How would you build a 240v controller that can power a 9kw element?

[bcook608]

This makes even more sense when I think about the fact that I was able to boil 2 gallons of warm tap water in about 60 seconds...

Guys, I think I'm just retarded...

Each hot wire you test should be testing at 120v. That's 240v total. 120v each side.

Yeah, so I'm just dumb because my meter can only monitor one hot wire at a time because if I try to measure both, it comes back with no reading.

[Bradster68]

Sorry for the delay. This may help you troubleshoot or verify what you've done so far. Just make sure to use the appropriate gauge wire for your amperage.

[quadra]

Bcook it looks like you still have the element wired to only one hot leg, that is why you are showing 120v. So let me give you a quick and dirty explanation.... the power that the utility brings to your house is 240v split phase- what that means is the transformer you are connected to has 3 taps a center tap that is neutral relative to the two other taps.. and two "hot legs" those two taps are out of phase with each other but each produce what we see as 120v of power relative to the center neutral. On the breaker panel in your house you have two columns of breakers and each of those columns are connected to a bus bar that connects to one of the two hot legs that third incom8ng wire the neutral had a buss bar of its own inside the breaker and when you wire a 120v outlet you take a black wire from a breaker to the outlet and a white wire " common " ot "neutral" back to the panel and attach it to the neutral buss. In a modern plug you also have a bare copper ground conductor and that also goes back to the panel and is attached to a heavy copper wire that connects to a rod or a plate that is buried in the ground near your electric service entry. It is literally an Earth grounding path and is designed as an emergency path that should only be used for grounding not as a conductor and not as an alternative to the neutral buss in the panel... when you hear stories of people's water heaters and plumbing having live voltage on them this is usually the reason why.
So.. when you want 240 volt you connect to two hot legs, each of which are at 120volts..but they are out of phase so they are actually 120v each in opposite phase directions from the neutral or common tap! So when you connect between those two the voltage difference totals 240 normally inside your house 240v is carried on wire rated for the circuit and it has a white ( neutral ) and either two black or one black and one red and those two are the hot legs (120v each relative to neutral / 240v between them ) in a code compliant install there will also be that copper ground conductor as well.
At your outlet you are plugging into there are three connections the center straight up one should be you neutral and each of the two angled ones are the two hot legs, if you probe it with your multimeter set to AC volts on a setting higher than the 240 you expect to see you should see 120v between each hot leg and the neutral and 240 between the two hot legs. The three wires coming into your controller system do not have a ground and do not have a ground fault circuit interuptor so you need to be sure you can connect and disconnect them safely - both hot legs need to connect to your element to produce 240v and both hot legs need to be disconnectable for it to be safe when not running, so both legs need to run through the electromechanical relay or contactor and the main on/ off switch is what will apply power to the ear coil- but! You also want your emergency stop switch on that coil control circuit... it is really just another switch, but it is a highly visible one.
After the relay but before the element you want to install the SSR in one of the legs, it is also a switch, but it will be controlled by the DSPR1 and the electricity will only flow between the two hot legs when it closes the circuit to heat up or maintain temperature based on what youu have told it to do and the input it receives from the thermoprobe.
Easy right!?

If you are showing 120v at your element right now one of your element legs is neutral not hot.
Remember, neutral is not the same as ground... it is a direct connection to the transformer out on the street! Do not use ground and neutral interchangeably neutral is bonded to ground at the breaker box in a very specific way and is intended to be an exclusive dedicated most direct path for current from that circuit and that circuit only back to the panel.
Do not bond your metallic enclosure or the ground lug on your element to neutral, it is not a safety ground and if a short occurred could allow your system to appear to be fine until you are electrocuted.
I would look at Ben's system above as an example, that big heatsink is going to keep his SSR nice and cool without the need for active fan cooling.
Make sure you are using the most direct wiring, with properly sized stranded conductors, properly sized relays and bus bars will make things go easier.

Good luck and post up your progress and questions.

[quadra]

Darn, sorry that is so hard to read... I am hunting and pecking on a tablet here and fat fingerings everything.

