Shore power cord set for Europe

[Auspicious]

Originally Posted by paul2884

In principle correct but a bit oversimplified, it doesn't work quite like that or you could just drop the voltage to make the kettle boil quicker, say use a 230v kettle in the US on 110v think how good that would be......

Your main problem with the larger cable will be safely terminating it in a 16a plug, some makes of plug will take it most dont. The idea of just stripping the outer sheath off and leaving the insulated cores showing isnt very safe but is quite common with imported motor boats imported from the US.

Exactly. In the end, E=IR, P=I**2R, and mechanical compatibility.

[Nicholson58]

Originally Posted by Auspicious

There is something wrong here. I-squared-R is power loss (i.e. heat) in a conductor. That's why 220V 16A cords are smaller than 117V 30A cords.



"Running cooler they have less resistance and draw higher amps" makes no sense at all.



Bigger conductors are not bad per se but not necessary for 220V 16A.



If you had a voltage drop of substance different between 220V and 117V there was something else wrong. Longer docks, poorly installed end connectors ... something. An IR thermometer and a voltmeter should have nailed that down pretty fast.

What you fail to appreciate is that resistance is not constant with a heating element. This initial inrush is high, quickly heating the element and causing resistance to increase dramatically. If there is an in-line resistor, the cord, he heater never gets hot enough to increase resistance. The heater current remains high and trips the breaker.

[Auspicious]

Originally Posted by Nicholson58

What you fail to appreciate is that resistance is not constant with a heating element. This initial inrush is high, quickly heating the element and causing resistance to increase dramatically. If there is an in-line resistor, the cord, he heater never gets hot enough to increase resistance. The heater current remains high and trips the breaker.

I don't think inrush current is relevant for this application. The temperature coefficient of the materials used is close to zero (0) and is measured in parts per million/°C. The effects are small. When you consider that the components are at ambient temperature to start with (which is likely cold for a boat heating application) and the ramp time is relatively fast it isn't going to matter. Remember all the terms are linked. You can change voltage without changing current or resistance, you can't change power without changing current or resistance.



This is why for circumstances where inrush current is a factor we turn to things like soft-start components to buffer inrush current.


Since we started this thread with regard to EU cord sets compared to US let's run some numbers.

We'll use a 1200W ceramic fan heater.

For the European case from I=P/E=1200/240=5A steady state. A 16A shore power cord uses #14 wire at 2.5Ω per 1000 ft. For a 50' cord that's a 100' (both conductors, out and back) or 0.25Ω. P=I²R=(5A)²(0.25Ω)=6.25W. For simplicity let's double that to account for connectors and connections, so 12.5W steady state. That is 1% of the load.

We can do the same for the US case. I=P/E=1200/117=10.3A steady state. A 30A shore power cord uses #10 or #8 wire at 0.63Ω per 1000 ft for #8 or 1.0Ω per 1000 ft for #10. For a 50' cord that's a 100' (both conductors, out and back) or 0.10Ω for the smaller #10 wire. P=I²R=(10.3A)²(0.10Ω)=10.6W. For simplicity let's double that to account for connectors and connections, so 21W steady state. That is 1.7% of the load. By the way, 12.7W for #8 wire - almost exactly the same as the EU case.

In neither case are we talking about a lot of power, but it is at least four orders of magnitude (multiple by 10,000) more significant than current (amperes) effects of temperature coefficients for materials. Even then it is only relevant for a positive coefficient. It still isn't enough to make a difference.

What is apparent (without numbers, so I have to depend on insurance statistics and anecdotal reporting) is that loose connections and corrosion DO make a difference. We can see that from the number of boat and dock fires attributable to shore power cord connections. Remember the power loss in the shore power connection is all turning into heat. Keep raising the heat and insulation starts to melt which can lead to fire. Corrosion at sliding connectors (like a plug) causes intermittent connections that can spark and lead to fire.



We do know that time is a factor. This is why you can use a 12VDC cigarette lighter power point to supply 30A long enough to heat a lighter coil (analogous to an inrush current case) but only 6A continuous (so your 90W laptop with 10% battery left can lead to smoke behind the lighter plug). It's also why a 70W slow cooker works so well on such little power: enclosed space and time. Small amounts of heat build up over time. In the case of resistive heating the seconds to reach steady state just wouldn't make a big difference even if the temperature coefficient numbers were much bigger.


There are inherent assumptions: that wire sizes are appropriately selected, that connectors are properly installed, that the installation is properly maintained and corrosion mediated, that the little fan in the heater is insignificant from a power draw perspective.

[Nicholson58]

Originally Posted by Auspicious

I don't think inrush current is relevant for this application. The temperature coefficient of the materials used is close to zero (0) and is measured in parts per million/°C. The effects are small. When you consider that the components are at ambient temperature to start with (which is likely cold for a boat heating application) and the ramp time is relatively fast it isn't going to matter. Remember all the terms are linked. You can change voltage without changing current or resistance, you can't change power without changing current or resistance.



This is why for circumstances where inrush current is a factor we turn to things like soft-start components to buffer inrush current.


Since we started this thread with regard to EU cord sets compared to US let's run some numbers.

We'll use a 1200W ceramic fan heater.

For the European case from I=P/E=1200/240=5A steady state. A 16A shore power cord uses #14 wire at 2.5Ω per 1000 ft. For a 50' cord that's a 100' (both conductors, out and back) or 0.25Ω. P=I²R=(5A)²(0.25Ω)=6.25W. For simplicity let's double that to account for connectors and connections, so 12.5W steady state. That is 1% of the load.

