single pull double throw double pole 120 volt switch?

[sdowney717]

something that can mount in a standard switch box?

something that is on - off in the middle-on

or perhaps even a single pole double throw switch.?

looking to switch between 2 separate 120 volt AC power source thru 2 60 amp contactors.
the switch energizes one contactor or the other.

ok found this but is there something less expensive?
http://www.amazon.com/dp/B001PNO3P4/?tag=atomicindus08-20

ok this one is cheaper and seems better. not so many poles
http://www.amazon.com/dp/B001FRE1E8/?tag=atomicindus08-20



Actually think the 4 pole one is better as I can totally separate the circuits? Which I what I would want.
The second switch share a pole

http://www.packetradio.com/catalog/index.php?main_page=product_info&products_id=30
this one is cheaper and 4 pole

thinking this will work but why a mini, would prefer something perhaps more robust
http://cgi.ebay.com/ws/eBayISAPI.dl...f715a4c&itemid=190323485653&ff4=263602_304652

ok perhaps this one is cheap enough to play with.
http://cgi.ebay.com/4PDT-miniature-...712?pt=LH_DefaultDomain_0&hash=item5ade4c5b58

 

[Alchymist]

Need more information - are both contactor coils on the same circuit? (Meaning do they get their power from the same breaker)? 120V coils? A standard 3 way switch can select between two contactors, use a double box and one 3 way and one standard switch if you want a "power off position. The plus side is those switches are available everywhere.

 

[mrb]

there are standard lightswitches available in the configuration you want. download the catalog from leviton's site (forget trying to use their online version) and you will find it.

what is the application?

 

[sdowney717]

what I was thinking and it gets a little complex here.
It is for my power cruiser boat.

I have shore power and a marine onan generator
Selectable with a shore - off - genset rotary switch.

I am looking to add an inverter into the mix.
I was thinking I would like to run the fridge off the inverter when the motors are running.
Otherwise the genset will run all the time to keep the fridge running. Then when anchoring switch to generator and power off the inverter.

I have an electric anchor winch which is 120 volt, that I want on the inverter
The starboard side outlets and the fridge also.


The oven and range. the cabin heaters, the Cruiseair Heat pump, the electric hot water heater all will stay on genset along with port side outlets which includes the kitchen outlets.

So the idea was to create some kind of switchable circuit switching between genset and inverter when the shore power switch is set to gen set. I have 2 3 pole 120 volt 60 amp ac contactors which I can use.

The inverter will be away from the engine room and powered with #2/0 cable about 5 feet long.
The inverter is a backup really, I got a 3000 watt one because I wanted to be able to run a fridge. I dont ever care to pull 3000 watts out of this.
I plan to mount the inverter under the galley sink inside a large cabinet on the shelf.

Onan gen set is 6500 watt ac also with a dc output to charge its starting battery.
The boat has a 30 amp 3 banks 12 volt DC builtin AC 120 volt charger for the main boat batteries.
I suppose the genset can charge the batteries and the inverter runs off the batteries.

So that is where I am at.

 

[Alchymist]

Sounds like the simplest approach would be to get a contactor with normally open and normally closed contacts. Put the load(s) to be switched on the common of the contacts, run the genset to one set of contacts (N.O.), and the inverter to the N.C. contacts. Wire the coil to the output of the genset. With the genset off, the load (s) is powered by the inverter, when the switch is set to genset the load will be powered from the genset (or shore power, depending on where the genset/shore rotary is set). Not sure if this is what you want, your description is still open to interpretation on some points.

 

[sdowney717]

the idea of double contractors and the on - off - on switch os to power the contactor coil using the switch. And never have both contactors energized at the same time.

The contactors can carry the load
the switch just energizes the coils
the switch would be powered from each source, so one side of switch gets power from gen set, the other gets power from the inverter. AND never the 2 will mix.
I suppose the inverter could run the whole AC circuit panel. It is a square-d 10 breaker panel
with 2 top lugs, an isolated neutral bar and a ground bar

 

[sdowney717]

I have 2 60 amp 3 pole contactors brand new which I would rather use.
I figure that switching contactor would be pricey.

 

[Joe92GT]

The normally open/normally closed contactor combination mentioned above is the easiest way to do it. Split the loads off that you want on the inverter and wire to the common side of that contactor, let the other loads bypass the contactor.