[bcook608]

Bcook it looks like you still have the element wired to only one hot leg, that is why you are showing 120v. So let me give you a quick and dirty explanation.... the power that the utility brings to your house is 240v split phase- what that means is the transformer you are connected to has 3 taps a center tap that is neutral relative to the two other taps.. and two "hot legs" those two taps are out of phase with each other but each produce what we see as 120v of power relative to the center neutral. On the breaker panel in your house you have two columns of breakers and each of those columns are connected to a bus bar that connects to one of the two hot legs that third incom8ng wire the neutral had a buss bar of its own inside the breaker and when you wire a 120v outlet you take a black wire from a breaker to the outlet and a white wire " common " ot "neutral" back to the panel and attach it to the neutral buss. In a modern plug you also have a bare copper ground conductor and that also goes back to the panel and is attached to a heavy copper wire that connects to a rod or a plate that is buried in the ground near your electric service entry. It is literally an Earth grounding path and is designed as an emergency path that should only be used for grounding not as a conductor and not as an alternative to the neutral buss in the panel... when you hear stories of people's water heaters and plumbing having live voltage on them this is usually the reason why.
So.. when you want 240 volt you connect to two hot legs, each of which are at 120volts..but they are out of phase so they are actually 120v each in opposite phase directions from the neutral or common tap! So when you connect between those two the voltage difference totals 240 normally inside your house 240v is carried on wire rated for the circuit and it has a white ( neutral ) and either two black or one black and one red and those two are the hot legs (120v each relative to neutral / 240v between them ) in a code compliant install there will also be that copper ground conductor as well.
At your outlet you are plugging into there are three connections the center straight up one should be you neutral and each of the two angled ones are the two hot legs, if you probe it with your multimeter set to AC volts on a setting higher than the 240 you expect to see you should see 120v between each hot leg and the neutral and 240 between the two hot legs. The three wires coming into your controller system do not have a ground and do not have a ground fault circuit interuptor so you need to be sure you can connect and disconnect them safely - both hot legs need to connect to your element to produce 240v and both hot legs need to be disconnectable for it to be safe when not running, so both legs need to run through the electromechanical relay or contactor and the main on/ off switch is what will apply power to the ear coil- but! You also want your emergency stop switch on that coil control circuit... it is really just another switch, but it is a highly visible one.
After the relay but before the element you want to install the SSR in one of the legs, it is also a switch, but it will be controlled by the DSPR1 and the electricity will only flow between the two hot legs when it closes the circuit to heat up or maintain temperature based on what youu have told it to do and the input it receives from the thermoprobe.
Easy right!?

If you are showing 120v at your element right now one of your element legs is neutral not hot.
Remember, neutral is not the same as ground... it is a direct connection to the transformer out on the street! Do not use ground and neutral interchangeably neutral is bonded to ground at the breaker box in a very specific way and is intended to be an exclusive dedicated most direct path for current from that circuit and that circuit only back to the panel.
Do not bond your metallic enclosure or the ground lug on your element to neutral, it is not a safety ground and if a short occurred could allow your system to appear to be fine until you are electrocuted.
I would look at Ben's system above as an example, that big heatsink is going to keep his SSR nice and cool without the need for active fan cooling.
Make sure you are using the most direct wiring, with properly sized stranded conductors, properly sized relays and bus bars will make things go easier.

Good luck and post up your progress and questions.

So I took some of the advice on this thread and the other and eliminated the terminal busses. This is what it looks like now:

Here's what you're looking at:

Power comes in on the left.
One hot goes to the left inlet of the electromagnetic relay with a jumper to the coil's left activation terminal.
The other hot goes to the right inlet of the electromagnetic relay with a jumper to a switch (utilizing only 1 pole) then to the coil's right activation terminal.

When the power to the coil is activated, the relay will close and allow the power to pass.

The left output terminal goes to the SSR 1 terminal along with the positive wires from the 120v accessories. That wire then exits the SSR 2 terminal and is connected to the heater outlet.

The right output terminal connects directly to the heater outlet.

The neutral (white for this controller) is connected directly to the heater outlet with a jumper for the 120v accessories.

I'm about to plug this in and see if it works... If not, I'm going to table this build and make a simple SCR-based controller and say to hell with it.

[bcook608]

And this is what I'm getting for a reading...

Is this because the loop for the meter is only on one run of the hot? Or is something messed up?

This is what it reads under max load. 37.73A is close to the 41A that I figured for the setup so I don't know what to make of it...

[bcook608]

According to my math, 9000w ÷ 240v = 37.5A

Im getting 9000w ÷ 37.73A = 238.53v

Would it be correct to say that the second run of hot would be supplying the other 4500w @ 120v in addition to the wattage that I'm measuring totalling roughly 9000w @240v?

