Learning experience re Electric (1 Viewer)

[Giddy Lynn]

Hi all

Please excuse the terminology I use as I am not yet up on the technical terms.
Just wanted to pass on this experience I had to all newbies (regulars will know this), regarding plugging in the campsite's electric.

On arrival I plugged in and had TV, battery charger, fridge on, all good, I then went to switch on the hot water heater and electrics switched off! Turned off hot water then reset electric on campsite's EHU box, all good, switched off TV, fridge, turned hot water heater on, electrics shut off again. I went to reception and explained and was told the hot water heater is taking too many (this is where I get mixed up) Amps as they only had 10amps. So we turned everything off and put the hot water heater on again it blew again so we used our gas. To cut a long story short we then turned on what we first had on arrival and it blew again! By the next day we turned everything off except the camping kettle and that blew the electric box. So not having any knowledge of electrics I (wrongly) assumed my MH was at fault and intended to book it in to the garage the next day. As we were packing up the next morning (only booked for 1 night) the warden (who is a member on here) came to me and enlightened me that their electric unit was possibly faulty, and that every time it blew it would take less and less amps until it couldn't take the camping kettle, aargh so it wasn't my MH.

So that weekend I learnt something but I wished I was told sooner. I had a word with the owner so they could put it right even though they already suspected a part needed replacing! Hope that helps any newbies that it may happen to, as had I had the knowledge of this I would have asked to be moved to another unit.

 

[Robin McHood]

@Giddy Lynn, What @emmitdb said is correct.
Lecktrikery 101 - The amps (A) are the amount you've got to play with, the voltage (V) is the push behind the amps, bit like volume and pressure on a hose. Generally all your appliances will be marked with what they use in watts (W).
Watts = Volts x Amps
It is simple to work out what to switch on and what not to.

When hooking up check on the box, or with the warden, what their supply is rated at. They should tell you an Amp figure.

16A = 3680W, 10A = 2300W, 6amps = 1380W, 3A = 690W on a 230v supply, which is the European standard (including the UK)

That's the amount you have to play with. As Giddy Lynn says, check your docs, bottom of kettles etc etc and look for the W figure. Thats what it is going to use.
Just add up all the W figures you want to use (demand), subtract it from the supply W and if demand exceeds supply, the breaker (which is simply a switch that shuts off automatically at its rated setting 16/10/6/3A) then your supply will trip.

This also applies to beer, as you will know if you've ever been in a pub that ran out of beer. I did that once to a GF's pub, long story, but it was the end of a beautiful relationship.

If you were definitely demanding less W than the supply W then the supply point is faulty. Don't use it!

The maths are the same regardless of supply voltage. If you want to work out what you can run off your 12v battery then volts x amps still equals watts.

 

[Jasz]

Interestingly a 16A B type circuit breaker should take 30A for around 35 seconds before tripping, and a 10A B type circuit breaker should take 20A for around 35 seconds before tripping. They only trip at their rated current after several minutes (taken from the chart in the regs book) - sorry yet another sparks

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[Robin McHood]

Absolutely right @Jasz but let's keep it simple. My response was to help a non lecky work out what he can run or not on different sized breakers and didn't feel the need to get into the intricacies of short time constant/high current trip points.
For EHU's it's the long term thermal rating that is important. The rest, as you know, is all to do with fault protection.

 

[peterc10]

I don't know how people manage on 3-6 amps abroad but with knowledge it will get easier.

We manage with no amps at all abroad and in the UK for most of the year. Couple of good batteries, couple of solar panels, LED lighting and 12V for almost everything works fine for us.

 

[Jasz]

My previous post was to point out that what was being run wouldn't normally trip the breaker out straight away, there would be likely to be a delay before it tripped. As has previously been commented on this suggested a fault in the supply.

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[Deleted member 29692]

Hope I'm not setting myself up for a fall here but Giddy Lynn,

In the UK, usually you get 16amps on the post. The 'stuff' you use in the van is 230volts. If you times the 16amps by the 230volts you get a figure of 3680. These are the watts you have to play with when you use your units.
Your example is easier 10amps x 230volts =2300watts. Your camping kettle is rated at about 1000watts (look on the base).

Lecktrikery 101 - The amps (A) are the amount you've got to play with, the voltage (V) is the push behind the amps, bit like volume and pressure on a hose. Generally all your appliances will be marked with what they use in watts (W).
Watts = Volts x Amps
It is simple to work out what to switch on and what not to.

