Chapter 11 Flue/Chimney systems

Question 1

A circular flue for a new gas fire requires a minimum cross-sectional area of what?

Answer 1

12,000 mm² this is the same as 5 inches or 125 mm

Question 2

What is meant by natural draught appliance?

Answer 2

No fan to get products of combustion out or air in.

Question 3

ACS exam question

If an appliance has a dodgy flue and products of combustion continue to enter the room is the draught diverter working?

Answer 3

Yes, but the flue isn’t.

Question 4

Name the four points on an open flue appliance.

Answer 4

1. Primary flue this will be covered.
2. Draught diverter (Looks like a skirt).
3. Secondary flue.
4. Terminal.

Question 5

What is the minimum length of a flue for a gas fire?

Answer 5

3 m straight pipe

Question 6

Bends shall not exceed?

How much does a bend or a terminal reduce the height of a flue by?

There must be a minimum of how many millimetres vertical rise before the first bend?

Answer 6

45°

0.5 m each

600 mm

Question 7

Flue twin walled will appear a dull grey colour what is between the first and second wall gap?

Answer 7

Air gap.

Question 8

Factory insulated flue will appear very shiny or black what length can this be?

Answer 8

28 meters

Question 9

Any opened flu appliance greater than 7 kW net will require ventilation how many cm² for every net kW above 7 kW?

Answer 9

5 cm²

The formula to work this out is:

Net kW -7×5 =

Question 10

The appliance must incorporate a control to automatically shut down the burner if it detects no air for more than how many seconds?

Answer 10

Six seconds

Question 11

If a chimney is 4 m high and has two 45° bends under terminal what would the height be?

Answer 11

2.5 m

The formula for this:

4 m - 1.5 m = 2.5 m

The bends and the terminal each equal 0.5 m .

Question 12

How many metres can a single wall pipe be outside or in the loft?

Answer 12

0 m single wall pipe cannot be outside.

Question 13

Sockets must be facing uppermost on what type of flue?

Answer 13

Cement based single wall flue.

Question 14

Where temperatures are expected to exceed 85°? The flue pipe shall be a minimum of how many millimetres from any combustible material?

Answer 14

25 mm

A non-combustible sleeve may be used to provide 25 mm air gap.

Question 15

BS EN 13501 - 1 : 2007 + A1:2009

Approved document B states what materials must be used in construction on external walls

Answer 15

Class A1

Question 16

How is class 1 chimney identified?

Answer 16

Unlined, classic, brick chimney

Identifiable by 7 inch diameter or greater (175 mm) minimum

Question 17

If a damper/restrictor is found in a chimney serving as a gas appliance, what must you do?

Answer 17

You must remove it or permanently fix it in an open position.

Question 18

What lining is suitable for a new build?

Answer 18

Concrete, ceramic or clay lining

(not poured concrete)

Question 19

What is the equation to measure the void volume?

Answer 19

W (mm) x D (mm) x height below spigot (mm) ÷ 1,000,000 = dm3

Question 20

If something is found on Landlord checks as AR, what do you do with your inspection?

What must you do if you put something AR?

Answer 20

Carry on with the inspection in case something is found that is ID.

Once all checks are complete informed the customer of the risk, put a warning sticker on the appliance not to use, complete all paperwork.

Question 21

What do you do if you find something is ID?

Answer 21

Stop all processes.

Question 22

I bricked up builders opening is classed as what?

Answer 22

At risk (AR)

Question 23

Pipework installed into base of unlined chimney connecting the appliance directly to the chimney base inside the base no less than how many millimetres?

Answer 23

250 mm

Question 24

The flu should project how many millimetres in a lined and lined chimney?

Answer 24

Lined minimum 150 mm
Unlined minimum 250 mm

Question 25

If a 5 inch steel liner was put into a class one chimney, what would this now make the chimney?

Answer 25

Class 2

Point to note: a 7 inch liner was installed this would still be class 1.

Question 26

The class 2 chimney is identifiable by how many inches diameter?

Answer 26

5 inches (125 mm)

Question 27

Installing a flue liner into a gas fire,, the protrusion of the liner through the plate should not exceed how many millimetres?

Answer 27

25 mm

Question 28

Pre-cast chimney must have how many starter blocks?

Answer 28

3

Question 29

A termination must be how many mm above the ridge of a roof if near the top and there’s not 1.5m of clearance?

Answer 29

600mm

Question 30

Open flue terminal is not required for a flue with an axis greater than?

Answer 30

170mm

Question 31

The openings in an open flue terminal must be sized to allow entry of ??mm ball but not a ??mm ball.

Answer 31

6 & 16

Question 32

Suitable terminals for open flues, all the holes on the terminal added together in total should be what size compared to the flue opening?

Answer 32

Twice the size of the flue opening.