Because if it were truly only getting 120v, I should only be seeing 2250w

And if that's all true, I'm getting roughly 9,055 watts. Considering I can boil 2 gallons of tap water in under 2 minutes, I'd say we're there. I'll just have to figure out how to accurately measure the wattage or switch to a simpler ammeter but a 50a ammeter is around $75 so I might just say screw it and run off the DSPR1 readout as a percentage to mark my target power.

[Yummyrum]

The neutral (white for this controller) is connected directly to the heater outlet with a jumper for the 120v accessories.

This sounds wrong . You don’t need Neutral to the heater .
This is the essential wiring that needs to be done .
Note there is no need anywhere to use the nuetral .
The whole thing runs off the two Lines( Hots )

( You could run the 240v to the DSPR1 from the switched side of the Contactor if you wanted )

What does concern me though , is that 3 pin plug doesn’t have an Earth on it . So how you Ground everything is a worry .

[shadylane]

I don't understand why the input green wire is connected to the relay.
That just ain't right.

Let's start at the beginning.
Have you got a pic of the plug wiring.

[bcook608]

The neutral (white for this controller) is connected directly to the heater outlet with a jumper for the 120v accessories.

This sounds wrong . You don’t need Neutral to the heater .
This is the essential wiring that needs to be done .21DEBB0B-28CB-4FEB-916F-7B2E3A0DCBA0.jpeg

So then where would the neutral go? I have 3 wires coming In via a 10-50p plug. Should I just disconnect the neutral from the element cord and only use the neutrals to connect to the 120v accessories?

[Yummyrum]

The neutral (white for this controller) is connected directly to the heater outlet with a jumper for the 120v accessories.

This sounds wrong . You don’t need Neutral to the heater .
This is the essential wiring that needs to be done .21DEBB0B-28CB-4FEB-916F-7B2E3A0DCBA0.jpeg

So then where would the neutral go? I have 3 wires coming In via a 10-50p plug. Should I just disconnect the neutral from the element cord and only use the neutrals to connect to the 120v accessories?

Terminate it in the control box for running your 120V accessory's if you need to . It doesn’t need to go to the element at all .

I have to agree with Shady , that green sounds wrong for a Hot wire .Is it Green or Blue …. It looks blue to me .

[bcook608]

I don't understand why the input green wire is connected to the relay.
That just ain't right.

Let's start at the beginning.
Have you got a pic of the plug wiring.

For the wiring, white=green. I wired up 5 plugs all this way and I don't really want to wrestle with 6ga wire again just to switch it around.

Here are the plugs.


Male:

Female:

They're wired so like colors connect at every junction.

[bcook608]

The neutral (white for this controller) is connected directly to the heater outlet with a jumper for the 120v accessories.

This sounds wrong . You don’t need Neutral to the heater .
This is the essential wiring that needs to be done .21DEBB0B-28CB-4FEB-916F-7B2E3A0DCBA0.jpeg

So then where would the neutral go? I have 3 wires coming In via a 10-50p plug. Should I just disconnect the neutral from the element cord and only use the neutrals to connect to the 120v accessories?

Terminate it in the control box . It doesn’t need to go to the element at all .

OK, I'll have to wire it up that way tomorrow and let you guys know how it goes.

[Salt Must Flow]

bcook608 I don't think that digital volt/amp meter will be useful except for when the element is fired at 100% power. When the controller is set lower than 100% power then the volt/amp meter will flicker as power is being pulsed on & off to the element.

[shadylane]

So then where would the neutral go? I have 3 wires coming In via a 10-50p plug.

The green wire is used for the ground and neutral.
The other 2 wires are hot wires.

[Windy City]

You do not have a neutral at a three prong 240 volt outlet
A three prong 240 volt outlet has two hots and a ground
To have a neutral at a 240 volt outlet you need four prong’s
2- line(hot) 1- neutral and 1- ground
The ground prong on a three prong plug/outlet is where you have your white wire
You are using ground as neutral DO NOT DO THIS you or someone in your home could get hurt
Also green color is designated as ground.

Edit posted same time as Shady

[ecir54]

bcook did i read earlier your dont have a multimeter. If so stop what you are doing till you get one then check that you have 240v at your plug before going forward.

All the pushback here about safety yet none in his two threads, scary shit

[shadylane]

You do not have a neutral at a three prong 240 volt outlet
A three prong 240 volt outlet has two hots and a ground
To have a neutral at a 240 volt outlet you need four prong’s

That's true, a 4 wire receptacle is needed to meet the modern standards.
But many older houses use the same wire for the neutral and ground.
Not saying it's right, but that's the way it is.

