Difference between US 230VAC and UK 240VAC? 6

[theboosh]

Hello, thanks to all who have answered previous posts, I appreciate it!

We are looking at buying machinery rated at 230VAC in the US and 240VAC in the UK, what is the difference (apart from the obvious one!) between the systems? How similar is the actual power available from each, as the machinery used does take a bit of power to heat up. Are both interchangable, ie. could be used in each others countries? Also, what is the impact of choosing 230VAC in the US? How available or widely used are outlets for this kind of voltage?

 

[waross]

What type of equipment are you buying? Heating equipment is often usable on either system. Motor ratings must be adjusted.
Note; In the US the system voltages are multiples of 120 volts at the transformer (120V, 240V, 480V), Motor voltages are multiples of 115 volts to ensure full voltage at the motor after line losses.
The big issue is frequency. 60Hz. in the US and 50Hz. in Europe. the frequency is 50Hz.
Please search this site for more information regarding the rerating of equipment from 50Hz. to 60Hz. and vice versa.
itsmoked has written an excellent FAQ on the subject.
respectfully

 

[itsmoked]

faq237-1224 (thanks waross)

In heating, a little voltage change can make a pretty big difference.

A single phase example:

V[sup]2[/sup]/ R = Power

So given 1 ohm heaters (for example)..

230[sup]2[/sup]/ 1 = 52.9kW

while

240[sup]2[/sup]/ 1 = 57.6kW

an 8.2% difference for a 10V difference.

This probably will make little difference, but the lower voltage might actually result in a slower process or lower throughput and should at least be considered.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[waross]

Agreed itsmoked;
As I write this, I am waiting for a pot of water to boil. The stove is rated for 240 volts and this appartment building has 120/208 V nominal, 123/214 V actual. That is a little more than 20% down and the extra time is noticable. I have often found that heaters used on lower than rated voltage are able to keep the heat up with no problem, once the desired temperature has been reached. Getting up to temperature does take longer and is an issue with some processes. (Been there also as I am sure you have.)
I'm hoping that the OP will post some more information. We have gone about as far as we can without more information.
Respectfully

 

[theboosh]

Thanks Waross and Itsmoked! The machinery used is an industrial glue/ adhesive malt tank. The problem is that the machine tends to go from the UK - US and vice versa. Ideally we'd like to go with the US spec machine, but we want it to work in both countries, without much 'tinkering'/ generator hire (if any) and just wondered what the effect on heat up times and stability of the tank in both countries or if they were compatible. Also, the availability of 240VAC one phase in the US, is it generally available?

We don't mind that the US version of the machine is a little slower to heat up in Europe but we wouldn't want it the other way round, it sees more use the the US so that's priority!
I really appreciate your posts!

 

[waross]

In the US, 240 volts (as 120/240V), single phase is the standard residential voltage for individual homes. You may have some issues at commercial or industrial sites. A very common three phase voltage is 120/208 volts. In some areas three phase is supplied as 120/240 volt center tapped delta.
You may add extra heaters to compensate for slower heating at 208 volts.
You may add an auto transformer to be used on 208 volt systems to boost the heater voltage up to 240 volts.
You may decide to live with slower heating when on 208 volts.
The most user transparent solution may be to add heaters or size the heaters for 208 volts.
Do you have any other suggestions, Keith?
Respectfully

 

[JBD]

Also when using the machine in the US remeber that the voltage to earth will be 120V not 230/240V like in the UK. So make sure that there are no internal control ciruits that reference earth unless they are isolated by a transformer

 

[itsmoked]

Yeah, figure out your required heat up spec time. Then size the heaters for Europe 230V and let your controller handle the higher voltage in the USA by limiting the average power to the same value.

I've designed about five hot melt glue controllers and this was a typical solution.

"Blue skying" this, you can monitor the voltage the unit is plugged into. Size/speed for 208V. Then power limit for 230V and 240V. Your customers would love you and you'd avoid things like "gee on 240 we get more charring of the melt on the tanks sides".

