Inverter and 2 way switches.. and possible issues..??

[ywhic]

More than likely I will be using a single 2000w inverter for the entire system..

So only a single 110V line coming thru..

All the 3 way switch pictures I have seen do not show anything saying only for 220 VAC systems on them..

I really don't see how a switch powering a circuit with another switch make/breaking the circuit can cause an issue..

[Cariboocoot]

I stand corrected on the term 2 way. Three and four way switches are designed to be used on a 220 volt system and it is against code to jumper an electrical box to use the two 110 volt lines in a single fashion. The electrical box is designed to have the two circuits 180 degrees out of phase. Any thing else in not code. The usage of both sides of a electrical box on a single inverter could nullify your insurance if a fire were to occur. I have seen these
jumpers in use last for years without problems and I just helped extinguish a fire due to this non code violation. The house was a total loss. You make the decisions and you live with the consequences.

erne, this is not so.
Three way and four way switches are designed to be used on 120 VAC systems to switch lights or other low current loads on and off from multiple locations. They are definitely not designed to switch 120 VAC loads between two legs of 240 VAC or two 120 VAC sources or any other such application.

Whereas a standard 240 VAC electrical service box is designed to split 120 VAC loads between the two legs of the service, this has nothing to do with 3 way switches.

There is really no problem with feeding both L1 and L2 from the same hot of a 120 VAC inverter. The neutral line can not be overloaded in this way, nor does it present any fire hazard as there is only one power source and the only power path is from hot to neutral, regardless of whether the hot output is split to handle two sets of breakers at the service panel.

The source of the fire you experienced could only be due to improper wiring from the service panel to the load. Someone obviously connected a greater than 15 Amp load between two hot lines and one neutral. This mistake could be made on any type of service including a full 240 VAC system (which would also start a fire). When the two breaker bus bars are fed from one source each breaker should have its own hot and return neutral. Never should a neutral be shared. Regrettably some 240 VAC in some locales are allowed to be wired thus with the notion that the current will balance between the two hots. This is in my opinion a bad wiring practice, yet it is allowed by code in some areas.

Even if a load were connected to two hot lines (same source) and one neutral so that the hot had double the current capacity the neutral can only be overloaded if the load exceeds the wire rating. There had to be a confluence of mistakes to cause that fire. Powering both breaker busses off one inverter would not do it, nor would the proper use of 3-way switches. Even any normal plug-in load would not cause the problem.

Fortunately inverters fault before breakers blow; they are not as dangerous a power source as the 48kW potential of a utility service.

[waynefromnscanada]

The only problem might be with "split" kitchen type outlets or circuits that normally on grid, have three wires (+ ground) going to the receptacle. In these cases, the receptacle is supplied with two hots, one from each leg of the utility supply, but only one neutral. If you have two loads plugged into this split outlet, or connected to such a circuit, the "neutral" only carries the difference between the two loads. If the two loads are exactly equal, the neutral carries no current. It is with these split circuits supplied with two hots and only one neutral, where problems can occur when both hots are connected together in the panel, to one 110 volt supply. In this case, if two electric kettles are plugged into one split receptacle wired with only one neutral, that neutral must carry the total load of BOTH kettles, while each of the two "hot" supply wires, each protected with a 15 amp breaker, only carry the load of one kettle each.
In other words, each hot is restricted to 15 amps by it's circuit breaker or fuse, and the neutral could end up carrying 30 amps. The cure? Run TWO neutrals to the receptacle, or circuit, one for each hot on the receptacle or circuit if supplying the two hots with single phase 110 volts.
This has nothing to do with "2 way", 3 way, or 4 way switches.

[icarus]

I have never seen anyone wire outlets that way, but I suppose it could be done. Typically, a split receptical is wired with 3 wire (red/black/white) with out outlet switiched from a wall switch, the other always on. Wiring two hots from the same phase would have the potential to over load the neutral. Instead of wring it with two neutrals, simply ensure that the two hots are on different phases of the buss. That said, if you are jumping a panel (feeding it all on one phase either from the grid, genny or inverter, there is no second phase so you would be forced to run either 2 2 wires, or a 4 conductor wire. Seems like a lot of trouble.

Tony

[Cariboocoot]

Tony;

It's allowed in BC and I guess NS. Probably not in Ontario. Wasn't in NY.
It is a bad practice in my book. If the neutral line fails for whatever reason you can have your toaster send 240 VAC through the clock radio!

[waynefromnscanada]

Tony;

It's allowed in BC and I guess NS. Probably not in Ontario. Wasn't in NY.
It is a bad practice in my book. If the neutral line fails for whatever reason you can have your toaster send 240 VAC through the clock radio!

Exactly re the toaster sending 240 to the clock radio. lol
I don't know the latest code updates here, things keep changing, but some years back, when I built my place, not only was it allowed, it was mandated for kitchen counter outlets and if I hadn't done it, wouldn't have received final approval. Be interesting to know if that's still the case.