[BoilerMaker]

So I took some of the advice on this thread and the other and eliminated the terminal busses. This is what it looks like now:



Here's what you're looking at:

Power comes in on the left.
One hot goes to the left inlet of the electromagnetic relay with a jumper to the coil's left activation terminal.
The other hot goes to the right inlet of the electromagnetic relay with a jumper to a switch (utilizing only 1 pole) then to the coil's right activation terminal.

When the power to the coil is activated, the relay will close and allow the power to pass.

The left output terminal goes to the SSR 1 terminal along with the positive wires from the 120v accessories. That wire then exits the SSR 2 terminal and is connected to the heater outlet.

The right output terminal connects directly to the heater outlet.

The neutral (white for this controller) is connected directly to the heater outlet with a jumper for the 120v accessories.

I'm about to plug this in and see if it works... If not, I'm going to table this build and make a simple SCR-based controller and say to hell with it.

I noticed the hot wire on left (green 6 AWG) is spliced to a much smaller wire before going to the relay and SSR. Perhaps double check the size and be sure the splices are really good.

(edit: maybe a mod can fix the photo, it didn't quote as expected...)

[Yummyrum]

Glad we got that sorted .
So it’s a designated Ground (Earth) lead ….not a Neutral.

Glad to hear that . Was confused as to why an appliance would not have a ground .

OK so in that case , you do need to route that wire to the boiler and use it as a Ground connection .

I agree that the ground should not be treated as a Nutral .

I know you have miss wired several plugs but I would strongly suggest you rewire them and follow proper colour codes. Only use Green as Ground .

You mentioned that you want to run some accessory's off 120v . I don’t think thats a good idea. Especially if you are going to try and use the Ground as a Nuetral .
Surely any Accessories can be purchases to operate off the 240v rails you have .

EDIT : after further dialog with Quadra (further down) , it appears that this 3Wire plug system is an old out dated system that did indeed have 2 Hots and a Neutral with no Ground and is totally unsafe to use for running a still .

The above diagram is correct to use on a 4 wire System that has 2 Hots , a Neutral and a Ground (Earth ) connection .

[RC Al]

Just to throw some water on the fire after its gotten away...
That 3 loop element could easily by hooked up with 2 switched loops and a much smaller ssr on the third.

But wheres the fun in that right? (Admittedly way harder to wire at the element end, it's pretty tight in those cups)
50amps... I wish lols

[Yummyrum]

And this is what I'm getting for a reading...

Is this because the loop for the meter is only on one run of the hot? Or is something messed up?

This is what it reads under max load. 37.73A is close to the 41A that I figured for the setup so I don't know what to make of it...

I think you have the Voltage input to the meter wired between one live and Ground ( what you thought was Nuetral)
So yes it will read 120ish volts .
The current reading is correct. So it appears that you have the wiring correct as regards the Contactor , SSR and element ( although the colour codes you use suck )

So your meter is just giving you a fucked up power reading because you have the voltage wires wrong .

Hook the voltmeter wires up to the 240v connections ( the switched output from the Contactor .)

[quadra]

Windy and shady he is in an older house this is an old 10-50p hookup and that is 2x hot and neutral - not ground.
Bcook, can you see why standardized wire colour conventions are used now?
First and most important point is that you can not use that 10g wire as pigtails..it does not have enough copper to handle the power you intend to run through it, it will get very fucking hot and cook off its insulation or melt and short out.... not a maybe.. it is not suitable period. The minimum wire size you can use is 6 anywhere in the element power path.
Now... let's see what you have done to connect those three wires to the element because one of your hot legs is not where it belongs. As has been mentioned there is no reason for the neutral to leave the control box, since you have nothing that requires 120v.
Also can you post the part # of the element? If it is the DN40 and has three elements I bet I know what you are doing wrong... do the electric connection on the back of the element have bus bars that connect the six terminals into two groups of three? .... did you connect your neutral to one of those and you line ( both..lines??? ) to the other group of three?

If that is the case, stop using it.
Is there any chance you are in the old city section of Philly? They are one of the few places left in the US that still has actual old style two phase with a 90 degree phase angle difference... that results in 125v to neutral ( as shown in your picture above ) and a maximum of 175 volts phase to phase.
If you run the system wire phase to phase it will pull 51.42Amps

There is a work around but I will not go into it at this point until we know what you are dealing with.
You really should go drop 15 or 20 dollars on a simple multimeter at hazard fraught or Homer depot.

[Yummyrum]

Quadra , you seem go know your stuff . So assuming that it is a Neutral , not a Ground which seems really weird , was this connection still used to ground an appliance ?