Of course the same thing works for the hoses and heads too.

The PIDs then keep things on target at any voltage.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[theboosh]

Hmmm...thanks itsmoked, that's a good point about the charring and the like. I'm still slightly confused about the actual wiring involved in the machinery, in the UK we have the hot/ live carrying the whole 240V, with neutral and earth/ gnd. Doesn't the voltage get split in the US between the Live/ hot and the Neutral? Or does this even matter? (Or am I thinking of something else!)
Basically, apart from the power difference issues, would we be free to plug the machine in, in each country?

I appreciate the posts though, I can definitely live with a 10/20% slower/ throughput gap, it's the $$$$$ cost of shipping a mchine somewhere else and it doesn't work that would give me a headache!

 

[waross]

Typical single phase distribution transformers in the US and Canada have two x 120 volt windings. The windings are typically connected in series for 120/240 volts and the center point is the neutral. The neutral is grounded.
When the transformers are to be used for three phase wye or star they are opened up and the 120 volt windings are reconnected in parallel, for just 120 volts. Three such transformers are connected in star for 120/208 volts. The center point is the neutral and is grounded.
The receptacle for an electric range in Canada (and I believe for newer installations in the US) has a ground connection, a neutral connection and two hot connections.
These receptacles always deliver 120 volts but deliver 208 volts on a star connected system, and 240 volts on a single phase system or a 4-wire delta system.
respectfully

 

[SierraJ]

One small detail to consider... From a safety (or code) point of view it will probably be better to buy the equipment as per US standards. Since the US 240VAC system has two(2) 120VAC 'live' wires, the main switch or contator for the equipment must be a 2 pole swith in order to disconnect both 'live' wires when turning the machine 'off'.

If done the other way (like I have seen with many imported residential HVAC equipments), the UK equipment will most probably have a 1 pole switch or contactor to switch only the 240VAC 'live' conductor. When using the equipment in the US this type of connection, in addition of not being code compliant, will be very dangerous since when the machine is 'off' only one of the 120VAC conductors will be disconnected and there will be 120VAC present within the machine enclosure.

As mentioned before, I have seen this many times with 230VAC imported air conditioning units.

 

[Rodmcm]

I cannot agree with SierraJ on this. In the UK and IEC it is illegal to switch the neutral so the 2 pole switch idea is not a good idea.

Voltage and frequency aside there are many other reasons why equipment will become uncompliant between the US and UK/IEC. Colours of conductors for one.

I would suggest that for a small fee you ask a UK consultant to design/specify up the US designed circuit to UK/IEC standards.

 

[ScottyUK]

I cannot agree with SierraJ on this. In the UK and IEC it is illegal to switch the neutral so the 2 pole switch idea is not a good idea.

The regulations do allow the neutral to be switched. The regulations prohibit fusing of the neutral or use of a single-pole switch or circuit breaker in the neutral. Use of a switching device which mechanically links the switching of all the phase conductors and the neutral associated with that circuit is permitted. Chapter 53 applies, specifically regs 530-01-01 and 530-01-02.

----------------------------------

Sometimes I only open my mouth to swap feet...

 

[SierraJ]

Thank you for the clarification ScottyUK. However, I think we all recognize that there are many differences between the US and UK electrical systems.

I only wanted to point out one of the many safety hazards related to the proposed equipment use. Many of the initial posts only addressed the electrical issues, i.e. power, voltage, frequency, etc. but did not consider the safety related issues.

 

[theboosh]

Well, the equipment has the CE marking on it, so I'm hopeful. In the past, other machinery had a voltage selector kit, basically a small wiring loom that was changed if the voltage and/ or the phase from 1 to 3 changed. But the overall machinery remained the same.

Although having said that, I'm still a little baffled and thought this would be a lot easier to get equipment working on both sides of the pond!