Gas Safe Registration (ACS) Commercial and Catering Gas (COCN1 / CORT) Syllabus

Commercial and Catering Gas (COCN1 / CORT) syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Commercial and Catering Gas (COCN1 / CORT) in Gas Safe Registration (ACS), not a summary of it.

1. 1

   Commercial Core Safety (COCN1)

   4 topics

   • Commercial standards and codes
     • IGEM/UP/1 strength and tightness testing
     • IGEM/UP/2 commercial pipework installation
     • Gas Safety (Management) Regulations awareness
   • Commercial pipework and pressure regimes
     • Low, medium and intermediate pressure tiers
     • Strength testing of larger installations
   • Commercial meter installations and governors
   • Ventilation and gas interlock systems
2. 2

   Commercial Catering Appliances (COMCAT)

   3 topics

   • Catering appliance categories
     • COMCAT1 ranges, ovens and boiling tables
     • COMCAT2 deep fat fryers
     • COMCAT3 griddles, grills and steamers
     • COMCAT5 combination ovens and large appliances
   • Commercial kitchen ventilation and interlocks
     • Gas safety interlock to extraction (BS 6173)
     • CO/air flow proving and emergency gas isolation
   • Commissioning and combustion testing of catering appliances
3. 3

   Commercial Heating and Plant

   3 topics

   • Commercial boilers and warm air heaters (CIGA/TPCP)
   • Overhead radiant tube and plaque heaters
   • Direct/indirect fired space heating

Commercial and Catering Gas (COCN1 / CORT) flashcards for Gas Safe Registration (ACS)

21 of 50 cards from the Commercial and Catering Gas (COCN1 / CORT) deck — real questions with worked answers.

1. What does the COCN1 assessment cover, and how does it relate to CORT and CODNCO1?

   COCN1 is the core commercial gas safety (changeover) assessment covering pipework, controls, ventilation, flues and gas safety in non-domestic installations. CORT covers commercial gas testing and purging, and CODNCO1 covers commercial laying/inspection of pipework and combustion. COCN1 is the foundation onto which appliance-specific modules (e.g. CCN1's commercial equivalents, CIGA1 boilers, CONGLP1, CDGA1 catering) are added.

2. Which standard is the primary code of practice for installing pipework, boosters and compressors in commercial gas installations?

   IGEM/UP/2 (Installation pipework on industrial and commercial premises). It governs pipework design, materials, jointing, boosters and compressors for non-domestic natural gas installations.

3. Which IGEM standard governs strength and tightness testing and direct purging of commercial natural gas installations?

   IGEM/UP/1 (and IGEM/UP/1A for installations up to 1 m³ working volume / IGEM/UP/1B for low-pressure small installations). It defines the strength test, tightness test and purging procedures for pipework operating above domestic pressures.

4. What is the maximum operating pressure (MOP) range that defines 'low pressure' gas in commercial installations?

   Low pressure is up to and including $75 \ \text{mbar}$. Medium pressure is above $75 \ \text{mbar}$ up to $2 \ \text{bar}$, and intermediate pressure is above $2 \ \text{bar}$ up to $7 \ \text{bar}$.

5. Define the terms MOP, OP and STP as used in commercial gas pressure regimes.

   MOP = Maximum Operating Pressure, the upper limit of normal operation. OP = Operating Pressure, the actual pressure during normal use. STP = Strength Test Pressure, the elevated pressure applied to prove mechanical integrity of the pipework.

6. In IGEM/UP/1A, what is the strength test pressure for a low-pressure installation, and how is the test result judged?

   The strength test is applied at typically $1.5 \times$ MOP (commonly held around $\ge 22.5 \ \text{mbar}$ for a $75 \ \text{mbar}$ MOP system, or a defined STP). The test passes if there is no pressure drop and no movement of the gauge over the stabilisation and test periods, confirming no failure of joints or fittings.

7. Why must commercial pipework be sized so that pressure loss does not exceed the permitted figure, and what is the typical maximum permitted pressure drop on a low-pressure natural gas installation?

   Excess pressure loss starves the appliance of gas, causing incomplete combustion and underfiring. The maximum permitted pressure drop between the meter outlet (governor) and the appliance inlet on a low-pressure natural gas system is $1 \ \text{mbar}$.

8. State the formula relating gas rate, calorific value and heat input used in commercial commissioning.

   $$\text{Heat input (kW)} = \frac{\text{Gas rate} \ (\text{m}^3/\text{h}) \times \text{CV} \ (\text{MJ/m}^3)}{3.6}$$ The factor $3.6$ converts MJ/h to kW since $1 \ \text{kW} = 3.6 \ \text{MJ/h}$.