[quadra]

Also... if both of your hot legs are connected to a common terminal at the element the ssr and DSPR are completely bypassed and not actually doing anything that will switch or control the element. If that is the case you have one leg that is running continuously when the relay is closed.

[quadra]

Quadra , you seem go know your stuff . So assuming that it is a Neutral , not a Ground which seems really weird , was this connection still used to ground an appliance ?

No, it predates the modern code and is one of those archaic things that some jurisdictions allow to continue.. sort of like knob and tube wireing in some old houses or that rural 240 to earth return you see in rural areas of the ÙS and Australia.
It was practical in its day as many appliances like stoves and dryers had lamps , clocks and 2 prong outlets that were 120v.

[quadra]

And appliances like that were the reason the modern safety ground became the norm... I just read that in 1947 laundry appliances in New construction required a ground, and in the late 1960s the three prong plug was only mandated in outdoor, basement and a few other locations residentially although UL had started requiring three prong plugs on appliances. It was not until 1971 that the National Electric Code mandated three prong outlets and all residential outlets included Earth ground. It is still not unusual to find this type of outlet in garages where a previous owner had a hookup for a welder.
The 10 50p receptacle has 3 flat blade slots, not the two flat blade slots plus a D or O shaped slot that typically is the Earth ground in North America.

[Yummyrum]

Thanks Quadra.
So is it acceptable to use the Neutral as a Ground in this case ?
I’m getting the innuendoes from Shady that perhaps it done …. Although not technically correct .

Or , is there an accepted alternative to Grounding appliances …. In this case a still , so that in the unlikely case that there may be electrical leakage from one of the live wires to the exposed metal ( say the element develops a leak and the boiler and still become live ) that could end in electric shock or electrocution , the user is safe .

EG , a seperate Ground wire that connects the Still to say , the copper water pipes in the house ( Which usually are connected to Ground )

It would be really important to the forum if we could get an affirmative solution on what to do to make stills safe where folk are using these older three pin plugs .

[quadra]

Thanks Quadra.
So is it acceptable to use the Neutral as a Ground in this case ?

Or , is there an accepted alternative to Grounding appliances …. In this case a still , so that in the unlikely case that there may be electrical leakage from one of the live wires to the exposed metal ( the boiler and still) that could end in electric shock or electrocution , the user is safe .

EG , a seperate Ground wire that connects the Still to say , the copper water pipes in the house ( Which usually are connected to Ground )

Haha.. uhm, no! There are already enough things wrong with this project but that would be really tempting the angry pixies.

Bcook... disregard all my meanderings about Philly etc. I just noticed your post with the amperage calculation and yes, you can only do that with 240v of potential... however what I said about the element still applies - disconnect the neutral from the element and terminate it properly inside the control box ( cut ,wire nut, and generous electrical tape to secure the nut to the wire ) and then connect each hot leg to each side of the element. Y9u need the power wires to the display connected to each hot leg ( not neutral ) You will now show the correct voltage and amperage on your display. Then turn it off and replace all the undersized splice wires before you burn your controller and house down
Keep in mind that you are running a lot of current through an ungrounded system, this Is a choice that puts you at avoidable risk. Make friends with a sparky and see about adding a proper 240 grounded outlet . It will cost way less than your still and may save your life. If you were to accidentally dry fire and warp/ short your element to the kettle it could be energized because there is no safety ground... if your element electrical somehow became wet... if your dog or a mouse chewed on wires.... you get the idea? There is a reason the NEC does not allow these type of hookups anymore. Never run this on damp ground or concrete or near any potential ground paths.

[Yummyrum]

Keep in mind that you are running a lot of current through an ungrounded system, this Is a choice that puts you at avoidable risk. Make friends with a sparky and see about adding a proper 240 grounded outlet . It will cost way less than your still and may save your life. If you were to accidentally dry fire and warp/ short your element to the kettle it could be energized because there is no safety ground... if your element electrical somehow became wet... if your dog or a mouse chewed on wires.... you get the idea? There is a reason the NEC does not allow these type of hookups anymore. Never run this on damp ground or concrete or near any potential ground paths.

OK this is good info Quadra .

This is the point I was hoping we could clear up .
It seems the bottom line is that unless a Sparkie runs a seperate Ground wire to the 3pin outlet and upgrades it to a 4 pin system , then bcook will effectively be running an unsafe still that potentially could become lethal .

Probably not the news bcook wanted to hear . But its better to be aware .