[erne]

I am not good with the written word and am afraid I have confused the matter. Let me try for the final time.

I did not say the switching was 220V it is 110V but when you use a 110V inverter you can only safely use only 1/2 of your 100 amp or 200 amp electrical box. If you jumper the mains and wire to the other 110V (which should be 180 degrees out of phase) side you are in violation of the NEC. That is when things happen in multiple switching.

In a normal a/c grid powered house a 3 way switch has a red wire, a black wire, a white wire, and a bare wire. The red wire (hot) is hooked to a circuit breaker, the black wire (hot) is hooked to another circuit breaker and are installed together (side by side) in the main box. The white (neutral) is connected to the neutral bar, and the bare (ground) to ground. This puts the red and black (hot) wires 180 degrees out of phase to each other. If a fault occurs on one while the other is running it allows the breaker to control and disconnect before the neutral is over heated. This is because the 180 degree phase difference is not using the same portion of the neutral. If the mains are run by a single 110 volt inverter and a jumper is installed to make active the side of the panel that should be 180 degrees out of phase “both breakers” are producing electricity to the neutral overloading it amp wise causing a dangerous condition. A normal plug or single light switch has only 3 wires in it. A black (hot) a white (neutral) and bare (ground). Jumping is putting your investment and well being in jepordity, and is violating the NEC.

[Ralph Day]

When originally wiring my kitchen (1983) split receptacles were required...3 wire, double pole breaker. When I went off grid and from 120/240 to 120 only I just wired the kitchen receptacles with both hots on the same leg (no other way, panel is all same phase). They are separated enough around the counters that heavy loads like toaster, microwave or whatever, are far enough apart that you don't plug them into the same receptacle, ever. They're also never used at the same time, ever. It didn't require re-thinking lifestyle, but it might for some who have lots of countertop appliances close together (and unlimited power).

Ralph

[Cariboocoot]

I am not good with the written word and am afraid I have confused the matter. Let me try for the final time.

I did not say the switching was 220V it is 110V but when you use a 110V inverter you can only safely use only 1/2 of your 100 amp or 200 amp electrical box. If you jumper the mains and wire to the other 110V (which should be 180 degrees out of phase) side you are in violation of the NEC. That is when things happen in multiple switching.

Nope. Powered from an inverter, jumpering the two legs is merely extending the size of the box. It may technically be a violation of the NEC, but it is in no way a problem or a hazard.

In a normal a/c grid powered house a 3 way switch has a red wire, a black wire, a white wire, and a bare wire. The red wire (hot) is hooked to a circuit breaker, the black wire (hot) is hooked to another circuit breaker and are installed together (side by side) in the main box. The white (neutral) is connected to the neutral bar, and the bare (ground) to ground. This puts the red and black (hot) wires 180 degrees out of phase to each other. If a fault occurs on one while the other is running it allows the breaker to control and disconnect before the neutral is over heated. This is because the 180 degree phase difference is not using the same portion of the neutral. If the mains are run by a single 110 volt inverter and a jumper is installed to make active the side of the panel that should be 180 degrees out of phase “both breakers” are producing electricity to the neutral overloading it amp wise causing a dangerous condition. A normal plug or single light switch has only 3 wires in it. A black (hot) a white (neutral) and bare (ground). Jumping is putting your investment and well being in jepordity, and is violating the NEC.

Nope. A normal 3-way switch has three terminals. One is the 'key', the other two the 'points'. The key goes to the hot wire. The two points connect to two points on another 3-way switch whose key then feeds the load with the current returning through the neutral.

What you are describing is a completely wrong way of wiring a 3-way in. NEVER should you power one load from two different legs and NEVER should a 3-way switch be connected in the manner you describe. Your circuit switches one load between two power legs and serves no purpose.

If both legs of a 240 VAC service were connected to the same load at the same time it would create a dead short across the 240 feed, and something would go up in smoke.

Feeding two wires from one leg to any load and back through a single neutral also will not overload the neutral. There has to be a load that exceeds the current capacity of the neutral line. That is the only way this can happen.

As a note to everyone and anyone, if you go to your local big lumber/hardware/electrical supply store up near the check-outs there inevitably will be a rack full of "how to" books. Get one on basic electrical wiring and read it before you undertake any such project. There's a million ways of wiring things wrong, and many of them can end up burning your house down or killing you.

[Photowhit]

Ok I was doing fine, have done a 3way switch for my dad, a quick diagram here;

http://www.homeimprovementweb.com/in...ch-option2.htm

...but now I'm worried about using my 200 Amp box by pulling my 200 Amp breaker and the 220 breakers (all on one side and using a 30 amp breaker as my main on that side of the box, guess I need to isolate it. Funny I described my plans to 2 brothers, both electricians and they didn't say anything...

Time to do some reading...

Here's a link to assorted ways of doing a 3way outlet, the link above is the way I choose to do it since it was an existing shed turned on from inside, I put switches at the doors. It is pretty convoluted(?)