Swimming pool 3 phase motor trips occasionally on earth leakage RCD

Thanks for the link.   

Well, it looks as if the EU has managed to double the cost of EC2 induction motors as the VSC cost more than the motor.  Why can't we table an amendment to state.  Induction motor run at full load all the time are exempt.   

Otherwise, we just go with Boris and forget about EU over the top nonsense directives like this. which is making no savings at all.  

BTW I did hear that the EU Lisbon agreement indicated that all member states should be using Euro's by next year which could be another reason for opting out of the EU.

I think they were hoping to encourage the manufacturers to switch to making  more efficient  EL3 motors, with the VSD clause as the way to allow old designs to be sold out.

- so for your 4kW unit,


3 figures are for 2, 4 or 6 poles though I suspect yours is 2.


Efficiency level 3 would allow

85,8    86,6    84,6 percent efficient, so a ~ 15%  can be burnt off as heat if you use a VSD.


or

Efficiency level 2 would be

88,1    88,6    86,8 percent efficient,  and so if the motor is improved to more like ~12% off as heat and then you do not need   VSD.

Of course what has happened, is that re-tooling factories to stamp out motors with more generous  metal is not in the motor maker's interest, as they do not pay the electricity bill, so they keep making the inefficient ones and then later the buyer has to add the price of the VSD.


Depending how many hours the motor runs, and the local price of electricity, the capital cost of the motor (with or without VSD ) may not be the largest cost.

Thanks Chris and Mike

My memory says motor efficiency is dependant on the iron and copper losses.  Now if we run at full load then whether the supply is direct from grid or via a VSD those losses cannot be avoided.

That means that the 10% extra loss of the VSD make it much less efficient overall and an amendment should be floated to the EU to exempt such machines.  Added bonus is it lowers the original cost and eliminates electronic flutter and unreliability.

the losses can be reduced by being less stingy with the copper and the iron,  but motor makes do not want to re-tool immediately . The better made motor cost is higher, but the cost to run over all but the shortest  lifetime is not. It might have been more effective to ditch the vsd requirement and just insist  on lower losses.

However there is an additional complication that motor frames are only made in a limited number of sizes so the chances are that your motor has to be  oversized for the pump, perhaps only by 10% or so, but still oversized. in such a case it can safely be run a little lighter than flat out and still pump the same.

This directive is another instance of 0.5kW kettles to save energy. It will save nothing and may well cause increased consumption! Stupid. Is it worth a tiny saving of 2% in the motor efficiency rating, at the cost of at least a couple of hundred pounds for a VSD? It will probably never save that much!

well this is a 4000w unit. Let us assume that the vsd saves us 5%, or 200 watts, could be more, or less, but a nice easy number to assume pump works just fine at 95% of full power.

. Now I do not know the OP's electricty supplier, but pretend that it is 10p per kw hr. Could be twice that, unlikely to be half.so, saving 48p a day assuming 24 hour running.

We get the hundred quid back in 200 days of operation, anything longer before it needs replacement is clear profit - That would be a disappointingly short working life, ten years might be more sensible, so it really should pay for itself.


I fully agree it is not worth bothering with kit that only runs very  intermittently, but fans and pumps often really are 24/7 and can often be left running but backed off at night, and again the VSD helps that


The kettle thing really is cobblers though - it is better to go the other way and flash boil water as required with lots of power, as there is then no time for loss of energy to the environment.

On mainland Europe EU grants were available to replace domestic central heating circulation pumps with new more energy efficient units.


The UK Government decided not to take part in the scheme and allow UK citizens to benefit from this EU grant.


On mainland Europe several old power stations were closed without replacement being required due to the new energy saving domestic central heating circulation pumps that had been installed.


Enough said!

Have found an advert for a type A 300mA RCD Siemens 5SV3644-6 which should not trip.  However, calling it a type A when a type B trips at around 100mA seems a little misleading.  Surely, it would be a type C.