Connect 120 volt circuits to get 240 volts

, Can you be 100 % certain, that the polarized 120 V sockets in the US are wired correctly ? If L and N are mixed in one socket. you would get 120 V over K3 and if both are miswired 0 V.

If non-polarized sockets and plugs are used, that relay protection would really needed.

On Saturday, December 29, 2018 at 9:09:50 PM UTC-5, snipped-for-privacy@gmail.com wr ote:

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bile adapter will connect to around a dozen different types of outlets incl uding a 5-15, 120 volt 15 amp circuit? There is also a 6-20 adapter which plugs into a 240 volt, 20 amp outlet and a 6-15 which plugs into a similar

15 amp outlet? Do you think larger than 12 gauge wire is required?

Which has nothing to do with the topic of conversation. We are talking abo ut 20 amp circuits.

Rick C.

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240 volts at a home or business that doesn't have 240 volt outlets is to pi ck off two outlets that are wired to separate circuits on opposite sides of the 240 volt power. There is a commercial product for this and designs on the web. I found this schematic.

ms the issue is that without the input relays when you plug the unit into o ne outlet the path through the output relay coil can energize an exposed pl ug pin. But I don't see the need for two poles. Running the 120 volt conn ection through the input relay contacts on just one side of the output rela y coil will prevent the two inputs from being energized when only one is pl ugged in.

nly advantage I can see is that with the two pole relays a single stuck con tact won't be dangerous. In a one pole approach it can pass a dangerous vo ltage to the input plug pin. But you can hear relays working so a stuck re lay can be detected. Also it has indicators on the inputs so you can tell the relay isn't clicking because of a failure rather than simply no voltage . So this risk seems minimal.

ed.

Yep, that's a given.

Rick C.

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On Sunday, December 30, 2018 at 12:32:22 AM UTC-5, snipped-for-privacy@downunder.com w rote:

40 volts at a home or business that doesn't have 240 volt outlets is to pic k off two outlets that are wired to separate circuits on opposite sides of the 240 volt power. There is a commercial product for this and designs on the web. I found this schematic.

s the issue is that without the input relays when you plug the unit into on e outlet the path through the output relay coil can energize an exposed plu g pin. But I don't see the need for two poles. Running the 120 volt conne ction through the input relay contacts on just one side of the output relay coil will prevent the two inputs from being energized when only one is plu gged in.

ly advantage I can see is that with the two pole relays a single stuck cont act won't be dangerous. In a one pole approach it can pass a dangerous vol tage to the input plug pin. But you can hear relays working so a stuck rel ay can be detected. Also it has indicators on the inputs so you can tell t he relay isn't clicking because of a failure rather than simply no voltage. So this risk seems minimal.

That is what K3 is for. Unless you get something close to 240 that relay w on't pull in and connect the load. I'm pretty sure 120 won't do it and I'm sure 0 volts won't of either polarity.

Rick C.

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So, you want to convert a normal 120VAC 1A slow phone charger into a

2A fast phone charger by plugging it into 240 VAC ? I think there is going to be a bit of a problem doing it this way...

I have gotten 240 VAC before in a pinch by doing something like this but it's not a good way to go as was already mentioned or you might tap into a business with 3-phase and get only 208VAC

I'd just use a small step up autoformer. Or by a proper fast charger ?

Nope it's for charging an electric vehicle he wants to put like 30 amps thru that arrangement.

e main via 4 #6 or #8 wires. 440V should be optional. I want 440V in my g arage.

he US. Hope it gets to residential users eventually. 240V is not enough f or EV, or aluminum melter. I want to charge up my EV and melt and cast alu minum.

.

I'm pretty sure existing generation capacity is adequate for a very large n umber of EVs. The fast DC chargers are only needed for the relatively few cars that are on trips away from home and the small proportion of EVs that don't have home charging. In general fast DC and other day time charging w ill be a small proportion of the total EV charge load. Most of it will be done from home since that is most convenient and cheapest.

Once EVs become a significant factor in the load on the electrical grid pla ns will be in place to do two things. First there will be time control ove r charging controlled by the grid. Second, to promote participation in thi s charging time control the reduced cost of generating this power will be s hared with the EV owners.

Rick C.

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et 240 volts at a home or business that doesn't have 240 volt outlets is to pick off two outlets that are wired to separate circuits on opposite sides of the 240 volt power. There is a commercial product for this and designs on the web. I found this schematic.

Seems the issue is that without the input relays when you plug the unit int o one outlet the path through the output relay coil can energize an exposed plug pin. But I don't see the need for two poles. Running the 120 volt c onnection through the input relay contacts on just one side of the output r elay coil will prevent the two inputs from being energized when only one is plugged in.

e only advantage I can see is that with the two pole relays a single stuck contact won't be dangerous. In a one pole approach it can pass a dangerous voltage to the input plug pin. But you can hear relays working so a stuck relay can be detected. Also it has indicators on the inputs so you can te ll the relay isn't clicking because of a failure rather than simply no volt age. So this risk seems minimal.

lay won't pull in and connect the load. I'm pretty sure 120 won't do it an d I'm sure 0 volts won't of either polarity.

