Any electricians out there

[Nick]

Hi,

I am hoping someone may be able to help I recently imported into the UK a complete hydraulic car lift with UK power supply this came with a 3 pin unfused US plug..

I was advised by the company that supplied the lift that the wiring was as follows,

USA UK

Black Live
White Neutral
Green Earth

and that I would need to fuse it at 30 amps. I put some 30amp fuse wire in place of a fuse as our plugs go to 13 amp only and switched it on. It worked for a short time and then, once the smoke had cleared I discovered the main 30 amp fuse in the distribution box had blown and a section of wiring had burnt out.

I bought a USA adaptor plug and traced the wiring which seems to indicate that white is in fact the live, not black (can anyone confirm this). I rewired the plug, and the unit is working but blowing 13 amp fuses. I am reluctant to try fusing the plug at 30 amps again but don’t know any other way of getting it to work.

I was thinking of buying a small generator to power it but this would be a slightly expensive solution. I have tried finding out information from the supplier to see what current the unit may draw but have received no answer. Is it normal for USA plugs to be unfused and plugs able to cope with 30amps does anyone have any ideas on how to over come this problem?

Thanks

Nick

 

[David Sturch]

I'm not an electrician. But first off it sounds like it is single phase. (220V 60Hz) 5 hp motor with capacitive start.
1. you need 30 amp circuit.
2. the panel you are supplying it from how many amp (is it enough)
3. wire size get a code book size the wire to the curcuit No.10 ? armoured wire in liquide seal conduit with proper connectors with a disconnect or pony panel at or near the hoist.
4. If you are not sure have a local electrical inspector check it and get the code book for your area they will tell you what you need before you burn your house down.
Dave

 

[Dave Wood]

In the U.S. white is the neutral(common) and black is power( black=death, is a way to remember). Is it 110 or 220?? Do you use 50 or 60 cycle?? Could you be wiring a 220 up to a 110 service? That would explain the fuse blowing....if it was a 110, the common is connected to the same leg at the box in the U.S. with a grounding wire run to a rod in the earth. The 220 would have the other wire hooked to the other power leg..not to ground as it would be for a 110.
I think minimum main circuit here is 100 amps now, so your comment about a 30/35 main fuse raises questions about the ability of the service to supply the needed power.

 

[David Sturch]

They run 220 in the UK 50 or 60 Hzts I don't know. The motor drives an hydraulic pump or a reduction unit and should work over there. Sounds like he made up an extension cord and plugged it in to a wall socket. He needs a separate curcuit from the main panel if he has enough amps left over. The white and black are hot 110 on each.
Dave

 

[David Morton]

This may be of help>
Three-phase electric power - Wikipedia, the free encyclopedia
There is a colour code table which I tried to copy here
unsuccessfully.

 

[Frank Catt]

DAVE, YOU MAY HAVE JUST CONFUSED THINGS, seems he has US single phase wiring, probably 110 V , Frank

 

[Nick]

Hi,

Thanks for the replies, the power unit is 115/230v, but the white wire goes to the plug pin that would be the live pin on UK plugs. Guess it's time to call in an Electrician before I burn the house down.

Regards

Nick

 

[David Sturch]

Nick,
You should be able to run it. Just have the electrician do a box off your service for the single phase. I don't know if you are in a shop or residence. Just try to be safe. We do have 3 phase 220v coming into our houses in North America but it is split at the service panel bus.
Good Luck
Dave

 

[Andy Besic]

If the unit is 115v/230v and the plug has 2 blades parallel and in line, with a single round pin looking something like this; this is single phase in both cases.
o
l l
you have 2 options. One of the blades (slightly larger) will be your "hot" the other blade the common and the pin a ground. The ground is essentially the same as the common but is a safety measure. This is the 115v set-up. It must be wired into the motor correctly and will draw the maximum amperage (30amp) off of one leg of your 230v service.
By wiring the black to one side of the motor and the white to the other you will be able to run the motor off of a 230v system with each 115v leg carrying 1/2 the total load so 15amp each.

Look for a junction box on the lift that the cord terminates in. Open that up and you will likely find a schematic for how to wire for the 2 voltages. I would take the US cord and throw it in the garbage. Take a 230v standard cord that you have a recepticle for already in your garage and wire it according to the 230v schematic. You may still occasionally pop a fuse once the motor gets good and hot and resistance builds but you will likely find you can manage by monitoring how much and how often you load the motor in a short period of time.

 

[Ross Nicol]

Well I'm an electrician or at least was before getting into electronics.It sounds indeed like you have placed 230v across a motor wired for 115v.The voltage being double what it should be causes a destructive current to flow with the associated smoke and smell.This happens in Australia a lot when people import from America so I get to see a lot of things afterwards to repair.The motor sounds like it could be altered internally for 230v but the smoke you had does not sound good and you have probably lost the insulation in the motor windings.Your best bet is to get an electrician to check if you really can alter the motor for 230v use and then let him apply the power to see if it is ok.Be sure to cross your fingers.
Ross

 

[Nick]

Ross,

Sorry, I may have misled you with my explanation, and I think I jumped to the wrong conclusions.

On checking, the power unit is wired up for 240v, I believe the main 30 amp fuse in the consumer unit blew because the cable supplying the spur socket could not take the current and melted the resulting short blowing the fuse.

A separate new 30amp supply from the unit should solve this but still leaves me with the following problem.

In the USA the black wire is live and white neutral, to check I purchased an adaptor to convert the USA (two flat one round pin) plug, to a UK 3 flat pin plug. Buzzing this through, if I had used the adaptor plug, the black wire connects to the UK neutral pin, and the white to the live, which I still do not understand.

Regards

Nick

 

[Julian]

Perhaps this diagram will help explain; In the US 230V is phase to phase in the UK it is phase to Neutral.