Now to actually decide when the loads are switched is the next issue. I'd assume you want this automatic. Alchymist nailed it right on, when the Generator is running, or when there is shore power the coil will be energized on the contactor and all the loads will be off of the inverter.

The other option is industrial switches. We sell control switches for boats, ships, generators, ect. I can design a custom switch that will have all of the positions you need, and do any combination of whatever you like, aka Shore -off-Gen-Inverter-Auto,. However, these are not cheap. They also are not extemely expensive, probably in the 3-500 dollar range. I'm not so much involved with sales, thats why the rough estimage. Having a switch that can actually carry the load is also an option, so no contactors needed. However, carrying the load is completely different than breaking/making into the load, so there need to be other considerations.

 

[ishiboo]

Here's what I'd do:

Buy two relays, one 20A DPDT AC relay with a 12VDC coil ($10-20). One standard automotive relay ($2).

Connect an ignition wire to the coils of both relays, so they are energized when the engine is running. Use the 20A AC relay to control your loads. Use the automotive relay to switch the inverter's power switch.

So, when the ignition is on, the loads on the relay will automatically switch to the inverter, and the inverter will automatically turn on.

You can then add a manual control switch for the inverter using small (~18-24ga) wire and easily put it wherever you want. You could also use a double pole switch and a single pole switch to have an "auto-off-manual" switch, when on manual it would turn the inverter on depending on another switch.

This way things are done right, work well and you have 30 bucks in parts including the switches

 

[mrb]

in transfer setups, you dont want to use a DPDT relay or NO / NC contacts on one contactor. you want two seperate contactors, preferably mechanically interlocked, or electrically interlocked so when one coil is on, the coil on the other contactor cannot be energized.

 

[theoldwizard1]

something that can mount in a standard switch box?

something that is on - off in the middle-on

or perhaps even a single pole double throw switch.?

Leviton 1257

 

[sdowney717]

Been thinking some more about this and really all I want to do is switch off one circuit form the breaker panel. Simpler here is better.

The outlets, fridge and anchor winch are all on one circuit.

So how about those 4 pole standard switch like used in 3 way lighting for switching both neutral and hot?

The best thing is too switch off neutral with hot cause say you plug in shore power and the thing is mis wired.

If I went with my double contactor idea to switch the panel there is another problem. That genset has an automatic run mode. It sends a dc volt thru the wiring to sense when a load is switched on. Then it automatically starts up and runs. If I break the circuit with a contactor I loose that functionality. It is nice to have it start and stop automatically.

likely back to this type of switch can handle 15 amps 4 pole
http://www.amazon.com/dp/B001PNO3P4/?tag=atomicindus08-20

or you could take two 3 way switches mount side by side in a box. One switch switches neutral, one switch switches hot.
The handles would need to be moved in unison locked together so one handle goes up the other moves with it etc... not sure how that could be done easily. glue on a bar across the toggle?

 

[dwilliams35]

Get a 3-phase reversing contactor and pull the jumpers off the bottom side: they're already interlocked, have two coils, etc.

 

[Joe92GT]

Get a 3-phase reversing contactor and pull the jumpers off the bottom side: they're already interlocked, have two coils, etc.

I was thinking the same thing after reading MRB's response.

MRB: Why does using no/nc poles pose an issue with a transfer scheme?

 

[mrb]

I was thinking the same thing after reading MRB's response.

MRB: Why does using no/nc poles pose an issue with a transfer scheme?

i forget. there was some reason it was a no-no. same as why manual transfer switches have an off position in the middle. I dont know if its the danger of closing into a fault, or if one contact welds itself together you have one phase on each supply...i just know there was some reason you dont do it.

 

[MBfreak]

Switching loads on a single ( or threephase) NC/NO contactor is not a very good solution.
The actual interruption of the arc in an opening ac-switch takes place when the ac current passes thru zero, which may be up to some 15 ms after the contact has reached its "Open" position, The actual current interruption time depends on the character of the load ( motor, lights, etc)
So there is a very real possibility that the other supply will be closed ( which happens instantaneously open metallic contact) while the openeing contact is stil arcing. Ifyou the apply a new source on the pole to be deenergized, current transfer, and some possible unpleasent consequences, can occur between the two sources.

By using two contators that have coil/contact interlocking there is a time delay introduced on more that 25 ms, much depending o what size you use, and the timing problem is most likely be solved.

