Does the NEC cover this 120 to 240 volt 'converter'

[K8MHZ]

For some reason, I don't think this is quite kosher:

Here is the product, somehow it got an ETL listing.

Where would I even begin to look for violations? It seems this came up a while ago about a similar device used on boat docks, but I don't remember the outcome.

 

[petersonra]

I have seen them too.

It has some kind of circuitry that prevents you from hooking up two hots of the same phase. I don't see any real threat to safety from it.

 

[augie47]

As long as everything remains factory cord and plug connected, I don;t think the NEC will be involved.

 

[K8MHZ]

As long as everything remains factory cord and plug connected, I don;t think the NEC will be involved.

What about breakers opening simultaneously or handle ties?

 

[K8MHZ]

I have seen them too.

It has some kind of circuitry that prevents you from hooking up two hots of the same phase. I don't see any real threat to safety from it.

After seeing the inside of a Helios 8, I would really doubt there is any such circuitry in this product.

 

[petersonra]

http://www.titancontrols.net/products/power/orion-1.aspx

?Patented safety circuit feature automatically locks out power circuit until connections and voltages are correct.
?Interlocking feature immediately disconnects all input and output power lines if one of the 110 volt power cords gets disconnected or loses power.

 

[Rick Christopherson]

I have seen them too.

It has some kind of circuitry that prevents you from hooking up two hots of the same phase. I don't see any real threat to safety from it.

Having both hots on the same phase isn't an issue, because all you would get is 0 volts between the two prongs.

The issue is if one plug gets disconnected while a load is in operation. This could result in a back fed voltage on the male plug. The circuitry prevents this back feeding condition.

 

[Rampage_Rick]

The issue is if one plug gets disconnected while a load is in operation. This could result in a back fed voltage on the male plug. The circuitry prevents this back feeding condition.

Could be as simple as a 120V relay on each input. If one input is energized it closes the circuit on the opposite hot.

There's something similar called a "Quick 220"

I'm sure such a beast is verboten in Canada ("cheater plugs" aren't allowed here either)

 

[hillbilly1]

More than likely, it's actually wired as an isolation transformer, one circuit feeds half the primary, while the second circuit feeds the second half of the primary, that way the neutrals are not paralleled on the input side, along with reducing the chances of the input cord becoming a suicide cord. A 120 volt relay wired in series powered by the respective input circuit gives further isolation. At least if I was designing something like this, that would probably be how I would do it.

 

[hurk27]

Could be as simple as a 120V relay on each input. If one input is energized it closes the circuit on the opposite hot.

Rick you having one of those nights:happyyes:

Lets call each 120 volt circuit, circuit A and circuit B

If you have a relay wired to circuit A with a contact to open circuit B, if circuit B plug gets removed from its receptacle why would the relay on circuit A open B? A is still powered? circuit B plug would be sitting there hot if this device has a 240 volt load on it.

The simple solution is a 240 volt relay to disconnect both 240 volt legs to the 240 volt receptacle.

 

[hillbilly1]

Rick you having one of those nights:happyyes:

Lets call each 120 volt circuit, circuit A and circuit B

If you have a relay wired to circuit A with a contact to open circuit B, if circuit B plug gets removed from its receptacle why would the relay on circuit A open B? A is still powered? circuit B plug would be sitting there hot if this device has a 240 volt load on it.

The simple solution is a 240 volt relay to disconnect both 240 volt legs to the 240 volt receptacle.

That's where the isolation transformer (if so equipped ) would come in play, the 240 volt load is isolated from the inputs, so a backfeed would not happen. The center tap on the secondary would be bonded to the EGC to provide a path for a ground fault. I noticed they are suggesting using a 16 ga drop cord to hit the second circuit if needed. Would make for a toasty connection if fully loaded on a 20 amp breaker. Of course I didn't notice what they have rated the maximum load on it is, or if its protected by an internal fuse or circuit breaker.

 

[hurk27]

That's where the isolation transformer (if so equipped ) would come in play, the 240 volt load is isolated from the inputs, so a backfeed would not happen. The center tap on the secondary would be bonded to the EGC to provide a path for a ground fault. I noticed they are suggesting using a 16 ga drop cord to hit the second circuit if needed. Would make for a toasty connection if fully loaded on a 20 amp breaker. Of course I didn't notice what they have rated the maximum load on it is, or if its protected by an internal fuse or circuit breaker.

The winding in the primary of the transformer would provide the back feed to the removed plug.

Think that would be worse

Or are you thinking of a dual voltage 4-wire transformer having the 120 volts from plug A connect to Hot-H1 Neutral-H2, and plug B, Hot to H4 Neutral-H3 that would isolate the input electrically but with 120 volts to either winding you would still get 120 volts out of the disconnected plug, this is because the other winding will now act as a secondary as well as the 240 volt side, the 240 volt will still pull its load from its winding, the transformer is going to have flux to each winding anytime there is a voltage on just one.

 

[hillbilly1]

The winding in the primary of the transformer would provide the back feed to the removed plug.

Think that would be worse

Or are you thinking of a dual voltage 4-wire transformer having the 120 volts from plug A connect to Hot-H1 Neutral-H2, and plug B, Hot to H3 Neutral-H4 that would isolate the input electrically but with 120 volts to either winding you would still get 120 volts out of the disconnected plug, this is because the other winding will now act as a secondary as well as the 240 volt side, the 240 volt will still pull its load from its winding, the transformer is going to have flux to each winding anytime there is a voltage on just one.

Yeah, a dual voltage 4 wire, both inputs are isolated. According to their literature, the output is automatically disconnected when either input is disconnected. But looking at the size of the unit, it does not look big enough to contain a transformer, so they are probably paralleling the neutrals, which should play havoc with any gfi's in the greenhouse it's plugged in to.

 

[n1ist]

This would work. I agree, this couldn't be fed from a GFCI.
/mike

 

[Rampage_Rick]

Rick you having one of those nights:happyyes:

Lets call each 120 volt circuit, circuit A and circuit B

If you have a relay wired to circuit A with a contact to open circuit B, if circuit B plug gets removed from its receptacle why would the relay on circuit A open B? A is still powered? circuit B plug would be sitting there hot if this device has a 240 volt load on it.

The simple solution is a 240 volt relay to disconnect both 240 volt legs to the 240 volt receptacle.

The winding in the primary of the transformer would provide the back feed to the removed plug.

There would be a similar risk using a 240V relay coil. If only one plug was connected, there would voltage at the exposed prong on the removed plug.

If you use a pair of SPST relays with each relay energizing it's own circuit, there would be some voltage at the output terminals with only one leg powered. The method I described when circuit A is powered the relay closes on circuit B, but since B isn't connected, no voltage at the output terminal. With power on circuit B the relay closes circuit A, which won't have voltage at the output terminal if circuit A isn't connected. The only way to get voltage at the output terminals is to have both circuit A and circuit B powered.