Electrical system - How to fail over from 110v AC to 12v DC?

JayMen

Hello, all. I'd like to use a 110V AC-to-12v DC adapter as the primary power source for my 12v pump, and I'd like to automatically switch to batteries should the utility power fail.

My question is this: What is the name of the component that will provide this automatic failover switching? I've seen it alluded to in several forum posts but I'm either searching incorrectly or it's referred to by a different name here in the U.S.A..

Any help would be greatly appreciated.

Jaymen

Tysonkb

If you used a contactor with two sets of contacts one normally open, one normally closed. Run ac power from your ac/dc adapter to the coil, assuming the contactor has an ac coil. Run your DC power from the adapter to the normally open contacts and the power from the battery to your normally closed contacts. Jumpers between the load side of both of these contacts and then to your pump. As long as there is power to the coil the normally open contacts will close. Providing power to your pump, if power fails the normally open will open and normally closed will close providing power from the battery. Probably more info than you needed

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tmaker

since the amperage is not high for your 12v pump this will do.

it's called a relay. LY2N will do.

if you need a schematic for wiring then I can help you.

dbird

There are several ways you can do this,one you can make the switch yourself.The electrical one you might have to buy and finding it could be a problem.It is done with a double solenoid so that when the power is on it is pulled down and will be connected to the 110 volts will be connected ,when then power goes off the plate goes up and connects to the 12v.You can make a pressure switch your self like the one in the photo.All you will need is two flanges ,piece of inner tyre tube and a switch that is turned off when the pressure is on it.you connect the bottom chamber to the delivery side of your air or water pump and when the pressure drops it switchs the 12v on.

BuiDoi

Naturally, there are many ways of doing what you want.. each with varying complexity and reliability..

Another way might be to have a 12V system that effectively runs from the battery, that is always floated (charged) from mains power, and thus if or when the mains fails, the system just keeps running..

The concept of using a pressure switch is practical and means that you are wasting NO power on a relay, there just for power fail.
I am assuming that there is a mains air pump and a battery air pump ..

BTW... That home made air switch. A lot of effort indeed.. do you know that most washing machines have one in them.. free of charge from old machines.. they are used to register a full water condition..
..
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gorotsuki69

easiest way is to use a UPS (uninterruptible power supply) , most of them use 7ah house alarm size batteries but you can upgrade that to a car battery which will run your 12v pump forever (well not quite

). Simply plug in an away you go, no soldering or electronics knowhow required

boss

yep. battery charger on a timer, super simple. I bought 12 gel cell 12 volt batteries for US$400 8 years ago from an off-grid guy, looking for an increase in storage. I also bought a cheap pure-sinewave inverter for proper house voltage. It's 1000 watt inverter battery AH (amp hours) aka how long the charge lasts at 1 amp usage is crazy long. As Buldoi said, you'll need to familiarize yourself with how much power you need. Power goes out here in New Mexico often but our WiFi and TV are always on, now so will our pumps. :lol:

Lot's of ways to do this. Pick one you like or are comfortable building

JayMen

Many thanks, everyone. @tmaker, thanks also for posting that product pic and name. That gives me something definite to go on.

@BuiDoi, the idea of running my system off of floated batteries intrigues me. At this time I only have the single pump -- no backup pump and no pump dedicated for air (FT gets its O2 via draining the GBs). Other than the lack of pump redundancy, do you see an issue integrating the power setup you describe into this system? In case it's needed, you can see relatively recent pictures of my system as well as the pump at viewtopic.php?f=18&t=24984&start=45. Look about midway down for the FT/GB arrangement and a picture of the pump at the bottom.

BuiDoi

..
Without going into the pros and cons of what u are doing...

So you have a basic water pump based system.. and you want to. Protect against power failure by having a DC back up ..

Your US based.. look four old washing machines.. Maytags and Speedqueen...
The water level sensor switch is normally a change-over contact...
If you look at how the sensor switch connects to the washer tub, you will see the plastic bell housing and air tube..
There is no reason why you can't fabricate a similar bell housing as a T piece. In the water line, with air in the bell and that pressurized air going to the sensor.
Thus the pump will pressurise the air chamber and the water pressure will activate the switch..
Thus , because you have two pumping systems, if the mains fails, the pressure will drop, the sensor should drop out and this can connect the DC to the BackUp - either directly or via a relay..

If the mains comes back, the water pressure will again rise and the sensor will disconnect the battery system..

I do wonder about the true value of what you are doing.. eg.. if outages are shortish, then the plants will be fine but the fush may need AIR, so would you be better just switching on an air pump? Via the same process..
..
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BuiDoi

.
And addressing the other points...

I see a small pool filter/pump and then a 12V pump and connected to a makeshift strainer box.. in the FT/ST
I did not try to read all of what you're doing but wonder about the pool pump and why you think it better to use a 12V pump as backup..

As you seem to have found, the DC pump is massively hungry for power..

I would wonder if you would be better sticking to the more efficient pool pump and use small AC-Dc. (Sine wave) inverter to switch in the batteries.. I would suspect that would be actually more efficient..

Were you to go that way, then you would need to go back to the suggestion of a mains relay that would drop out and connect the inverter or the UPS..
Ie.. just a small relay connected to the mains that is ON when house power is there, and drops out when power fails..
You would need to be confident about fabrication, as you would be mixing mains and DC which could be very dangerous..
..
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LowCarbTNPer

You could probably use a cheap solar charge controller pretty easily for battery backup, with a "wall wart" or PC power supply or whatever supplying 12V to on the solar connection. Then the load connection to your 12V equipment or inverter. It probably would be cheaper than using a relay and battery charger/tender too.

JayMen

First, I have to apologize to everyone. After looking through the answers so kindly provided and looking at my equipment, I realize I asked the wrong question. I don't need to automatically switch between 110vAC and 12vDC, I need to switch between 2 different 12vDC sources.

If I'm understanding my options correctly, this is a very basic diagram of what I think my electrical system will look like. Am I understanding this correctly or am I still off the mark?

The "mystery device" will either be gorotsuki69's suggestion of a UPS like this one:

http://www.amazon.com/DROK-Charging-110V-240V-Uninterruptible-Switchin/dp/B00EAIG17E/ref=pd_sim_23_3?ie=UTF8&refRID=09TP50DA7MSMJYRSZAQP

or it will be a small DC switching relay like what tmaker recommended:

http://www.amazon.com/wonderfullshopRelay-Omron-LY2NJ-12V-10A/dp/B00P2KFA62/ref=sr_1_1?ie=UTF8&qid=1436374516&sr=8-1&keywords=omron+LY2Nj

Again, the goal is to provide for a method that fails over to battery power in case of an electrical outage. The pump, which will be on a timer, will either be on a 15/45 cycle or, because of the actual time it takes my pump to go through the entire FT, 23/37.

I'm leaning towards the UPS if for no other reason than that I am more familiar with them, and also because the switching times (in case of power outage) are usually pretty quick. Also, this one that I'm looking at will provide for an additional charging source for the battery, including overcharge protection. Any feedback on this would be welcomed.

LowCarbTNPer

I don't know how much they cost but you can get a solar charge controller that has 2 solar inputs and hook one up to your solar panel and the other to your AC/DC converter, it may be simpler. The relay is probably the next best option. Not sure about that UPS module, I guess check your amperages and see if 10 is enough.

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