Thermostat

Under Construction This page is still being written, and has not had any form of review or comment. Do not rely on any information presented here. --John Rumm 03:56, 18 November 2007 (GMT)

This article discusses some of the many and varied ways in which thermostats are wired into domestic central heating systems.

<cautionary statements about mains voltages etc>

What does a thermostat actually do?

A thermostat is a simply a temperature controlled switch. In its simplest form the switch will default to closed or "On" until the stat reaches a preset temperature. Once it is warm enough, it opens or turns "off".

The temperature at which this happens is usually selected by a user adjustable control.

Do I need one

Yes. If you dont have one, the boiler will keep cycling when the programmer switches it on, even through a hot summer, thus wasting fuel and adding wear and tear to the boiler.

TRVs alone don't maintain a fully stable temperature, so again heat will be wasted when temps rise above what's required for comfort.

Cover heating system interlock, TRVs etc.

How many should I have

Discuss cylinder stats, multiple zones, UFH etc.

Types of thermostat

Mechanical Thermostats

diagrams and piccies of trad Honywell style stat

Thermostat features

Cover why there are a number of variations and explain things like:

• Anticipator / Compensator heaters
• Changeover contacts
• Frost protection
• Aux switching and contacts
• Optimising stats

What does the thermostat control

• Connecting to a boiler
• Controlling a zone valve

How should I wire it

• Type of cable
• Earthing or lack of
• what to do with spare neutrals

What else can I control with a thermostat

• other apps including switching electric heating loads directly
• cooling loads
• over temperature alarms and sensors.