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Connect 120 volt circuits to get 240 volts

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Guest

Sat Dec 29, 2018 8:45 pm   



For faster charging when not at a public charger a portable way to get 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.

https://cdn.hackaday.io/images/2004701426644738630.png

I'm wondering if the two pole relays are needed on the input side. Seems 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 connection 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 plugged in.

Am I missing something or is this design a bit over complicated? The 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 tell the relay isn't clicking because of a failure rather than simply no voltage. So this risk seems minimal.

Rick C.

- Get 6 months of free supercharging
- Tesla referral code - https://ts.la/richard11209

Tim Watts
Guest

Sat Dec 29, 2018 9:45 pm   



On 29/12/2018 19:28, gnuarm.deletethisbit_at_gmail.com wrote:
Quote:
For faster charging when not at a public charger a portable way to get 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.

https://cdn.hackaday.io/images/2004701426644738630.png

I'm wondering if the two pole relays are needed on the input side. Seems 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 connection 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 plugged in.

Am I missing something or is this design a bit over complicated? The 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 tell the relay isn't clicking because of a failure rather than simply no voltage. So this risk seems minimal.


Bearing in mind I'm English and don't know your rules (NEC etc), so I'm
replying with general principles.

I see that K1 and K2 are ensuring neither of the 240V "hots" are
energised until both 120V supplies are present.

Yes you do need K1 and K2 (reasons next):

I don't see the point of K3 though.

a) Normally a 220/240V outlet would be fed by a double pole breaker in
the house panel so if either hot is overloaded or trips the GFI, both
hots are isolated rather than leaving you with a live by unpowered
appliance.

b) (Much worse) - If you put any non trivial load over the 240V load
end, and only plug one 120V supply in, the other 120V plug is now hot
and in your hand. You have in effect an overly complicated "Jesus Cord".


I wouldn't trust K1 and K2 in this scenario though - if either sticks
closed, you have an unsafe and dangerous failure scenario.


My gut reaction is that the whole thing is a sucky hack waiting to go
wrong - bit like trying to run a 3 phase machine in the UK by tossing
your neighbours a couple of extension leads.

You'd be *much* better off with a simple step up transformer, depending
on the VA required. All of my device chargers are 100-250V (or
thereabouts) capable, so I assume you are talking about something chunky
like an electric car?

Cheers,

Tim


--
Email does not work


Guest

Sat Dec 29, 2018 9:45 pm   



On Saturday, December 29, 2018 at 2:58:35 PM UTC-5, bitrex wrote:
Quote:
On 12/29/2018 02:28 PM, gnuarm.deletethisbit_at_gmail.com wrote:
For faster charging when not at a public charger a portable way to get 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.

https://cdn.hackaday.io/images/2004701426644738630.png

It looks mad.

I'm wondering if the two pole relays are needed on the input side. Seems 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 connection 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 plugged in.

Am I missing something or is this design a bit over complicated? The 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 tell the relay isn't clicking because of a failure rather than simply no voltage.. So this risk seems minimal.

Rick C.

- Get 6 months of free supercharging
- Tesla referral code - https://ts.la/richard11209


I always appreciate a well thought out criticism.

Rick C.

+ Get 6 months of free supercharging
+ Tesla referral code - https://ts.la/richard11209

bitrex
Guest

Sat Dec 29, 2018 9:45 pm   



On 12/29/2018 02:28 PM, gnuarm.deletethisbit_at_gmail.com wrote:
Quote:
For faster charging when not at a public charger a portable way to get 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.

https://cdn.hackaday.io/images/2004701426644738630.png


It looks mad.

Quote:
I'm wondering if the two pole relays are needed on the input side. Seems 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 connection 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 plugged in.

Am I missing something or is this design a bit over complicated? The 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 tell the relay isn't clicking because of a failure rather than simply no voltage. So this risk seems minimal.

Rick C.

- Get 6 months of free supercharging
- Tesla referral code - https://ts.la/richard11209



Guest

Sat Dec 29, 2018 9:45 pm   



Connect 120 volt circuits to get 240 volts

Quote:
https://cdn.hackaday.io/images/2004701426644738630.png

It looks mad.


