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12-03-2013, 05:21 AM
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#1
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1 Rivet Member
1971 27' Overlander
1963 16' Bambi
1959 30' Sovereign
Wadhurst
, East Sussex
Join Date: Nov 2013
Posts: 11
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How many watts needed for a 31ft Land Yacht
My 1973 31ft Land Yacht is now safely here in the UK and is in almost completely original condition thanks to its careful one owner. I am planning to use a step down transformer from 240v to 120v to run it of UK mains. It has an electric/gas fridge and air conditioning - does any one know how many watts it will draw with everything on? I will get a bespoke transformer made which is 3 times the maximum draw to avoid it tripping or overheating.
Many thanks
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12-03-2013, 05:29 AM
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#2
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Figment of My Imagination
2012 Interstate Coach
From All Over
, More Than Anywhere Else
Join Date: Dec 2011
Posts: 10,868
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Quote:
Originally Posted by bobbett750
My 1973 31ft Land Yacht is now safely here in the UK and is in almost completely original condition thanks to its careful one owner. I am planning to use a step down transformer from 240v to 120v to run it of UK mains. It has an electric/gas fridge and air conditioning - does any one know how many watts it will draw with everything on? I will get a bespoke transformer made which is 3 times the maximum draw to avoid it tripping or overheating.
Many thanks
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You can tell by looking at the shore power cable. Three-prong is 30 amps single-phase 120vAC. Four-prong is 50 amps three-phase 120vAC. That gives you a target value to aim for.
It may not be quite that simple, though. How many cycles does the UK power grid provide? My memory wants to say 50 Hertz, but my memory lies to me incessantly. US appliances are designed for 60 Hertz.
__________________
I thought getting old would take longer!
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12-03-2013, 05:38 AM
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#3
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Rivet Monster
1975 31' Sovereign
1980 31' Excella II
Sprung Leak
, North Carolina
Join Date: Jun 2003
Posts: 7,172
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In the US you would need around 5,000 watts at 120 volts AC to power everything effectively. Protagonist is correct about the cycles too, in the US it is 60 cycles. From my dim memory I believe that motors and compressors are the most likely to be affected by the difference in cycles, some will work on different cycles others won't. Need to talk to a good electrician and check out ALL of the data plates. I am sure someone over the pond there has figured it all out before, there are quite a few Airstreams over there now.
Aaron
__________________
....so many Airstreams....so little time...
WBCCI #XXXX AIR #2495
Why are we in this basket...and where are we going
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12-03-2013, 05:55 AM
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#4
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Figment of My Imagination
2012 Interstate Coach
From All Over
, More Than Anywhere Else
Join Date: Dec 2011
Posts: 10,868
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Quote:
Originally Posted by wahoonc
In the US you would need around 5,000 watts at 120 volts AC to power everything effectively.
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Thanks. I put everything in my response BUT the watts, which is what the OP specifically asked for. Good thing you were more paying more attention than I was…
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I thought getting old would take longer!
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12-03-2013, 06:30 AM
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#5
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Rivet Master
2005 39' Land Yacht 390 XL 396
Common Sense
, Texas
Join Date: Sep 2007
Posts: 5,319
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Quote:
Originally Posted by Protagonist
You can tell by looking at the shore power cable. Three-prong is 30 amps single-phase 120vAC. Four-prong is 50 amps three-phase 120vAC. That gives you a target value to aim for.
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Actually, this has been discussed before almost to extreme, but RV's in the US with a four-prong plug are 50 amps 240 VAC split phase, not three-phase.
__________________
Regards,
Steve
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12-03-2013, 06:34 AM
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#6
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Figment of My Imagination
2012 Interstate Coach
From All Over
, More Than Anywhere Else
Join Date: Dec 2011
Posts: 10,868
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Quote:
Originally Posted by SteveH
Actually, this has been discussed before almost to extreme, but RV's in the US with a four-prong plug are 50 amps 240 VAC split phase, not three-phase.
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Thank you. Senioritis strikes AGAIN! Darn it!
__________________
I thought getting old would take longer!
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12-03-2013, 07:38 AM
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#7
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Rivet Master
1974 Argosy 20
2014 20' Flying Cloud
Kooskia
, Idaho
Join Date: Jul 2009
Posts: 4,591
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All '73 Airstreams came with 30 amp, 120 volt service. Watts = volts x amps. So 120 x 30 = 3600 watts.
The refrigerator will take about 300 watts, but does not have a motor in it, so it does not care about frequency, which in the UK is 50 vs. US 60. The Air Conditioner motors were designed for 60 hz and so may not run well or at all, but they are the largest load. The original Univolt converter/charger (which everyone will recommend be replaced anyway) has a large special transformer in it, which may or may not work on 50 hz.
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12-03-2013, 08:46 AM
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#8
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1 Rivet Member
1971 27' Overlander
1963 16' Bambi
1959 30' Sovereign
Wadhurst
, East Sussex
Join Date: Nov 2013
Posts: 11
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Thanks for the help, I have temporarily set it up with a 110v transformer to see what works. The battery charger makes a constant hum which may improve when 120v is put in or it may be because it is 50hz in the UK and not 60. The fridge and AC are not working which they did when in the US but I think 110v is too low for them?
Many people over here swap to 240v but I want to keep it as it was built with all the original appliances.
I should probably call an electrician!!
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12-03-2013, 09:08 AM
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#9
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Rivet Master
1977 Argosy 24
Currently Looking...
Milltown
, Wisconsin
Join Date: Mar 2006
Posts: 1,087
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The fridge has a heating element in it, I don't think 50 vs 60 cycles will matter with that. 110 volt should be fine with the fridge also, unless it has been replaced with a new one with a control board. Then all bets are off using 50 cycle power instead of 60 cycle power.
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12-03-2013, 09:20 AM
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#10
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Rivet Master
1974 Argosy 20
2014 20' Flying Cloud
Kooskia
, Idaho
Join Date: Jul 2009
Posts: 4,591
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The control boards us 12 volt DC to operate, so there should be no problems with a newer refrigerator.
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