CENWAT System Controls and Zoning 1 — Questions and Answers
Question 1: What is the primary function of a thermostatic radiator valve (TRV)?
- To regulate boiler flow temperature
- To control water flow through a radiator based on room air temperature (Correct answer)
- To measure system pressure at the radiator
- To control pump speed
Correct answer: To control water flow through a radiator based on room air temperature
A TRV senses the air temperature in the room and throttles the flow of hot water through the radiator to maintain the set temperature.
Question 2: Why must a TRV not be fitted to the radiator in the room containing the room thermostat?
- TRVs are too large for that room
- Both controls would compete to regulate temperature, causing short-cycling and inefficiency (Correct answer)
- The room thermostat requires maximum heat flow at all times
- TRVs cannot be fitted near electrical devices
Correct answer: Both controls would compete to regulate temperature, causing short-cycling and inefficiency
If a TRV and room thermostat are in the same room, both will independently try to control the temperature, leading to conflict, short-cycling, and loss of accurate control.
Question 3: Under Building Regulations Part L, at what minimum floor area does a new domestic heating system require at least two independently controlled temperature zones?
- 100m²
- 150m² (Correct answer)
- 200m²
- 250m²
Correct answer: 150m²
Part L of the Building Regulations requires dwellings over 150m² to have at least two independently controlled heating zones to improve energy efficiency.
Question 4: Why is an automatic bypass valve (ABV) essential in a system where TRVs are fitted throughout?
- To allow air to escape from the system
- To prevent pump cavitation and boiler overheating when all TRVs are closed (Correct answer)
- To increase flow rate to distant radiators
- To reduce the amount of inhibitor required
Correct answer: To prevent pump cavitation and boiler overheating when all TRVs are closed
When all TRVs close simultaneously, an ABV maintains minimum circulation through the boiler and pump, preventing pump cavitation and boiler thermal cut-out.
Question 5: On a standard TRV head calibrated 1–5 with a frost symbol (*), what room temperature does setting 3 approximately represent?
- 15°C
- 18°C
- 20°C (Correct answer)
- 25°C
Correct answer: 20°C
Setting 3 on most TRV heads corresponds to approximately 20°C, which is a typical comfortable room temperature for living areas.
Question 6: What is the recommended temperature range for setting a room thermostat in a domestic property?
- 15–18°C
- 18–21°C (Correct answer)
- 22–25°C
- 25–28°C
Correct answer: 18–21°C
A room thermostat is typically set between 18–21°C to balance occupant comfort with energy efficiency in UK homes.
Question 7: What is the purpose of a lockshield valve on a radiator, and who should adjust it?
- To allow the homeowner to fine-tune room temperature daily
- To balance system flow during commissioning; adjusted by the installer using a tool (Correct answer)
- To isolate the radiator in an emergency; adjusted by any competent person
- To control heating circuit pressure; adjusted automatically
Correct answer: To balance system flow during commissioning; adjusted by the installer using a tool
A lockshield valve is set by the installer during commissioning to balance flow across all radiators and is protected by a cap to prevent unauthorised adjustment.
CENWAT System Controls and Zoning 1
What is the primary function of a thermostatic radiator valve (TRV)?