It looks crazy.

Are you trying to save wires from main circuit box to the garage, which are usually next to each other?
Or are you trying to skip 240V circuit breakers and exposing the 120V breakers to 220V?

Don't forget J1772 are usually 240V 30A. It will brow the 120V 15A immediately.

John Robertson
Guest

Sat Dec 29, 2018 10:45 pm   



On 2018/12/29 1:19 p.m., gnuarm.deletethisbit_at_gmail.com wrote:
Quote:
On Saturday, December 29, 2018 at 3:34:53 PM UTC-5, Tim Watts wrote:
On 29/12/2018 19:28, gnuarm.deletethisbit_at_gmail.com wrote:
For faster charging when not at a public charger a portable way to get 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.

https://cdn.hackaday.io/images/2004701426644738630.png

I'm wondering if the two pole relays are needed on the input side. Seems 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 connection 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 plugged in.

Am I missing something or is this design a bit over complicated? The 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 tell the relay isn't clicking because of a failure rather than simply no voltage. So this risk seems minimal.

Bearing in mind I'm English and don't know your rules (NEC etc), so I'm
replying with general principles.

I see that K1 and K2 are ensuring neither of the 240V "hots" are
energised until both 120V supplies are present.

Yes you do need K1 and K2 (reasons next):

You are starting with a misapprehension. I never said you could or should eliminate K1/K2. I said they can be single pole.


I don't see the point of K3 though.

Yes, I get that. K3 is the one that prevents the output from being energized if the two inputs are not providing 240 volts.


a) Normally a 220/240V outlet would be fed by a double pole breaker in
the house panel so if either hot is overloaded or trips the GFI, both
hots are isolated rather than leaving you with a live by unpowered
appliance.

So you do understand what K3 is doing???


Do you understand that relays are not circuit breakers and can fail shorted?

Quote:


b) (Much worse) - If you put any non trivial load over the 240V load
end, and only plug one 120V supply in, the other 120V plug is now hot
and in your hand. You have in effect an overly complicated "Jesus Cord".

So you do understand what K1 and K2 are for then?


I wouldn't trust K1 and K2 in this scenario though - if either sticks
closed, you have an unsafe and dangerous failure scenario.

Ah, you don't understand... K1 and K2 are in series so both have to be plugged in an active before there is a path from one to the other.


I think you are the person who is misunderstanding here - what he is
saying is if either (or any) relays stick closed (contacts welded for
example) then you have a dangerous situation.

This would have any competent electrician running out off the building.
It is too bloody dangerous and the fact that you found it on a hack web
site should be enough information to realize this is not the best idea
out there.

Quote:


My gut reaction is that the whole thing is a sucky hack waiting to go
wrong - bit like trying to run a 3 phase machine in the UK by tossing
your neighbours a couple of extension leads.


I agree!

Quote:

You'd be *much* better off with a simple step up transformer, depending
on the VA required. All of my device chargers are 100-250V (or
thereabouts) capable, so I assume you are talking about something chunky
like an electric car?

Ok, if you have reached this point, do you understand better? Care to reevaluate?


Step up transformers are safe when used as designed and should work
here, otherwise get an electrician in and have hi/her run our proper 220
wiring and outlet for you.

You want to risk your life that is your choice, but I wouldn't use that
circuit around anyone I cared about! Much like buying electrical stuff
off Amazon - electrical safety is not one of Amazon's concern. And I
take it electrical safety is not one of your concerns either.

Pretty sure your home/business insurance wouldn't cover you if something
goes wrong with that design.

John :-#(#

Quote:


Rick C.

-- Get 6 months of free supercharging
-- Tesla referral code - https://ts.la/richard11209


bitrex
Guest

Sat Dec 29, 2018 10:45 pm   



On 12/29/2018 03:40 PM, edward.ming.lee_at_gmail.com wrote:
Quote:

Connect 120 volt circuits to get 240 volts

https://cdn.hackaday.io/images/2004701426644738630.png

It looks mad.


It looks crazy.

