Backyard Aquaponics
A place to discuss aquaponics

I had 3 goes. shouldn't that be 1/3. Have you been putting my answers through Franks Pump efficiency calculator.

That's how I thought Myles got the answer he did Duff....

I've just realised though... it probably makes a difference whether you use "1/2" .... or "0.5" ... in your calculations.... could well lead to two different answers....

Oh shit, sorry your right. 3/100 xh @ ghkd x 83 hjcjd ^ 99 - hoxtl = 1/7 I forgot to do something but not sure what it was.

No, I refuse to give 1/7 th of a mark either. Just bloody give up will you or come up with something useful

I like the efficiency calculator. Did my tax with it and got double back. But now I have 2 dependents that I didn't know I had.

Just stop it Duff your making my sides hurt.

I think we are getting a little of topic.

No one has given me a definitive answer for which pump yet?

I still like the blue one.

Question 1

I have no idea.

Question 2

Definitely pump A because it uses less power to produce the same results for that setup.

I have and I'll interpret Franks answer so that he has too.

Question 1



Translate: Pump B

Question 2



Translate: Pump B

Since Frank has said B for question 1 can I change my answer to A?

Still reckon we should let them discuss it and reach a compromise. I can factor the other shit in myself.

Stuart I hope you didn't mind me hijacking your thread, sorry.

Oh, and I forgot to give Frank a mark for calculating the values so we could all look at them and ponder on them, and then look at them again, and then ponder them again and... +1 to Frank

The answers to the quiz:

Question 1:

Pump A and Pump B are the exact same pump operating at exactly the same head height, but at different total head heights. [These are actual figures of one of my pumps.]

So, I think a mark should go to Stuart's method because he called it as "I have no idea", which I'll interpret as there's not enough information to be certain because the pump(s) are operating under different conditions. +1 Stuart

Question 2

Pump A and Pump B are indeed different. I made Pump B up (sorry) to show that even though the flow is identical to Pump A and it uses more power, its efficiency is actually better. But from a practical point of view, Pump A uses less power to pump the same flow of water, which is typically what AP'ers are more interested in. So again, I think a mark for Stuart's method? +1 Stuart

But it was discovered that Pump B's flow has considerably more force (thanks Sleepe) - this may or may not be useful.

A point I had hoped might have been discovered is that if the 20 mm pipe used by Pump B in Question 2 was changed to 40 mm pipe (making it the same as Pump A), the flow would have increased to 2,300 l/h and the head would have been reduced to 1.0m (the same as Pump 1). This has the effect of reducing Pump B's efficiency below that of Pump A, but increasing it's flow above that of Pump A.

Just to clarify that last point - by reducing the operating efficiency of Pump B, by reducing its total head, the flow was increased.

But we need to remember that Pump B uses 40 Watts and Pump A only uses 35 Watts. So now we have two values Power and Flow, that both differ - so it makes it very hard to compare the two pumps.

That's really why pumps are so hard to compare - there are 3 variables, power, flow and pressure (head) - make any two of those variables the same of similar and the other one can be compared directly.

One point I would like to make that I don't think has actually ever been made:

If a pump is operating at or around its best efficiency, it should be operating at its most quiet and lowest vibrations - and in theory should last longer due to wear caused by vibrations etc. So perhaps another mark to Frank, cause efficiency does matter. +1 Frank

And so ends tonight's lesson - ensure you study hard so if you are ever faced with a pump exam you can effectively and efficiently answer the questions

Sounds good - I won't hijack the thread again

Oh, and I've reconsidered Duff, 1/2 mark for persistence - just to make Rupe have to work that much harder next time +1/2 to Duff

So does that mean for the best efficiency results we need both methods for every pump?

Ie Short list that pumps that have their "sweet spot" at the Head height required and then chose the pump that has the highest L/Whr?

Frank said that more force was good because it would provide better aeration but wouldn't the water be oxygenated by the GBs flooding and draining rather than by the water flow out of the outlet from the pump?

Mind you I'm assuming that we are talking about FnD systems rather than any others.

been away for the day, and found out some people meanwhile have tried to conclude my choice for me
... grrrr ...
there was on purpose no conclusion in my post on either question
well, there was a hidden one you seem not to have discerned
while it was very clear

here is what my answer would have been:
first: a pump has no brain
it doesn't know if the head it is fighting
is caused by level difference or by friction in pipes or appendages
for a pump the only head that counts is total head

my answer for question 1 was:

I did not write: "these are excellent pumps", but "this is an excellent pump"
nailed you there: I had a hunch this was one and the same pump:
the results are perfectly acceptable for the same pump @ different total head

for question 2 I knew there were two different pumps involved as your description left no doubt:

in question 2 you describe two different pumps for two different applications,
but only the results of each pump at one application

to be able to choose, both pumps should be tested at both applications
even then the conclusion of which pump to buy could be different for both applications

so not enough data to reach a conclusion for either application

but that is not all:

all of the results show these pumps to be comparatively "excellent":
they show efficiencies of over 16% in all applications described,
which is not less than double of the pumps I use
so in this range of pumps they are a better choice

these efficiencies also reflect on pump quality:
these pumps are likely to be equally reliable too
which would then make my choice go to the cheapest pump.

lastly, but not less important:
there is the question of standardization:
four different applications (actually only 3: Q1 PA = Q2 PA) would ideally call for 4 (or 3) different choices
having 3 (or 2) different pumps in your system
would call for 3 (2) spare pumps and 3 (2) spare impellers on the shelve in case of a problem at night or in weekends
I would gladly give up 1 or 2% efficiency (on 16% or more) in exchange for only one spare pump and one spare impeller on the shelve

price of these pumps and spares would need to be considered

this sums up why I cannot answer your question

but please let's not forget that these pumps, tough comparatively "excellent"
still in each and every one of these applications waste 80% energy

to sum up the data as I interpreted them:
PA 1.000 m 35.0 l/min 2100 l/hr 35 watt 0.100 bar 100 mbar 6 watt 16.67% 60 l/w
PA1 1.500 m 28.5 l/min 1710 l/hr 35 watt 0.150 bar 150 mbar 7 watt 20.36% 49 l/w

PA 1.000 m 35.0 l/min 2100 l/hr 35 watt 0.100 bar 100 mbar 6 watt 16.67% 60 l/w
PB 1.200 m 35.0 l/min 2100 l/hr 40 watt 0.120 bar 120 mbar 7 watt 17.50% 53 l/w
PA 1.200 m 32.4 l/min 1944 l/hr 35 watt 0.120 bar 120 mbar 6 watt 18.51% 56 l/w

the bottom line is an interpolation of the data of P1 @ 1m and 1.5m head to a head of 1.2 m, so is only an interpretation by me

I believe you to be as smart as I
and would, like me, standardize your pump choice
so I also had a hunch (but a weaker one) that the data of pump B were made up

this was a fine and fun challenge

thanks
please count my points on this exam

frank