Power Control Puzzle

[Yianie123.]

I have a different situation.  I have solar panels to an inverter connected to a split ac unit and an electric hot water tank.  Both are 220v AC.  So, I want to control this system .  WITH THEM ALL TIED TOGETHER, when the aC is off the power is used to heat water in the electric hot water tank. When the ac is on, I need a relay or a method to disconnect the hot water heater because my solar panels are not enough for both. I looked for a solid state relay, normally closed, but there is none, yes this is a battery less inverter by CyboEnergy.  All help is welcomed.

[MagnetJuice]

This should work for you. It is a remote control 10 amp relay. It can be wired to be normally open or normally closed.



If 10 amps is not sufficient, you can get these with up to 30 amp relays.

The remote control uses an A23 12 volt battery.

https://www.amazon.com/ELENKER-Wireless-Control-Transmitter-Receiver/dp/B012ZR49LQ/ref=sr_1_3?dchild=1&keywords=ELENKER+DC+12V+10A+Relay&qid=1594402945&sr=8-3

I installed one of those inside my teenage boy desktop computer. Sometimes he is stubborn and doesn’t want to get off his computer late at night. In that case, he gets a warning, then a second warning. If he still doesn’t turn off his computer, I cut the power to the power supply of his computer without leaving my computer chair. I get to stay on my computer as late as I want because I am a big boy. 

Ed

[Scruff]

Those blue relays are a Chinese 10A...they're very lite duty. I'd be cautious about putting big loads on one. I'd say go for a ≥20A. Omron are not bad, Schneider, Crydom, Pheonix Contact, Panasonic, TE Connectivity.

[Scruff]

If you wired the relay coil  parallel downstream of the AC thermostat you can use the open signal to drive the immersion with a NC relay any of these would do if the current capacity is suitable.

[Yianie123.]

 Thank you for your comments but Normally closed Solid state relays do not exist.  Opi need solid state for the speed so I do not overload the inverter.

[DanG]

https://www.newark.com/sensata-crydom/a2450-b/solid-state-relay-spst-90-280v/dp/37M1639

Contact Configuration:     SPST-NC
Load Current:    50A
Operating Voltage Max:    280VAC
Relay Mounting:    Panel
Relay Terminals:    Screw
Switching Mode:    Zero Voltage Turn On
Operating Voltage Min:    24VAC
Control Voltage Min:    90VAC
Control Voltage Max:    280VAC

Item spec sheet pdf (they claim it is) : https://tinyurl.com/ycp46vg2

[Yianie123.]

Thank you.  I even called this company today and spoke to some one and they said that Normally Closed SSR DOES NOT EXIST in this size. Thank you!!!

[Scruff]

No SSR would do NC you need a mechanical component for this. 

[Scruff]

Opi need solid state for the speed so I do not overload the inverter.

Drive an NC mechanical relay with a teeny SSR so and take the coil power for the electromechanical one through the switched output of the SSR from an independent supply.

As I mentioned earlier, in the interest of keeping it simple, you could trigger the immersion isolation from your air-con thermostat controls...leave the Opi outtov it altogether.

[MagnetJuice]

Yianie123, Solid State relays come in Normally Closed.

There is a CRYDOM, assembled in Mexico and a Deltrol, a mechanical relay made in the USA and also in China.



Scruff, The link that you provided has the brands Finder, Hongfa, TE Connectivity, Phoenix and Omron.

Hongfa is made in China.

TE Connectivity is made in China

Phoenix is made in Romania

Omron is made in Indonesia

Finder is made in Italy, Spain or France





It is always good to have choices. You can choose Chinese Amps, Romanian amps, Indonesian Amps, Italian Amps, Spaniard Amps, French Amps, Mexican Amps or American Amps. 

Ed

[richhagen]

I just use simple magnetic relays for this type of stuff.  I have a stash of Potter Brumfield 20 Amp DPDT relays, and they come in larger amperages if needed and you can get them with 240VAC coils.  just hook the water heaters lines across the connections closed when no power is to the coil and hook the AC's line voltage across the connections closed when power is applied to the line.  When you power up the AC, the coil will engage and will disconnect the water heater and connect the AC unit.  If you need it to do this only when the compressor is engaged, then you would have to intercept the AC units wires to the compressor motor - which should be 240AC -  to accomplish the same.  Rich

[richhagen]

Here is a 2 cent sketch of what my thoughts were on this: 

[richhagen]

Here is an example of a relay that might work for it.  I found this one for $25 USD on Ebay here in the U.S.

[Scruff]

Oh right, there's loads of NC SSRs...I wonder why I thought there wasn't...maybe it was SPDT I was confused with.

I'm not knocking Chinese manufacturing by the way. Just those cheap teeny blue relays. They're not confidence-inspiring. I'd rather one with a datasheet and no messin'; air-con is inductive and immersions are high current. It's a meat and potatoes application.

Anyways, I've managed to burn up the contacts of a 6A Omron slim relay with 4.5A resistive from arch bridging so...errr..

I love the RF relay in boy toys idea by the way...I might steal that...

[Yianie123.]

Thanks to all. I greatly appreciate every single on of you to respond.  This is the best of humanity when perfect strangers reach out to help.  Thank you.  I think of all the solutions provided I think the simple SSR NORMALLY CLOSED.  Connected to the thermostat or AC fan power wire to open the connection to the heating element.   Think a heat sink on the relays may be required.  Thanks again !!!!