How do you get 30 amps from 15 or 20 amp outlets???

Rick C.

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Yes, 20 amps, I beg your pardon. More than 2.

If you have 2 x 20 A at 2 x 120 V that is 4.8 kW.

If you have 3 x 20 A at 120/208 V that is 7.2 kW.

Why do you need an autotransformer ?

Well spotted - yes it would.

A 240V GFI would have both hots and neutral running through the current transformer.

2 separate GFIs would see the full load as an imbalance.

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Right - here's a failure scenario that's quite likely:

JP1, JP2 supplies are energised and K1, K2 latch in.

JP2 supply trips at the breaker panel. I am assuming the breaker is single pole and only isolates the hot.

JP1 now backfeeds via the 240V load into JP2 energising JP2 supply's hot wire.

K3 *may* trip. But will it? What's the effective hold in voltage once it is closed - lower than the operating voltage I would imagine.

So we have found a reason for K3's existence But I'm not convinced it will provide that function reliable under every fault scenario.

Also how fast will it disconnect? In the time required by the code/regulations prevent risk of fire or shock?

Now, as it has become an isolating device for a circuit for protective reasons, it *must* meet your code as an isolating device. In my land, that's a 3mm contact gap plus other conditions.

So this setup is without a doubt quite dangerous unless it was very carefully designed and tested to meet all required regulations. Which seems doubtful.

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240 volts at a home or business that doesn't have 240 volt outlets is to pi ck off two outlets that are wired to separate circuits on opposite sides of the 240 volt power. There is a commercial product for this and designs on the web. I found this schematic.

No, as soon as JP2 power source drops the K2 drops and disconnects JP2 from the circuit. This also causes K3 to drop out no matter what since there i s no closed circuit for the current.

The only problem I've seen is that if a relay sticks, it can create a dange rous situation.

K3 will drop out if either power input is lost because the current to K3's coil is cut. But if an input is reversed the input relays still close. In this situation the initial voltage to K3 is only half and I very seriously doubt the relay will kick in. This can be verified in the specs. If the minimum drop out voltage is above the maximum voltage you will see on the i nput, this is not a problem.

Rick C.

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Not if it's being backfed via the load.

Assuming as I did that JP2's neutral remains unbroken (I've seen American panels with neutral bars, so this seems reasonable) then also any load on the 240V end will allow enough current from JP1's hot to energise K1 to JP2's neutral.

This is where K3 comes in. *If* K3 operates - and I cannot prove there is not a fault condition and a particular type of 240V load that could keep K3 energised once already closed.

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It sems to me that the first contacts prevent back-feed from the circuit when only one input is plugged in.

The third relay checks that the input are not in the same side of the two-phase feed or one plugged upside down.

Anyway, the circuit is a monstrous hack. I'd keep myself away from it. It could not be relevant here (continental EU), as the domestic feed is three-phase 3*230/400V. A standard car charging socket will have up to 32A, for 22kW charging power. The car units can be commanded by the logic in the socket unit to use less power, if all is not available.

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240 volts at a home or business that doesn't have 240 volt outlets is to p ick off two outlets that are wired to separate circuits on opposite sides o f the 240 volt power. There is a commercial product for this and designs o n the web. I found this schematic.

It would function. It would also be dangerous.

It did seem odd.

NT

Old fuseboxes can have as few as 4 circuits, with all the sockets on 2 circuits.

Sockets are mostly on 30/32A circuits. Immersion heaters don't exceed 3kW. Showers are 7-10kW. Ovens vary widely.

NT

ote:

t 240 volts at a home or business that doesn't have 240 volt outlets is to pick off two outlets that are wired to separate circuits on opposite sides of the 240 volt power. There is a commercial product for this and designs on the web. I found this schematic.

eems the issue is that without the input relays when you plug the unit into one outlet the path through the output relay coil can energize an exposed plug pin. But I don't see the need for two poles. Running the 120 volt co nnection through the input relay contacts on just one side of the output re lay coil will prevent the two inputs from being energized when only one is plugged in.

only advantage I can see is that with the two pole relays a single stuck c ontact won't be dangerous. In a one pole approach it can pass a dangerous voltage to the input plug pin. But you can hear relays working so a stuck relay can be detected. Also it has indicators on the inputs so you can tel l the relay isn't clicking because of a failure rather than simply no volta ge. So this risk seems minimal.

ome dangerous when 2 or more component failures occur. Hopefully the relays use the 3mm+ contact spacing required to be acepted as safe isolation. K3 just takes the same principle further.

ty levels of K1,2,3. No electrical equipment is free from shock risk after all. Personally I'd not want to bet on its safety, I'm not hugely confident that relay contacts wouldn't weld from carrying/switching EV charger curre nts. But to be fair I don't have the figures that the engineer or hack who designed it might have.

ven interlocks use.

that common. Thanks

microwaves have no other.

NT

K3 contacts shorting would not cause any immediate hazard.

??

NT