amps & intelligent mains panel

[Steve Jones]

Just bought two of these from Maplin. One I wanted for my computer and the other I had the idea of using it for my TV. So when TV goes off, DVD, video and STB go off as well. A pal of mine had a small house fire from a TV left on standby.

The one for the computer works great. But I am unsure about whether to try the other on the TV. The problem being that the master socket on the mains panel is rated at only 5amps. The TV plug has a 13amp fuse and the power consumption is 150watts. A 13amp fuse seems high to me but I don't understand the relationship between power consumption and ampage.

I could just try it and see but I would like to understand it a bit more first. Does the TV really need a 13amp fuse?

Can anyone help?

Thanks,

Steve

[Alan]

No. 150 w = 0.62 amps assuming 240v mains voltage. (150 / 240 = 0.62) Fit a 3 amp mains fuse instead.

Alan.

[Christian McArdle]

No it doesn't, unless it is quite a huge thing that could stretch to a 5A (my hungry 36" CRT model is happy on 3A). Remove it immediately and replace it with a 3A fuse. Everything in your house should have a 3A fuse, with some exceptions for high rated appliances, usually involving powerful motors or heating elements. The exceptions which require 13A might include:

washing machines tumble dryers dishwashers kettles microwave ovens conventional ovens toasters vacuum cleaners fridges/freezers (some will be happy with 5A)

Anything to do with lighting or entertainment should have a 3A fuse (or lower if you can find supplies). I would suggest going around your house and examining every fuse to be the right value. Whilst doing this, ensure that the following look good:

1. Cable condition.
2. Strain relief on plug and appliance ends.
3. Outer sheaf goes all the way into plug and is secure.
4. No blackening of plug pins or socket.
5. Appliance cases in good condition.
6. Plugs fit securely and tightly in sockets.
7. No cracks on sockets or plugs.
8. No more than 2 multiways in a daisy chain. Preferably none at all.

Then get one of those plug in testers with the neon lights. Plug it into every socket in the house INCLUDING any multiway adapters. Ensure that all 3 lights come on.

Obviously, even better would be to get the whole installation tested and all appliances PAT tested, but this is unlikely to happen, unlike the simple cheap tests above.

Christian.

[usenet]

If the television really only takes 150 watts then the current should be less than an amp unless the power factor is truly awful.

The 13 amp fuse is protecting the flex more than the television but even so I would have thought a 5 amp one would be more sensible. However lots of equipment seems to be supplied with 13 amp fuses regardless of whether it makes sense or not.

[Set Square]

In simple terms, watts = volts x amps, or amps = watts/volts

So if your TV is 150 watts, it takes a current of 150/240 amps = 0.625 amps.

It sounds like a 13A fuse is a bit of an overkill - even allowing for a slight surge on turn-on!

Your intelligent mains panel should work fine with the TV.

[Steve Jones]

Thanks for all the answers. Even with my limited knowledge I thought the

13amp fuse was overkill. But it was manufacturer fitted!

Anyway I tried the mains panel and it does work fine except what I didn't realise is that it also detects low power states such as standby. So everything goes off when I put the TV into standby. Not what I had in mind, I wanted it to power down everything else when I physically switched it off before going to bed. Otherwise to record a programme I would need the TV and/or STB actually on.

Steve

[Steve Jones]

and while I'm at it I might as well go up onto the roof and check the tiles/pointing/guttering etc. :)

[Christian McArdle]

You're getting there!

Christian.

[Alan]

Probably because standby draws such a tiny ammount of current that the panel assumes the TV is off. No easy fix for this. Maybe use an X10 appliance module(s) to allow you to send an off signal to everything you want off at night??

[Dave]

The TV has a static power consumption (shown on the plate) which can be roughly converted to current (ignoring power factor) by dividing power by 230 but there's a much larger (and unspecified) current drawn after switch-on to degauss (demagnetise) the metalwork inside the CRT. The degauss current may be 5-10A on the first half cycle and exponentially decays to zero over the first few cycles. This is no worse than a CRT monitor so if that's not popped the other mains panel you should be OK with the TV. A 13A fuse does sound too big but you may find that the switch-on inrush causes a smaller one to fail occasionally - suck it and see.

[Christian McArdle]

Also, it is how you would want it to work surely?

Most people just want to sense standby to turn all the other stuff off and still be able to use the remote to turn it back on again. If you can actually be bothered to stand up, walk across and flick a real switch, then you might as well hit the one on the socket instead of the TV. No need for electronic assistance.

Christian.

[Ian Stirling]

The fuse is utterly irrelevant. Turn the TV round. You should find a panel listing "240V 50Hz 250W" or similar. In practice, I'd be extremely surprised if any TV (barring really huge projectors for 10m screens.) took 5A.

[Ian Stirling]

The really, really trivial way to check that you're not likely to burn it out is to replace the 13A fuse with a 3A one.

[Alan]

I agree, what most people would want, however the OP was trying to prevent a similar case as his friend who had a fire caused by a TV left on standby.

[Dave Plowman (News)]

I shudder to think of the number of things I have powered 24/7. And never had a fire.

Certainly it wasn't advised with the very early remote control sets, but these days? After all, anything with a clock in it etc is powered up to some extent all the time.

[nightjar]

The fuse in the plug is only there to limit the current flowing in the flex. If the flex is rated at 13 amps, then a 13 amp fuse is quite correct. The consumption of the TV is irrelevant to the rating of the fuse in the plug. The TV should have its own internal overcurrent protection, matched to its actual consumption.

Colin Bignell

[mike ring]

"nightjar" wrote in news:41b5fac3$0$10994$ [e-mail]:

At last a reference to what we learnt when God was a lad.

"Fuse for the cable"

I think this rush to 3A is a bit of an overkill - has this group suddenly gone politically correct and joined Nanny state ofr the manufacturers' benevolent club.

Even failing lightbulbs often take out a 3A fuse, and they've got a builtin fuse!.

5A will do for me.

The consumption of the TV is irrelevant to the rating of the

I don't think I'd go *that* far

Nothing modifies the other posters good sense that overfusing is very dangerous unless the cable and appliance are appropriate

mike

[Steve Jones]

The slave sockets are rated 13amp, it is only the master socket that is rated 5amp.

[Set Square]

Well, they might be individually rated thus. BUT don't forget that the plug on the end of the input lead has a 13A fuse in it, so the TOTAL current used by the master and all 5 slaves mustn't exceed 13A!

[Andrew Gabriel]

That is a requirement for appliances, where an internal fault which draws excess current would otherwise result in an unsafe condition (such as fire or explosion risk). A TV is not allowed to rely on an external fuse for it to remain safe during an internal fault.