Ventilation: Approved Document F, Volume 1 — Dwellings

F1(2), R39,O RN L4I N2E , VRE R4S I4O N Ducted systems 4.7 For all ductwork and terminals, the following checks should be made and the results recorded in the checklist in Appendix C. a. That the system has been installed to achieve both of the following. i. The design criteria. ii. A standard that will not reduce its performance. b. That the number, size and location of the air terminals provide effective air distribution in the space. c. That all ductwork and terminals are in good condition with no obvious defects that will affect the performance of the system. d. That the air flow direction is correct at each room terminal. e. That there are no abnormal noises from the ventilation system, including in all of the following situations. i. On start-up. ii. When running in background ventilation mode. iii. When running at the high rate. 4.8 For continuous mechanical ventilation systems, such as continuous mechanical extract ventilation or mechanical ventilation with heat recovery, the system should be balanced to achieve design air flow rates at each room terminal. The fan manufacturer’s instructions should be followed when balancing the system. If specific details are not available from the manufacturer, the relevant set of instructions from sub-paragraphs (a) to (e) below should be followed. a. For adjustable terminals with a fixed (stepped) speed fan, the following apply. i. The fan speed should be set to achieve the desired continuous flow rate. ii. The index terminal flow rate should be set with the terminal fully open and all other terminals should be adjusted to achieve the required flows at each terminal. iii. If the total flow rate cannot be achieved through all the terminals, then the fan speed should be increased. iv. If all the terminals have to be set to a significantly closed position to achieve the required air flow rate, then the fan speed should be reduced and the terminals rebalanced. b. For adjustable terminals with a controllable speed fan, the following apply. i. The fan should be set at a speed that will approximately achieve the desired continuous flow rate. ii. The index terminal flow rate should be set with the terminal fully open and all other terminals should be adjusted to achieve the required flows at each terminal. iii. If the index terminal has to be set to a significantly closed position to achieve the required air flow rate, then the fan speed should be reduced and the terminals rebalanced. c. For fixed terminals with flow adjustment by duct damper or a similar device at the fan unit, the guidance in sub-paragraphs (a) or (b) above should be followed, depending on the type of fan speed control. 32 Approved Document F Volume 1, 2021 edition Building Regulations 2010 O N L I N E V E R S I O N