Chimneys And Flues

Question 1

What are the 3 classifications of flues?

Answer 1

Flue-less (Type A), Open (Type B), Room sealed (Type C)

Question 2

What are the 4 parts of an open flue?

Answer 2

1. Primary
2. Down Draught Diverter
3. Secondary
4. Terminal

Question 3

What is the max change in direction allowed on a metal flue?

Answer 3

45 degrees

Question 4

What is minimum required length of vertical rise before any change in direction?

Answer 4

600mm

Question 5

What is upstream?

Answer 5

Upstream is when the position of the fan is before the heat exchanger causing positive pressure on the case

Question 6

What is downstream?

Answer 6

Downstream is when the position of the fan is after the heat exchanger causing negative pressure on the case

Question 7

How many starter blocks does a precast chimney have?

Answer 7

3

Question 8

What is the max change in direction allowed on a precast chimney system?

Answer 8

30 degrees

Question 9

What is the minimum diameter of a flue where a terminal is not required?

Answer 9

170mm

Question 10

What is the max length allowed for a twin wall metal flue to run externally?

Answer 10

3m ( Any longer and it should be factory insulated)

Question 11

What is the minimum height from a gas fire spigot to the hearth?

Answer 11

250mm

Question 12

Where can you find a hearth plate fitted?

Answer 12

Stop clock or the consumer unit

Question 13

What is the purpose of a down draught diverter?

Answer 13

To dilute POC and help with the pull of the flue

Question 14

What is the minimum cross sectional area of a pre cast flue?

Answer 14

16,500mm2 with no dimension less than 90mm

Question 15

What is the minimum cross sectional area of a brick built flue?

Answer 15

12,000mm2

Question 16

What size should the air gap between the walls of a twin metal flue be?

Answer 16

25mm

Question 17

What must be carried out where a back boiler unit is fitted to a brick chimney?

Answer 17

It must be lined

Question 18

How does a balanced flue work?

Answer 18

By POC going out the middle and cold air drawn in by the outer part

Question 19

What is the max clipping distance for a metal flue pipe?

Answer 19

1.8m

Question 20

What size terminal guard is required for a room sealed fanned draught appliance?

Answer 20

Below 2m

Question 21

What size terminal guard is required for a room sealed natrual draught appliance?

Answer 21

Below 2.1m

Question 22

What is required if replacing a solid fuel fire with a gas fire?

Answer 22

A chimney sweep

Question 23

What is the minimum up stand of tile/ slated roof penetration at any point where the flue passes the roof?

Answer 23

150mm

Question 24

What should the vent size be of a brick built chimney with a slab on top?

Answer 24

12,000mm2

Question 25

Where should the annular space be sealed for flue liners down brick chimneys?

Answer 25

Top and bottom

Question 26

What is the minimum diameter where a precast chimney converts to a metal flue in the loft space?

Answer 26

125mm

Question 27

What size should holes on a terminal guard be?

Answer 27

no bigger than 16mm

Question 28

How many appliances can be fitted to one chimney?

Answer 28

1

Question 29

How much clearance is required from any combustible material; for a twin wall metal flue going through the ceiling?

Answer 29

25mm

Question 30

Before fitting any gas appliance what must be applied to a damper plate?

Answer 30

That it is permanently fixed open

Question 31

What is the clearance required from a ridge terminal on roofs from any structure?

Answer 31

1.5m

Question 32

What height is required if both ridge terminal and psv are fitted on the same face of a building?

Answer 32

They must be fitted at the same height

Question 33

Which British standard regulation covers flueing on appliances under 70kw?

Answer 33

BS 5440 part 1