Electrical Appliance Wattage when on EHU?

Captain Caveman

Captain Caveman

Joined
Nov 5, 2023
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Location
Rural Cheshire
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99,706
MH
Adria Supersonic 890
Exp
Newbie
Hi guys, apologies in advance, this is probably a stupid question from a total newbie! :smiley:

Does anyone know how to work out the maximum possible appliance wattage that can be used (say, an air fryer) in the van whilst it is hooked up on EHU on a campsite?

Does the campsite specify the maximum ampage of their EHU supply, e.g. 6A, 10A or whatever - and in that case can you work it out from there?

Or is it vehicle-specific/governed by the ring main fuse size?

We have an Adria Supersonic, but it doesn't come with much of a user manual!
 
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My understanding is that Watts = Amps x Voltage. So if you have 6 Amps at 240 Volts, you cannot run any more than a 1.4 kW device.
 
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Many thanks Guigsy and Lizbiebrowne, that is a very useful rule of thumb. Amazing to get an answer literally in minutes! (y)

However, I'm assuming that there's a limit in terms of the van's electrics as well, so if you have a 10A fuse and a 13A supply, it's still going to be 2.4kW max regardless? That's Mrs C's hairdryer out lol.... I don't need one :ROFLMAO:
 
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Your MH electrics will have a small consumer unit. This will show the internal rating. The Campsite EHU will also have a maximum rating on the post so could be 6A could be 10A.

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I know little of electrics so the way I do it while on EHU is,
Anything above a1000watts, use with great care and don't use anything else electric at the same time.
Wattage is usually written on product.
Good Luck! 🙂
 
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Cheers again guys. Must be 10A because the Alde heating has both 6A and 10A options to run on electric.
 
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Sonic consumer unit is under the bench seat behind the drivers seat, on 15 amp we can run upto 3kw appliances without tripping the unit

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Meterd EHU on campsites is costed in KW/h. So add up all the watts (Most if not all will be stated on the applinace) calculate the amout of time in use and you can work out how much you need to pay.
 
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FrankNicklin said:
Your MH electrics will have a small consumer unit. This will show the internal rating. The Campsite EHU will also have a maximum rating on the post so could be 6A could be 10A.
Click to expand...
Or 16Amps also, as on most Caravan and Motorhome club sites.
Not sure, but think Camping and Caravan club sites are also 16 Amp, but some of the CL and CS sites to both clubs could be significantly less.
 
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Marie-Claire said:
Sonic consumer unit is under the bench seat behind the drivers seat, on 15 amp we can run upto 3kw appliances without tripping the unit
Click to expand...
Many thanks Marie-Claire , I imagine the Supersonic is the same as the Sonic here, I will check it out.

Whilst writing I do have a semi-related issue. Probably naivety on my part, but I always assumed that the Adria's Dometic fridge freezer would run off the leisure batteries (which are topped up by the solar panel on the roof), but it doesn't - unlike the (admittedly smaller) fridge freezer that was in my Grand California? I know it can run on gas as well, so going off grid away from EHU doesn't mean you have no fridge freezer (and the unit also runs when the engine is running, so stuff doesn't melt when you're on the road), but it just seems daft to me. Why bother with twin leisure batteries and solar when all you can run off them are the interior lights and USB? (I'm guessing an inverter could be the answer, but wouldn't want to connect this to the fitted fridge/gubbins)
 
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12V when the engine is running and on the road, Gas if not EHU and 230V when on EHU. Certainly the fridge should run off mains when connected and gas when not. There is no way solar would keep up with running a fridge freezer on 12V and it would not stay very cold. It acts like a cool box on 12V. In fact mine doesn't work on 12V unless the engine is running otherwise it will kill the battery.

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Cheers FrankNicklin , yeah it's a 3 way fridge and it does run fine when the van is on EHU, I was just (probably stupidly) expecting it to be okay off the batteries, at least for short periods. (To be fair, the little fridge freezer in my VeeDub could do this, but wasn't 3 way and was quite a bit smaller)

Lots to learn for me! :smiley:
 
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The fridge is most economical on gas when no ehu, we did 22 days in france through the heatwave in september, fridge and hot water for showers etc used £16 .
 
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Captain Caveman said:
Many thanks Marie-Claire , I imagine the Supersonic is the same as the Sonic here, I will check it out.

Whilst writing I do have a semi-related issue. Probably naivety on my part, but I always assumed that the Adria's Dometic fridge freezer would run off the leisure batteries (which are topped up by the solar panel on the roof), but it doesn't - unlike the (admittedly smaller) fridge freezer that was in my Grand California? I know it can run on gas as well, so going off grid away from EHU doesn't mean you have no fridge freezer (and the unit also runs when the engine is running, so stuff doesn't melt when you're on the road), but it just seems daft to me. Why bother with twin leisure batteries and solar when all you can run off them are the interior lights and USB? (I'm guessing an inverter could be the answer, but wouldn't want to connect this to the fitted fridge/gubbins)
Click to expand...
Hymer wire their vans so they can run from the leisure battery if required. If your Adria has a CBE distribution unit there is a link that can be removed to change the fridge to the leisure battery providing the vans wiring supports this. The fridge will run fine on 12v but it draws 15 amps and uses approx 4.2kw over 12 hours so you would need a big Lithium bank to run on 12v so not practical for more than the odd hour.
 
