Amps/Watts????

[Guest Mike Norsworthy]

Hello, Does anyone know of a simple approximate guide or list as to what Amps the electric accessories usually found aboard a Motorhome draw? We are venturing abroad to France for the first time in May and the site we are staying on has a 10Amp hook up not the 16Amp we are used to! I know that basically if it produces heat or has a motor it draws a lot, but how much is a lot? We have a 15inch LCD TV, a playstation and Sat system in addition to the usual fittings! I have always found the replies on this site very helpful and i tank you all in anticipation. Mike Norsworthy

[Guest Mel E]

It's pretty straightforward really: just remember AMPS = WATTS / VOLTS Thus a typical 14" CRT TV is around 45 watts, mains voltage in France is 220 volts, so amps at 220 volts equals 45/220 = 0.2 amps. An electric fire running at 1000 watts is just over 4 amps. So you need to find the watts consumed by each piece of equipment you use - it will be on a label withe model number and serial number somewhere on the item. If some of your items are 12 volts only, then you will either be running them from the leisure battery (allow a couple of amps at 220 volts for recharging that battery) or via an inverter. If the latter then it's still the same formula: Amps @ 220 volts = Watts / 220 But add 20% to the answer to allow for heat losses in the inverter. Hope that helps.

[Guest Clive]

Mel beat me to it! Mike, If you have a European van then you are very unlikely to take the full 10 amps from the mains hookup unless you have brought the high speed home kettle with you. In which case it will be about 10 amps if its a Russell Hobbs 2.4 Kw. However a 2 Kw compact fan heater will take just over 8. Mel, modern inverters are a tad more efficient that 80%, nearer 90 under half load conditions is not unusual. But the rule of thum is a good one. Take care and enjoy.

[Guest Brian Kirby]

Mike Also be aware that a 10A supply on a French site is quite good. If you wander further afield you'll have to be prepared for supplies as low as 3A. You should, generally, expect 5A, but many don't offer much more than that. Clive is right, low wattage kettle very useful (say 600/750W), that leaves plenty of scope on 10A. On the lower amperage connections, the low wattage kettle becomes more or less essential. Apart from the kettle, you can re-charge the battery/s, just about get away with the Truma supplementary electric water heating if you have it (500W), run the fridge and/or a laptop but not necessarily all at once, and reliably, not a lot more. Look at what you intend taking, add the wattages (usually stated on a rating plate somewhere on the equipment), look in your 'van hanbook for the installed stuff, add that, then apply Mel's advice on Watts, Amps and Volts. Then, at least you'll know which bits you can switch on together, and which you'll have to ensure are only switched on alone! It isn't that punitive really, and in any case you'll be so busy rushing around sightseeing you'll hardly have time for the telly and the satellite stuff anyway! Have fun Brian

[Guest Mel E]

Two other things we all forgot to mention: 1. 220volts AC is the standard supply in France. But camp sites are often wired as long strands with hookups run off them rather than as rings where the voltage is applied at both ends of the ring just like your ring main at home. The effect of this can be very severe voltage loss if you're a long way from the power source. I've measured as little as 160 Volts at the hookup (no load) which means: - some voltage sensitive items may give up (mains TVs for example) - you will be taking a significantly higher amerage out of the hookup. 2. We all keep our hookup cables neatly coiled, often on a reel. It is important to completely unreel the cable if you are likely to draw more than a trivial amount of amps. Run it up and down just underneath the motorhome and you'll be OK. Without boring you with the physics, a coiled cable is likely to get much hotter when serious current is being drawn through it and even, near the limit, overheat - it's to do with magnetic induction. Hope that covers everything!

[Guest Yorkshire Tyke]

Yes Mel Some of them are on long runs One in particular in Karlshure had an electric distribution centre over 400 m form where we were pitched On top of that the lines were 50 m long - with the distribution board at ONE END We were camped in the shade with two 25m leads connected together We didnt have a meter with us so I couldnt measure the voltage we were receiving Anyway it was only for one night - the site didnt seem very secure and was surronded by a Motorway and between a railway junction This WAS a municipal site

[Guest Mike Norsworthy]

Once again you have excelled yourselves, thanks very much everyone. No doubt I will have more questions before I set off. Mike

[Guest Bill]

Virtually all electric (mains) appliances sold in the UK have their wattage printed on them (I THINK it's a legal requirement). Given that watts = amps x volts it is easy to work out what you are drawing but, as pointed out above, do be wary of voltage drop.

