Installation manual

4.2. Measuring Flow

IMPORTANT: "Gallons," "gals," and "gpm" refer to the US Imperial Gallon (3.8 litres),

as opposed to the UK Imperial Gallon.

Try and find a place in the stream where it drops quickly over a rock, place your bucket

below and measure the time to fill it.

At lower flow rates, less than 150 gpm (10 l/s) you need to be accurate in measuring the

flow. If you have a 2 gallon paint pail and the river can fill it in 2 seconds you have 1 gps =

60 gpm, which equates to 227 l/min, 3.8 l/s.

Use the largest possible bucket you can find as the longer it takes to fill the more accurate

your reading will be.

For flows greater than 150gpm try to estimate your flow using a larger bucket in the river and

measure at various places across the river. It will not be as accurate but at higher flows it is

not that critical.

A "notched weir" is useful for monitoring flow over time as it can be used to take quick

readings on a regular basis, but it takes some effort to construct.

Click here for a recent Home Power article on how to measure flow rate.

4.3. Choosing the correct turbine for your site

Different sites will need different PowerSpout models depending on the head and flow.

All PowerSpout products are named with one of the following model abbreviations:

 PLT (PeLTon turbine)

 TRG (TuRGo turbine)

TRG and PLT model turbines are connected to pressurised pipework that feed water

through jets towards the turbine runner, spinning the runner and hence the generator,

which generates electricity. These are normally referred to as "impulse turbines".

 LH & LH Pro (Low Head propeller turbine)

LH model turbines direct the water through guide vanes that spirals on to a propeller

shaped runner, causing it to spin. These are normally referred to as "reaction turbines".

The turbine sits close to the intake water surface with the alternator on a stalk above

flood levels. Water is actually driven by suction created by the weight of water in the

draft tube below the turbine. The head is measured from the water surface at the

turbine to the water surface of the tail race where the draft tube discharges.