Commissioning a Reinstated Commercial Kitchen Range After a Long Shutdown
A 12-month-vacant café is being reopened. Its kitchen has a six-burner commercial range (rated input 168 MJ/h) and a gas-fired stockpot boiler (rated 95 MJ/h), both connected to a 50 mm nominal bore supply from a 900 L LPG cylinder bank via a two-stage regulator. The incoming pressure at the meter outlet reads 2.8 kPa. The previous tenant's compliance plate shows the range was commissioned four years ago, but no service records exist. The new owner reports that when they briefly lit the range, flames were yellow-tipped and lifting on the rear burners, and a faint gas smell lingered near the stockpot boiler. The kitchen has a 600 mm mechanical exhaust hood, two 300 mm high-level wall vents and one 300 mm low-level vent. The building surveyor has asked for written evidence of compliance before occupancy.
1. Before lighting anything, what sequence of checks and tests should you perform, and which results would stop you from proceeding?
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Start with isolation and documentation, then work outward.
- Confirm the appliance and installation details against the compliance plate and any prior certificate; a four-year gap with no service history means you treat the whole installation as unverified.
- Pressure-test the installation section you intend to disturb, or the whole installation if integrity is doubtful, using air or inert gas at the appropriate test pressure for the pipework class. Any drop indicates leakage and stops work.
- Check the cylinder bank: cylinder restraint, valve condition, regulator breather clear of obstruction, and that the two-stage regulator is rated for the connected load (168 + 95 = 263 MJ/h plus any other appliances).
- Verify ventilation openings against the appliance's requirements. The three vents as described may not satisfy the combustion air and exhaust needs of a 263 MJ/h kitchen; if the aggregate free area is short, do not commission.
- Test the gas pressure at the meter outlet and at each appliance inlet under flow. 2.8 kPa at the outlet is plausible for LPG two-stage, but you must confirm the appliance inlet pressure matches the manufacturer's rating; a mismatch stops you.
- Leak-test every joint with approved detection fluid or an electronic detector, including the appliance connections.
Stop conditions: any pressure loss on test, any leak detected, incorrect or unverified ventilation, appliance inlet pressure outside the rating, damaged or expired hoses, or a smell near the stockpot boiler that cannot be positively located and repaired. Do not light to 'see if it works' while a leak is suspected.
2. The range burners show yellow tips and flame lift. How do you diagnose and correct this, and what does it tell you about the installation as a whole?
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Yellow tipping and lift on multiple burners of a newly reinstated appliance usually point to a supply or air problem rather than six coincidental burner faults.
Diagnosis order:
- Check the inlet pressure at the range under full flow. If it is below the manufacturer's rated pressure, the burners run lean on gas and lift; if it is too high, flames can blow off the ports.
- Inspect the burner caps, ports and injectors for debris, spider webs or corrosion from the vacancy period. Blocked primary air ports cause yellow tipping.
- Check the primary air adjustment on each burner; a shutter knocked during transport or cleaning changes the mixture.
- Confirm the regulator is delivering stable pressure and not passing or starving under load.
Correction: clean and set injectors and air shutters to the manufacturer's specification, then re-test each burner at full and turned-down flow. Only adjust after confirming the supply pressure is correct.
Implication: if the cause is supply pressure or ventilation-related, the stockpot boiler and any other appliance on the same line are likely affected too. The whole installation must be re-tested and the ventilation re-evaluated before you sign anything. A single-appliance fix would leave a systemic fault in place.