[Guest Brian Kirby]

Last thought. I forgot to mention that the polarity of your connection is likely to be reversed, i.e. the neutral will be a live and the live a neutral. You'll need to be equipped with means to detect this, and a polarity reversal lead to correct it. I wrote to MMM on this a while back, and understand it is to be published soon, so won't go into details here unless you need me to. Regards Brian

[Guest Mel E]

Brian, I think you're being a bit hard suggesting that polarity 'is LIKELY' to be reversed. I've come across this problem just once in many years of Continental travel. Most modern mains chargers can, I believe, handle reversed polarity so it's only a potential problem for direct mains sockets (rather than ones wired via an inverter) any way. I have a means of checking for reversed polarity but have, so far, not felt the need to carry a crossover lead!

[Guest Mel B]

Sorry to disagree Mel E, but our experince of electrics abroad is different to yours. When we were in France last year for 2 weeks, we used a mixture of campsites and aires. On 3 different campsites we found reversed polarity, 2 were the continental connectors, the other was the normal one we're used to in England which we were most surprised about especially since these weren't cheap sites! Fortunately we have various connectors with normal and reserve polarity (clearly marked of course!) so we were able to still use the power supplies.

[Guest Brian Kirby]

Well, Mel E, I'm afraid I'm in Mel B's camp! We have also travelled Europe for quite a few years: tent, trailer tent, two caravans and a recently acquired motorhome and, since the trailer tent, which had a mains hook up, I have encountered reversed polaritys all over. I had thought the CEE blue connectors might bring an end, but have since gained the impression they don't. For our maiden motorhome voyage last year, therefore, I kept a log, just to see whether my impression was correct. So............ France, Northern Spain, Portigal, Southern Spain and back via France again. 27 sites visited, 11 with the newer, blue, “Euro” type plugs familiar in UK, the remaining 16 having “Continental” (two male pin with female earth) type plugs. The Euro vs. Continental plug scores were: France 5/4, Spain 4/7 and Portugal 2/5. Of the Euro sockets, 6 (55%) had reversed polarity: of the Continental, 10 (63%). So, on that showing, reversed polarity is still quite common with Continental sockets and is, indeed, "likely" to be met. So far as the risks are concerned, I think they are a bit more serious than you imply. The main effect of reversed polarity is that the live feed will by-pass all circuit breakers (or fuses) in the on board consumer unit. These are now on the return wiring, instead of between your appliances (and you) and the mains. In the absence of a polarity test, you’d be unlikely to be aware of this, because everything would still look and work as usual, but your protection against of shock and electrical fire would have been reduced. Why, then aren'tthe Europeans electrocuted or going up in smoke in droves? I wondered, so I did some digging and discovered that, in short, mains polarity is a UK preoccupation. Most of Europe doesn't distinguish earth and neutral: although both are (mostly!) present they are treated as much the same thing. In effect, you have two return paths with equal earth resistance. The other wire is the live and, so long as the two returns are correctly connected, it doesn't really matter much which wire is made the "live". In the UK domestic wiring we only switch or fuse the live feed, leaving the return un-controlled and un-protected. Our wiring is polarity sensitive. In most (if not all, but I'm not expert) of Europe both live and neutral are switched. Their wiring is not polarity sensitive. In other words European practice is simply different to UK practice, and it's only for us that it matters. They're not wrong, just different, and they're likely to remain that way, so there is no realistic prospect that the CEE plugs, or more expensive sites, or anything else will eliminate polarity reversal in Europe. The greatest danger, if the reversed polarity isn't corrected is, probably an electrical fire. That none of your on board electrical installation is effectively fused or switched is a safety risk, but provided you have a working RCD on your intake, you shouldn't suffer fatal shock. Regards Brian

[Guest peter lambert]

I fully agree with the idea of unrolling a hook-up lead fully before use. They WILL overheat if let tightly coiled and pull a lot of amps (electric fire?). As for French sites, we encountered a site with 5A supply last year and fell foul of the trip going out when our Truma heating was left switched to full electric heating at 1800 Watts. This, coupled with the battery charging etc, overloaded it (my fault, I admit it!!). So take care.

[Guest Mel E]

Brian and Mel B, I can only conclude that I stay at a better sort of camp site than you !!! A couple of serious points: 1. The isolator/trip switch on our mains hookup is double pole, switching both live and neutral off together. I may be wrong, but I thought this was fairly standard practice - certainly both our last two motorhomes had the same. 2. In the UK mains electricity is alternating current (sine wave) provided in three phases (each sine wave is 120 degrees displaced as the coils around the generator are at 120 degrees around the circumference). The result is that, when all three phases are added together, the return (or neutral) has zero voltage. Hence pylons typically have 6 main wires (the three phases duplicated) attached by heavily insulated pots and one thin wire across the top of the pylon attached with virtually no insulation - this is the return or neutral. It's why, in a power cut, nearby houses may still have power when you don't - they're on a different phase. It's also why we do not have double pole switched sockets or fuses on both live and neutral: the neutral should be just that with no voltage. So we are highly sensitive to reversed polarity as Brian says. Continentals use basically the same system but are much less concerned about safety than our own cotton-wool wrapped world. So plugs have no plastic sheething to avoid fingers touching live parts as they are withdrawn, many appliances (and sockets) have no earth connection, and so on. As a parallel, imagine the furore if Network Rail removed all the fences alonside rural railway lines - they've never had them in France or Spain or . . . Just thought I'd add a touch of controversy . . .