We can do the same for the US case. I=P/E=1200/117=10.3A steady state. A 30A shore power cord uses #10 or #8 wire at 0.63Ω per 1000 ft for #8 or 1.0Ω per 1000 ft for #10. For a 50' cord that's a 100' (both conductors, out and back) or 0.10Ω for the smaller #10 wire. P=I²R=(10.3A)²(0.10Ω)=10.6W. For simplicity let's double that to account for connectors and connections, so 21W steady state. That is 1.7% of the load. By the way, 12.7W for #8 wire - almost exactly the same as the EU case.

In neither case are we talking about a lot of power, but it is at least four orders of magnitude (multiple by 10,000) more significant than current (amperes) effects of temperature coefficients for materials. Even then it is only relevant for a positive coefficient. It still isn't enough to make a difference.

What is apparent (without numbers, so I have to depend on insurance statistics and anecdotal reporting) is that loose connections and corrosion DO make a difference. We can see that from the number of boat and dock fires attributable to shore power cord connections. Remember the power loss in the shore power connection is all turning into heat. Keep raising the heat and insulation starts to melt which can lead to fire. Corrosion at sliding connectors (like a plug) causes intermittent connections that can spark and lead to fire.



We do know that time is a factor. This is why you can use a 12VDC cigarette lighter power point to supply 30A long enough to heat a lighter coil (analogous to an inrush current case) but only 6A continuous (so your 90W laptop with 10% battery left can lead to smoke behind the lighter plug). It's also why a 70W slow cooker works so well on such little power: enclosed space and time. Small amounts of heat build up over time. In the case of resistive heating the seconds to reach steady state just wouldn't make a big difference even if the temperature coefficient numbers were much bigger.


There are inherent assumptions: that wire sizes are appropriately selected, that connectors are properly installed, that the installation is properly maintained and corrosion mediated, that the little fan in the heater is insignificant from a power draw perspective.

Lovely calculations.

It’s not the cords or connectors I’m talking about.

It’s the heating element that changes resistance. If it cant heat fast enough due to resistance of a poor cord set then it’s resistance stays low too long. This is evident as the OP noticed by tripping the breaker. Breakers trip for a number of reasons based on design. In this case, the longer period of higher start up current tops this threshold. I have seen this running my own space heaters. I’m just a mechanical PE but one of my EEs explained the the effect of time and variable resistance. If the heater is right on the cusp of drawing full rated circuit protection load then messing with resistance can increase total start up power within the time constant of the tripping device.

[Dockhead]

Originally Posted by Auspicious

There is something wrong here. I-squared-R is power loss (i.e. heat) in a conductor. That's why 220V 16A cords are smaller than 117V 30A cords.



"Running cooler they have less resistance and draw higher amps" makes no sense at all.



Bigger conductors are not bad per se but not necessary for 220V 16A.



If you had a voltage drop of substance different between 220V and 117V there was something else wrong. Longer docks, poorly installed end connectors ... something. An IR thermometer and a voltmeter should have nailed that down pretty fast.

That's it.


But in any case, it's simple to make up a brand new cordset for Europe.



We don't have 30 amp single phase power here; at least not in Northern Europe -- doesn't exist. 30 amp power up here is three phase with the red plug. The single phase 230v power is maximum 16 amps, and sometimes 12, 10 or even 6.



You want a 16 amp blue plug for the dock side and much lighter cable than you need in the U.S. There is no need to buy a specially made up cordset -- just buy good waterproof flexible cable in the needed size and buy a blue plug at any chandlery or hardware store -- as usual these things are much better standardized in Europe than they are in the U.S.. Move your boat-side plug from your U.S. cordset or buy an extra one, and you're done. Should cost you well under €100.







One other tip: if you have one of those awful 32 amp Marinco connectors, throw it away! This is a horrible prewar design which is a fire waiting to happen, and could be the source of your problems. Use a SmartPlug for the boat side, or one of the different European types.


https://smartplug.com/marine/connectors/


I like the SmartPlugs very much, but there are some European equivalents which are cheaper and also look very good. For example, Mastervolt make a lovely one which takes a standard blue socket:


https://images.mastervolt.nl/images/...16arvopena.jpg

[Auspicious]

Originally Posted by Nicholson58

It’s not the cords or connectors I’m talking about.

Correct. I was showing that there is a four order of magnitude difference in effect.

Originally Posted by Nicholson58

It’s the heating element that changes resistance. If it cant heat fast enough due to resistance of a poor cord set then it’s resistance stays low too long. This is evident as the OP noticed by tripping the breaker. Breakers trip for a number of reasons based on design. In this case, the longer period of higher start up current tops this threshold.

All true. Look at the numbers and what the slow-blow time is on a circuit break. It's milliseconds. Even when everything is working correctly it takes several seconds for a resistive heat element to reach steady state.



As you say, there are a number of reasons breakers to trip. For large enough heaters and for particular materials with high thermal coefficients this could be a factor. In the real world this is second and third order effect, overwhelmed by other more likely causation. Occam's Razor.


I'm just a naval architect/marine engineer.

Originally Posted by Dockhead

One other tip: if you have one of those awful 32 amp Marinco connectors, throw it away! This is a horrible prewar design which is a fire waiting to happen, and could be the source of your problems. Use a SmartPlug for the boat side, or one of the different European types.

Or cut off the boat-side connector entirely, fit properly installed ring terminals, and hardwire on the boat side. SmartPlug is definitely better than Marinco. Hardwire is better yet. It works for the big boys and it works for me.

[Dockhead]

Originally Posted by Auspicious

. . . Or cut off the boat-side connector entirely, fit properly installed ring terminals, and hardwire on the boat side. SmartPlug is definitely better than Marinco. Hardwire is better yet. It works for the big boys and it works for me.