Plug timer socket for 3kw blow heater

Turner

Can anybody recommend a mains plug timer socket for a 3kw blow heater.

Am looking to set the heater to come one at a certain time for two hours then turn off.

Is this possible considering the 3000w heat load.

Thanks.

Sleeper12

https://purchase.ie/product/all-products/plug-in-timer

2011

What type of heater do you have in mind?
I would be more concerned about leaving some types unattended than others.

Turner

A dimplex fan heater placed on a tiled floor. Nowhere near any combustables

coylemj

They sell them in all the electrical stores, just check out the accessory rack and make sure it's rated to 13A.

Turner

I have a timer plug socket here, it says the following on it

Maximum wattage 3200w resistive load
Maximum wattage 480 inductive load
Max current 13(2)amp.

Is a dimplex 3kw fan heater resistive or inductive??

coylemj

Turner wrote: »

Is a dimplex 3kw fan heater resistive or inductive??

The (fan) motor could be inductive but the vast majority (>98%) of the 3 kW load is consumed by the heating elements and is resistive.

xl500

Turner wrote: »

Can anybody recommend a mains plug timer socket for a 3kw blow heater.

Am looking to set the heater to come one at a certain time for two hours then turn off.

Is this possible considering the 3000w heat load.

Thanks.

I would be very careful leaving a 3Kw Load unattended that's right at the limit of a 13a socket and depending on the quality of the socket and connections you could get issues I have seen poor quality sockets fail when subjected to high loads

Skedaddle

If the load is genuinely 3000W at 230V that's over the limits of a 13 amp plug at 230V - 2990Watts is as much as you can go.

I'm always surprised they sell appliances here rates 3000W. 2800 is the upper safe limit in Ireland with those plugs as we are originally on 220V, not UK 240V. We should probably be using 16amp Schuko.

Supplies were only ever nominally rated 230V for pan EU compatibility purposes. The Irish and continental voltage is often still centred around 220V and the UK is often still 240V.

13 amp at 220V = 2860W (UK plugs used on 220V Irish supply)
13 amp at 230V = 2990W (UK plug on harmonised EU voltage)

16 amp at 220V = 3520W (Schuko Continental plugs)
13amp at 240V = 3120W (UK plug on UK 240V)

A lot of heating appliances will be rated something like 2800-3000W depending on the 220 or 240V range. But anything actually drawing 3000W at 220 or 230V is over the limits for our domestic plugs and you should use a 16amp plug with appropriate circuit protection.

2011

Skedaddle wrote: »

If the load is genuinely 3000W at 230V that's over the limits of a 13 amp plug at 230V - 2990Watts is as much as you can go.

I'm always surprised they sell appliances here rates 3000W. 2800 is the upper safe limit in Ireland with those plugs as we are originally on 220V, not UK 240V. We should probably be using 16amp Schuko.

Supplies were only ever nominally rated 230V for pan EU compatibility purposes. The Irish and continental voltage is often still centred around 220V and the UK is often still 240V.

13 amp at 220V = 2860W (UK plugs used on 220V Irish supply)
13 amp at 230V = 2990W (UK plug on harmonised EU voltage)

16 amp at 220V = 3520W (Schuko Continental plugs)
13amp at 240V = 3120W (UK plug on UK 240V)

A lot of heating appliances will be rated something like 2800-3000W depending on the 220 or 240V range. But anything actually drawing 3000W at 220 or 230V is over the limits for our domestic plugs and you should use a 16amp plug with appropriate circuit protection.

I disagree, in Ireland single phase supplies are 230V.

At work we have installed many PQ meters on a large number of sites across Ireland and these verify this (400/230V). I have also measured 230V in many domestic installations.

Skedaddle

It's not unusual to measure 245V in the UK and I've seen quite a few 215-222V readings here and on the continent.

In theory as transformers were replaced, we are all supposedly moving to 230V but the standard was specifically designed to allow for both 220V and 240V legacy standards to exist for as long as needed without causing any need for power companies to actually change transformers.

The issue still stands even at 230V, a 13 amp plug is not rated to carry 3000W. It's maxed out at 2990W.

There shouldn't be any 230V 3000W devices on sale in Ireland or the UK as it's outside the spec. of the plugs and sockets.

2800W is about as high as is safe. You need a safety margin. That's why you can't really use 13amp plugs with 3kW cooking devices without burning our the pins of the plug. Even if the fuses have a bit of margin, the plugs invariably run hot at their full load.