9. A commercial appliance burns gas at $5 \ \text{m}^3/\text{h}$ of natural gas with a CV of $38.7 \ \text{MJ/m}^3$. Calculate the gross heat input.

   $$\frac{5 \times 38.7}{3.6} = \frac{193.5}{3.6} \approx 53.75 \ \text{kW}$$

10. How is gas rate determined from a metric (m³) meter using the timed test-dial method?

    Time how long the test increment takes, then: $$\text{Gas rate} \ (\text{m}^3/\text{h}) = \frac{3600 \times V}{t}$$ where $V$ is the measured volume in $\text{m}^3$ and $t$ is the time in seconds for that volume to pass.

11. What is the standard nominal calorific value and relative density of natural gas used in UK commercial calculations?

    Natural gas: gross CV approximately $38.76 \ \text{MJ/m}^3$ (often taken as $\approx 39 \ \text{MJ/m}^3$) and relative density (specific gravity) of about $0.6$ relative to air.

12. What is the Wobbe number, and why does it matter for interchangeability of commercial gas appliances?

    The Wobbe number (or Wobbe index) is $$W = \frac{\text{CV}}{\sqrt{d}}$$ where $d$ is the relative density. Two gases with the same Wobbe number deliver the same heat input through a given orifice at the same pressure, so they are interchangeable without rejetting.

13. What is the function of a commercial meter governor (regulator), and what two protective devices may be integrated with it?

    The governor reduces and stabilises the incoming gas pressure to the required outlet pressure regardless of inlet variation. It may incorporate an Over-Pressure Shut-Off (OPSO) which trips closed if downstream pressure rises too high, and an Under-Pressure Shut-Off (UPSO) which trips if pressure falls dangerously low.

14. What is the purpose of a meter regulator relief vent / breather, and where must it terminate?

    The breather/relief allows the governor diaphragm to move and vents gas in a fault/over-pressure condition. The vent pipe must terminate safely in open air, away from ignition sources, openings and air intakes, so that any discharged gas disperses safely.

15. In a commercial installation, what distinguishes a primary meter from a secondary meter?

    A primary meter measures total gas supplied to the premises from the network and is the billing meter. A secondary (check/sub) meter is downstream of the primary and measures consumption of a section or tenant for internal apportionment, not for the supplier's billing.

16. What is the purpose of an Emergency Control Valve (ECV) in a commercial installation, and what additional valve is often required on larger systems?

    The ECV is the main manual isolation valve allowing the whole installation to be shut off in an emergency, sited as close as practicable to the meter. Larger or remote installations also require an Additional Emergency Control Valve (AECV) located near the point of use or building entry for the relevant occupancy.

17. Why is purging required after testing or pipework alteration, and what is the key hazard purging eliminates?

    Purging removes air from the pipework (so gas can flow and burn correctly) or removes gas at decommissioning. The key hazard is the flammable air/gas mixture forming within the pipe; purging displaces this through the flammable range quickly and vents it safely outside, preventing an explosive accumulation.

18. Define 'gas interlock' in the context of a commercial kitchen.

    A gas interlock is a safety system that automatically prevents gas from being supplied to catering appliances unless adequate mechanical ventilation (extract and supply air flow) is proven to be operating. Loss of airflow causes the gas safety shut-off valve to close.

19. Which document specifies ventilation and interlock requirements for commercial catering establishments?

    BS 6173 (Specification for installation and maintenance of gas-fired catering appliances), supported by the Gas Safe Technical Bulletin TB ‑ and CATERSAFE guidance. BS 6173 sets out air supply, extraction rates and the requirement for a gas/air-proving interlock.

20. List the essential components of a typical commercial kitchen gas interlock system.

    An air-proving device (air pressure/flow switch or current sensor on the extract and supply fans), a gas pressure proving system or proving valve, a gas solenoid (safety shut-off) valve on the supply, a control panel, and an emergency stop / manual reset. Some systems add a CO sensor that also trips the gas off.

21. What is the function of a gas pressure proving (tightness proving) system fitted with an interlock?

    Before energising the main gas solenoid, the proving system automatically pressure-tests the downstream pipework and appliance valves to confirm they are gas-tight (no appliance left open/leaking). Only if the proving test passes will the system allow the gas valve to open, preventing release of gas into the kitchen.

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