Home user, very concerned over middle east wiring safety

[msdunkel]

Good day,

I recently moved to Abu Dhabi from the United States. Abu Dhabi has what I imagine to be a very bad copy of the British electrical system, my home has 240v 3 pronged outlets. I have a variety of electrical equipment; some can accept 110v-240v, some can only accept 110v - 120v.

I decided to try and make things a little easier by installing 2000w 240v to 110v transformers throughout the house but I'm having some trouble. The transformer has a typical US-style 3 prong plug. When I plug that into a 3 prong British style adapter the transformer runs fine; however, the instant I plug anything into the 110v transformer output (even something as benign as a simple surge suppressor) it takes the house's main electric panel offline -- not just the individual plug' circuit, but the circuit breaker for the entire floor.

I tried to use the European style 2-prong adapter instead of the 3-prong British adapter and I'm able to run pretty much anything off the transformer now. The down side to this is I'm pretty sure I've defeated the ground in the system since anything I plug in now delivers a mild tingling when metallic parts are touched. I can even daisy chain the tingle through speaker wire, HDMI, and all kinds of other cables I never thought carried much electricity .

This leads me to 3 questions:

1) Any idea why the 3 pronged Brit adapter causes the entire panel to shut down on me when a 2 prong European style works fine?

2) Working with the 2 prong European style adapter, am I in any real danger of electrocuting myself, or am I limited to these slightly painful electrical tinglings I've given myself over the past couple days?

3) Am I going to damage sensitive electronics (Denon receiver, Paradigm speakers, desktop computer, LCD TV, Blu-Ray DVD player) by having this rampant power running around?

I've been running my computers and monitors on this goofy setup for a couple weeks with no issues unless I inadvertently brush up against a metal part of the case. I only post now since I was very surprised to get a really strong tingle from simple speaker wire when the only connection those wires had to electricity was wall (power) -> transformer (power) -> power strip (power) -> blu-ray player (HDMI) -> amplifier (speaker cable) -> speaker. Items in parenthesis delineate the connection between components.

Thank you for your time.

 

[Golden_Boy]

Absolutly correct. Cheap autotransformers are no substitute for the real thing. Splash out on a few 1KVA Isolation transformers, jobs a good un.

 

[msdunkel]

One reason why you should have purchased ''double wound'' transformers instead of ''auto transformers''!! There is no direct connection between primary and secondary windings on the former, while there is on the latter... The GFI's would not then have seen a problem with the suppression MOVs on the leads or on the power conditioner.

The former would of also added a good deal of protection in eliminating noise on the line... while the auto transformer offers none...

1st, thanks to you and all the others who have replied. My brain hurts from following this thread but that's probably a good thing.

As to what I should've bought, perhaps... But I'm just a guy with some electronics he wants to protect not an electrician or engineer. How would I have known that these problems would ensue? I had these types of transformers when I lived in Germany and never had a problem (was it grounded there on the 2 prong European system?).

So based on this info, is there any relatively simple way to make my current transformer work, or do I have to purchase different ones?

 

[WDMDL]

If your surge protection strips are causing the GFI (RCD) to trip, there must still be a polarity issue which is resulting in there being more than 140V AC between hot and ground, or neutral and ground.

Remember what happened when you turned the plug the other way up with the non-grounded adaptor? the shock hazard was gone.
This is because the common connection of the transformer was then connected to neutral.

Well basically you need to create the same situation, BUT with the ground properly connected.

Think about it:
The autotransformer is a single winding of wire round an iron core.
Let's say for instance you have one turn for every volt.
we'll call the start "zero"
We put on 110 turns, make a connection out and then call that the 110 tapping.
We put on another 110 turns, make another connection out and then call that the 220 tapping.
We put on another 20 turns, that's the 240 tapping. 240 turns altogether.

Now if we put 240V between the zero and the 240 tapping, we will get 110V between the zero and 110 tapping, whichever way round the 240V went in.

BUT

The supply in your house is configured such that the neutral and ground are connected together at the transformer (Pole, substation, etc)
So, there is 240V between hot and neutral, and also hot and ground.
(You may measure a small voltage between neutral and ground, but can be ignored for this purpose)

Now, you connect your autotransformer.
Let's assume the connections within the transformer case, including the front panel outlets are the correct polarity.
If it is connected correctly, with the "zero" connected to the neutral, you will have 110V between hot and neutral, 110V between hot and ground and zero volts between neutral and ground. Surge protection MOVs are not conducting.

If there is incorrect input polarity, with the "zero" connected to hot / line, you will STILL have 110V between output hot and output neutral, BUT you will have 130V between output hot and ground, and 240V between output neutral and ground. Surge protection MOVs between neutral and ground will be conducting, and depending on exact type, the MOV between line and ground may start to conduct too.

If you've put the UK plug on and still got the same problem, cross the line (hot) and neutral in the plug and try again.

If this cures the problem, you need to have the polarity of your socket outlets checked. You can do this with one of those plug-in testers I mentioned, or if the apartment is rented, get the owners to sort it out.

Having one of those socket testers is a good idea, especially if you're likely to want to plug your transformers in anywhere else.

Simon.

 

[Engineer54]

msdunkel wrote....
''I had these types of transformers when I lived in Germany and never had a problem (was it grounded there on the 2 prong European system?).''

The DIN plugs you talk of here ''are'' grounded, the earth is via 2 scraping earth contacts either side of the plug.
These German outlets and plugs are however not polarised, you can insert into the wall outlet either way!!!

Were the transformers of the same make and model type?? The transformers you have just purchased are manufactured in China, using Japanese transformers. It would have been good to see a photo or two of the opened (lid off) transformer, so that we could see the connections and the components used in it's manufacture.

Simon has given you a few pointers here, and will be well worth investigating. But if you can take the lid off one of those transformers, it would give us a much better understanding of the unit and could probably lead to a conclusion for you.... So, any chance of posting a couple of snaps or so here, for us to look at ???

 

[msdunkel]

Going to bed now, but taking off the lid is no problem, just a few screws. I'll get after it tomorrow if I haven't solved my problem by then. thanks!

 

[msdunkel]

Ok, did a few more tests and I think I found the problem.

I tried checking continuity between the output hot and output neutral leads, and got continuity -- not a lot, but it's there. I've got to assume that when I plug in an appliance there is enough resistance in the appliance to keep the GFI from tripping but when I plug in a surge suppressor, there is pretty much no resistance.

Would you agree this is most likely the cause of my house GFI tripping every time I try to plug a power strip into my transformer?

 

[msdunkel]

I am composing an email to the manufacturer and wanted to make sure I had this one fact correct before I hit send.

With the transformer unplugged, and the on/off switch in either position I am getting continuity between neutral and hot. Can you please confirm that this is indeed a bad thing?