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With the effieiency on gas I would rather use the batteries to power a inverter when off grid and leave the fridge on its 3 way.

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For easy calculations

using the formula .. watts / volts = amps

UK , 1kw at 240v uses 4 amps
Europe, 1kw at 220v uses 4.5 amps

therefore on a

16A UK EHU you have 3.8kw
10A UK EHU you have 2.4kw
6A European 220 v EHU you have a mere 1.33kw to play with ..

you may be wondering why I use 240v instead of 230v for my UK calculation ?

In the UK, the declared voltage and tolerance for an electricity supply is 230 volts -6%, +10%. This gives an allowed voltage range of 216.2 volts to 253.0 volts.

This was to 'harmonise' with the European voltage of 220v
Nothing actually changed, in the UK the mains supply is still 240v.

So for calculations I use 240v

If interested
 
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Captain Caveman said:
Why bother with twin leisure batteries and solar when all you can run off them are the interior lights and USB? (I'm guessing an inverter could be the answer, but wouldn't want to connect this to the fitted fridge/gubbins)
Click to expand...
I agree. My previous motorhome had 2 TVs, satellite dish, Wi-Fi router, many lightbulbs (not all LED). Large inverter connected to power sockets. I could justify 360ah (lead acid).

Now a PVC. Wi-Fi router, LED lights. That’s sort of it. Dinky little water pump etc. Use my laptop to watch any TV, and can charge it from a modest 300w plug in inverter. 150ah lithium seems … almost over the top!
 
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PaulW2 said:
I agree. My previous motorhome had 2 TVs, satellite dish, Wi-Fi router, many lightbulbs (not all LED). Large inverter connected to power sockets. I could justify 360ah (lead acid).

Now a PVC. Wi-Fi router, LED lights. That’s sort of it. Dinky little water pump etc. Use my laptop to watch any TV, and can charge it from a modest 300w plug in inverter. 150ah lithium seems … almost over the top!
Click to expand...
I've come to a similar conclusion. I have a 6m coachbuild. No TV, hairdryer or Nespresso machine. The fridge, kettle and coffee pot are gas. Laptops, phones, tablets and even the vacuum can charge on USB C PD. So I don't even have an inverter. My lithium 280Ah battery keeps me going for more than a week even with no solar. It's total overkill.
 
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Captain Caveman said:
Many thanks Marie-Claire , Why bother with twin leisure batteries and solar when all you can run off them are the interior lights and USB? (I'm guessing an inverter could be the answer, but wouldn't want to connect this to the fitted fridge/gubbins)
Click to expand...
Your batteries also power the heating fan and the water pump, TV, controls for heating and fridge, maybe electric bed or extractor fan also run from your leisure batteries. A 3 way absorption fridge could run on leisure battery if you fool it into thinking your engine is running but as they can draw around 15 Amps on 12v your batteries wouldn't last long.
 
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I would still check the individual sockets for their limits. I've got several 240v sockets in the van, but they're labelled "max 4A".
You don't want to melt any wiring.
 
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Captain Caveman said:
However, I'm assuming that there's a limit in terms of the van's electrics as well, so if you have a 10A fuse and a 13A supply, it's still going to be 2.4kW max regardless? That's Mrs C's hairdryer out lol.... I don't need one :ROFLMAO:
Click to expand...
In your consumer unit there will be a switch that trips off if the amps is too high. it's called a Miniature Circuit breaker (MCB). The amps rating is written on it,with a B or C in front, eg C16, C10, C6, B16, B10, B6. So multiply the amps by the volts (230V usually) to get the maximum watts that switch will allow. There is also one in the hookup post that is often visible so you can see the amps limit yourself.
www.cef.co.uk

MC 16A Double Pole 6kA C Curve MCB

For use in the Cudis range of consumer units and enclosures, and for 3-phase installations
www.cef.co.uk
 
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Lizbiebrowne said:
My understanding is that Watts = Amps x Voltage. So if you have 6 Amps at 240 Volts, you cannot run any more than a 1.4 kW device.
Click to expand...
And that fórmula, P=IV, if you use, it shows why decent 12v hairdryers, kettles, etc aren't a thing.
For, say, a 1750w appliance ...
P=IV
P/V = I
1750/12 = 146 amps
 
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Marie-Claire said:
With the effieiency on gas I would rather use the batteries to power a inverter when off grid and leave the fridge on its 3 way.
Click to expand...
Yeah I totally get this Marie-Claire , as you say the fridge will eke out the gas at a very low flowrate, leaving the leisure batts/solar to do other things and not get drained. Plus, the reality is we will rarely if ever be anywhere truly off grid, we're bound to be on a site wherever we go. :)
 
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