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Boiler safety check and servicing

What’s the difference between a boiler “safety check” and a “service”?


Getting a gas boiler inspected on an annual basis by a Gas Safe registered engineer is key to maintaining boiler efficiency, reliability and, most importantly, safety. But we often get asked what is the difference between a boiler ‘safety check’ and a ‘service’?

When it comes to booking a boiler service we know that some consumers will be driven purely by price and choose the cheapest options available without fully understanding what will and won’t be covered during the engineer’s visit. However, not knowing the difference between a service and a safety check could prove to be a false economy and may even invalidate any manufacturer’s warranty. That’s why we always advise engineers to make the differences clear to their customers. Let’s start by looking at the basic checks to ensure the safety of the user and the appliance

Safety check

First and foremost, always start by asking the customer whether they have had any issues since your last visit, as much can be gleamed in a five minute conversation with the customer before you put your toolbox down.

  • Visual inspection of appliance and entire flue system to ensure there are no signs of distress and installed as per manufacturer’s instructions.​

  • Flue gas analysis (room sealed boiler) to verify combustion characteristics; including but not limited to leaks within flue system and adequate supply of air for combustion.

  • Check ventilation is adequate for appliance type and/or location.

  • Gas rate check to ensure adequate fuel supply with inlet working pressure and burner pressure as necessary.

  • If a sealed system, relieve pressure in the water circuit and check expansion vessel pressure is correctly charged.

  • Refill a sealed system to the correct operating pressure and disconnect the filling loop or link. (Permanent connection to class one potable water without fitting a specialist valve can be subject to a fine).

  • On an open vented system, locate the feed and expansion cistern to check the ball valve is operating correctly, that there is sufficient water in the cistern and that gaps between water level, overflow outlet and ball valve outlet are correct (these provide the expansion space and backflow prevention). Also ensure Open Vent Pipe is free to discharge back into the tank.

  • Ensure the condensate outlet(s) from the flue or heat exchanger are clear, free running, with sufficient fall (Vokèra recommends at least 3°) and terminated correctly.

  • Visually inspect the condensate trap, but preferably dismantle, clean, refill and complete an operational check.

  • Remove combustion box or cover to inspect seals on internal automatic air vents and check for evidence of any leaks.

  • If a sealed system, check any pressure relief devices for signs of leakage or malfunction.

  • Check operation of all safety devices to ensure they are working as intended.

Annual service

In addition to these safety checks, manufacturer’s instructions may also include

  • Removal of burner door / cover and physical cleaning of heat exchanger flueways, inspection of flame rectification probes, spark gap etc.

  • If appliance has a separate secondary heat exchanger, remove access cover and clean inside.

  • Inspect insulation panels / shields.

  • Replace door seals as required by manufacturer when reassembling.

  • Check dilution levels of inhibitor and top-up if deemed necessary.

  • Bleed any vent points around the system.

  • Record Service Intervention in Benchmark Log, typically located in back of manufactures instruction booklet.

Gas  safe

Example Gas Safe certificate (CP12)

Gas safety record CP12
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