Module 4 - Ventilation Flashcards
Ventilation Requirements (all kW net)
O/F Boiler 20kW
DFE 10kW
LFE 7kW
Cooker 14kW, 15m3 room, opening window
Boiler = 20 x 5 = 100
DFE = 100
LFE = 7 x 5 = 35
Cooker = 0
Answer = 235cm2 free area
Can this ventilator with a flyscreen be used with gas?
No - catches lint and can be blocked + the picture also shows a hit and miss vent
If 4 = 100cm2 what do 7 and 8 need to be?
7 and 8 need to be 50% bigger than 4 i.e. 150cm2
If you have multiple F/L appliances in a room how much additional ventilation would you require?
Simply add up all their heat inputs and consult the table in BS4440-2000 Part II ‘Ventilation for Flueless Appliances’
Building regulations state that all flueless appliances must have:
a) No window (or equivalent) or ventilation, if required, to an internal room
b) Window (or equivalent) and, if required, vent to outside
c) Window (or equivalent) and, if required, vent to internal room
b) Window (or equivalent) and, if required, vent to outside
Ventilation Requirements
DFE 10kW net plus
LFE 4.5kW net
DFE = 100cm2
LFE = 4.5kW x 5cm2 = 22.5cm2
Total free area required = 122.5cm2
Remember fixed vent requirement take the adventitious
What is adventitious ventilation and how much can you assume it is?
1) Air that enters via cracks around door fames etc.
2) 35 cm2
Compartment vents – 4 key reminders when installing
1) Internal vents, same room, external, same wall
2) Range rated – use max kW
3) Two or more flued appliances – add them all up
4) Ducting – separate for top/bottom
Compartment ventilation
What are the 4 things to remember?
1 Vents can be direct to outside air or to inside space
2 They must communicate to the same space
3 Two vents are required, one at high and one at low level
4 DO NOT deduct 7kW from appliance max. input before calculating
compartment vent sizes - use max. heat input
Ventilation Requirements
O/F boiler 20kW net plus
O/F fire 5.5kW net
20kW + 5.5kW = 25.5kW – 7kW = 18.5kW x 5cm2 = 92.5cm2 free area
Both O/F, both space heaters, add then together
A data plate does not indicate whether the kW is gross or net. When doing a ventilation calculation which one do you assume it is?
Net - gives you a bigger vent requirement
Unless you are sure that the appliance is pre 2000 then you assume it is gross (gross / 1.1 = net)
If vent 4 = 100cm2 what does vent 5 need to be?
The same - 100cm2
What are the two key reason for compartment ventilation?
1) For O/F appliances - combustion & cooling
2) For R/S appliances - cooling
Compartment Ventilation
What sized vents are required on the outer wall?
Top - 5cm2/kW
Bottom - 5cm2/kW
By rule of thumb what is the difference between a room and a compartment?
A compartment is 3
Compartment Ventilation
What sized vents are required on the outside wall?
5cm2/kW top
10cm2/kW bottom
The ventilation requirement for a domestic oven, in a room 5 to 10m3, is 50cm2.
If the room has a door and a window to the outside what is the new ventilation requirement?
None
When doing a vent calculation do you use gross or net kW?
Net
You have a type B appliance of 27 kW how much ventilation is required?
27kW – 7kW (adventitious air) = 20kW x 5cm2 = 100cm2
Ventilation Requirements
10m2 room with opening window and door to inside room
Cooker and DFE in room
Cooker = 50cm2
DFE = 100cm2
Answer = 100cm2
Take the largest of the two since a cooker is involved
Three Vents in series
What size to vents 2 and 3 need to be relative to 1?
50% more free area
If 4 = 100cm2 what do 7 and 8 need to be?
Assuming it is an O/F boiler in the compartment what size per kW do these vents need to be?
7 and 8 need to be 50% bigger than 4 i.e. 150cm2
Compartment
Top vent 10cm2/kW
Bottom vent 20cm2/kW
Compartments - can you use adventitious air in the ventilation calculations?
No
For a terracotta air brick do you measure A or B to calculate the free area for ventilation?
A - the smallest side
Ventilation Calculations
Name three types of space heater
1) Central heating bolier
2) Warm air unit
3) Gas fire or convector
How much ventilation does an appliance > 7kW require?
5 cm2
You have a type B radiant gas fire rated at 6.5kW – how much ventilation is required
Type B appliance which is < 7kW – no additional required since the adventitious air is enough
If you appliance has a range rated input (say 20 – 27 kW) what value do you use for a ventilation calculation?
The largest - 27 kW
Ventilation Requirements
Same room, O/F water heater (33kW) and an O/F gas warm air heater (25 to 32kW net)
Key – one is a space heater and one is not so they need to be calculated separately
Water heater
33kW / 1.1 = 30kW net
30kW – 7kW = 23kW x 5 = 115cm2
Warm air heater
32kW – 7kW = 25kW x 5 = 125cm2
Free area needed = 125cm2 (larger of the two)
What are the max and min hole sizes allowed in a ventilator?
5mm to 10mm
A compartment – if you have a 21kW Net O/F boiler in there what are the vent requirements
NB
Internal T =10cm2 B = 20cm2
External T = 5cm2 B = 10cm2
Internal
T = 10 X 21 = 210cm2
B = 20 x 21 = 420cm2
The room would also need vent:
21kW – 7kW = 14kW = 14 x 5 = 70cm2
OR
External
T = 5 x 21 = 105cm2
B = 10 x 21 = 210cm2
If there is nothing on the data plate how do you convert from gross to net kW?
Gross kW / 1.1
Can you use this type of ventilator for gas?
No - hit and miss vents are not allowed since they can be closed!
There are three classifications of ventilation:
1) Adentitious
2) Additional
3) Compartment
Key points about each
1) Ventilation occurring naturally through badly fitted doors and windows (draughts)
2) Ventilation installed by the plumber/gas fitter to ensure good combustion
3) Ventilation installed in a room of less than 5 cubic metres volume to permit cooling/combustion air to enter
Compartment – what vent area is required per kW, room sealed, for both the high level and low level vents
Internal – 10cm2 top, 10cm2 bottom
External – 5cm2 top, 5cm2 bottom
Ventilation Requirements
Same room, flueless water heater (50cm2 vent + window required) plus a fire (5kW net) and back boiler (16 to 19kW net)
a) FL water heater = 50cm2 + window
b) Fire & boiler both O/F so 5kW + 19Kw = 24kW – 7kW (adven) = 17kW x 5cm2 = 85cm2
Rule = max of the three type, so the answer is 85cm2 + an open window (FL requirement)
Vents in series
How much bigger should the second vent be?
Same size as the first vent
Where should vents in a compartment be located:
a) Internal – T, external – T
b) Internal – T&B and external – T
c) External – T&B
d) Internal – T&B and External T&B
e) Internal – T&B or External T&B
Top = T Bottom = B
e) Internal – T&B or External T&B
How much ventilation does a type B fire require with a heat input of < 7kW?
None
Compartment – what vent area is required per kW, open flued, for both the high level and low level vents
Internal – 10cm2 top, 20cm2 bottom
External – 5cm2 top, 10cm2 bottom
If a data plate is not clear whether the kW is net or gross which one do you assume it is?
a) Net
Except
b) If you are sure the appliance is older than Jan 2000 then gross
