Electrical problem, help please!

[Martyn_374555462]

Howdy!

To cut a long story shot, my caravan was dry, but previous owners had fitted a sink and water pump, however they never connected the pump up properly.

I'm now looking to sort that out. I have bought a mains transformer, but that soon burnt out after a minute or so. So common sense tells me to get a more powerful transformer. However, I cant seem to find any!

Always seem to stumble across 12v 300mA (which all means nothing to me anyway...). Which is the size that soon burnt out.

So basically, anyone know what size transformed I should be looking for, and where I can get one?

(I apologise if this is an idiotic question, but I am new to caravanning, and I dont know a single thing about electrics...)

Cheers!

Martyn

 

[TonyH1]

Hi Martyn,

Sorry to say this but if you haven't a clue about electrics, it's probably best to get some one else to either do it or show you how to.

Most modern caravans have a 12v system already installed but would also have a water pump so I'm guessing yours isn't too modern. You need a leisure battery and ideally, if your going to use your caravan for more than week-ends, some means of charging it. That could be with a mains unit or solar panel etc.

 

[antrimboy]

Not sure why you are using a transformer. Do you have a 12 volt battery fitted? If so, you should be using that to power your pump, and make sure you have a fuse fitted to the red supply wire.

 

[Philspadders]

some pc psu's have 12v 5amp outputs. Check your local PC second hand shop.

 

[Philspadders]

oh, sorry, there are never any stupid questions... if you dont know something ask... its the way we learn.

 

[Martyn_374555462]

My van is permanently sited at a holiday park in Skegness. I dont have a battery (at least I dont think I have), its hooked up permanently via the electricity cable.

Please dont all run away and ignore me now, my caravan is Hobby, but I am not a traveller, I'm a holidayer

I figured it would be easier to wire it to a mains transformer hand just plug it in, as appose to the mains of the actual van.

It is a 12v pump but unfortunetly I dont know how many watt's it is.

 

[Martyn_374555462]

Basically, does anywhere know where you can get mains transformers from? I have only found a few shops and they all the same one, which is the same power as the one I burnt out.

 

[SBS]

Martyn

Your 300mA PSU is for powering phones, toy cars etc and is providing 0.3 amps. Most caravan chargers/power supply units are 8 to 20 amps - that's why it's burning out. If you do not want to fit a battery, you need a PSU capable of handling all the 12v appliances you wan to use. A 10w light will use about .85 amps.

Talk to Gary at Arc Systems, he has some Amporer ones, which are good value.

Mike

 

[Martyn_374555462]

I only want to run one appliance off of it, the water pump. Would a 550mA transfomer be enough? Or do you need to know how many watts the pump is?

 

[JamesH]

Make a note of all the details on the pump manufacturers rating plate then go into the link below to find a local transformer manufacturer and ask them for their recommended rating. It may be a good idea to have your transformer supplied in a steel case with cable entry/exit holes in it, also ask for a terminal block connecter.

http://www.thephonebook.bt.com/publisha.content/en/index.publisha

 

[TonyH1]

Hi Martyn,

It would be good to know either the wattage or perhaps the pump make & Model.

I think you can dismiss a 550mA supply, your probably going to need upwards of 3.5amps.

 

[antrimboy]

Here's an example for you;(Copy & Paste);

http://www.leisureshopdirect.com/caravan/water/product_28090/Whale_Pump_Premium_submersible_-_12v_-_GP1352.aspx?aff=122
This one draws off just under 3 amps.

 

[Martyn_374555462]

I dont have any box or instructions with the pump...

I think some people have got a bit confused, I just need a mains (plug) transformer. Everything else is fine with the van, I just want to plug the pump in.

Surely its easier doing it that way?

(Thank you all so much for your help, it is very much appreiciated!)

 

[Martyn_374555462]

Sorry Tony (and Phil) didn't realied you had posted a message.

Can you get a mains plug transformer with a 3.5amp supply?

 

[Martyn_374555462]

Another question (so sorry to keep going on)

Can it be wired to the main transformer of the caravan itslef? I presume that would be powerful enough to run it.

 

[ProfJohnL]

Hello Martyn,

I will give you the benefit of the doubt about what you purchased. You describe it as a "transformer", but I suspect you actually purchased a DC (direct current) "power supply". A transformer only produces AC (alternating Current) not DC. It's a common mistake mainly because the DC power supply usually contains a transformer but also essential other components needed to convert the AC to DC, and to smooth and regulate the output voltage.

One problem is that the device you purchased was rated at 12Volts at 300milliAmps. Simple mathematics tells me that the power supply can only provide 4watts of power (Watts = Volts x Amps).

Whilst I don't know exactly which model of water pump you have, but most submersible pumps need at least 60Watts to start them turning. I should explain that electric motors use more power to get them turning, but once they are spinning the power they use reduces in the case of a pump it will still be about 20 to 30W. Lights will use 12 to 20W depending on the type of light so you can begin to see that that your little power supply was just not man enough for the job. You need a better plan.

Usually a caravan will be fitted with a 12V battery. This acts as reservoir for the 12V electrical needs of the caravan. Charge the battery and it will run the pump and lights until the battery is discharged. Caravans need a special type of battery called a leisure battery. They look similar to a car battery but they are built differently to cope with the demands of a caravan. If you were to use a car battery, its life will quickly diminish and it will not accept a full charge. So go for a Leisure battery. They are usually available in two sizes 85Ah and 110Ah. Go for the biggest you can fit in the special battery box of your caravan.

These days, most caravan sites are available with a Mains supply (230Volts Alternating Current AC) for the caravan. So most modern caravans have a special power supply unit (PSU), This will run on the mains and convert it to 12V DC, suitable for running a limited number of items and keeping the battery charged up.