Are you trying to save wires from main circuit box to the garage, which are usually next to each other?
Or are you trying to skip 240V circuit breakers and exposing the 120V breakers to 220V?

Don't forget J1772 are usually 240V 30A. It will brow the 120V 15A immediately.



IMO all designs that use AC line powered relays as some kind of "relay
logic" to control their own line currents are mad and disasters waiting
to happen.

I remember a number of years ago there was some guy who regularly posted
line powered relay logic designs to control stuff in his
serial-killer-looking barn at his serial-killer/cult headquarters farm
(where wearing yellow aviator sunglasses is a requirement for male heads
of household) or something. They were all mad, too


Guest

Sat Dec 29, 2018 10:45 pm   



On Saturday, December 29, 2018 at 3:34:53 PM UTC-5, Tim Watts wrote:
Quote:
On 29/12/2018 19:28, gnuarm.deletethisbit_at_gmail.com wrote:
For faster charging when not at a public charger a portable way to get 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.

https://cdn.hackaday.io/images/2004701426644738630.png

I'm wondering if the two pole relays are needed on the input side. Seems 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 connection 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 plugged in.

Am I missing something or is this design a bit over complicated? The 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 tell the relay isn't clicking because of a failure rather than simply no voltage.. So this risk seems minimal.

Bearing in mind I'm English and don't know your rules (NEC etc), so I'm
replying with general principles.

I see that K1 and K2 are ensuring neither of the 240V "hots" are
energised until both 120V supplies are present.

Yes you do need K1 and K2 (reasons next):


You are starting with a misapprehension. I never said you could or should eliminate K1/K2. I said they can be single pole.


> I don't see the point of K3 though.

Yes, I get that. K3 is the one that prevents the output from being energized if the two inputs are not providing 240 volts.


Quote:
a) Normally a 220/240V outlet would be fed by a double pole breaker in
the house panel so if either hot is overloaded or trips the GFI, both
hots are isolated rather than leaving you with a live by unpowered
appliance.


So you do understand what K3 is doing???


Quote:
b) (Much worse) - If you put any non trivial load over the 240V load
end, and only plug one 120V supply in, the other 120V plug is now hot
and in your hand. You have in effect an overly complicated "Jesus Cord".


So you do understand what K1 and K2 are for then?


Quote:
I wouldn't trust K1 and K2 in this scenario though - if either sticks
closed, you have an unsafe and dangerous failure scenario.


Ah, you don't understand... K1 and K2 are in series so both have to be plugged in an active before there is a path from one to the other.


Quote:
My gut reaction is that the whole thing is a sucky hack waiting to go
wrong - bit like trying to run a 3 phase machine in the UK by tossing
your neighbours a couple of extension leads.

You'd be *much* better off with a simple step up transformer, depending
on the VA required. All of my device chargers are 100-250V (or
thereabouts) capable, so I assume you are talking about something chunky
like an electric car?


Ok, if you have reached this point, do you understand better? Care to reevaluate?


Rick C.

-- Get 6 months of free supercharging
-- Tesla referral code - https://ts.la/richard11209


Guest

Sat Dec 29, 2018 10:45 pm   



On Saturday, December 29, 2018 at 3:40:28 PM UTC-5, edward....@gmail.com wrote:
Quote:
Connect 120 volt circuits to get 240 volts

https://cdn.hackaday.io/images/2004701426644738630.png

It looks mad.


It looks crazy.

Are you trying to save wires from main circuit box to the garage, which are usually next to each other?
Or are you trying to skip 240V circuit breakers and exposing the 120V breakers to 220V?

Don't forget J1772 are usually 240V 30A. It will brow the 120V 15A immediately.


Hmmm... auto chargers are not all J1772 and they can all be configured (all that I have seen) for a given current for each situation. Even so, I'm not using a J1772. Care to guess what I'm charging?

Rick C.

-+ Get 6 months of free supercharging
-+ Tesla referral code - https://ts.la/richard11209


Guest

Sat Dec 29, 2018 10:45 pm   



On Saturday, December 29, 2018 at 4:08:21 PM UTC-5, bitrex wrote:
Quote:
On 12/29/2018 03:40 PM, edward.ming.lee_at_gmail.com wrote:

Connect 120 volt circuits to get 240 volts

https://cdn.hackaday.io/images/2004701426644738630.png

It looks mad.


