Backyard Aquaponics
A place to discuss aquaponics

You sticking up for Monya

Will you all stop scaring the newbies?!?!?

Hi Skygazer,
Welcome. I agree with 'Ell's formula.

im gonna change my mind and agree with monya....
Tried gogling it, but as of yet just found some useless equations

the given power usage (i am thinking) is probably the "under ideal conditions" power usage, and any change in the ideal conditions would result in decreased flow and increased power usage (although i wouldn't imagine the power would increase as much as the flow can decrease)
*i reserve the right to change my opinion though*

does anyone have one of those power usage meters and a spare couple of minutes?

you can borrow the home energy kit from the library tomorrow on the way up. they have a meter in them...

On the topic of saving money with inductive motors I just have to share this. When your house is far from the power generator the voltage gets somewhat out of phase with the available current in the line. When you correct this you can save up to %25 on your electric bill.

Here is a site that sells an expensive ($300) product to do that Power Saver

My parents bought one and I took it apart. Its only a 80uF Capacitor(360 volt or higher)!
So I ran down to the local supply house and bought one for $16 USD. I hooked a wire to each of the two terminals and wired it into a double pole 220 volt breaker. It cut my power bill from $180 to $130!!! Thats like 27%!! Of course most of my house in running inductive loads (transformers and motors) and we are more than 50 miles from the power generators.

I`ll agree with that.
Can you believe the pump`s spec plate? I guess there must be some leeway, even with two identical pumps.
One way to find out for sure is to measure the current with a high enough head to cause a zero flowrate ..tape the pipe to a vertical pole

You can adjust the head height and log what the power consumption is.

Most multimeters have an AC current function.
Put the meter in series with the hot wire (red probe to supply, black probe to pump hot wire)..unless you have a clamp meter.

Voltage x Amps = Watts

For the sake of accuracy you could measure your actual supply voltage too

DDM
How do they get away with that advertising..

"your local utility delivers that reactive power to your home without knowing how much you really need"

A classic case of smoke and mirrors

hiya guys, i've just speed read this thread so excuse me if i've missed something, but when yu see a W rating on a motor it is usually the mechanical power output of the motor.

When you multiply the Voltage by the amps you will get a Watt figure upto 45% higher, this is the electrical consumption.

typical motors are around 65% efficient at converting electrical to mechanical with the remainder going as heat. I know there a new regs coming into force (for larger motors i think?) that will mandate greater than 90% efficiency and with a corresponding price rise.

okay, using some very rough times for my two pumps I get:
750W * 6hours = 4.5kWhrs
250W * 12 hours = 3kWhrs
total = 7.5kWhrs

That is the rating according to the plates on the pumps.

However, according to Steve's calculation using the amps * voltage, I get:
3.3A * 240V = 792W * 6hours = 4.8kWhrs
1.9A * 240V = 459w * 12hours = 5.4kWhrs
total = 10.2kWhrs

there's a big difference there
So, which one do I believe for my estimated daily usage?

No way of knowing for sure without testing it with a meter

The most important thing to know is the actual £££ running cost of the pump, so Steve`s calculation method is the more useful.
Always assuming the spec plate is accurate and also that the figure relates to a constant maximum current draw whilst it`s pumping at any head or flowrate... which is unlikely.

right, so I get my brother or a mate down the road to come and visit with a multimeter.

I would ..if only to check the spec plate is correct

It is difficult to know from your name plate because you have increased consumption when the pump starts up, and if you have the pump throttled back with a valve, then you will use less power.. Also, don't you have to allow a power factor in the calculations there somewhere, which I think is generally 0.8...?

I have had a "microvip" hooked up to my system for the past 3 weeks measuring the power consumption.. It's a very complicated piece of electronic equipment, but I have a much simpler way to measure consumption that should be ready soon..

I know someone in the power meter game, so got hold of a standard household digital power meter like in your meter box, they are very cheap.. Now I'm just waiting for my electrician mate to stick it inside a box with a male power lead on one end, and female on the other. Then I'll have an extension lead with a box in the middle that measures all power that flows through it, on a simple LCD screen.. Very easy to plug in either one pump, or a whole system, then leave it for a week to see how much power has been consumed..

My understanding is the nameplate power is the maximum electrical power the device can consume. Normal running will use less than this, not more. In some cases things like pumps have larger start up currents and the nameplates can show the startup power, meaning normal running is significantly less than nameplate data.

"Since nameplate amps reflect the total current consumption of the motor (which includes both the current converted to output power and the current lost to heat due to design inefficiency)...."
From here

Jaymie my bet would be you're using less than 7.5kWhrs.

As others stated measuring is way to go. Joel currently (no pun intended) has a power usage recorder hooked up to one of his systems. After the dust has settled on Faye's apuaponics for the masses adventure, he may be able to shed some light on this.

Edit : Speak of the devil

The power factor is sometimes used (abused) by manufacturers to manipulate (reduce) the advertised wattage rating. Some don`t even have amps on the spec plate.

The tricky part may be getting the shop to lend the pump for a week to test it