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Adventitious ventilation per room
35cm2 per room
The two types of ventilation.
What must flueless and open-flued appliance have.
Purpose provided ventilation.
Why must flueless heaters have purpose provided ventilation sited away from the appliance.
If the vent is fitted adjacent to the appliance it may affect the correct operation of the ASD.
What affect can extract fans have on open flue systems.
Extract fans can draw air out of the room creating a negative pressure in the room which can counter the natural pull of the open flue system pulling POCs into the room. I.E. spillage.
Maximum time that a flueless instantaneous sink heater can operate continuously.
Maximum 5 minutes.
Open flue ventilation calculation.
(Net heat input (in kW) - 7) × 5 = cm2
Multiple open flue appliances ventilation calculation.
((Total net heat input) - 7) × 5 = cm2
What does an open flue appliance in a compartment require.
An open flue appliance in a compartment requires high and low ventilation to supply combustion air and cooling air.
What is the purpose of the low level ventilation for a compartment with an open flue appliance.
The low level vent provides flue dilution air and cooling air in to the compartment.
What is the purpose of the high level ventilation for a compartment with a open flue appliance.
The high level vent allows warm air to leave the compartment, keeping the compartment cool.
Why are air vents needed in an open-flued appliance compartment.
The vents provide air for combustion, correct operation of the flue and appliance compartment cooling.
What is the standard for ventilation
BS 5440 Part 2.
Where should air vents be situated, where practicable on new installations.
The air vents should be positioned on the same wall so that they are subject to the same pressure and ideally on an outside wall.
Ventilation requirements for a compartment with an open flue appliance. Air from room
High level 10cm2/kW
Low level 20cm2/kW
Ventilation requirements for a compartment with an open flue appliance. Air from outside.
High level 5cm2/kW
Low level 10cm2/kW
Ventilation requirements for a room sealed appliance fitted in a compartment.
High & Low ventilation of 10cm2 per kW if air from a room.
5cm2 per kW if air direct from outside.
Compartments containing room-sealed appliances that require high and low vents also require.
A warning notice advising against blocking the vents.
Procedure for determining multiple appliance ventilation where there is a mixture of flueless and open flued appliances in the same room.
Calculate the individual requirement for each appliance.
Provide the ventilation based on the LARGEST of the individual requirements.
What are the requirements for air vents.
Not be closeable.
Not contain a mesh or fly screen.
Be ducted across a cavity.
Be thermally stable.
Allow the entry of a 5mm diameter ball.
Prevent the entry of a 10mm diameter ball.
What are the general installation requirements for vents.
Vents should not be fitted where they can cause nuisance draughts.
Vents should not be fitted at low level to the outside where they could get blocked by leaves, debris, snow and flood water.
What are intumescent air vents.
Intumescent air vents allow air through under normal conditions but will automatically close and seal if they get too hot e.g. in the event of a fire.
Vents in series. Two adjacent rooms. Vent 1 & Vent 2 equal
(Heat input - 7) x 5 = cm2
Vents in series. More than 2 vents in series (i.e. 3 adjacent rooms). Procedure for determining vent sizes.
Vent 1 = (net heat input - 7) × 5 cm2
Vent 2 = vent 1 + 50%
Vent 3 = vent 1 + 50%
Where multiple vents are fitted in a compartment or room they should be positioned to avoid.
When does cross ventilation occur.
Cross ventilation occurs where 2 vents are on opposite walls of a room or compartment.
What happens when a room or compartment is cross ventilated.
The air flow goes directly across the room or compartment between the vents and does not provide an air flow into the appliance. This can result in spillage.
Positioning of passive stack ventilation and open flue terminals.
Terminals of passive stack and open flue appliances should be located on the same face of the building and the appliance flue should terminate at the height or higher than the passive stack terminal.