G23 vs 2G7 CFL lamps are easy to confuse when both use the same narrow single-turn tube shape. The difference that matters is at the cap: G23 is a two-pin format, while 2G7 uses four pins in a straight line. Before ordering a replacement, read the code on the old lamp and the luminaire label, count the pins, confirm the wattage and check the control gear. Matching the shape alone is how the wrong lamp ends up on the job.
Quick Shop: G23 and 2G7 Plug-In CFL Lamps
Crompton 9W G23 2-Pin CFL, 4000K
Stock code CLS9SCW. A single-turn S-type compact fluorescent lamp with a G23 two-pin cap, 9W rating and 4000K cool-white output. Check the old lamp and fitting label for the same wattage and cap before ordering.
Crompton 11W G23 2-Pin CFL, 4000K
Stock code CLS11SCW. This is also G23 and two-pin, but it is rated at 11W. Do not treat it as an automatic substitute for the 9W version: the luminaire and control gear must be specified for the lamp fitted.
Crompton 7W 2G7 4-Pin CFL, 4000K
Stock code CLSE7SCW. This four-pin 2G7 lamp is the useful visual comparison: the tube shape is similar, but the base and electrical arrangement differ. A 2G7 lamp is not a plug-in replacement for a G23 socket.
Browse APM's CFL lamp range or check the wider light bulb collection when the job list includes other cap types.
G23 vs 2G7 CFL Lamps: Start with the Pins and Cap Code
Remove guesswork before removing the old lamp. Photograph the printing on the tube or base, then photograph the fitting label. The useful details are the cap code, wattage, colour temperature and manufacturer stock code. On the products above, CLS9SCW identifies the 9W G23 lamp, CLS11SCW identifies the 11W G23 lamp and CLSE7SCW identifies the 7W 2G7 lamp.
A G23 cap has two contact pins. A 2G7 cap has four contact pins arranged in one line. That physical difference is the fastest site check, but it should not be the only check. Other plug-in CFL families can also look similar from the tube end, and keyed bases are designed to prevent unsuitable combinations. Never file, trim or force a plastic key to make a lamp fit.
Look at the complete cap designation, not just the word “CFL”. A screw-in compact fluorescent lamp, a G23 plug-in lamp and a 2G7 plug-in lamp may all use fluorescent technology, but their holders and operating arrangements are different. If the marking is worn away, take clear front, side and underside photos and measure the overall lamp carefully before visiting the trade counter.
G23 vs 2G7 CFL Lamps: Wattage Is Part of the Match
Two lamps sharing a G23 cap are not automatically interchangeable. The Crompton CLS9SCW 9W G23 2-Pin CFL and the Crompton CLS11SCW 11W G23 2-Pin CFL have the same cap family and both are listed at 4000K, but they carry different wattage and stock codes. Use the wattage stated on the old lamp and luminaire unless the fitting or control-gear manufacturer explicitly approves another lamp.
The same rule applies to colour appearance. All three linked Crompton lamps are listed as 4000K cool white, so selecting one of them does not change the cap check. A correct colour temperature cannot rescue an incorrect base or wattage. For a multi-lamp fitting, match the specified lamp throughout rather than mixing types and accepting uneven appearance or operation.
Physical length can also change with wattage and lamp family. Check that the replacement will sit correctly inside the fitting without touching a diffuser or being forced against the lampholder. The label and original stock code are more reliable than estimating from a product photograph.
Check the Ballast and Dimming Arrangement
Plug-in fluorescent lamps operate with control gear in the luminaire. Pin count gives a strong clue to the lamp family, but it does not prove that a particular lamp is compatible with every ballast or dimming system. Read the ballast label where it can be accessed safely and compare its approved lamp type and wattage with the replacement. Do not bypass, rewire or replace control gear as part of a simple lamp swap.
APM's current listing describes the Crompton CLSE7SCW 7W 2G7 4-Pin CFL as dimmable. That does not mean any four-pin socket will dim it correctly. The complete luminaire, ballast and control method must support that exact lamp. The two linked G23 products are not presented as dimmable products in APM's current catalogue, so do not promise dimming performance from them.
If a new, correctly identified lamp flickers, starts slowly, cycles or fails to strike, do not keep changing wattages at random. Confirm the lamp is seated correctly, then investigate the fitting and control gear through the proper electrical fault-finding process. Repeated lamp failure can be a fitting problem rather than a lamp-selection problem.
A Five-Point Replacement Check at the Counter
- Cap: confirm G23 or 2G7 from the old lamp and fitting label.
- Pins: count two for G23 or four in line for 2G7; do not rely on tube shape.
- Wattage: match the specified 7W, 9W, 11W or other value exactly unless an approved compatibility table says otherwise.
- Colour: confirm the required colour temperature; the linked range is 4000K cool white.
- Control gear: verify the ballast and any dimming arrangement support the exact lamp code.
Bring the failed lamp to the counter intact where practical, or bring clear photographs of every marking and the socket. Do not carry a cracked tube loose in a tool bag. Compact fluorescent lamps belong in an appropriate lamp-recycling or WEEE route rather than general rubbish; follow the current local disposal guidance, especially if a lamp is broken.
Why This Check Saves a Return Visit
Most errors happen because the tube looks right from a distance. The cap is hidden inside a bulkhead or downlight, the old lamp is discarded before its code is recorded, and a replacement is ordered from wattage alone. A sixty-second pin, code and label check avoids another trip and prevents force being applied to the wrong holder.
For planned maintenance, record lamp codes by area. A small schedule listing fitting location, cap, wattage, colour temperature and stock code makes later replacements faster, particularly across communal areas, corridors and commercial units with several generations of luminaires.
APM Electricals supplies the linked G23 and 2G7 CFL lamps from 24 Western Avenue, Acton, London W3 7TZ. For a lamp-identification or job-list check before collection, call 020 8702 8080. Bring the old lamp or clear photos of the cap and fitting label; the exact match matters more than the tube shape.
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