Backyard Aquaponics
A place to discuss aquaponics

Ok, can't argue the "electrical" side of things... coz I just don't know...

But I've always been lead to believe that "throttling" a pump back was detremental.. in terms of pump life...

In my experience with pond pumps, most of the ones we would use have the impeller mounted to a magnet.
Their life will not be affected by higher back pressure generally.
The ebara style ones with the famous caps may be a different story.

to a point you can throttle back but too much restriction will cause damage to the impeller over time, obviously each pump is different and so will react differently to throttling back

By the way, I am loving this thread. Next tangent?

I thought I could pull a decent debate but who am I kidding? I havnt got a debating bone in my body heheheh

Ill try harder tomorrow Andrew when I pick the brains on these (dare I say it)... auto-sparkies

Does an "auto-sparkie"... light up when you enter the room...

I look forward to continuing to prove you wrong Charlie

Eventually I will make a video proving my point, but I am enjoying myself too much right now

I know that this load vs wattage bit has been proven in an other thread. I think even, dare I say his name, hydracel was involved in it. Multimeters were brought out, tests were done, and yes, the higher the load, the less power. Before everyone draws up plans for their perpetual motion machines, it was not giving free power, but it did have lower wattage. That does make a good excuse to throw a nozzle on one, like one, say, in an eductor...

The pump life could be affected if it was an external pump. If the pump was running churning the same water it would heat up and stuff the seals...
I'm not sure if heating inside the "bearing" of a submersible pump would be an issue...
If there was even a small flow of water it would probably be ok..depends on the pump.

Slowing the impeller down would decrease general wearing damage on the plastic/ceramic parts and so those bits should last longer...
Reducing the current in the motor would decrease the long term effects of vibration and wire insulation degradation as well... perhaps, also leading to extending the life of the motor.

But increasing the pressure in the pump may lead to a reduction in life of seals, housings etc. Although the pressures involved are so small that this doesn't really seem feasible.

blah blah blah..

I'm sure there are different designs of eductors but the one on my old spray tank requires 30 psi
( good as 2 bar ) to run at optimum.

To me this just seems to defy the concepts of energy.

Are you telling me that a normal household pedistal fan will consume less energy without the blades on it?

Or what about when you first start up a an AC motor, that is when its under most load and it isnt spinning real fast at that stage?

Or another example would be (using your methodology), an AC electric motor would need a lower value circuit breaker on it the higher the load I put on it?

Just doesnt make sense

I think what is being claimed by SuperVeg, Werdna, Freebz, et al is that the fan will use more energy if it isn't under load, ie if it is operating blade-less.
I think that, based on the arguments presented thus far, I would have to agree with them.

This was the claim....


DC motors increase power draw with load, ac motors increase power draw with speed.
Increasing load on a dc motor increases current draw, like you are suggesting.
AC motors work differently.
The current draw is directly related to motor speed, so increased load reduces flow, which reduces impellor speed, which reduces draw.



back at ya


your actually agreeing with what Im saying, you just dont realise it.

Charlie, you are right - I don't realise that I am agreeing with you.

Wouldn't seem to make sense...

Surely the resistance of the blades cutting through the air.. would effectively slow them....

Therefore to keep them spinning at a given rate/speed... then surely... more energy is required...

And a "bladeless" fan... would require less energy... just to spin the bearing... as it doesn't have the air resistance of the blades to overcome...