points fitted at the lowest point,
regardless of the number of radiators installed on the circuit. Isolation
shall be provided on all high level heating pipe work where dropping
from ceiling voids and shall be installed on all pipe work where a circuit
serves in excess five heat emitters in series.
U10 - General ventilation
15. Natural ventilation - natural ventilation is to be designed into all new
and, where practicable, refurbishment projects in existing buildings.
Ventilation openings shall take account of the effects of prevailing
winds, external noise issues and the control of such systems. Natural
air inlets should be designed in such a way as to eliminate the use of
heating sources to temper the incoming air whilst being controllable as
required to avoid the need for heating quantities of air above the
requirements of the building regulations and building bulletin 101.
Where possible BMS control of opening windows and roof ventilators
(wind catcher type or roof lights) shall be adopted, but with provision
for a manual over ride of such control for each area thus automatically
controlled. Automatic control of natural ventilation will utilise CO2
sensors in preference to generic air quality sensors which can react to a
number of pollutants unrelated to CO2 concentrations, particularly in
new buildings where paint fumes, carpeting etc will cause air quality
sensors to allow large quantities of unheated air into the buildings when
not required.
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U11 - Toilet ventilation
16. Toilet ventilation - toilet accommodation in general requires the use of
artificially aided ventilation solutions to achieve the required air flow
rates. The large volumes of heated air requiring extraction should give
rise to a system incorporating some form of heat transfer from the
extract to pre warm the supply air back into the toilet. Typically, a
cross flow type heat exchanger would be the preferred option where
practicable. Individual units incorporating this technology are available
from various manufacturers to suit most circumstances. The toilet
ventilation may consist of several toilet areas linked to a larger common
extract system or a single unit in individual, small toilets. All shall be
controlled by the use of a suitably mounted PIR type detector with an
over run timer. Filters on fans shall be easily accessible and cleanable.
U60 - Air conditioning units
17. Air conditioning - air conditioning of spaces is to be avoided as far as
practicable by the use of controlled natural or forced ventilation. In
certain circumstances (such as specific IT suites) air conditioning may
prove to be the only way to alleviate the high temperatures
experienced. Efforts to design IT installations using low energy
computers with LCD screens should be considered prior to this being a
final solution. Air conditioning is not to be specified for any area of
accommodation unless all options of natural or mechanically assisted
ventilation have been exhausted. In general, it may only be considered
for specific IT areas, but current thinking is that general purpose
classrooms shall be suitably equipped for IT usage; utilizing low power
laptops or low energy desktop computers with LCD screens which do not
generate as much heat gain.
W60 - Central control/building management
18. Control systems – these systems shall be provided to all heating and/or
mechanical services installations in accordance with the current building
regulations/BISRIA/CIBSE guidance. The scope and complexity of these
systems shall be appropriate to the building scale, type and usage and
must provide cost effective efficient controls compatible with the
Council’s key objectives of reducing energy consumption, reducing
carbon emissions and providing maximum accommodation availability
within the Council’s property estate. The following items are considered
to be the essential elements of any controls system to be installed:
• Only one manufacturer of controls system should be deployed on
any one site. On sites where multiple installations already exist
they must be interconnected to allow full central and remote
control through one of the approved manufacturers. All systems
should be accessible from a minimum of two locations on the site
and a third by remote access.
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• The specification of the controls manufacture shall be carefully
considered by the consultant in order to allow effective and
efficient maintenance of the controls systems in the future. On
the grounds of maintenance rationalisation and efficiency, the
Council wishes to limit the number of different controls equipment
manufacturers used across its estate to a maximum of three.
• Where the installation of a full building management system is
considered appropriate, the system must be provided with full
web based interactivity for both remote user information and
remote re-engineering.
• Consultants’ specifications shall be produced for review/approval
and must include detailed operational strategies for the systems,
technical requirements and standards the system is to comply
with.
• Contractors will ensure technically competent controls specialists
are employed to deliver these installations and the consultant will
be responsible for witnessing the initial setting up of the system
and performance monitoring during the initial 12 months of
operation. A written post commissioning report must be
submitted to document the satisfactory completion of the controls
installation.
• Comprehensive end user training must be provided for all
installations, demonstrating operation at both the local and
remote location.
Testing and commissioning
19. The testing and commissioning of all mechanical services is of
paramount importance and must be fully integrated into the project
programme. All test certificates, manuals and commissioning data must
be available to the supervising engineers in sufficient time for checking
and agreement prior to handover of the building to the client. The
project team must refuse acceptance of the building until these
documents have been presented and agreed as there are legal health
and safety implications for proving the compliance of many mechanical
systems with statutory testing procedures prior to occupation of the
buildings.
Prepared by:
Chris Jackson
Policy and Training Manager
Property Services
17 February 2016
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If you would like this information
in another format please contact:
Cornwall Council
County Hall
Treyew Road
Truro TR1 3AY
Telephone: 0300 1234 100
Email: enquiries@cornwall.gov.uk
www.cornwall.gov.uk
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