3 wire 240v receptacle in garage

[DPB]

I am considering creating a control panel sort of like Kal's only a little simpler-element selector switch for two 5500W elements, one pid with a rtd sensor an ssr, possibly a timer ( I have no pumps however). I noticed that he used 4 wire and 4 wire receptacles instead of the 3 wire route. Would it still be possible for me to have the aforementioned controls in my panel with just the 3 wires and 3 wire receptacle I currently have in my garage?

If I absolutely needed to go the 4 wire route in order to create the control panel, would I need to run 4 wires from the subpanel in the garage to a new 4 wire 240 receptacle or run 4 wires from my homes main breaker to the subpanel and then to a new 4 wire receptacle? I only have 3 wires running from the main breaker to the sub panel as it stands (not sure if this even makes a difference).

Thanks.

 

[yjfun]

As long as the 3 wire receptacle is fed with black, red, and white wires then just run from your existing 3 wire receptacle in your garage into a spa panel with a gfi breaker and then feed your control panel from that.

If your receptacle is fed with a black, white, and bare copper wire then you will need to run a new circuit from your sub panel to your spa panel with 4 wires.

 

[Bernie Brewer]

As long as the 3 wire receptacle is fed with black, red, and white wires then just run from your existing 3 wire receptacle in your garage into a spa panel with a gfi breaker and then feed your control panel from that.

Then he has no ground. Bad idea.

 

[yjfun]

That's partially the reason for the gfi. This is what is required when replacing the receptacles on an old 120 volt wiring system that only has two wires with no ground. Every receptacle has to be replaced with a gfi. The repair also works with 240 volt devices.

 

[sketerbuck]

If he has a black red and white there should also be a bare ground.

 

[yjfun]

Depends on the age of the wiring. If it's new then yes he should but if it's older then it's not very likely. If it's really old then there's not a snowballs chance in hell that it's got a ground.

 

[Bernie Brewer]

That's partially the reason for the gfi. This is what is required when replacing the receptacles on an old 120 volt wiring system that only has two wires with no ground. Every receptacle has to be replaced with a gfi. The repair also works with 240 volt devices.

Agreed. But I would still rather have a ground. In a garage it shouldn't be difficult to put in some newer wiring, especially if it is not a finished garage.

 

[DPB]

Thanks for the responses.

I'll have to check the wires in the receptacle. What if it is two black wires and a white wire?

 

[Bernie Brewer]

It wouldn't be, unless it is in a conduit. What you need is two hots (black or red), a neutral, (white) and a ground (bare or green). If it is in a conduit, and if the conduit is big enough, you can pull in another conductor. And if the conduit is metal all the way back to the panel, you can use the conduit for the ground.

 

[yjfun]

I agree having a ground wire would definitely be the better route I was just pointing out that you have an alternative if rewiring is to cost prohibitive. Remember that the minute you don't respect electricity is the last minute you'll ever need it.

 

[DPB]

Had a black, red and white and wired it to the spa panel. Everything including the GFI works! Thanks.

 

[DumpsterDave]

The only reason to run a 4 wire vs 3 wire setup is if you are running both 120v and 240v components from the same feed. Since alot of people control their 240v Elements and 120v pumps from the same feed, they need that 4th wire. With a 3 wire 240v system, you have two hot feeds; Red, Black (with each hot phase off by 180deg) and a ground. With a 4 wire system, you add the White neutral wire. If you are not going to need to hook up 120v devices to the same feed, then you don't need the neutral wire.

 

[DPB]

Dumpster Dave that was one the most concise and clear answers I've received on the 3 and 4 wire question. Now if I wanted to have a control panel with a selecter knob (to switch between HLT and BK elements), pid, rtd sensor and a timer (no pumps, I don't mind turning the lever) would I need a 4 wire system? Thanks!

 

[aquenne]

I was faced with a similar challenge, what I did was 3 wire (2 hot + gnd) 240V fed thru contactors for the elements, and then a seperate 120V circuit for control&pumps. If you want pilot lights for the elements, they will need to be 240V

 

[DumpsterDave]

Dumpster Dave that was one the most concise and clear answers I've received on the 3 and 4 wire question. Now if I wanted to have a control panel with a selecter knob (to switch between HLT and BK elements), pid, rtd sensor and a timer (no pumps, I don't mind turning the lever) would I need a 4 wire system? Thanks!

I don't see why you would need a 4 wire system. All of the things you listed should be able to opperate off of 220. The only thing I am not sure of is your timer. Although I am sure you could find a 220v timer.

