Looking for recommendations for 12v relay to control 120v circuit

Cyber2lzCyber2lz Registered Users Posts: 2
New to Solar.  I would like some recommendations for a 12v control of a 120 volt ac circuit.
I have a Midnite Classic CC and want to use Aux1 (in Diversion mode) to control a 120v relay that turns a 120v / 20 amp circuit on/off. The Classic will monitor the battery voltage and turn the relay on @ 13vdc and turn off @ 12.4vdc.
The 120V AC circuit is coming from my Magnasine inverter.
This relay only needs to turn on/off the hot wire! (Yes/No ?)  I'm no electrician!  I do computers,

Russ
http://www.cyber2lz.com/solar.htm

Comments

  • dennis461dennis461 Registered Users Posts: 95 ✭✭
    Are you switching pure sine wave, and how many amps.

    High Reliability Solid State Relays

     

    PART NUMBER: SSRL660DC50

    Camden County, NJ, USA
    19 SW285 panels
    SE5000 inverter
    grid tied
  • EstragonEstragon Registered Users Posts: 1,699 ✭✭✭✭
    Yes, the relay would normally (but not always) switch just the live 120vac (hot) wire. It's a pretty simple device, coil voltage (12v in this case) switches the load connection. It could be normally off (NO - the load circuit is open unless coil voltage closes it), or normally closed (NC - the load circuit is closed unless the coil forces it open). As I understand it though, the load and use matters.

    One factor is power needed to hold state. A mechanical relay takes power to hold "other" state (so a NC held open takes power to stop a load from running, a NO held closed takes power to run the load). As a general proposition, we don't care a lot about the current needed to keep a NO relay closed to run an opportunity load, but your use may be different.

    Another is whether the load needs or can withstand rapid switching. You usually want to avoid bouncing between open and closed states (load comes on, voltage drops, controller drops control voltage, relay opens, battery voltage recovers, apply coil voltage, relay closes, load starts .... ). As I understand it, a solid state relay would be better if you wanted a "bouncy" relay (since the switch is done at the zero crossing of the ac wave), but in less " bouncy" applications there are advantages to a mechanical relay.

    So it would help if we knew more about what you're trying to switch. Others here know far more than me about relays, but I think I know enough to know the load matters.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • Cyber2lzCyber2lz Registered Users Posts: 2
    Dennis461    Thanks a lot.  Just what I was looking for.  
    Answers to your questions  Yes, and up to 15 amps @ 120v

    Estragon       Great primer for newbs on relays.  Want NO, no load until Diversion battery limit is exceeded.
                          up to 15 amps @ 120v, Frequency of use, some times a much as three times a day !!!!

    Thank you both !!!
  • mcgivormcgivor Registered Users Posts: 1,352 ✭✭✭✭
    Solid state relays are nice but have drawbacks, as do electromechanical. Solid state have extremely low trigger current but tend to get hot if loads are high, some can fail in an unsafe mode which is undesirable. Electromechanical relays have a higher operating coil current but can be configured fail safe using a normally open contact, they do not heat up under load, but can generate reverse EMF on dropping of coil voltage, a subbing diode will prevent this from damaging the controller. Auxillary outputs on charge controllers are usually current limited, so it's important to not exceed the rated output, one method is to use a solid state relay switched by the controller to power the coil of an electromechanical contactor or relay, if the coil current is greater than the controller's output. When using the auxiliary output, its a good idea to include a time delay to the cut in and cut out values to prevent nuisance switching when voltages are close to the setpoints.
      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • Raj174Raj174 Solar Expert Posts: 495 ✭✭✭✭
    The current limit on the Classic's aux output is 200 mA, just fyi.
    12 x 300W Renogy PV, MNE175DR-TR epanel modified, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 195AH HI Power LiFePO4 no BMS, 4000W gen.
  • mike95490mike95490 Solar Expert Posts: 7,359 ✭✭✭✭
    When using a CC output to trigger something, I'd use an opto-isolator and let THAT drive a relay, no way do I want to let some accident get 240VAC into my CC control circuits.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

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  • dennis461dennis461 Registered Users Posts: 95 ✭✭
    dennis461 said:
    Are you switching pure sine wave, and how many amps.

    High Reliability Solid State Relays

     

    PART NUMBER: SSRL660DC50

    FYI, I use these to switch fans on for woodstove application.  Mine is controlling two 20" box fans for several years now.  Switches on-off several times a day.  Another application is a rather large duct fan, again cycling several times a day.  I did not need to make any changes due to inductive load, keep it simple right?

    I like the electronic relays due to the large range of working voltages.  I have used mechanical latching relays in the past (latches on or off with no holding current required.  These are getting hard to find for high current and odd coil voltages.
    Camden County, NJ, USA
    19 SW285 panels
    SE5000 inverter
    grid tied
  • mcgivormcgivor Registered Users Posts: 1,352 ✭✭✭✭
    edited December 2017 #9
    Here is an excellent relay for the purpose, I've used these extensively in building automation, interlocking lights and fans to security and fire alarm systems. They are baseless have screw terminals, rated at 25A 120V resistive, are horsepower rated 1Hp at 120V, I installed thousands of them, many to replace SSR type due to heating issues on higher current applications, never had a failure  (they were the 24VAC coil version ) the 12VDC coil draws 156 mA
    https://www.ebay.com/itm/OMRON-Enclosed-Power-Relay-6-Pin-12VDC-DPST-NO-G7L-2A-BUBJ-CB-DC12/253179840861?_trkparms=aid=222007&algo=SIM.MBE&ao=2&asc=41451&meid=122db0750c984e36bc7c371056106462&pid=100623&rk=2&rkt=6&sd=112710891410&_trksid=p2047675.c100623.m-1
      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • 2manytoyz2manytoyz Solar Expert Posts: 364 ✭✭✭
    I purchased and tested a handful of the solid state relays.  They work well for resistive loads, motors, etc.  But I wanted to control CFL lighting.  I discovered that the power pulsed through the SSR, causing the CFL to blink.  The pulse is so brief that the filament doesn't produce any visible light in an incandescent bulb.

    I've since gone to mechanical relays.  This model is inexpensive, and has worked flawlessly when I installed them 3 years ago.  12-28V coil, 20A relay @ 240VAC.

    https://www.jameco.com/z/HSINDA-953-1C12DM-R-General-Purpose-Power-Relay-SPDT-12VDC-77mA_137358.html



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