When hooking up check on the box, or with the warden, what their supply is rated at. They should tell you an Amp figure.

16A = 3680W, 10A = 2300W, 6amps = 1380W, 3A = 690W on a 230v supply, which is the European standard (including the UK)

Nearly right but not quite.

There's a bit more to it than just multiplying volts by amps. What that gives you is VoltAmps usually expressed as VA.

To get a true power figure in Watts it's Volts x Amps x Power Factor or VIcosφ

The power factor is a variable but always less than 1 so to take the 16A example you will never have 3680W to play with. It will usually be nearer 3000W or sometimes even lower.


EDIT: I'm well aware that power factor isn't usually taken into account on single phase domestic installations but that doesn't mean it isn't there.

 

[Andy in Lossie]

Mhe .... electrical theory is boring (I know it's a necessary evil in our trade .... still boring though ) what I get a real kick out of is fault finding and seeing stuff work again .... love that

 

[scotjimland]

what I get a real kick out of is fault finding and seeing stuff work again .... love that

you would love a Swift van then

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[DBK]

Electric kettles? You won't trip anything with one of these:

 

[Zigisla]

you would love a Swift van then

Now stop it @scotjimland look what you started on the who owns a German MH thread.
I cannot afford the time to keep looking at the arguments / I need the last word that occurs. I need to work hard today cos of loosing so much time on the last thread. Either that or I will have to wait until I am sitting at Eddie's having my growler fitted to watch the fall out.

 

[shawn&emma]

Interestingly a 16A B type circuit breaker should take 30A for around 35 seconds before tripping, and a 10A B type circuit breaker should take 20A for around 35 seconds before tripping. They only trip at their rated current after several minutes (taken from the chart in the regs book) - sorry yet another sparks

I understand the fact that it should say take 30A but should that not be for around 35 milli seconds?
The rated current should then trip within a second from overload, several miniutes would cause possibly damage?

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[peterc10]

Either that or I will have to wait until I am sitting at Eddie's having my growler fitted to watch the fall out.

Don't do that. Taunton has 2 Weatherspoons and Eddie will take you there for free.

 

[Zigisla]

Don't do that. Taunton has 2 Weatherspoons and Eddie will take you there for free.

I have seen the weather report so may just do that. As long as they allow dogs.

 

[Jasz]

The 35 seconds is correct, a large overload or short circuit would trip it out significantly faster. The 35(ish) milliseconds is to do with the RCD trip times, in the event of a loss of power on switch on check the RCD as there could well be an earth fault in one of the appliances.

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[shawn&emma]

The 35 seconds is correct, a large overload or short circuit would trip it out significantly faster. The 35(ish) milliseconds is to do with the RCD trip times, in the event of a loss of power on switch on check the RCD as there could well be an earth fault in one of the appliances.

Hello @Jasz thanks for that.still couldn't get my head round it so found regulation 433, which I believe is the right one and it makes a little more sense to me now and answers some questions I had when we'd had problems on a site I worked on. This was never mentioned to me.

Just to say I'm not a sparkie but have had to be on occasions lol.

 

[pappajohn]

Electric kettles? You won't trip anything with one of these:
View attachment 103135

Wanna bet....I once tripped our gas when I overfilled the whistling billy.

 

[Jasz]

Hello Shawn, yes you found the right bit, rather confusing but the overload is just designed to protect the cables before they overheat. Old fuses let even more current through before blowing!

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[Robin McHood]

@NickNic, yep true but as I said before this whole thread was about explaining to a non-lecky what he could reasonably hook-up and what he couldn't so KISS.
I know all the rest of that stuff is fascinating to us but probably pretty boring to anyone else. If he sticks to the rules of thumb @emmitdb and I gave him then @Giddy Lynn will do just fine. If he's sticking to those rules and the breaker trips then he needs to tell the warden and preferably avoid using that connection. If he tries a second connection for his EHU and that breaker trips too then he needs to get his electrics checked out.
I really don't think it needs to be any more complicated that that. Time for beer......

 

[Deleted member 29692]

@NickNic, yep true but as I said before this whole thread was about explaining to a non-lecky what he could reasonably hook-up and what he couldn't so KISS.
I know all the rest of that stuff is fascinating to us but probably pretty boring to anyone else. If he sticks to the rules of thumb @emmitdb and I gave him then @Giddy Lynn will do just fine. If he's sticking to those rules and the breaker trips then he needs to tell the warden and preferably avoid using that connection. If he tries a second connection for his EHU and that breaker trips too then he needs to get his electrics checked out.
I really don't think it needs to be any more complicated that that. Time for beer......

