Motor Protection Circuit Breaker (MPCB) - on a small pump

[fjr1300]

Hi All

A customer had a small 3 phase water pump (water from a well) which had a MPCB Legrand 02806 (via a 10A 3 phase breaker)
e-catalogue 2012/2013 - © Legrand

The customer has changed his supply to single phase and the pump over to a single phase one - 3.6Amps 230V

Now the MPCB can be rewired to single phase but the dial setting (FLA) is 2.5A max so I think I need to get a new one 02807 (4 amp max)
For the moment I have removed the MPCB and 10A breaker, and put in a 6A dP breaker and everything appears to be working

Now the question - (at last everyone says)
For such a small motor, which just sits in the cellar corner pumping water for the garden, do I need a MPCB (new one costs 80€)

Lee

 

[Marvo]

I'm not sure from a UK regs point of view but sometimes with very small motors and pumps you've got to weigh up the price of protection against the price of a new pump and decide where to draw the line.

The overload you refer to is just a thermal overload, if you're going to spend that kind of money maybe consider a pump protector with phase angle detection capabilities which will detect dry run and several other fault conditions. Something like this.

 

[fjr1300]

The rhomberg item looks cool, just hate to think about the cost of a similar item in France.

The the whole pump below with 20L tank/pressure regulator costs 70€, so if it failed every few years it would probably still be cheaper in the long run.

 

[malcolmsanford]

Lee unless you are working somewhere that is under a separate set of regulations, for instance Mine and Quarries, then any electric motor over 0.37KW must have overload protection as per regulation 552.1.2

 

[fjr1300]

Would the 6Amp breaker not provide enough protection ?

 

[malcolmsanford]

The reg reads mate

'Every electric motor having a rating exceeding 0.37KW shall be provided with control equipment incorporating means of protection against overload of the moor ........................etc etc "

In France Lee it may be different mate I don't know.

The reg as I post does go an an say that if your working to other standards that specifically say that the motor does not require then the jobs a good'un

 

[Knobhead]

For peace of mind I would fit an overload to any motor. Nothing to do with the reg’s it’s just my preference.

 

[Paul505]

Exactly what Malcom has said.... plus just to add to that, close motor overload protection is required if greater than 0.37kw which is normally incorperated with the control equipment, (adjustable thermal overload protection), plus your normal fuse protection up-stream.
If below 0.37kw then standard fuse protection is adequate or if its a motor thats incorperated within a piece of equipment to a relevant standard.

 

[fjr1300]

Been looking around - can get this LSIS device for 30€ so the customer should be OK with that (the pump was free second hand)
Green Innovators of Innovation, LSIS

Since the motor takes 3.6Amps, I assume I have to go for the 2.5 - 4 amp max version and turn down to 3.6A - the next one up, 6A only goes down to 4A


This is my first motor I've had to work on but I've seen 5 or 6 water pump configurations and they were just on a breaker/Fuses.

Lee