Two Input Power Strip? (for transfer switch between two A/C sources)

[Ron Hardin]

Is there a simple power strip that has two male plug-in cords instead of one, with a switch controlling which cord connects to the female outlets on the strip?

It's needed for quickly switching some stuff between solar power and regular house A/C mains power.

Extension cord comes from the solar panels and inverter to the power strip, and the power strip is also plugged into the A/C mains.

When there's enough sun, the idea is to throw the switch on the power strip to it takes A/C input from the solar side.

The same thing could be achieved by unplugging from A/C mains and plugging into the solar inverter, but that gives a couple seconds of no power, which is not desired.

[Evan]

Is there some reason why your solar power system is not permanently wired into your home's mains power ?

What sort of battery array do you have to store the solar power ? You make it sound as if the solar array is directly connected to the inverter...

A properly outfitted alternative energy system to provide power to your home would be wired up with a proper automatic transfer switch so that there is no chance of ever cross circuiting things by making improper connections...

There is no extension cord that I have ever seen in 30 years which would do what you describe, sure you could construct something which could accomplish what you want to do, but I don't recommend that...

~~ Evan

[hrhofmann]

A large double pole, double throw switch would be what he needs, but if he doesn't know how to do it and has to ask here, he shouldn't try to do it himself

[Dean Hoffman]

Is this a regular sized 15 amp extension cord? It wouldn't be that hard or expensive to make a junction/ switch box if so.

[Mark]

If you wire up a DPDT switch to switch quickly between two LIVE sources, you will have big problems unless the sources are phase locked....It is not easy to phase lock your inverter to the grid.

The more practical thing to do is wire a switch that has a center off position. If you don't phase lock the sources then you MUST go to the OFF position when switching from one source to the other.

Note that a UPS when it is running on batteries, when the grid power returns, it does not immediatly switch back to the grid, it first phase locks itself to the grid which can take a few seconds, and then it switches. If you don't understnad what this means, then the simplest course for you to take is to go through an OFF setting between the two sources. Unfortuntly this means you have to interpupt the power for a brief time.

If you don't do this, you can destroy the inverter. Don't ask me how I know this.

Mark

[Twayne]

Use a relay instead: Make after break type, as many poles as you need. Sunpower comes on, relay flips, disconnects from mains. Might need a zener to keep it from coming on too early.

HTH,

Twayne`

[N8N]

I'm assuming that said switch should be break-before-make otherwise bad stuff could happen. Or just use one with a center-off position in case for whatever reason you would ever want to completely disconnect the attached devices.

nate

[trader4]

I hope he has batteries in that solar system to even out the power. Otherwise, it sounds like a problem, depending on what the loads are and how sensitive they are to power variation. For example, sun goes behind a cloud, power starts to brown out.

[mkirsch1]

Yes, there is. Such devices are used in data centers to provide redundant power to computer equipment that does not have its own redundant power system.

All you need to do is search Google for "redundant power strip" and all sorts of products will come up.

They are not cheap.

[Evan]

Right... So if he can not locate one of those which has the proper rating, and create his own junction box to install it on his power strip, then he shouldn't be pondering that direction...

I still wouldn't construct such a device as it wouldn't be UL tested or approved and just sounds like it could cause trouble... At least having to manually unplug the power strip leaves no room for both sources of power to short to each other as could happen if the switch broke or the connections to it fail...

~~ Evan

[trader4]

Along those lines and as I said before, I'd be interested in hearing what the loads are. Even without a switch, unless the solar system includes a battery to even out the power, it would be unsuitable for many loads. Every time the sun goes behind a cloud there will be a brown-out condition. And batteries quickly drive up both the initial cost as well as maintenance costs, as they need to be replaced. That's why full house systems rarely have them and instead rely on the grid to stablize the power.

Like so many posts, this one seems to be hit and run, with no further info from the poster.

[jamesgangnc]

We never heard any more from the op. But I can see small loads working with a center off switch. Anything with a power supply probably has enough reserve power to handle a fraction of a second without ac power. Simpler loads like small motors, etc don't really care of the power is lost for a little bit of time.

[Ron Hardin]

I wanted what I asked for.

The load is a couple of laptops. If you interrupt the power for more than a couple of seconds, it discharges the internal batteries, and when it goes on solar power each laptop draws hugely more power because it's started recharging its battery (100w vs 30w each), which won't work on the solar array.

So I want a fast switchover, not using any noticeable internal laptop battery charge.

If such a device is ready-made I wanted to hear about it.

On a sunny day, I could run the laptops on solar power all day, which would help keep the electrical load below the low-rate load balancing minimum on the billing.

[Sjouke Burry]

See if you can remove the batteries, that would solve some problems.

[Ron Hardin]

If you remove the batteries, then the laptop can't tolerate any power interruption at all and it won't work period.

[jamesgangnc]

depends on the effort you want to put into it. A few fairly decent sized capacitors on the various power out lines from the power supply and the laptop will run without a battery for many seconds.