[Guest Brian Kirby]

Mel I mustn't get beyond myself, I'm not an electrical engineer. However, (he said about to do exactly that!) yes, there should be a main isolator, and yes that isolator is (should be) a DP switch. The main isolator should be an RCD, meaning that if the current flowing into your 'van is not exactly equal to that flowing out, the RCD will "trip" and shut off the electrical supply into the 'van. That is to provide protection against shock or short circuit, but it is, I believe, generally undesirable to rely upon that alone as your protection. For example, I understand that some types of RCD may not function when the polarity is reversed. However, this is easily tested if you have, or contrive, a reversed polarity connection, and then press the RCD test button. If it trips under that condition it will provide shock/short protection. I think the bit about 3 phases is a bit of a red herring. There can be a "neutral" in a 3 phase supply, known as three pahse and neutral (TP&N) or the neutral can be omitted, in which case it is just a three phase supply(TP). The point is that between the phases you get 415 volts and between any phase and neutral 230 volts. The TP supplies are mainly used in industry where, for example, multi horsepower electric motors are required. Large commercial premises will have TP&N supplies, so that, for example, alternate floors in an office building will use different phases, plus the plus the neutral, to balance the demand across the phases. Domestic supplies and single phase and neutral (SP&N), but each house (or group of houses) will be supplied by a different phase, so that overall demand is spread more evenly across the three phases. The single wire on HV pylons is, I believe, only a lightning conductor. I believe there is no neutral on HV transmission, since all the current "returns" via earth. The neutral cable only originates from the local step down transformer. This is connected, generally, to an earth point at the transformer, along with the cable's armoured sheath, so that at the transformer both neutral and earth have the same (low)resistance. I do not believe there is any fundamental difference between the safety of electrical installations in Europe and UK. There may be laxity in practice in certain areas, but that does not mean that the design fundamentals are more, or less, dangerous than our own. Some European electrical engineers regard our reliance upon correct polarity as inherently more dangerous than their system. The problem for a UK installation which encounters reversed polarity, is that the unswitched and unfused neutral becomes the live feed. Correctly wired, the live site supply should enter via the RCD/isolator in a consumer unit, thence to circuit breakers and from these to individual appliances or socket outlets. All the "neutral" or return wires from appliances/sockets then connect to a single terminal strip inside the consumer unit that in turn connects to the RCD and then returns to the site supply pillar. If the RCD sees current in = current out, all is OK. If there is an imbalance, current is leaking, and the supply is cut. Now, when the live is reversed at the site pillar, the incoming live connects to what is designed to be your neutral terminal strip and thence to the appliances/sockets. It is only after it reaches the appliance or the socket that it encounters a switch, and only after that will it encounter a circuit breaker. The function of the circuit breaker is to protect the circuit wiring, not the user. If it has become the last item in the circuit because the polarity is reversed, the only bit of wiring it will protect is the very short length between the breaker and the RCD. Not much use. If the vibration of travel has caused wiring to loosen or chafe somewhere in your van, for example, and that has resulted in a live and a neutral coming into contact, current will flow unabated up your wires until they burn out, rather than the circuit breaker intervening to cut the circuit supply. You will note that in this case there is no earth fault, so the RCD won't trip. The exact location of the fault may not be found, perhaps because the wires are concealed, but heat from the burn out will remain and may be sufficient to cause insulation to soften, smoulder or burn, with further uncontrolled current flows, further overheating and eventually, actual fire. These are all risk scenarios: the actual risks are low but the possible consequences are serious if, for example, the faults developed while occupante were asleep. To me this is not the cotton wool wrapped world, it is just an easily avoided risk. To test for reversed polarity, and correct it when encountered, is no more nor less fuddy duddy than looking both ways before crossing the road. Of course, you can just walk across without looking and take the chance, but that does seem a bit like wanton recklessness. The thing about risks, surely, is to recognise them, and then act to minimise them. There is no great merit, in truth, in joining the Darwin Club! Regards Brian