In recent years, central heating boilers have become highly complex, so correct commissioning is now more important than ever. Mike Heads looks at the procedure changes that come into force on 1 April 2014.
Before installing or replacing a boiler, certain checks should be carried out. These would include the design of the system, the quality of the central heating water, the pressure and flow rate, whether the cold water pressure is adequate, and whether the gas supply is large enough to provide sufficient volume at maximum gas rate.
If a combi boiler is installed, it is necessary to assess whether a scale inhibitor is required. The condensate drain requirements also need to be taken into consideration as do the minimum servicing dimensions and the chimney termination position.
Once the boiler has been installed, the Benchmark book should be filled in. It is important to remember that this is not only good practice but is often a requirement of the manufacturer’s warranty. The Benchmark book
has been prepared by the HHIC and is part of the manufacturer installation instructions. It includes the following information:
- Customer, boiler and installer details
- Controls details
- Cleansing and inhibitor details
- Gas rate/pressure, flow and return temperature (CH flow rate)
- Combination boiler section scale reducers, domestic hot water gas rate/inlet pressure, hot water temperature rise and flow rate
- Condensing boiler discharge pipe correctly installed
- Flue gas analysis
- Commissioning engineer and customer signatures
NOTE
Flue gas analysis is currently a requirement of the benchmark for all manufacturers and hopefully will be incorporated within the Gas Safety Installation and Use Regulations when it is revised.
Flue gas analysis is now part of the ACS assessments CPA1, CCN1 and CENWAT. Gas Safe Technical Bulletin 143 was first launched in January 2013 but has since been revised. It was re-issued on 10 July 2013 and provides the procedure for commissioning a condensing boiler incorporating an air/gas ratio control valve technology.
This technical bulletin also provides guidance on checking CO levels and ratios for newly installed condensing boilers.
The procedure does not apply to service and maintenance because they are covered by the manufacturer’s servicing instructions and Gas Safe Technical Bulletin 126.
The reason for the issue of Technical Bulletin 143 was to ensure all newly-installed boilers are left in a safe and efficient working condition. The Electronic Combustion Gas Analyser (ECGA) must comply with the requirements of BS7967.
The flowchart provided in Technical Bulletin 143 is intended as a generic guide. All HHIC boiler manufacturers have agreed that this process will form the basis of their own installation instructions.
NOTE
The boiler manufacturer’s installation instructions must always be followed.
Technical Bulletin 126 already provided the ratio action level of 0.004 for boilers with air/gas ratio valves, but Technical Bulletin 143 goes further in providing us with a maximum CO level of 350ppm and information on flue integrity testing if possible (see Figure 2).
If the manufacturer provides lower readings than the HHIC generic figure, the manufacturer instructions should be followed.
This procedure is in five stages:
- Set the boiler to its maximum rate according to the manufacturer’s instructions.
- Verify the flue integrity using the ECGA (if possible).
- Check CO level and combustion ratio (some manufacturers also specify CO2 readings), taking remedial action if required.
- Set the boiler to minimum rate (where possible and specified).
- Check CO level and combustion ratio (some manufacturers also specify CO2 readings).
NOTE
Where the readings are found to be outside the specified tolerances, remedial action should be taken. If this is unsuccessful, then the manufacturer should be contacted.
When the CO, combustion ratio and – where necessary – CO2 readings are within expected limits, their values can be recorded on the commissioning documentation.
It important to know that the air/gas ratio valve has been factory set and should not be adjusted unless recommended by the manufacturer. The location and flue length may have an impact on the original settings.
If adjustments are required, the installer/service engineer must be competent to carry out this work
and be able to use an ECGA. If a boiler requires conversion to operate with a different gas family (for example, conversion from natural gas family 2 to LPG family 3), separate guidance will be provided by the manufacturer.
Some manufacturers provide a conversion kit and instructions, which must be followed.
Prior to CO level and combustion checks
The manufacturer’s instructions must be followed, the gas type verified and the gas supply pressure/gas rate checked (as required) prior to commissioning.
As part of commissioning (especially if the flue has been fitted by persons other than the boiler installer), visually check the integrity of the whole flue system to confirm that all the components are correctly assembled, fixed and supported.
It is also essential to check that the manufacturer’s maximum flue lengths have not been exceeded and all guidance has been followed (for example – Gas Safe Register Technical Bulletin 008 where chimneys/flues are in voids).
The ECGA should be the correct type, as specified in BS 7679, and have been maintained and calibrated as specified by the manufacturer. The engineer must have the relevant competence to use the analyser. The zero
calibration should be carried out in fresh air in accordance to the manufacturer’s instructions.
To sum up
- From April 2014, boilers should be commissioned according to Technical Bulletin 143.
- Boilers should be commissioned according to their manufacturers’ installation instructions (this may include
CO2 levels). They should have a maximum ratio reading of 0.004 and have a maximum CO reading of 350ppm. - Some manufacturers also specify combustion flue gas readings for CO2 and or O2.
- Whenever possible, the air inlet duct should be checked for flue integrity to ensure there is no leakage of any products of combustion. An O2 reading of less than 20.6% (the correct figure is approximately 20.9%) or a CO2 reading of 0.2% would indicate contamination.
