CENWAT Central Heating System Design 2 — Questions and Answers
Question 1: What is the purpose of a bypass circuit in a central heating system?
- To maintain minimum flow when all thermostatic radiator valves are closed (Correct answer)
- To increase system pressure during peak demand
- To direct flue gases away from the boiler
- To balance flow between upstairs and downstairs circuits
Correct answer: To maintain minimum flow when all thermostatic radiator valves are closed
A bypass (or automatic bypass valve) ensures a minimum flow rate through the boiler even when TRVs close off all radiators, preventing damage from overheating.
Question 2: Which type of central heating pump is most common in modern UK domestic installations?
- Electronically commutated (ECM) variable-speed pump (Correct answer)
- Fixed-speed single-phase pump
- Diesel-driven pump
- Gravity-fed circulator
Correct answer: Electronically commutated (ECM) variable-speed pump
Modern installations use ECM variable-speed pumps that adjust output to demand, improving efficiency and reducing energy consumption significantly.
Question 3: What does LTHW stand for in heating system terminology?
- Low Temperature Hot Water (Correct answer)
- Long Temperature Heat Wave
- Low Thermal Heat Work
- Liquid Transfer Heating Water
Correct answer: Low Temperature Hot Water
LTHW (Low Temperature Hot Water) refers to heating systems operating at flow temperatures typically below 90°C, which is standard for domestic central heating.
Question 4: In a two-pipe system, what is the advantage over a one-pipe system?
- Each radiator receives water at the same flow temperature (Correct answer)
- It uses less pipework overall
- It requires no pump
- It eliminates the need for balancing valves
Correct answer: Each radiator receives water at the same flow temperature
A two-pipe system has separate flow and return mains, so each radiator receives water at approximately the same temperature, allowing better control and efficiency.
Question 5: What is hydraulic balancing in a central heating system?
- Adjusting flow rates so each radiator receives its design heat output (Correct answer)
- Equalising the gas pressure to each burner
- Setting the boiler to equal flow and return temperatures
- Levelling the boiler installation
Correct answer: Adjusting flow rates so each radiator receives its design heat output
Hydraulic balancing involves adjusting lockshield valves on radiators so that water flow is proportioned correctly, ensuring every radiator achieves its design heat output.
Question 6: Which regulation requires new heating systems in England to meet minimum efficiency standards?
- Building Regulations Part L (Correct answer)
- Building Regulations Part P
- Gas Safety Regulations 1998
- Water Supply Regulations 1999
Correct answer: Building Regulations Part L
Part L of the Building Regulations (Conservation of Fuel and Power) sets minimum efficiency requirements for new and replacement heating systems in England.
CENWAT Central Heating System Design 2
What is the purpose of a bypass circuit in a central heating system?