Power cord ratings (Volts, Amps) for monitor?

Question

I recently bought the HP w2228h monitor on the cheap locally. It didn't come with a power cord and I was amazed at the price of the HP 8121-0739 power cord that originally comes with it.

I am not too keen on spending £30 pounds on a power cord - but I know little about power cords and transformers. I spotted a £5 C13 power cord on ebay claiming it can be used for LCD monitors. However, this cord is rated at 250V, 5A.

The HP w2228h manual has this to say about the power cord:

The monitor power supply is provided with Automatic Line Switching (ALS). This feature allows the monitor to operate on input voltages between 100–240Vv, 50/60 Hz, 1.5A.

The power cord set (flexible cord or wall plug) received with the monitor meets the requirements for use in the country/region where you purchased the equipment.

If you need to obtain a power cord for a different country/region, you should purchase a power cord that is approved for use in that country/region.

The power cord must be rated for the product and for the voltage and current marked on the product’s electrical ratings label. The voltage and current rating of the cord should be greater than the voltage and current rating marked on the product. If you have questions about the type of power cord to use, contact your HP-authorized service provider.

However, this specifies a 240V, 1.5A input voltage. I do not know whether the cheap 'alternative' will work. Please advise!

Solution 1

250V, 5A exceeds 240V, 1.5A so it will be safe and will work.

The fuse in a UK plug is there to protect the cord, so make sure it is rated at no more than 5A if that is the cord rating.

There are plenty of reputable vendors of inexpensive C13 power cords.

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About Volts and Amps: By analogy with household water pipes

Voltage is analogous to pressure, the force pushing water through the pipes. If the taps are turned off the pressure is still there but no water flows.

The pipes must be strong enough to resist the pressure, if you use too thin a pipe the pressure will burst it. If a cord is not rated for the voltage used, the insulation may break down and the cord become unsafe or cause a short-circuit and fire.

Amps measure electrical current which is the rate of flow of electrical charge. Roughly analogous to litres per second of water flowing in a pipe.

Cords have resistance that cause the wires to heat-up at higher currents. Thicker wires have lower resistance and are used for higher current ratings to prevent the wires heating to melting point (more fire probably).

So a 5A cord is thicker than a 1.5A cord and can easily carry 1.5A of current.

Solution 2

As long as it has the correct connector, a suitable current rating for the devices needs, a suitable voltage rating for the supply in your country and actually meets it's specifications it will be fine.

There is no need to pay rediculous prices for a HP branded cord, but equally I would be very wary about buying cords from "marketplace" sites. There are some dodgy manufacturers in China producing cords whose specifications are lies and then either selling them directly to customers in the west on these marketplace sites or selling them to small sellers in the west who do not do their due diligance before putting them up for sale on said marketplace sites.

Generally I find the best places to get such cords is from electronics suppliers, for example https://cpc.farnell.com/volex/152610-2/power-cord-uk-plug-to-c5-connector/dp/PL15107?st=uk%20power%20lead

Comments

[Ian Haggerty]

Thanks for the answer RedGrittyBrick. Any idea why my monitor 'buzzes' when it is not even turned on? It is very unsettling! (plugged in a 250V, 10A with 5A fuse)

[user5249203]

@IanHaggerty: You could ask that as a separate question. Check the power cord is pushed in all the way.

[Ian Haggerty]

Never mind - it seems to have stopped. Think the monitor was just warming its bones. Thanks again - you saved me £5 and I now feel a little more competent with power plugs!

[Ian Haggerty]

Turns out it is a common problem with these monitors. Respectfully 'acknowledged' by the HP engineers. I do hope it doesn't affect the working lifetime of the monitor.

[plugwash]

It's not uncommon for switched-mode power supplies to buzz, especially when under light load.