I am from Sweden, and have no idea how stuff like this is regulated in the US. But here, you would be in deep trouble if you hooked up a non approved/ non professional switch over scheme that could backfeed out on the public power grid at a malfunction. So my advise is to go to a licensed outfit, buy their stuff including the final inspection. Install yourself if you have the skills and make 100 % sure to have whatever inspected/tested/approved certificate issued and in your posession b4 using the stuff.

Ola

 

[Joe92GT]

Switching loads on a single ( or threephase) NC/NO contactor is not a very good solution.
The actual interruption of the arc in an opening ac-switch takes place when the ac current passes thru zero, which may be up to some 15 ms after the contact has reached its "Open" position, The actual current interruption time depends on the character of the load ( motor, lights, etc)
So there is a very real possibility that the other supply will be closed ( which happens instantaneously open metallic contact) while the openeing contact is stil arcing. Ifyou the apply a new source on the pole to be deenergized, current transfer, and some possible unpleasent consequences, can occur between the two sources.

By using two contators that have coil/contact interlocking there is a time delay introduced on more that 25 ms, much depending o what size you use, and the timing problem is most likely be solved.

I am from Sweden, and have no idea how stuff like this is regulated in the US. But here, you would be in deep trouble if you hooked up a non approved/ non professional switch over scheme that could backfeed out on the public power grid at a malfunction. So my advise is to go to a licensed outfit, buy their stuff including the final inspection. Install yourself if you have the skills and make 100 % sure to have whatever inspected/tested/approved certificate issued and in your posession b4 using the stuff.

Ola

Thanks for the explanation. All of the above solutions are for the poster's boat, so not much chance of back feeding, unless something really messes up when on shore-power.

For the actual grid power, we are just as regulated here.

 

[sdowney717]

yes cant really backfeed at all seeing the shore - off - gen 60 amp switch currently on the boat means the switching I am talking about takes place between boat gen set and inverter.

I like how 2 contactors are better, your explanation makes sense.

Really since I am simply switching my own isolated circuits, I dont see why I could not just switch the single hot. My wiring is not affected by plugging into shore since that switch is off when the gen side of the switch is set to on.
Is there any reason then to switch the neutral between inverter and generator?
OR, is there a special reason to switch hot and neutral when using an inverter?

 

[sdowney717]

http://www.amazon.com/dp/B001FRE1E8/?tag=atomicindus08-20

this switch looks useful, 20 amp on-off-on DPDT
I like the off middle position.
This switch is fairly cheap and it will let me switch hot and neutral. I think I might get 2 of these and setup 2 circuits switching between inverter and gen

 

[praybould]

I have a similar problem with a battery back up for my office and security system... using an inverter charger that is tied into the home's main power circuit box.

An outside backup generator that is supposed to automatically start up with a power failure - no longer does, since is senses power (from the batteries/inverter). I need to isolate the inverter when there is a power outage.

I could run 2 simple switches in parallel (one controlling the white wire and the other disconnecting the black). Wouldn't that be the simplest?

 

[Alchymist]

I have a similar problem with a battery back up for my office and security system... using an inverter charger that is tied into the home's main power circuit box.

An outside backup generator that is supposed to automatically start up with a power failure - no longer does, since is senses power (from the batteries/inverter). I need to isolate the inverter when there is a power outage.

I could run 2 simple switches in parallel (one controlling the white wire and the other disconnecting the black). Wouldn't that be the simplest?

Not the safest thing in the world. Shouldn't break the neutral without breaking the hot with a mechanical interlock between the two.

 

[sdowney717]

yes, use a DPDT switch with off in the middle so an arc does not interconnect them when you switch circuits. And they switch together. I read that with the MSW inverters they have power on the neutral and the hot, the power is split between them. If you ever ground the white neutral you will blow the internal inverter fuses. So make sure ground and neutral are never connected in any circuits or any devices you will hook up.

 

[mrb]

I have a similar problem with a battery back up for my office and security system... using an inverter charger that is tied into the home's main power circuit box.

An outside backup generator that is supposed to automatically start up with a power failure - no longer does, since is senses power (from the batteries/inverter). I need to isolate the inverter when there is a power outage.

I could run 2 simple switches in parallel (one controlling the white wire and the other disconnecting the black). Wouldn't that be the simplest?

can you post a diagram or picture of how you have this set up?