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GREEN SYSTEMS | SOLAR SOLUTIONS | CONTINUED FROM PAGE 24


their circulator as “the stator” since it has no moving parts. The Ivan SID motor was designed to fit on the March


pump body, which can be seen in Figure 39-1. The March impellor enclosure is designed to allow motor replacement without breaking into the plumbing. A motor replacement can be made without leaking any glycol or glycol pressure, and it is possible to replace a March 809 brush motor with an Ivan SID motor (or vice versa) using only a screw driver. The Laing D5solar circulators are perhaps the most


innovative and unusual, as seen in Figure 39-2. A hemispherical rotor is balanced on a single ceramic ball bearing, and magnetic material embedded in the hemisphere moves in response to the field generated by


are small circulators that typically run on 20 to 30 watt PV panels. The larger circulators are more popular and typically produce around two to four gallons per minute of flow through a solar collector loop. They are most easily applied to water heater systems where there are only a few collectors and where the pipe runs are not very long. I have also used them on larger banks of collectors (six to eight in parallel) successfully, as long as the pipe resistance, the size of the collectors and the PV panel are carefully matched to the capabilities of the circulator.


Control options Early morning startup, when the solar collectors are still


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cool, can sometimes be an issue with PV-direct circulators. Sometimes the owner or installer will want to delay startup until the solar heat collector reaches a certain high temperature before allowing the circulator to turn on. The optional voltage knob on some versions of the Laing D5solar offers one solution to this issue. It can be adjusted to wait until a certain minimum PV voltage is generated before allowing the pump to start up. Also, on some systems, I have added a snap-disk or cap-tube temperature switch to the hot pipe on the collector to prevent the pump from running until a minimum temperature is available. There are also several PV-direct differential temperature controllers available that allow precise electronic control of the circulator pump (e.g., Eagle D2E1). In some cases, the solar circulator is


used for heat dissipation functions that require it to run at night occasionally. This is used, for example, to automatically cool an overheating solar storage tank when the


the stator. The stator/pump motor screws onto the pump body with a threaded ring that resembles a large O-ring union that is very easy to handle. This is the same motor attachment that they have used on their hot water re- circulator pumps for decades, so the D5solar pump motor is interchangeable with other motors from this line of Laing circulators. In some installations, we have swapped the D5solar DC motor with the E1 or the E3 AC motor to provide more pump flow when more collectors were added or when an AC control system was retrofitted. The Laing D5 is not just an ECM device; it is also


endowed with “brains” built into its integrated circuits. It features a soft start, maximum power point (MPP) tracking and an over-temperature protection shut off capability. Most models also include a selector switch to allow the user to choose a speed or a startup voltage (depending on the model). This is the most commonly used PV solar pump used in our region of northern New Mexico today.


Pumping power Figure 39-3 shows the pump curves for some of the


most common DC solar circulators. As you can see, these


occupants are on vacation. In these cases, we have used an AC to DC power supply to run the pump at night, wiring it in parallel with the PV panel so that it has two power sources (e.g., Tripp-Lite PR-7b). These articles are targeted toward residential and small


commercial buildings smaller than 10,000 square feet. The focus is on pressurized glycol/hydronic systems, since these systems can be applied in a wide variety of building geometries and orientations with few limitations. Brand names, organizations, suppliers and manufacturers are mentioned only to provide examples for illustration and discussion and do not constitute recommendation or endorsement. l


Bristol Stickney has been designing, manufacturing,


repairing and installing solar hydronic heating systems for more than 30 years. He holds a Bachelor of Science in Mechanical Engineering and is a licensed mechanical contractor in New Mexico. He is the chief technical officer for SolarLogic LLC in Santa Fe, N.M., where he is involved in development of solar heating control systems and design tools for solar heating professionals. Visit www.solarlogicllc.com for more information.


phc october 2011 www.phcnews.com


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