Glow-worm Betacom combi (24a, 28a)
Combi, natural gas (convertible to LPG)
Combustion figures
| Figure | Natural gas (G20) | LPG (G31) |
|---|---|---|
CO₂ at high rate More infoHide infoBoiler forced to maximum with test mode P.01 set to HI, wait about 5 minutes for a stable reading, at the combustion analyser sample point on the flue. Case on is the check figure and case off is the setting figure (MI 19.3.3); the technical data (MI 5) calls this rate Qmax DHW. The manual contradicts itself: the gas conversion table (MI 17.1.2) gives the case on and case off figures the other way round (G20 case ON 9 ± 0.2 %, case OFF 9.2 ± 0.3 %; G31 case ON 10.1 ± 0.2 %, case OFF 10.3 ± 0.3 %). For LPG case off, the technical data gives ± 0.3% and MI 19.3.3 gives ± 0.2%. MI 19.3.3 prints the NG case off figure as 9 ± 0.2%. |
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CO₂ at low rate More infoHide infoAt Qmin. Given in the technical data (MI 5) only. |
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Maximum CO | Not given in MI | Not given in MI |
CO/CO₂ ratio More infoHide infoSafe combustion can only be verified by measuring the CO/CO₂ ratio; it must not exceed this value (MI 19.3.1, 19.3.3). | 0.004 | 0.004 |
O₂ | Not given in MI | Not given in MI |
Working inlet pressure More infoHide infoNominal supply pressure, checked at the gas service isolation valve test point with all other gas appliances running (MI 12.6.1). The technical data (MI 5) gives the same inlet pressures without saying where they are measured. MI 12.6.1 adds that maximum heat input can be achieved at an inlet pressure down to 15 mbar. |
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Gas rate at maximum More infoHide infoApproximate, at least 10 minutes after the burner has lit from cold, checked at the gas meter (MI 12.6.2). These match the maximum DHW gas flow rate in the technical data (MI 5), which also gives maximum heating gas flow rate: NG 24a 1.96, 28a 2.64 m³/h; LPG 24a 1.44, 28a 1.94 kg/h. |
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From 0020105022_01 - 12/10
Enter service mode for high and low rate
High rate
Steps not added yet. Follow the MI.
Low rate
Steps not added yet. Follow the MI.
Ending the test: follow the MI.
Models and GC numbers
| Model | GC number | Gas |
|---|---|---|
| Betacom 24a | 47-019-13 | NG |
| Betacom 28a | 47-019-14 | NG |
Source: Glow-worm Betacom 24a, Betacom 28a Installation and Servicing, 0020105022_01 - 12/10.
Sections: 5 Technical data; 12.6 Gas rates; 12.6.1 Operational gas inlet pressure; 12.6.2 Gas rate; 14 Installation settings (test modes); 17.1.2 Adjusting the maximum power setting; 19.3 Combustion check and setting the air/gas ratio valve.
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Check these figures against the MI for the appliance in front of you, matched by GC number and manual date. Combustion work needs a calibrated analyser and a Gas Safe registered engineer.