A customer in Borehamwood, Hertfordshire WD6 contacted TNG Services Ltd to carry out an annual service on a Worcester Bosch 8000 Series system boiler. The boiler was operating and its combustion readings were satisfactory, but the inspection identified important issues involving the flue, gas working pressure, unvented hot-water cylinder discharge arrangement and electrical installation.
An annual boiler service is not simply about cleaning the appliance. It also provides an opportunity to inspect the boiler, flue, gas supply and associated installation for defects that could affect safety, reliability or compliance.
Worcester Bosch 8000 boiler service
The Worcester Bosch 8000 system boiler was serviced and its operation checked. As part of the service, we carried out the relevant visual and operational checks, including combustion performance and gas rate.
- Boiler combustion readings were satisfactory.
- Gas rate was satisfactory.
- Boiler operation was checked.
- The flue installation was visually inspected.
- Working gas pressures were measured.
Although the boiler itself was operating and the combustion readings were satisfactory, significant installation issues were identified.
Boiler flue classified At Risk (AR)
During the visual inspection, we found that the boiler flue had not been installed in accordance with the boiler manufacturer’s installation instructions. Because of the identified flue installation defect, the installation was classified as At Risk (AR) and remedial work was recommended.
Correct flue installation is an essential part of a gas boiler installation. The flue must be installed, supported, sealed and terminated in accordance with the appliance manufacturer’s instructions.
Satisfactory combustion readings do not automatically mean that the complete installation is satisfactory. The flue installation must also be assessed.
Excessive gas pressure drop to the boiler
We checked the working gas pressure with the Worcester Bosch boiler operating at maximum rate. The readings recorded were:
| Measurement | Working pressure |
|---|---|
| At the gas meter | 17.72 mbar |
| At the boiler | 13.53 mbar |
| Measured pressure loss | 4.19 mbar |
This represented a significant pressure loss between the gas meter and the appliance. The installation should be designed so that the pressure loss through the installation pipework remains within the applicable requirements and the appliance receives the working pressure required by the manufacturer.
The pressure recorded at the boiler was also below the minimum specified for the appliance.
Cadent contacted regarding incoming gas pressure
Because the working pressure recorded at the gas meter was low, Cadent was contacted. Cadent subsequently attended the property and confirmed that the pressure at the meter had been restored to a satisfactory level.
The next step is therefore to recheck the working pressure at the Worcester Bosch boiler under maximum load. If an excessive pressure loss remains between the meter and appliance, the property’s internal gas-supply pipework will require further investigation. Depending on the results, this may require alterations or upgrading of the existing gas pipework.
Cadent confirmed satisfactory pressure had been restored at the meter.
Measure appliance working pressure under maximum load.
Assess internal gas pipework if excessive pressure loss remains.
Unvented hot-water cylinder inspection
The property also has an unvented hot-water cylinder. During a visual inspection of the accessible parts of the installation, we identified several concerns with the safety-discharge pipework:
- D1 and D2 safety-discharge arrangements requiring remedial work.
- D2 connected into the boiler condensate discharge arrangement.
- Condensate/discharge pipework without a satisfactory continuous fall.
- Expansion-relief valve discharge arrangement requiring correction.
- Safety-valve operation not provided with an appropriate visible discharge arrangement.
- Discharge pipework requiring correction to its fall and routing.
- Final discharge termination requiring improvement.
Why unvented cylinder discharge pipework matters
An unvented cylinder stores hot water under mains pressure and incorporates safety devices designed to protect the system from excessive temperature and pressure. If one of these safety devices operates, the discharge arrangement must be capable of safely conveying the discharged water to an appropriate termination.
The pipework must therefore be correctly sized, routed and installed so that it remains unrestricted and allows a discharge to occur safely.
The existing arrangement at this property requires remedial work to bring the D1/D2 pipework, visible discharge arrangement, continuous falls and final termination into an acceptable configuration in accordance with the relevant requirements and cylinder manufacturer’s instructions.
Electrical defects identified during visual inspection
Several visible electrical installation concerns were identified around the boiler and hot-water-cylinder controls:
- Outer cable sheathing terminating outside the heating wiring centre.
- Individual insulated conductors visible outside the enclosure.
- Fused spur faceplates not correctly seated against their surface boxes.
- Tape applied around fused spur switches to cover gaps.
- Immersion-heater supply cable requiring assessment and replacement with a suitable cable for the application.
- Cable entries, enclosures and connections requiring further inspection.
Tape should not be used as a substitute for correctly fitted and secured electrical enclosures. We recommended that these items be inspected and tested by a qualified electrician, with any necessary remedial work completed.
Scope of the electrical observations: these were visual only. Electrical covers were not removed and electrical testing was not undertaken as part of the boiler service. These observations therefore do not constitute an Electrical Installation Condition Report (EICR).
Boiler service uncovered more than a boiler fault
This Borehamwood visit is a good example of why a professional annual boiler service should involve more than simply checking that the boiler turns on. The Worcester Bosch 8000 was operating and its combustion readings were satisfactory, but the wider inspection identified several issues requiring attention:
- Boiler flue installation: At Risk (AR).
- Excessive gas pressure loss: further investigation required.
- Unvented cylinder discharge arrangement: remedial work required.
- Electrical installation: qualified electrical inspection recommended.
The customer was provided with our findings and supporting photographs so that the necessary remedial work could be planned.
Worcester Bosch boiler servicing in Borehamwood WD6
TNG Services Ltd provides professional Worcester Bosch boiler servicing, fault finding, repairs and gas safety inspections throughout Borehamwood WD6, Hertfordshire, Stevenage and North London.
We also work with system and combi boilers, unvented hot-water cylinders, central-heating systems, gas-supply and installation issues, boiler replacements and upgrades, and heating controls and system improvements.
Is your boiler due for its annual service?
If your boiler is due for servicing, or you have concerns about an existing installation, contact TNG Services Ltd to arrange an inspection.
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