Greetings Larry, I can think of a number of ways this may be done. Not knowing the details of the existing system configuration, if the switching needs to be manual or automatic, what (if any) cycle of the NEC is in effect at the project location, and if the PV array is ground mounted or mounted on a building I do not know what design thoughts/suggestions may be most appropriate and helpful.
If I understand the general goal and manual operation is acceptable this could be as simple as installing an appropriately rated double-throw switch (on-off-on switch) or transfer switch into the PV output circuit between the array and the charge controller. The PV output circuit would be the feed to the switch and the charge controller and pump would be the selectable loads. Some details to consider for this would include; if the double-throw switch or transfer switch is load break rated or not, where the array over current protection device(s) (OCPDs) and disconnect(s) are located, where the charge controller input disconnect is located, and if and how this configuration impacts any GFDI (Ground-Fault Detector Interrupter) and AFCI (Arc-Fault Circuit Interrupter) protection provided by the charge controller or other components in the system. Proper labeling and signage for sequence, operation, safety, and applicable NEC requirements will need to be considered as well. I installed some double-throw switches manufactured by Eaton not too long ago. I believe they were 250VDC rated. If you are interested in looking into double-throw switches you may want to call the folks at the Eaton Flex Center (1-888-329-9272) to get assistance with specifying an appropriate double-throw switch. Circuit breaker type bypass assemblies and transfer switches are available and may be less expensive than a double-throw switch, but these may not be readily available with the DC rating this project requires and most I have seen are only rated for indoor installation. I am not sure if you will be looking for a solution which will be installed indoors or outdoors, but this is a detail to consider. If you are looking for an automatic or semiautomatic solution I believe the Magnum PT-100 charge controller does have an auxiliary relay which can be triggered based on battery system voltage. I have not worked with the PT-100, but it is my understanding it needs to be networked with a Magnum remote control to use the auxiliary relay based on battery voltage. This auxiliary relay could signal an automatic transfer switch system or contactors to perform the needed switching. Also; I believe Morningstar has a DC transfer switch for use with their 600VDC TriStar charge controller... I do not know if they may offer this as a separate item, but you may want to reach out for them to inquire as well. Learning the details about the switch they use in their product and sourcing it as a separate item could provide you with a solution you custom build to suit the project. I hope you may find some of these thoughts helpful. Please let us know how you proceed and how it all works out. Best regards, ----MATT Matthew Sirum P.O. Box 1227 Greenfield, MA 01302-1227 USA phone: +1.413.773.0611 email: [email protected] ------ Original Message Below ------ [RE-wrenches] Using same PV array for water pump, battery charging Starlight Solar Power Systems larry at starlightsolar.com Thu Feb 16 14:24:44 PST 2017 Hello Wrenches, A customer has 3250 Watt PV array @ 139Voc. The PV controller is Magnum PT100. He wants to install a Grundfos SQFlex pump and be able to switch the DC from the PV controller to run the pump directly. He would like to switch midday after the battery (48V) is at a high SoC. I’m looking for a switching arrangement to do this without arcing since it will be used a few times each week. Any have a recommendation? Thank you, Larry Crutcher Starlight Solar Power Systems _______________________________________________ List sponsored by Redwood Alliance List Address: [email protected] Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/[email protected]/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org