It looks crazy.

Are you trying to save wires from main circuit box to the garage, which are usually next to each other?
Or are you trying to skip 240V circuit breakers and exposing the 120V breakers to 220V?

Don't forget J1772 are usually 240V 30A. It will brow the 120V 15A immediately.



IMO all designs that use AC line powered relays as some kind of "relay
logic" to control their own line currents are mad and disasters waiting
to happen.

I remember a number of years ago there was some guy who regularly posted
line powered relay logic designs to control stuff in his
serial-killer-looking barn at his serial-killer/cult headquarters farm
(where wearing yellow aviator sunglasses is a requirement for male heads
of household) or something. They were all mad, too


So you completely fail to understand the circuit? Got it.

Rick C.

+- Get 6 months of free supercharging
+- Tesla referral code - https://ts.la/richard11209


Guest

Sat Dec 29, 2018 11:45 pm   



On Saturday, December 29, 2018 at 1:21:38 PM UTC-8, gnuarm.del...@gmail.com wrote:
Quote:
On Saturday, December 29, 2018 at 3:40:28 PM UTC-5, edward....@gmail.com wrote:
Connect 120 volt circuits to get 240 volts

https://cdn.hackaday.io/images/2004701426644738630.png

It looks mad.

I always appreciate a well thought out criticism.

It looks crazy.

Are you trying to save wires from main circuit box to the garage, which are usually next to each other?
Or are you trying to skip 240V circuit breakers and exposing the 120V breakers to 220V?

Don't forget J1772 are usually 240V 30A. It will brow the 120V 15A immediately.

Hmmm... auto chargers are not all J1772 and they can all be configured (all that I have seen) for a given current for each situation. Even so, I'm not using a J1772. Care to guess what I'm charging?


My Nissan Leaf, when i visit you? I can't use your non-standard T-charger anyway. Are you planing to down-grade your T-charger to 6KW (15A)?

The only reason i can think of is your builder is totally ignorance of EV and put the garage on far side of the main breaker. In that case, the #10 or #12 wires would not be enough.

My idiot rule to add to the NEC: A garage should be connected to the main via 4 #6 or #8 wires. 440V should be optional. I want 440V in my garage.

Tim Watts
Guest

Sat Dec 29, 2018 11:45 pm   



On 29/12/2018 21:22, gnuarm.deletethisbit_at_gmail.com wrote:
Quote:

So you completely fail to understand the circuit? Got it.


The functionality of the circuit is orthogonal to its safety. The
functionality is not in much question except with whether 1 or 2 pole
relays are needed.

It will function.

It is not safe in my opinion. Several people have told you that.



--
Email does not work

Tim Watts
Guest

Sat Dec 29, 2018 11:45 pm   



On 29/12/2018 21:19, gnuarm.deletethisbit_at_gmail.com wrote:

Quote:
Yes you do need K1 and K2 (reasons next):

You are starting with a misapprehension. I never said you could or should eliminate K1/K2. I said they can be single pole.


No misaprehension - I did skip your query about 2 pole, but I wanted to
get my general understanding down first. I haven't thought about the 2
pole aspect in detail, though it dis briefly occur...

Quote:

I don't see the point of K3 though.

Yes, I get that. K3 is the one that prevents the output from being energized if the two inputs are not providing 240 volts.


So this is an edge case where you plug into 2 120V sockets on the same
phase? Given the failure scenario is safe (zero PD) I still can't see
much point in it.

Quote:

a) Normally a 220/240V outlet would be fed by a double pole breaker in
the house panel so if either hot is overloaded or trips the GFI, both
hots are isolated rather than leaving you with a live by unpowered
appliance.

So you do understand what K3 is doing???#


Nope - well, nothing very useful as far as I can see.

Quote:


b) (Much worse) - If you put any non trivial load over the 240V load
end, and only plug one 120V supply in, the other 120V plug is now hot
and in your hand. You have in effect an overly complicated "Jesus Cord".

