This just doesn't make sense to me

[trents]

Why does a low restriction water loop produce higher pump temperatures than a high restriction loop? I've been reading this in relation to the Swiftech MCP50X. It seems counter intuitive to me. A loop with more restriction would make the pump motor work harder and draw more amps to produce the same flow rate.

 

[ssjwizard]

Ok so dont quote me on this, but this is how I see it. Low restriction loops allow a greater flow rate, and while this all sounds well and good its not completely. In a low pressure environment the impeller would suffer from almost 0 friction and thus spins faster. That increased RPM in turn generates more heat in the bearings of the motor and thus suffers from a higher temperature at the pump.

 

[trents]

Hmmm. Those bearings are very tiny. Not much frictional surface area there.

 

[Flat-6]

Heat generated has nothing to do with the ceramic bearing.

It all boils down to the RPM the pump is operating at.

The impeller in your pump is driven by a magnetic field which effectively rotates. This rotating magnetic field is generated by a number of coils and there associated driver IC('s). The coils are switched on and off at the correct interval to mimic a rotating magnetic field.

The coils are basically an inductor and inductors have IR (Inductive and Resistive) losses. As current flows through an inductor these losses cause it to generate heat. There are a couple of other technical thermal losses due to the coils as well - but just keeping it simple, the coils and drivers are the heat culprits.

As the RPM increases, the coils (and driver IC's) switch on\off faster and faster and thereby generate more heat due to the losses mentioned above.

The heat generated simply comes down to how fast the pump is spinning at and has nothing to do directly with pressure itself.

 

[trents]

I thought it was something like that but even so, that's works differently than my electric drill which gets hotter when there is more resistance to rotation of the shaft. Of course, it also has a fan on the shaft which doesn't turn as fast under heavy load.

So l take it just limiting the RPM will help keep the heat down. The MCP50X pump will be overkill anyway on my system which only has one 360 radiator and no elbows or splices. I just couldn't find anything less powerful that looked like it was quality.

 

[Flat-6]

works differently than my electric drill which gets hotter when there is more resistance to rotation of the shaft.

Your electric drill motor operates differently as it is more than likely a brushed motor fitted with a commutator.

If it is a more modern expensive drill, then it may have a brushless motor which is more along the lines of our pump motors.

 

[trents]

Yes, I'm sure my electric drill has a brush/commutator type motor as it is a relatively inexpensive (and quite old) consumer level tool.