Also the design of the plugs used here has one dangerous flaw - the fuse holder. If it's deformed or if the fuse isn't seated very well, they can get very hot and that's where you typically end up with the burnt out plug top or the very hot live pin discolouring the urea formaldehyde sockets.

The fuses should be snapped into a fitting that cannot make a bad connection.

All that's in most rewrirable plugs is a brass clip fuse holder that can be removed. It may not be fully in contact with the fuse caps. I've seen that quite a few times on heaters and friers.

On two occasions I've seen high powered oil filled radiators (close to 3kW) cause a plug to catch fire.

They're a good design in terms of the shutters and child safety having been around on them for a very long time, but they're not as good at carry high loads as a continental style recessed socket and plug.

I just wouldn't trust one plugged in with a sustained maxed out load.

2011

Skedaddle wrote: »

It's not unusual to measure 245V in the UK and I've seen quite a few 215-222V readings here and on the continent.

I working in Spain right now and it’s 400 / 230V and I was in Poland 2 weeks ago, it’s the same. I know there are exceptions but I have mostly worked on projects outside of ireland for the last 5 years and this is what I have seen.

The issue still stands even at 230V, a 13 amp plug is not rated to carry 3000W. It's maxed out at 2990W.

There shouldn't be any 230V 3000W devices on sale in Ireland or the UK as it's outside the spec. of the plugs and sockets.

A lot of kettles in Ireland are 3kW and they work just fine on a 13A plug.

Bruthal

Skedaddle wrote: »

The issue still stands even at 230V, a 13 amp plug is not rated to carry 3000W. It's maxed out at 2990W.

There shouldn't be any 230V 3000W devices on sale in Ireland or the UK as it's outside the spec. of the plugs and sockets.

2800W is about as high as is safe. You need a safety margin.

How do we know 2990 is maxed out? Maybe its maxed out at 3200 watts, and 3kw has a safety margin.

I know one poster at least, who will say 2990 is the max, and 2991 is overloaded alright, because 13 amp plugs are what they are called. Or is that plug tops?:pac:

3kw sustained will be testing them most likely alright.

Skedaddle

2011 wrote: »

I working in Spain right now and it’s 400 / 230V and I was in Poland 2 weeks ago, it’s the same. I know there are exceptions but I have mostly worked on projects outside of ireland for the last 5 years and this is what I have seen.



A lot of kettles in Ireland are 3kW and they work just fine on a 13A plug.

Big difference between sustained load and 2 min boil.

Bruthal

Bruthal wrote: »

I know one poster at least, who will say 2990 is the max, and 2991 is overloaded alright, because 13 amp plugs are what they are called.

Our plugs are way, way over-engineered. Just compare the mass of the contacts between our 13A plugs and EU 16A schuko.

The Aussie and Yanky ones are the problems amazingly the continents haven't set fire yet.

245V right now in this gaff in Cardiff.

Skedaddle

Yet despite the bulk they only have very limited contact surface area, which is all that really matters for hot pins.

trellheim

I disagree, in Ireland single phase supplies are 230V.

At work we have installed many PQ meters on a large number of sites across Ireland and these verify this (400/230V). I have also measured 230V in many domestic installations.

As someone who measured this for a summer on work placement you can see some wild voltage fluctuations out the end of the lines see some farmhouses !!!

Skedaddle

The official range is 207 to 253 volts.

The network was originally designed to deliver 220V / 380V and there was never any requirement to remove or replace equipment delivering those voltages.

New transformers should be targeting 230V but that doesn't mean that everyone's connected to one.

There were actually 210V supplies in some old parts of Dublin including the Phoneix Park area until the early 2000s. I'll link you an article later.

Bruthal

Sir Liamalot wrote: »

Our plugs are way, way over-engineered. Just compare the mass of the contacts between our 13A plugs and EU 16A schuko.

The Aussie and Yanky ones are the problems amazingly the continents haven't set fire yet.

245V right now in this gaff in Cardiff.

3.4kw heater there so. Unless it pulls the voltage back down a bit. Or it's a 3kw 240v one. I've seen 240 here before. Voltage is stepped up and down to compensate for demand changes throughout the day. Automatic tap changers on 38kv transformers etc.

2011

Skedaddle wrote: »

Big difference between sustained load and 2 min boil.

