# Simple spdt relay wiring.



## RecoveringA55hole (Sep 29, 2014)

I'm know this is very basic for the majority of the members of this forum. I'm not an electrician by all means but I work in a industrial maintenance department and they are starting to give me more and more electrical projects at work.

My latest project - We run the boilers and a few other equipment on R.O. water, we are running into the reserve tank running dry and things getting deprived of the water they need. My boss gave me a N.O. float for the tank, and a N.C solenoid valve. I have it all plumbed in and have the wires ran into the enclosure I'm using but I need to basically make that Normal Open float, normally closed? Couldn't I do that with a single pole double throw relay? If someone could break it down to me in layman's terms, I would really appreciate it.


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## RecoveringA55hole (Sep 29, 2014)

This is to bypass the RO system and turn on the city water until the RO water catches up.


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## wildleg (Apr 12, 2009)

switch leg for relay thru the float switch. terminals 11 and 14 for the circuit to the switch leg to the pump.


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## RecoveringA55hole (Sep 29, 2014)

Thank you for the advice, I'm still a little unsure. Is there anyway someone could make a wuick hand drawing? Im not trying to ask for a hand out, im just trying to understand how the circuit is wired. Thank you.


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## JRaef (Mar 23, 2009)

So the valve is closed against the city water, and you want to open it if the float switch drops down, is that right? So you want to have the NO contact of the float switch keeping the relay pulled in, and a *NC* contact in the relay feeding the solenoid valve coil. When the float drops because the tank is too low, the relay drops out and the NC contact re-closes, which energizes the valve and opens it.

So 120V hot goes to one wire of the float, the other wire goes to A1, then jumper from A1 to 11. Next wire goes from 12 to the solenoid coil. Then run the Neutral to A2 and to the other side of the solenoid coil.

Not really a great plan in that the relay will have to be energized almost all of the time, and things like that tend to fail. It's an OK temporary workaround, but I would order a float with a NC contact and wire it directly to the valve solenoid, forget the relay.


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## RecoveringA55hole (Sep 29, 2014)

Jraef, thanks for breaking it down to something I understand. When my supervisor came in this morning that was the first thing i told him, that he ordered a NO float and we need a NC float. He mentioned he did that for a reason because he wasn't sure if the float would be able to engage the coil on the solenoid? Does that make sense? It was the end ofnmy 12 hour shift so I could have mistaken what he said.


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## DriveGuru (Jul 29, 2012)

Hmmm... Are you sure that float is normally open? I might be mistaken, but I thought red ones were NC and yellow ones were NO. If it is NC wire it just like JRaef said, except take 14 to the solenoid coil. That way when the switch closes, the relay energizes and applies power to the solenoid, If you're worried about the load current of the solenoid, instead of pulling power from the junction of the float and relay coil, take the other side of that NO (11)contact to your 120v.


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## dronai (Apr 11, 2011)

I like your user name


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## RecoveringA55hole (Sep 29, 2014)

DriveGuru said:


> Hmmm... Are you sure that float is normally open? I might be mistaken, but I thought red ones were NC and yellow ones were NO. If it is NC wire it just like JRaef said, except take 14 to the solenoid coil. That way when the switch closes, the relay energizes and applies power to the solenoid, If you're worried about the load current of the solenoid, instead of pulling power from the junction of the float and relay coil, take the other side of that NO (11)contact to your 120v.


When the float is down (low waterlevel) it does not energize the coil in the solenoid. When the float is up (high water level) it energzes thr coil. Thats normally open since when its in a relaxed state its not sending power to the solenoid. I need it to do the complete opposite.


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## RecoveringA55hole (Sep 29, 2014)

Do I even have te correct solenoid valve for this operation. I need the valve to be closed (no water flow) until the level in tank is low. All this talking and thinking abojt NO and NC might of got me confused with thinking the valve is close(no flow) if its a NC contact.


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## The_Modifier (Oct 24, 2009)

RecoveringA55hole said:


> I'm *not* an electrician by all means


By what means are you an electrician?:001_huh::001_huh::001_huh:


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## JRaef (Mar 23, 2009)

dronai said:


> I like your user name


Speaking of which, did you change your sig line just because you read in the OT forum that I hate that word now??!!!

:laughing: :thumbsup:


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## dronai (Apr 11, 2011)

JRaef said:


> Speaking of which, did you change your sig line just because you read in the OT forum that I hate that word now??!!!
> 
> :laughing: :thumbsup:


 
Yep, "and by all means" belongs on the list :laughing:


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## DriveGuru (Jul 29, 2012)

Actually the float down would normally be considered it resting state, so NC if the contact is closed when the float is hanging and not in contact with fluid.


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## Jlarson (Jun 28, 2009)

This sounds like a great cross connection in the making.


Do you have proper back flow prevention on this system?


A far better option would be to top fill the reserve tank with city water via an air gap.


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## DriveGuru (Jul 29, 2012)

RecoveringA55hole said:


> When the float is down (low waterlevel) it does not energize the coil in the solenoid. When the float is up (high water level) it energzes thr coil. Thats normally open since when its in a relaxed state its not sending power to the solenoid. I need it to do the complete opposite.


JRaef told you how to wire it if the float was Normally Open. If you wired it that way and it was a normally closed float, that's exactly what would happen. I'd bet if you wired it the way I drew it for you, it will do what you want 😄


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## wendon (Sep 27, 2010)

What type of a float are you using? Why don't you just get a pump up float? They make them both ways, NC and NO.


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## RecoveringA55hole (Sep 29, 2014)

Jlarson said:


> This sounds like a great cross connection in the making.
> 
> 
> Do you have proper back flow prevention on this system?
> ...


There are two check valve up stream. One before the city water line tees into the RO line and the other on the RO line before the city water tee.


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## RecoveringA55hole (Sep 29, 2014)

Alright fellas, thanks for the help and advice.


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