I don't agree that he will be fine if he follows the advice of trying to load a 16A breaker to 3.6kW. I actually think that's bad advice.

If you want to keep it simple then the rule of thumb is to never go over 3kW on a 16A supply.

As anyone with even limited understanding would know anything more than that needs to be on a 20A supply.

 

[Robin McHood]

As anyone with even limited understanding would know anything more than that needs to be on a 20A supply.

I'm so sorry, my 50 years of experience, with the last 25 as lead engineer of a 12MW power station generating at 6KV and distributing at 440v/220v etc etc and supplying a huge range of complex electrical and electronic equipment including stuff supplied by EHU cables...and on my knowledge of which lives depend on a daily basis, is a pretty limited understanding I guess and I grovel at the base of your superior knowledge...



The original question stated that of the loads he was connecting, 99% were resistive loads.... as I recall..... "TV, battery charger, fridge on, all good, I then went to switch on the hot water heater" oh yes so they were....

The Camping and Caravanning Club site recommendations, obviously also written by someone of limited knowledge ......

"You need to ensure the total rated wattage (rated power) of equipment switched on at any one time is less than the power supplied to you. Power (in W) = voltage (in V) x current (in A), so for a 10A hook-up, 230V x 10A = 2300W, hence 2,300W (2.3kW) of power can be supplied to your unit. At a 16A site this rises to 3.68kW."

Now I'm off for another beer and a lie down in a quiet place....
Robin McHood,
I.Eng., M.I.E.T. (in case you don't know it, the IET is the new name for the combined IEEE & IEE, you know, Faraday's old mob....)

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[Robin McHood]

I understand the fact that it should say take 30A but should that not be for around 35 milli seconds?
The rated current should then trip within a second from overload, several miniutes would cause possibly damage?

@Jasz is telling you correctly. As we are getting into the nitty gritty.. an mcb (miniature circuit breaker) protects against two types of fault.

Your reading has probably already shown you that they have a curve response, the type of curve being described by the letter, in the case of the one jasz is quoting (B) there are others. You have to match the curve to what the circuit is supplying. For example a direct on line motor starter or a transformer can generate a very high inrush current so the breaker must have the correct curve to handle that for a very short period while still maintaining the second level of protection which I will describe below.

The first thing they protect against is for things like short circuits, which generally produce a very high spike of current. They can run up to several hundred amps or higher on a nominally 16A supply so the mcb must react as quickly as possible to break such a faulty circuit, response times to this sort of fault are in milliseconds. Quite impressive when its a 6kV breaker opening under a short circuit of 27,000 Amps....... Flash just doesn't come into it ...

The next type is the overload fault. This uses a different mechanism to produce the trip. It will allow small overloads for a short period but eventually trip if the load above the rating continues. This allows the start of things like say fluorescent lighting or your compressor fridge which need a higher current on start but then settle down to a low level. So this trip is looking for long time loads that are a bit higher than normal.

This trip in standard mcbs is achieved using a bimetallic metal strip through which the load current flows. As it heats up, which is a function of curent flow over time, (the more current the quicker it gets hot), it bends and this bend eventually trips the breaker and the integral spring snaps it open. So how long it stays on is purely a function of how much overload there is.So a low level say 18A on a 16A mcb can take several minutes to trip but raise that to 30A and it comes down to seconds.

Where they can also trip is if you have a fault in the nearby wiring, a bad connection. This heats up due to the high resistance and the heat can travel along the wire to the mcb, heat up the metallic strip and the breaker trips.. You know you haven't got an overload but this time its heat causing the problem.

That's why in an earlier post I suggested that if you KNOW you haven't just switched on 3kW of heaters on a 6A supply that you need to go looking to see what caused the trip, Hot joints in domestic wiring are more common than you'd think and in EHU supply posts exposed to the elements... You just dont want that socket hot joint melting your plug.....

There you go clear as mud!

 

[Giddy Lynn]

OMG guys I am getting worried with all this electric jargon. I thank you all for your time and input but don't want to cause any arguments. Most of it is going over my head but will keep the simplest bits tucked away. Now.....all of you have a beer .....and cheers Lynn