So you do understand what K1 and K2 are for then?


Well, yes...

Quote:


I wouldn't trust K1 and K2 in this scenario though - if either sticks
closed, you have an unsafe and dangerous failure scenario.

Ah, you don't understand... K1 and K2 are in series so both have to be plugged in an active before there is a path from one to the other.


My gut reaction is that the whole thing is a sucky hack waiting to go
wrong - bit like trying to run a 3 phase machine in the UK by tossing
your neighbours a couple of extension leads.

You'd be *much* better off with a simple step up transformer, depending
on the VA required. All of my device chargers are 100-250V (or
thereabouts) capable, so I assume you are talking about something chunky
like an electric car?

Ok, if you have reached this point, do you understand better? Care to reevaluate?


No - I understand it well enough to know it's a pretty rubbish setup,
with a non zero risk of a wrong side failure.


--
Email does not work


Guest

Sun Dec 30, 2018 12:45 am   



On Saturday, 29 December 2018 23:16:30 UTC, Tim Watts wrote:
Quote:
On 29/12/2018 23:04, edward.ming.lee_at_gmail.com wrote:
On Saturday, December 29, 2018 at 2:52:24 PM UTC-8, Tim Watts wrote:
On 29/12/2018 22:40, edward.ming.lee_at_gmail.com wrote:

My idiot rule to add to the NEC: A garage should be connected to the main via 4 #6 or #8 wires. 440V should be optional. I want 440V in my garage.


Dumb question from a Brit used to a different system:

Are you suggesting a new type of company transformer?

440V (perhaps 3 phases) is available for certain industrial users in the US. Hope it gets to residential users eventually. 240V is not enough for EV, or aluminum melter. I want to charge up my EV and melt and cast aluminum.


Interesting. Thank you.

Yes, the whole EV thing is going to open a can of worms.

In the UK, we already have 240V (well 230V officially thanks to EU
harmonisation, but it's really 240V most of the time) - and many of us
have 100A supplies with 60A being the smallest domestic supply I've seen.

Even then, a dedicated EV charging circuit is likely to be 32A (one of
our standard breaker ratings) but compared to a supercharger, it would
still be slow.

We could get 3 phase supplies (although we'd need a new breaker panel
design for that - UK domestic panels are tiny, we'd need to switch to
industrial panels more like the US ones in size and layout).

But it's all a bit mute as we're hard on the line for power generation
as it is thanks to the greens shutting coal power stations and NIMBYs
rejecting new nuclear:

http://www.gridwatch.templar.co.uk/

A few years ago in a particularly cold winter, I saw that peak at over
60GW demand for the UK.

Now we only have 50GW generating capacity assuming something doesn't go
bang unexpectedly Sad


We're stuck with 240v at anything from 40A to 100A incomers. 240v 100A is 24kW, not so good for small flat dwellers with only 40A = 9.6kW. Of course one could only use all of it to charge when there's no other draw.

To upgrade from there would require new underground feeds, 3 phases are generally not available at the incomer. And new incomer, new CU etc. And quite likely a major upgrade in the whole infrastructure.

We can surely have 240v 40A sockets without any new CU or incomer, and probably more. 100A car sockets would require demand management, which isn't hard to retrofit, it's just more equipment.


NT


Guest

Sun Dec 30, 2018 12:45 am   



On Saturday, 29 December 2018 23:04:44 UTC, edward....@gmail.com wrote:
Quote:
On Saturday, December 29, 2018 at 2:52:24 PM UTC-8, Tim Watts wrote:
On 29/12/2018 22:40, edward.ming.lee_at_gmail.com wrote:

My idiot rule to add to the NEC: A garage should be connected to the main via 4 #6 or #8 wires. 440V should be optional. I want 440V in my garage.


Dumb question from a Brit used to a different system:

Are you suggesting a new type of company transformer?

440V (perhaps 3 phases) is available for certain industrial users in the US. Hope it gets to residential users eventually. 240V is not enough for EV, or aluminum melter. I want to charge up my EV and melt and cast aluminum.


240v at 200A is 48kW. I struggle to believe that isn't enough to melt ali!


NT

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