Page 499 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

Chapter 7 Central heating systems

Delayed start
Here, the end user sets the time to switch on the heating, taking into account
the time it would normally take to warm the dwelling – for example, most
people would set the heat to come on at 5 pm if they were due to arrive home
from work at 6 pm. A delayed start unit will, at the time the heat is due to
come on, compare the current indoor temperature to that required by the room
thermostat. It will then delay the start of the boiler firing if required. The benefits
are that during milder weather, when the heat requirement is less, energy will be
saved. Room thermostats with a delayed start function are now available.

Optimum start
With an optimum start system, the end user sets the required occupancy times
and the required room temperature, and the controller calculates the necessary
heat-up time so that the rooms are at the required temperature irrespective of
the outside temperature. The idea is based around comfort rather than energy
savings.

Internal
temperature (°C)

20
Potential
Earliest energy saving
16 normal
start

12 Delayed start

8

5 6 7 8 9 10
Time (hours)
Typical settings
Maximum heat-up period, e.g. 6am to 8am
Normal occupancy period, e.g. 8am to 10am
p Figure 7.58 Delayed/optimum start function

Domestic boiler management systems (home
automation systems)
A boiler management system (BMS) is an electronic controller that provides
bespoke control solutions for domestic central heating systems.
Standard functions of BMS control include real-time temperature and boiler/
controls monitoring, room temperatures (known as set points) and time
schedule adjustment, optimisation, and night set-back control.

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