It should not come as much of a surprise but the PSU's are available in different capacities. A small caravan with just a pump and few lights will only need about a 12V at 5A PSU. If you have other 12V equipment, you may need a more powerful PSU to keep the battery topped up.

I have given you just a taste of what's involved. There are regulations that apply to the electrical wiring in caravans. Proper safety techniques must be employed. Don't be fooled by 12V systems. They need to be treated with just as much care as mains wiring. Whilst the risk of electric shock may not be there, the power (current) available in a battery system is enough to cause any short circuits or poor connections to heat up and cause a fire.

In short; If you do not have the complete relevant knowledge and experience of wiring in caravans, it should be left to a professional.

 

[Damian]

Hello Martyn,

As a Hobby owner also I know th eproblems you face.

However, none of the plug in transformers will be of any use in a Hobby.

Also, because of the way they are wired, the mains comes in and then apart from th e230v sockets and any 230v lights, it goes into a 12v transformer to feed all the 12v items, including the pump.

When you say the previous owner has fitted a pump, what kind of pump? is it a drop in or is it a floor mounted one?

In either case there will be 2 wires to it,12v positive and negative.

The negative gose straight back to the 12v transformer and the positive goes from the transformer to each tap and then th epump, so you are only ever completing the positive part of the circuit to make the pump work.

If you do not know anything about electrics I stongly suggest getting an engineer who does, as if you make a mistake with Hobby electrics it wil cost you over

 

[ProfJohnL]

Hello Martyn,

As a Hobby owner also I know th eproblems you face.

However, none of the plug in transformers will be of any use in a Hobby.

Also, because of the way they are wired, the mains comes in and then apart from th e230v sockets and any 230v lights, it goes into a 12v transformer to feed all the 12v items, including the pump.

When you say the previous owner has fitted a pump, what kind of pump? is it a drop in or is it a floor mounted one?

In either case there will be 2 wires to it,12v positive and negative.

The negative gose straight back to the 12v transformer and the positive goes from the transformer to each tap and then th epump, so you are only ever completing the positive part of the circuit to make the pump work.

If you do not know anything about electrics I stongly suggest getting an engineer who does, as if you make a mistake with Hobby electrics it wil cost you over

 

[Martyn_374555462]

Lol, I'll read your post (John) in a sec, it may take a while

But Damian, its a drop in pump. It has one wire which goes from the pump to the wall switch that was fitted, and then one wire from that, that apparently used to be wired up to a mains transformer, hence why I'm searching the planet for another one.

I did actually call an 'expert' to my van at the weekend, but he pretty much said he wasn't going to do anything with it because its German and has a German output (even though its a UK special, UK spec...)

So basically the so called expert was useless, so I'm doing something about it myself.

 

[Damian]

Thank you John for your input.

Martyn, the wire should have been wired into the AC-DC Converter (I say AC-DC Converter as this is what Hobby refer to it as) which should be located near the mains inlet, usually in the wardrobe and has blade fuses in the front panel.

Although your Hobby may be termed a UK spec, that does not mean it is anything to do with being built differently and wired differently, it is purely a level of finish and equipment.

Please do not think it means it wired any differently to all the production vans, it is not

 

[Martyn_374555462]

Lol, all these bloody letters and what not is starting to confuse me! I thought the little plug adaptors/transformers were AC/DC converters, purely because they have 'AC/DC' on them!

But I guess you're on about the main converter for the caravan. There is a few big 'blocks' of stuff in the wardrobe, so I can make sense of what you're saying.

Would it be ok to wire it to that (not me, a professional), as in would it have enough power? Is there a way I can find that out?

And again, I'll take your word for it about the wiring of the van, after all you're the expert. I only said that in the tone I did because of the 'expert' that came to my van, he was in shock when he saw a 'British' plug socket, saying that the previous owners must have fitted them as its a German van, and should have European sockets...!

So should I completely rule out getting a 3.5amp adaptor/transformer plug?

 

[Damian]

Martyn, it is a nightmare lol.

However, it depends how the previous owner fitted the taps and whether he fitted microswitched taps or not.

If he fitted microswitch taps the cable from the pump needs to have the negative wire taken to a suitable 12v return, or direct to the negative in the 12vAC/DC Converter. The positive wire comes from the converter and runs through each tap(where it is switched)to the pump.

If on the other hand he has fitted a pressure switch, then the negative still runs the same way, but the positive needs to be run from the converter through the pressure switch to the pump.

With what you have described, it may be he has simply wired it so that when he operates the switch on the wall the pump runs and is controlled entirely from that switch.

The UK style sockets are Berker sockets and are a direct repalcement for the 2 pin Euro sockets.

Make sure your electrician taps into the right box, as one is the AC/DC converter , and wil hav emore than enough power for the pump, but one of the "boxes" supplies 12AC for some of the lighting, and the pump simply will not run on that.

 

[Martyn_374555462]

**"With what you have described, it may be he has simply wired it so that when he operates the switch on the wall the pump runs and is controlled entirely from that switch"**

Yes that is what has been fitted. I've found some adaptors that are strong enough, so I'm going to give that a go first, as its currently the better value option.

What is you opinion on these:

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=260572160767&ssPageName=STRK:MEWAX:IT
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=310204934234&ssPageName=STRK:MEWAX:IT
Would this one be ok, as its just an AC adaptor?:

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=190382685602&ssPageName=STRK:MEWAX:IT
(As appose to everything else being AC/DC/. Unless they have just not bother putting the DC in the title?

 

[Damian]

Martyn. I can understand what you are trying to do, but I cannot comment on the items you have found.

Personally I would not risk them and would get the pum sorted out properly

 

[Martyn_374555462]

Why? Whats the problem with them? I am going to Maplin on Thursday to see if I can get on from there?