Liquid Pump for Thermal Solar System

The Liquid Pump for Thermal Solar System is a Wilo Star-RS 15/6. Wilo Star RS 15/6 PumpWilo Star RS 15/6 PumpThe RS means Standard pump (screw-end pump). The 15 is the nominal connection diameter R. The 6 is the Nominal delivery head [m] at Q = 0 m3/ h (this means the maximum head pressure height the pump in meters can pump at certain pressure, temperature and viscosity of the liquid).

Below the Wilo pump is a flow meter.
Solar WorkStation: Parts of the Solar Thermal WorkStation and all its parts labeledSolar WorkStation: Parts of the Solar Thermal WorkStation and all its parts labeled

I believe it is in liters per minute. In the shown chart for the Wilo pump on high at 5 meters (which may be the distance to the top of the solar collector from the pump) the flow rate is about .5 m3/hour (.5 meters square per hour). This converts to about 8 liters per minute. Pressure makes a difference, with more line pressure increasing the flow.
Note: If any air gets to the pump (especially if there is much head pressure) the screw impeller it will not pump a gas, so flow will stop until the air is removed. The pump will heat up at this time.

Glandless circulation pump with threaded connection. Preselectable speed stages for power adjustment.
Hot-water heating systems of all kinds, industrial circulation systems, cold water systems and air-conditioning systems.
Special features/product benefits
* Suitable for any installation position with horizontal shaft; terminal box in 3-6-9-12 o'clock position
* Pre-selectable three speed stages for load adjustment
* Easy, safe installation with the practical wrench attachment point on the pump body
* Simplified electrical installation through the terminal box with removable threaded cable connection that can be used on both sides; quick connection with spring clips.

Wilo RS 6 Pump ChartWilo RS 6 Pump Chart
Technical data
* Permissible temperature range --10°C to +110°C
* Mains connection 1~230 V, 50 Hz
* Protection class IP 44
* Threaded connection Rp ½, Rp 1 or Rp 1¼
* Max. operating pressure 10 bar

Manual functions
* Selection of speed stages (3 speed stages)

* Wrench attachment point on pump body
* Cable entry possible on both sides
* Quick connection with spring clips
* Blocking current-proof motor

* Pump housing: Cast iron
* Impeller: Plastic
* Shaft: stainless steel
* Bearing: metal-impregnated carbon

We tested the pump volume manually into and from an open top bucket to measure into a quart jar how many seconds on each speed it took to fill the jar. Below are the results and conversions.
Notice that the small flow meter in the work station showed 6 when the pump was on low and manual results showed 3.75 liters per minute.

Solar Pump Results 2/26/2011
Liquid Temperature at 130° Fahrenheit, Relative Pressure is 0, lift is 5
meters, lines are .5" copper 
Speed Seconds/Quart Quarts/Minute liters/minute meters³/hour
High 3 10 6 5.7 0.34
Medium 2 12 5 4.7 0.28
Low 1 16 3.75 3.5 0.21
converter from