Laing Eco-circ pump

   It was probably too much to expect everything to work perfectly and it hasn't.

   When the Laing Eco-circ pump turns, it is designed to use as much electric power as possible from the solar panels (PV).  Unfortunately that causes the system voltage level to drop to 17 volts and the battery charge controller stops working and eventually the controller would shut down due to lack of power.  A secondary problem is that the pump is circulating the water too fast.  It is pumping well in excess of 5 gpm (gallon per minute) which is much faster that the 2.5 gpm that is recommended by Heliodyne for the solar panels.  Too much gpm and using too much electricity.

    So I contacted Laing technical support (which appears to be Xylem Inc part of ITT) and got some great help from Amy Flores.  Long story short, it looks like Caleffi made a mistake by using the D5 "strong" pump.  That pump is really intended more for maximizing flow of fluid which is not what you want in solar hot water panels.  It is probably great for well water pumping, but not for solar hot water panels where flow control is needed.

   Fortunately Laing makes an Eco-circ D5 "Vario" pump which has, as the name suggests, variable flow settings.  There is a dial on the side of the pump where you can adjust the volumetric flow.  The image shows the two different pump types.  On the left is the "strong" pump that pumps the water as fast as possible.  The pump on the right is the "vario" version with a small red dial that allows the flow to be adjusted and save some electric power as well.

 The design of the eco-circ is really excellent.  The pump/impeller side can be easily separated from the involute/pipe fitting side.  This allowed me (really Amy gets credit for this idea) take the new motor and attach it to the Caleffi fittings (which are custom).  So I took half of one eco-circ and screwed it to the other half of a second eco-circ pump to get what I needed.  The "vario" pump was purchased from Sun Volt Energy (www.sunvoltenergy.net) for $179 which is an excellent price considering I paid $325 for the Caleffi pump.  Sun Volt got the pump out to me in just a couple of days which was great.  The image shows the two halves of the pump.

 As can be seen in the picture, the official part number for the "Vario" is D-38/710B.  I found the Eco-circ part numbers to be confusing.

  The Results:  This is the best part.  Using the dial, I could adjust the speed of the motor until I had 2.5 gpm flow as shown in the picture.  I give Caleffi credit for including this nice flowmeter into their pumping station design.  Without the flowmeter, I would have no idea what kind of flow I was getting.

   Now for the best part, connecting the pump to a power supply and the power supply to a Kill-a-watt, I found that the power used is only 9 watts versus the 50 watts used by the old eco-circ pump.  Can't wait to see if it works as well on sun-light power.  Think about it for a minute. 2.5 gpm for 9 watts!  Many home circulators require more than ten times the power to do the same job.  Well done Laing.

   The hot water tank still needs to be connected to the domestic hot water system.  Hope to do that soon.  A plumber is coming tomorrow to look at the system and another plumber said he would do it for $1100.  I would prefer to do this myself, but officially, only a licensed plumber is supposed to do the job.  The whole project has turned out to be way too expensive.  However, I must complete the project at this point to be done with it and get the benefits.