Page 544 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

The City & Guilds Textbook: Plumbing Book 1

IMPROVE YOUR MATHS
PVCu has a coefficient of linear expansion of 0.06 mm/m/°C. This means that for every metre (1 m) of gutter,
PVCu expands by 0.06 mm for every degree rise in temperature. For example:
If a 1 m length of gutter is subjected to a rise in temperature of 10°C, it will expand by the following amount:

1 × 0.06 × 10 = 0.6 mm
This might not seem a lot, but let’s look at this in more detail.
Example 4
A south-facing gutter 15 m long is subjected to a 25°C temperature rise. What is the expansion of the gutter
when the coefficient of linear expansion of the gutter is 0.06 mm/m/°C?
All the information we need to be able to calculate this is in the question:
Length of gutter = 15 m
Temperature diff. (Δt) = 25°C
Coefficient of linear expansion = 0.06 mm/m/°C
Therefore:
15 × 25 × 0.06 = 22.5 mm

ACTIVITY

Calculation of thermal expansion
Using the method shown in the worked example above, calculate the following:
1 A south-facing gutter 10 m long is subjected to a 15°C temperature rise. What is the expansion of the gutter
when the coefficient of linear expansion of the gutter is 0.06 mm/m/°C?
2 A south-facing gutter 20 m long is subjected to a 30°C temperature rise. What is the expansion of the gutter
when the coefficient of linear expansion of the gutter is 0.06 mm/m/°C?
3 A south-facing gutter 5 m long is subjected to a 20°C temperature rise. What is the expansion of the gutter
when the coefficient of linear expansion of the gutter is 0.06 mm/m/°C?

KEY POINT
To counteract the expansion, all manufacturers build in to their fittings a 10 mm expansion gap. This must
be observed when installing PVCu gutters if problems with thermal expansion are to be avoided.

Guttering retaining clips

Rubber gutter seal
Gutter installed up to the
thermal expansion marks
Thermal expansion marks

p Figure 8.10 Expansion gap on PVCu gutter fittings 1 p Figure 8.11 Expansion gap on PVCu
gutter fittings 2

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