 

[Doug Clark]

What did the plug that came with it look like?
If it looks like either of these then it was not meant to take 30A

These are 15A max in the USA.

As pointed out before 220V in the USA is achieved b going across 2 phases where as in the UK its a single phase.

A 30A plug in the US will look something like this...

In the UK obviously each appliance is fused to a max of 13A so if you want to run a 30A motor of it I'd be concerned that the wiring in the walls is up to the job or you might burn your house down.

 

[Ross Nicol]

Ok Nick I can resolve your worries about the black and white wire.I get a lot of American amps through my workshop and quite often I find the black and white wires are wired reverse in the plug.What I'm saying is it wouldn't stop the unit from working properly.Basically the motor has a field coil that the black and white wires attach to after going through a switch.On a single phase motor there is a start winding coil too which is switched out when the motor is up to speed.I believe you have a short circuit which blew the fuse so you need to check every connection.Hopefully the motor is ok.There is nothing that matches the smell of a burnt out motor so it's fairly easy to identify the worst case scenario.By the way I doubt the unit will draw 30A of current but may be protected by a 30A fuse.
Ross

 

[John Fitzpatrick]

Keep in mind that a device which is designed to draw 1 amp at 110 volts will draw 2 amps when connected to 220 volts. If you saw or smelled smoke, something was damaged, probably insulation, and possibly in more than one place. Please be safe and have a licensed electrician check things out thoroughly before you power back up.
I don't mean to sound patronizing, but my grandmother burned to death in her home one night five years ago in a fire started by a bad lamp cord.
John

 

[Duncan Potter]

Keep in mind that a device which is designed to draw 1 amp at 110 volts will draw 2 amps when connected to 220 volts.

Don't think thats true for induction motors. At least in three phase motors, a motor will pull about 1/2 the amps at 460 that it draws in 230. Believe this is true for single phase induction motors also.

Make sure your motor (and any other equipment on the lift) is wired for 220/240 volts. Don't assume the manufacturer did it for you or that they did it correctly. Open up the motor junction box. There should be a wiring diagram inside.

In the US, as others have stated, a three wire 220 v connection will have white to phase, black to phase, and green to ground. There is no neutral connection. A US 110V connection will have black to phase, white to neutral, and green to protective ground (earth).

US 110V wiring connects white to earth ground at the service entrance (Main fuse or breaker box) and nowhere else.

Nick, in your original post you said the US manufacturer said black was hot, white was neutral, and green was ground. If that's accurate, then he was describing 110V wiring. I would definitely check his motor connections!

 

[Nick]

Hi,

Advice has now changed to :-

Nick,
On this power unit since it is wired for 230 volt, both of the black and white wires are hot legs of 110 volt. there
is not a neutral wire. the green is still the ground. so you should be fine if you wire with a three prong plug. 2 hots and 1 grnd.

Not to sure what this means yet.

Thanks

nick

 

[Ross Nicol]

Nick
Ok I understand you have a single phase motor driving an hydraulic pump.
The supplier states it is wired for 230v and you have actually had it running but with what seems a high current.This probably rules out a short circuit.Now you must make sure the earth wire is connected to the motor case and whatever happens from there at least you are safe.the fact that the motor actually ran ok but blew a fuse after a time interval makes me think it has a heavy load,maybe a problem in the hydraulics.An electrician with a clip on ammeter will suss this out quickly.It sounds like the manufacturer sent it to you prewired for 230v and you are tied up in knots with wire colour code but your problem could lie in the hydraulics.Time to get an electrician for sure mate.I have a "Direct" brand hoist with a 3 phase motor 3HP motor/380volt/15Amp, so I assume your single phase motor to be 3HP/2.24kw and at 230V this equates to just under 10A. There will be a current draw on the motor and if the electricians ammeter reads no more than this you are on the right track.Amazing how the wire colour coding has turned up so much confusion, not unlike a rumour that develops wildly.

Ross

 

[John Fitzpatrick]

Keep in mind that a device which is designed to draw 1 amp at 110 volts will draw 2 amps when connected to 220 volts.

Don't think thats true for induction motors. At least in three phase motors, a motor will pull about 1/2 the amps at 460 that it draws in 230. Believe this is true for single phase induction motors also.

Yes, that was an oversimplification, but the point I was trying to make wasn't about reactive and resistive loads. Fuses and circuit breakers do not protect against localized, partial short circuits, the sort that occurs between two wires separated by damaged insulation. Enough current can flow to create a localized hot spot but remain below what's needed to trip the breaker. The same thing can happen when a wire is nicked or has been damaged by a transient high-current spike, and if the hot-spot is near something combustible, you may have a real problem.

Smoke and "a section of burned out wire" is evidence of a major over-current. Just because the motor still turns doesn't mean it or the house wiring is undamaged, and that isn't the sort of possibility you want to take lightly.

 

[Ross Nicol]

My thoughts were that the burnt wire was into the fuse that Nick uprated with larger fuse wire and the wire into the fuse was not terminated properly by the screw.Hence when the hoist dragged more current than this circuit has ever been subjected to before, the loose terminal got hot and burnt the wire. One trick I use a lot is to observe a blown fuse, especially the glass ones.Copper sprayed around inside the glass and very black indicates a short has occurred causing the fuse to blow but if you can see both ends of the wire with a blob on them and clear glass it's just an overload,replace the fuse and go.Equipment that I suspect to have a short I plug into my variable voltage unit called a Variac. I wind up the voltage while watching the power meter.If the meter starts ramping over at very low voltages I switch off and chase the short.Saves a lot of blown and wasted fuses.I've developed a lot of similar test jigs in my time but I am bored with it and now it's cars for me.
Ross