Absolutely, I was just pointing out how in reality we have plenty of 3 kW loads supplied at 230V from 13A plugtops which conflicts with your post.

Skedaddle

Yeah but you are basically maxing out the plug spec for a short time without consequences.

If you ever notice burnt plugs and sockets they are almost always something like a 3kW heating appliance, or a piece of catering equipment that runs constantly.

I've always thought that BS1363 plugs are a totally over praised design. They get the shuttering and polarity issues covered very well but they have a lot of issues with heat due to two design choices:

1. The very crude fuse carriers that can be deformed or allow the fuse caps to slide out of line, yet remain connected.

2. The original design didn't use sleveed pins. To proceed finger protection they keep the contacts very deep in the socket so really only the tips of the pins connect.

Both of those limit the current carrying capacity even though the plug is enormous compared to other designs.

Continental 16amp Schuko uses recessed sockets so you can't touch the pins at all as the plug and socket completely cover them, so there's there's no need to have those 3/4 plastic coated pins them. This allows for longer contact tubes and less overheating.

(Only the little flat 2.5 amp "europlug" found on small appliances has sheathed pins because it exposes the pins on insertion. It's designed to fit several other types of sockets used in Italy, Denmark and Switzerland etc)

Also on voltage tolerances, Ireland's in a much better position than the UK as we come from the original 220/380V legacy. So you're more likely to see 230V or something lower (still within tolerances). In Britian, you'll see voltages that are normally sitting in the upper limits of the 230V spec and a spike can take you into over voltage much more easily.

Some continental equipment is most definitely not tested for more than 230V +/-6% and I've seen numerous examples of equipment failing in the UK on voltage spikes.

New networks equipment is definitely spec'd for 230/400 and in reality withing a lot narrower range than +/-10%. Old Irish or continental 220V/380V supplies aren't going to cause any issues. It's more of a concern when you get UK 240/415V and something is sitting close to the transformer and way up at the top of that range.

Australia also was standardised on 240/415 with a few areas actually having a legacy of using 250V as standard.

With heating appliances they're usually something more like 2800-3000W 220-240V and have been specified with a curve that in effect gives you about 12.9 amps. The wattage output varies depending on the voltage.

The elements being simple resistors, ohm's law applies

V^2/R = I^2R

Element designed to be (240 V)^2/ 3000 W = 19.2 Ohm.

If you use 220V

220^2/19.2 = 2520W

If you use 230V

230^2/19.2 = 2755W

(This is also why some electric showers will be significantly cooler on 207-220V than on 240-240V)

So, I'm just curious as to why they're selling 3kW appliances are all in the UK or here as the plug doesn't support more than 13amps.

Calculating the element rating as 3000W at 240V makes sense. I assume they're doing their calculations to target just slightly shy of 13 amps and shoving "3000W max" on the label as the theoretical maximum consumption.

It's actually easier to see loads in amps. That's how US appliances were traditionally rated. As for practical purposes in a house for sockets and adaptors you need to calculate maximum amp loads not power outputs and inputs.

You shouldn't be able to draw 3000W from an Irish socket at Irish voltage without blowing the 13 amp fuse. So I suspect in reality, we aren't drawing those wattages at all. They're just theoretical max. at the upper range of the voltage tolerances.

2011

Skedaddle wrote: »

Yeah but you are basically maxing out the plug spec for a short time without consequences

Yup, just pointing out that this conflicts with your earlier statement.

2011

trellheim wrote: »

As someone who measured this for a summer on work placement you can see some wild voltage fluctuations out the end of the lines see some farmhouses !!!

Small installations in rural areas are impacted more by changes in load profiles.

Bruthal

Skedaddle wrote: »

If you ever notice burnt plugs and sockets they are almost always something like a 3kW heating appliance, or a piece of catering equipment that runs constantly.

Could it be that heaters are in the 2 and 3kw range, while must other items people plug in are 60 watt tvs and lamps?

Ive a 3kw heater on for an hour out in the shed there. It is plugged into a lightwaverf plug in adaptor. Pins on both are not even noticably warm.

What happens if I plug in a 10 watt lamp now as well?

Skedaddle

If you overload it beyond 13 amps the fuse blows (eventually). It doesn’t matter what the wattage is, only the ampage.

What I see a lot is the sockets and plugs struggle at high load for long periods and I’m pretty sure the source of the heat that I’ve seen cause melting plugs is the fuse holder design.

