Rv 110v/20v tranformer question

Jackomet

Jackomet

Joined
Nov 10, 2008
Posts
342
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78
Location
Forest Row, East Sussex, UK
Funster No
4,895
MH
5th Wheel
Exp
10
Hi, (re-posted on here as maybe not seen on 5er board)
Anybody have a mains wiring diagram for . I'm trying to eliminate/circumvent the 110v/240v transformer on my KountryLite 5th wheel. I've emailed Calder in the past, Eurocruiser (new dealers) and Allen Campers, the manufacturer in the USA. so far zip.
The reason is that the tranny sucks amps just charging a toothbrush and electric is getting expensive, can live without the A/C and microwave in the winter here.
I've tried 240v into the CU via disconnecting its 240v input to the CU via the tranny, but the output appears to go back into the tranny and therefore it may need to be in circuit. Switch/relay? Because although there is 240v output from the CU, nothing at sockets. Trouble is, without taking out the electric fire and some panels out, access is only by a 20cm x 20cm cable entry locker and difficult to see what's what.
I'm in Spain at the moment and don't fancy ripping bits out just yet.
JK
(BTW I am/was a qualified Electrician)
 
The transformer can't suck amps, it will loose a few of percent due to efficeny loss in the windings but will be negligable and doubt if you would notice it.
 
Lenny HB said:
The transformer can't suck amps, it will loose a few of percent due to efficeny loss in the windings but will be negligable and doubt if you would notice it.
Click to expand...

Sorry that's wrong, it will draw current even if nothing is connected to the output. Mine draws about 5amps at 12v if I power it from my inverter. I have separate mcbs for the 240 and 120v, so it's just a matter of turning the 120 mcb off for me.
 
olley said:
Sorry that's wrong, it will draw current even if nothing is connected to the output. Mine draws about 5amps at 12v if I power it from my inverter. I have separate mcbs for the 240 and 120v, so it's just a matter of turning the 120 mcb off for me.
Click to expand...
That's 5a from the battery though.
At 230v it's only drawing 250ma

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5amps at 12v is 60watts papa, 60x24 1440watts, so over a unit of lecky a day, add that up over a month and that's a bottle or two of wine.:D
 
olley said:
5amps at 12v is 60watts papa, 60x24 1440watts, so over a unit of lecky a day, add that up over a month and that's a bottle or two of wine.:D
Click to expand...
But you're taking it from your battery Ian, not the mains.
You said
Mine draws about 5amps at 12v if I power it from my inverter.
Click to expand...

If you were drawing from the mains you wouldn't need your inverter and would draw 250milliamps.
 
As John & I said it will draw naff all from the mains. You are getting mains & 12v confused.
 
Guys 60 watts is 60 watts, voltage is irrelevant. Watts is voltage X amps.
 
Fight, fight, fight. :rofl::rofl::rofl:

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olley said:
Guys 60 watts is 60 watts, voltage is irrelevant. Watts is voltage X amps.
Click to expand...
Watts are a constant... Amps are variable with voltage.
The higher the volts the lower the amps

Watts ÷ volts = amps

60watts ÷ 12v = 5amps
60watts ÷ 230v = 0.26amps

OR

If volts x amps = watts

12v x 5a = 60watts
230v x.0.26a = 60watts

230v x 5a = 1150watts
 
Last edited:
A transformer will be about 98% efficient, losses are elsewhere, inverter? They eat power.
 
In my RV The power (240) comes in and then goes to ATS and then on to RCD and splits to feed step down Transformer and that then goes to OE CU for all 110v The other split feeds all 240V . The trans also feeds oe charger unit . So if I switch off trans then all the 110v inc charger is dead. HTSH
 
Can you clarify what the problem is? Is the 5er a straight American import that is expecting 120V AC, or has it already been fully/partly converted using a transformer? Is the problem that some appliances are expecting 120V AC but some are 240V AC?

I'm sure a simple solution is possible. A 3 kilowatt 110/240V transformer of the type used on building sites is easily available and costs less than £100.

As has been said already, transformers a generally extremely efficient, I would expect 99% efficiency. A possible problem is the inverter might be 'modified sine wave' rather than 'pure sine wave', which will induce losses in even the most efficient transformer.
 
tacr2man said:
In my RV The power (240) comes in and then goes to ATS and then on to RCD and splits to feed step down Transformer and that then goes to OE CU for all 110v The other split feeds all 240V . The trans also feeds oe charger unit . So if I switch off trans then all the 110v inc charger is dead. HTSH
Click to expand...
As it should be.
Turning off the tranny you removed ALL 110v mains power...

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Dont transformers get quoted as the input voltage then the output voltage?
 
autorouter said:
A 3 kilowatt 110/240V transformer of the type used on building sites is easily available and costs less than £100.
Click to expand...
They aren't rated for constant use. They are rated something like 2 hours on 1 hour off for heavy duty cycle.
Even on a building site they don't usually get that kind of constant use other than for low current lighting.
Have you felt how hot they get after an 8 or 10 hour day on a building site.
I wouldn't have one in an enclosed locker.
 
pappajohn said:
They aren't rated for constant use.
Click to expand...
Correct. It's 3 kilowatts intermittent, 1660 watts continuous.

