Magnetic pump question-restricting output and electrical consumption?

[lilrobb]

I followed this with interest,

thanks Dave for solving this ..

 

[grouper therapy]

dawgdude;379243 wrote: Increased friction might be whats causing the lower wattage?

How so?

 

[grouper therapy]

ares;379241 wrote: if its pulling less watts, it has to produce less heat. Perhaps more heat per gallon moved? But less heat overall than running full open for sure. Heat can only come from energy consumed, if its consuming less, its heating less. Though it may be less efficient about the ratio of energy used for moving water vs heat loss.

+1

 

[oldschool52]

Very interesting tests. I would have thought that restricting would cause an increase but real world test are the proof. I'll accept actual tests any day before theories. There is proebably a formula and scientific expannation for the results but I DON"T REALLY CARE as long as the bottom line is "It Works". Numbers don't lie.

I did the exact plumbing suggested a few posts back, that is,T'd the output and put a valve with hose off one leg back to sump. Reason: when setting up sump wanted to try different returns before purchasing so I would get the correct size. Borrowed a mag 18 which was way overkill for my 72 but the T let me use it for a week till I tried a Mag 7 which was ideal. That is what is running my tank now successfully. Nice to have the valved option on the return in case pump bites the big one so I can use about any size till a replacement is obtained.

 

[acroholic]

oldschool52;379610 wrote: Very interesting tests. I would have thought that restricting would cause an increase but real world test are the proof. I'll accept actual tests any day before theories. There is proebably a formula and scientific expannation for the results but I DON"T REALLY CARE as long as the bottom line is "It Works". Numbers don't lie.

It seems to depend on the pump drive system. Magnetic drive pumps like Danner Mag Drive and Eheims use less when valved down. Pumps like Reeflos and Dolphins (only connected by the drive shaft), where the drive mechanism is separate from the Pump head, seem to use less watts when valved down (Joe tested his Reeflo), whereas external pumps where the pump head is connected to the drive mechanism, like Pan World and Iwaki, pull the same watts regardless of the output.
Dave