Frequently asked questions
about light bulbs and lampholders
11 December, 2019 by
Frequently asked questions
Lampfix, Deryck Smith
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Frequently asked questions

At Lampfix, we are often asked questions by qualified electricians about the various lamps and lampholders we supply. Here, we have answered some of the more common queries to benefit you and your customers when they are looking for advice and guidance.  

If you are looking to sell lamps made by your own company, you must ensure all the components you use are compliant with BS EN regulations. Getting CE certificates for each component will help you with this.

You must document the assembly and wiring procedure for each line you produce. This is called a ‘Technical File’ for the product. You must also make sure it has been electrically safety tested, and that this is included in the procedure. At Lampfix we perform this on every light fitting we produce.

Introducing light fittings to the market, either by import or manufacture is now covered by WEEE Regulations. You must register with a recognised WEEE organisation and report to them the total weight of liable products you have sold out to the market on a quarterly basis.  

Production should be recorded on a register showing serial/batch numbers along the followed manufacture procedure, signed/initialled by the person who has performed the final test.

Each fitting should hav a CE symbol and WEEE ‘wheelie bin’ symbol on it. A single sticker could be used.

For more information on this subject you can visit the LIA website.

First, ask yourself if you really need to dim the bulb? Often dimmers are used as light switches at the highest brightness anyway. So, to save cost, you can consider using non-dimmable bulbs at the right lumens, switched either by a light switch or a dimmer fitted with an on/off module. 

If you really do need to dim the lighting, firstly ensure the LED bulbs you purchase are dimmable and clearly state on their description that they are so. 

Then you need to select the right dimmer. If you have a wall plate, ensure the module is LED compatible. These are available to trade and wholesalers from Lampfix.  If it is a table lamp, make sure the inline dimmer is LED compatible, as here

If you are unsure, consult your wholesaler before you purchase the bulb or dimmer, to ensure you have the appropriate compatible parts.

Either is the correct answer! Just make sure you state what you are measuring. 

If it is just the glass you are measuring, then state this. If you are worried that the bulb won’t fit in your fitting, make sure you state the length and width of the space the bulb is going into. Then when you are ordering the bulb, check the overall top-to-bottom height of the glass part of the lamp to check it will fit. 

To find out what screw cap the bulb is, measure the distance of the screw part. If it is 14mm wide, you need an E14 (or ‘SES’) cap bulb. If it is 27mm, you need an E27 (or ‘ES’) cap.  Other sizes exist, but they are quite rare – 12mm dia (E12) for some continental or USA fittings, and 10mm diameter (E10) for torch bulbs, etc.

To measure what size bayonet cap you need, measure the width of the bayonet; if it is 15mm across, you will need B15 (or ‘SBC’), or if is 22mm, you will need B22 (or BC).

The 4 main caps for domestic lamps:

  • ES stands for Edison Screw

  • SES stands for Small Edison Screw

  • BC stands for Bayonet Cap

  • SBC stands for Small Bayonet Cap.



First, disconnect the lamp from the mains, take the plug out of the socket. 

Unscrew the top part of the lampholder. If it is an E27 lampholder, you can watch the Lampfix instruction video here.

Pull the insert away slightly and unscrew each of the 2 or 3 terminals and remove the wire from them.

Then look inside the base. If there is a locking screw securing it to the stem, unscrew this and remove it. Twist the base anti-clockwise from the stem to bring it away. The stem is now ready for a new lampholder to be fitted.

Using an electric tester depends on the instructions given with that particular model. Electric testing should only be conducted by a qualified electrician.

If you are in the lighting trade, you can apply for an online trade login. This will give you access to trade discounts. 

If the bulkheads are brass, they will age naturally. They don’t corrode and are not compromised safety-wise. The powder-coated black bulkheads won't age but will become matt over time. Satin nickel finish bulkheads will not corrode, but may develop over time a further matt finish.

Most importantly, only replace a lampholder if you are confident with electrics and understand how to conduct a safety test. 

Ensure the light fitting is disconnected from mains. Unscrew the top of the lampholder. If this is an ‘ES’ lampholder, watch the Lampfix blog video on how to do this.  If this is a bayonet lampholder, unscrew the loose shade ring, if there is one, then unscrew the next ring and take the lampholder apart, pulling the insert gently towards you. 

Next unscrew the wire terminals, there will be 2 or 3. Then pull the insert away and you can unscrew the base cap.

If this has been locked down with an internal locking screw, unscrew this to assist removing from the base.

Once you have exposed the base thread, ascertain if it is half-inch or 10mm wide and ensure you have the correct lampholder to install. If it is neither of these, consult a professional. 

If not done already, take apart the new lampholder, base, insert and/or top part. Screw the new base down with the existing wires coming up through the hole in the middle. Wire the 2 or 3 cores of the wire to the correct live and neutral and earth terminals on the lampholder insert.

Press the insert back into the base, ensuring none of the wires are trapped or pinched. Then screw or click on the top part, to complete this part of the process.

Unless you are quite sure that all is well, ask a qualified electrician to conduct an electrical safety test.


Typically, pendant cords will take fittings weighing up to 1 kilo; however, this is not set in stone and is only a rule of thumb. If you are worried about the weight of the fitting, contact a professional to find out if the cable you intend to use will take the weight. If the fitting weighs over 1kg, a chain could be used to take the weight.

Most walls will suit a variety of fixing methods, from plasterboard speed fixings, to red wall plugs, to woodscrew fixings, all of which can be used to affix light fixtures. If the wall is damp or the timber is wet, you should consult a builder to advise on the way forward.

We're always here to help.

We hope these Q&As will help you with your understanding of lamps, bulbs and lampholders. If you have any queries or can’t find what you’re looking for, we are always happy to help. You can contact us on our online form or call us on 01462 73 11 73 to discuss your trade requirement. 


# Help
Frequently asked questions
Lampfix, Deryck Smith
11 December, 2019
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