That's probably OK for a motorhome, for running battery charger etc. Any electric heating would be better powered from the 240 volt circuits. But that's why I asked for more details.
 
OK,
Watts are watts, whether you get them via your batteries or mains, voltage and amps are irrelevant, they just add up to watts. So that power has to be replaced and that costs money.
My set up is that the unit was built to expect 110v input to drive everything, A/C, battery charger, microwave etc. inc. ring main. A 110v/240v has been installed which provides a 240v ring main and the extant 110v still drives the appliances.
Now I've been on sites that monitor your usage, well most of them do nowadays, and my unit doing nothing, probably trickle charge on the batteries uses over 1Kw a day, so if the batteries are optimal and charged, say 13v, if you chuck in 0.5 amp for charging, that's over 3amps (40 watts) that's doing SFA. On some Spanish sites, that I'm on most of the year, that adds up to over £120 for nada.
Now the transformer does get warm, so it's doing something but not very inefficiently.
So I now have three Cee17 sockets, the first two for 240v mains input, one, as supplied as above, second, provides 240v mains to a 13amp extension cord skillfully fitted to provide a couple of 240 v sockets for PC, phone chargers, etc., Third connected to small inverter and along with a 120 w solar panel again supplies the extension for 240v.
Obviously the first one is the only one that allows me to use A/C, F/F on mains (never, it's always on gas), 2 bar "glow" fire and microwave, all of which I can do without most of the time.
So back and re-read my original question please.
JK

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So, have I got this right? The 230V pitch hookup connects first to a big transformer that drops 230V mains to 110V. Everything then runs off this.

To get 240V there is another transformer that boosts the 110V back up to 240V, with two blue circular CEE17 sockets. One of these sockets supplies a circuit with some domestic sockets (UK or Spanish type?), the other supplies a 13amp extension.

Also you have a small inverter that outputs 240V to another CEE17 socket, which you can plug the 13amp extension into, when not on hookup.

If I've got it right so far, here's a suggestion.

Is there any room in the CU for an extra MCB? you could run a separate cable direct from the mains inlet to the new MCB, then wire the MCB output an extra CEE17 socket or two near the existing two. Either that or disconnect the existing two from the transformer and wire them direct to the extra MCB.

You could then disconnect the 110V-to-240V transformer, to avoid wasting power.
 
Been a while since I had an RV. ..

Jackomet said:
my unit doing nothing, probably trickle charge on the batteries uses over 1Kw a day, so if the batteries are optimal and charged, say 13v, if you chuck in 0.5 amp for charging, that's over 3amps (40 watts) that's doing SFA.
Click to expand...

Furnace control panel
Fridge control panel
(or are they 12v)
Microwave (standby)
all sucking watts even if they aren't running.
 
Both above are correct.
No room for extra MCB but it would be trivial to replace the CU with a larger one, it's in a wardrobe and easily accessible.
Problem is that the output from the CU goes back into the transformer box (which may hold more that one tranny?), can't see where it connects to from there, but obviously generates the 240v ring main, but to get to that I would need to remove the tranny box, remove the fire, remove panels, and may have a pretty big job on, so that's why I would like a wiring diagram before I started all that, on a plot, on a campsite in Roquetas. Oh and a wife that would not understand when she could use anything electrical for days, and you know these things always go completely to plan (yeah right!), and how I'm enjoying myself doing it.
Some how I'm getting the feeling I'm not going to get a wiring diagram. So I think I'll stick with my regime of switching the sockets to suit my environment, hardly ever need 110v, and then it'll only cost a few quid, (I'm a northerner and don't like losing money, no matter the amount) but I will solve this bugger whenever I get the rig back to the UK.
Thanks for the comments.
JK
 
Is the CU input/output 240V or 110V? I'd be tempted to add a small garage-type CU wired straight back to the mains inlet, bypassing the transformers. you can wire it to a couple of sockets, either CEE17 type or domestic type.

If you choose Spanish type sockets because you can't buy UK sockets where you are, they are German type 'schuko' sockets. They are reversible, in that they do not have a well-defined order for live and neutral. When you buy the MCB, make sure you get a double-pole MCB. They are rare in the UK but standard for schuko sockets. Double pole MCBs are easy to find in most big DIY stores (Leroy Merlin etc). Look for 'bricolage'. Also try a 'ferreteria' which is a small Spanish hardware shop.
 
Thank you but Nope,
The CU input is 240v coming out of the transformer box and for some reason the output goes back into it (single 6mm wire).
All the ring main wiring is in the transformer box, so I would have to do all the things I don't want to do here, to get to it, to do what you suggest. If I had a wiring diagram BEFORE I started I may have a go now, otherwise I will wait.
I've been in Spain, on and off, for 10 years or so, carried out a lot of fairly substantial jobs, new kitchen floor, cooker and F/F overhauls etc., I think I might even have accounts with the firms you mentioned ;). SWMBO likes clothes shops, I wander all day round Bricomat and Leroy Merlin.
JK

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