Some plugs have better designs (the old MK type etc etc) but the most basic design is just a a loose piece that’s pressed out brass spring that can be easily deformed to make it too loose or it can slide out of place.

Just because it’s making contact with the fuse cap doesn’t mean it’s very good contact.

I’ve seen a few BS1363 plugs spontaneously melt over the years and I am just unconvinced that the design is reliably able to cope with maxed out loads.

On heaters and other heavy appliances always worth checking the plug is wired well with good contact with the terminals and that the fuse is properly seated.

Also check the socket isn’t loose or worn.

I just think if you’re going to have fuses in plugs, a modern design like a car fuse that plugs in and can’t be badly connected makes a hell of a lot more sense.

We forget a lot of these fittings we use are very old tech. The plug design is from the 1940s.

If you’re going to put a heater in a shed permanently, I would hardwired it to a double pole spur and use a high quality 16amp timer. Not a plug in thing.

Also a lot of those plug in timers are only 10amp max.

Also something like an oil filled radiator is less of a fire hazard. Small fan heaters are usually plastic and also depend on the fan spinning to work safely.

Motor stops or something falls on the air intake and you’ve a hot pile of plastic.

Unattended stuff is best kept low tech and fail safe.

Bruthal

Skedaddle wrote: »

It doesn’t matter what the wattage is, only the ampage.

If you’re going to put a heater in a shed permanently, I would hardwired it to a double pole spur and use a high quality 16amp timer. Not a plug in thing.

Us carpenters are more experienced at electrickery than ye might think.

Skedaddle

Well unless you bypass the fuse in an Irish plug, you can't overload it.

I would love to see some proper like-for-like fire statistics for that BS1363 system Vs the simpler continental systems in modern installations and real world scenarios.

It's a shame the UK blocked the rollout of the proposed harmonised European plug that was intended to replace Schuko, BS1363, the Italian and Danish systerms.

They had come up with a small, recessed,16 amp plug and socket systems that was ultra safe, child proof, polarised and neater than a US plug.

So naturally enough it was rejected by the UK as euro meddling back in the late 1990s.

The standard still exists and weirdly South Africa adopted it recently and Brazil adopted it but changed the specs.

2011

With respect I think you are looking for a solution to a problem that doesn’t really exist.

I use good quality socket outlets and plugs in my home and have never had any issues, even with 3 kW loads.

I have seen some give trouble in the past but these were in poor condition and / or low quality. The same applies to all things electrical, for reliability use quality components that are in good condition.

As socket circuits are frequently protected by 20A MCBs I like the fact that there is a fuse in the plug that can provide a degree of protection to the smaller downstream cable (feeding the appliance). A 20A MCB will not provide much protection to a 0.75 mm sq. cable.


Edit: Just to add I accept your point that a 20A DP switch is preferable for 3 kW fixed appliances.

Skedaddle

The fuse itself is a good idea, it's just the way it's implemented in a lot of cheap plugs is pretty questionable.

All they need to do is design the fuse holders in such a way that the fuse can't be out of line. The only plugs I've seen this done correctly in are the big heavy old MK ones and also most moulded plugs are fine as they've a carrier and proper fuse holder.

All I'm saying is if you're using a heavy appliance for extended use, check your fittings are in good condition and that the fuse is actually firmly in place.

I've seen 3 of those plugs literally catch fire. Twice in a restaurant situation with a large panini toaster and once in a domestic situation which was behind a book shelf! Someone had a very heavy convector heater plugged in the plug just melted from the fuse holder.

Type "melted UK plug" into Google Image search and you'll see exactly what I mean.

2011

Skedaddle wrote: »

The fuse itself is a good idea, it's just the way it's implemented in a lot of cheap plugs is pretty questionable.

So the moral of the story is buy quality electrical components / accessories, I agree fully

I've seen 3 of those plugs literally catch fire. Twice in a restaurant situation with a large panini toaster and once in a domestic situation which was behind a book shelf! Someone had a very heavy convector heater plugged in the plug just melted from the fuse holder.

I would be much more concerned about this sort of thing as the currents are far higher.

Skedaddle

2011 wrote: »

So the moral of the story is buy quality electrical components / accessories, I agree fully



I would be much more concerned about this sort of thing as the currents are far higher.

Some real eye openers on that thread!