How many appliances can you plug into a power strip?

How to avoid power strip overload

No number of plugs is safe by itself. What matters is the total load, measured against what the strip and the wall socket are rated for.

EMA warns that overloading power points may lead to over-heating and start a fire. Its advice on adaptor overload is direct: do not "piggy-back" multiple plugs into one socket with double adaptors.

SCDF's Fire Safety at Home leaflet also says to avoid overloading electrical outlets. The Consumer Product Safety Office (CPSO) adds that overloading wall socket outlets can cause fire hazards, and says to consider installing additional socket outlets if needed.

See the home electrical safety checklist for other checks around the home.

Ratings on plugs and strips

The CPSO guide to mains plugs explains which plugs are suitable for use in Singapore. It also notes that 13A and 15A plugs are Controlled Goods and must carry the SAFETY Mark.

HDB's home care guide adds that a 13A plug should have a 13A fuse. Treat the rating marked on a strip or adaptor as the limit for everything plugged into it together.

Appliances to keep off strips and adaptors

CPSO's safety tips on electric water heaters say a water heater should not be connected to a 3-pin socket outlet. It should be wired directly to the mains through a double pole switch, and you should not use extension cords or multi-way outlets to power it. CPSO says to hire a Licensed Electrical Worker to make sure the heater is properly wired.

Aircons generally use a 15A 3 round-pin (Type M) plug, which the CPSO plug guide describes as the plug for energy-intensive appliances. For other appliances that draw a lot of power, CPSO's electrical hazard tips say to follow the installation and user manuals.

For extension cord safety, switch an appliance off before unplugging it, and hold the plug, not the cord, when you connect or disconnect it, as CPSO advises.

SAFETY Mark to look for

Under CPSO's list of Controlled Goods, multi-way adaptors for household use, with more than one set of socket contacts, are Controlled Goods. So are 3-pin portable socket-outlets, including portable cable reels, with 13-amp shuttered socket-outlets on a flexible cord.

Controlled Goods must be tested, certified and carry the SAFETY Mark before they can be supplied in Singapore, and it is illegal to advertise or supply them without it. CPSO's SAFETY Mark guide explains how to check a product:

• Find the unique 8-digit registration number on the SAFETY Mark.
• Search the Register of Registered Controlled Goods by model number or registration number.
• Confirm that the registration has not expired.
• On an appliance with a 3-pin plug, look for two marks: one on the appliance and one on the plug.

Warning signs

HDB lists two warning signs. Overheated plugs or frequently blown plug fuses can be caused by loose connections, overloaded circuits or broken cables. Burnt marks at a socket can come from a plug that is not fully inserted or from an overloaded circuit.

EMA says not to use cracked or broken power points or extension sockets, and to have damaged ones replaced by an LEW. Replace cords with broken or frayed insulation, and do not join cut or frayed cords with insulation tape.

HDB explains that a miniature circuit breaker (MCB) trips to cut supply to a circuit on an overcurrent from an overload or short circuit. If that keeps happening as you add appliances, see power trip help. If the RCCB or ELCB trips instead, see what to do when an ELCB keeps tripping.

When to stop and call a professional

If you regularly run out of sockets, CPSO suggests considering additional socket outlets if needed in its tips on electrical hazards. EMA's guide to engaging licensed workers lists the addition, extension or replacement of power points such as socket-outlets as work to be carried out or supervised by a Licensed Electrical Worker (LEW). EMA says electrical work in an HDB flat needs a Licensed Electrician, the class of LEW approved for loads of up to 45kVA.

Call an LEW if you notice any of these:

• Burnt marks at a socket or plug.
• Buzzing from a socket, plug or strip.
• A socket or plug that feels warm.
• Power that keeps tripping.

For new points, see power socket installation and which work needs an LEW. The cost depends on the job, so compare electricians and their published prices.

Before work starts, EMA says to verify the LEW's licence card, which shows a photograph, name, identity card number and licence number. See how to check a licensed electrician for more.

Questions