 

[copyright1997]

The only reason to run a 4 wire vs 3 wire setup is if you are running both 120v and 240v components from the same feed. Since alot of people control their 240v Elements and 120v pumps from the same feed, they need that 4th wire. With a 3 wire 240v system, you have two hot feeds; Red, Black (with each hot phase off by 180deg) and a ground. With a 4 wire system, you add the White neutral wire. If you are not going to need to hook up 120v devices to the same feed, then you don't need the neutral wire.

Doesn't the $50 home depot spa panel with gfi solve this issue? Wire the 3-wire to it (the spa panel) and have downstream gfi protection plus 4-wire setup?

 

[yjfun]

The spa panel only works if you start with 2 hot wires and a neutral which was used a lot for dryers before the code was changed to require a ground wire. A gfci will not create a neutral for 120 volt circuits.

 

[DumpsterDave]

Also, it should be noted, that Ground should NEVER be used as a neutral. The only place ground they should ever meet is in the breaker panel.

 

[copyright1997]

So, to confirm: P-J's 3-wire spa panel wiring schematic is providing downstream gfi protection but only for 240vAC components, correct? (I don't have it with me as I am doing this post from my phone.)

 

[DPB]

I'm not familiar with P-J's wiring schematic and am pretty much a novice when it comes to electric...hopefully someone can help. I am certain though the gfi works on my system.

 

[P-J]

From P-J...

You all need to understand the NEC code (by the date of the home electrical wiring installation) before spouting off about stuff. Also, there must be an understanding about how cables were fabricated during that time period.

'Nuff said... You all are the NEC rulers... Continue your arguments without the basic information or the reasoning behind it all ...

Some of the posters are right on the money. Others? ?? Give me a break!

 

[P-J]

Doesn't the $50 home depot spa panel with gfi solve this issue? Wire the 3-wire to it (the spa panel) and have downstream gfi protection plus 4-wire setup?

YES.!!

That is the basis of the whole theme.

This whole theme is based on the NEC code and home wiring at the time when the home was constructed and wired. The plan is absolutely within the current NEC code as long as the 'building' wiring is not modified.

 

[lschiavo]

YES.!!

That is the basis of the whole theme.

This whole theme is based on the NEC code and home wiring at the time when the home was constructed and wired. The plan is absolutely within the current NEC code as long as the 'building' wiring is not modified.

The basis is also atiquated and should only appeal to the contractor looking to save money on an installtion. The homeowner should be looking to do things to current code or better...

 

[lschiavo]

From P-J...

You all need to understand the NEC code (by the date of the home electrical wiring installation) before spouting off about stuff. Also, there must be an understanding about how cables were fabricated during that time period.

'Nuff said... You all are the NEC rulers... Continue your arguments without the basic information or the reasoning behind it all ...

Some of the posters are right on the money. Others? ?? Give me a break!

You speak of shortcuts and not current accepted standards of safety.

 

[P-J]

You speak of shortcuts and not current accepted standards of safety.

You do not have a clue.

BTW: Thanks for your repeated attacks. I used to think better of you.

 

[lschiavo]

You do not have a clue.

BTW: Thanks for your repeated attacks. I used to think better of you.

I respect your opinion. Others reading this my want an explanation or just chose to see you as a god.

How do you view my "attacks"? This forum is about giving our fellow brewers good information right? I would meet you for a beer right now. It's not personal

 

[copyright1997]

The basis is also atiquated and should only appeal to the contractor looking to save money on an installtion. The homeowner should be looking to do things to current code or better...

You speak of shortcuts and not current accepted standards of safety.

I respect your opinion. Others reading this my want an explanation or just chose to see you as a god.

How do you view my "attacks"? This forum is about giving our fellow brewers good information right? I would meet you for a beer right now. It's not personal

So where is your explanation? The above isn't providing facts.

I posted my original question/comment about using the Spa panel while flying on a plane. Now that I'm grounded (ok, bad pun) I decided to research the following things that kept rattling around my head:

Question: Since neutral and ground are bonded at the main service panel, how could doing the same thing in the SPA panel be an issue (and also since any 3-wire 240vAC appliance (like my dryer) does the same thing?)

Answer: While I'm still not perfectly clear on this, there is plenty of discussion on other forums about sub-panel installs and the neutral to ground bonding. (The NEC code has changed over time and now neutral is not to be bonded to ground unless it is a sub-panel in a building that is physically disconnected from the Mains.) Why? The main reason I've read is the concern that the ground leg not carry current under normal operating conditions, and that If you bond the neutral and ground at the sub panel, then stray currents from the neutral return could go thru the equipment ground on the electrical devices fed from this sub panel.

But then I read this: https://www.homebrewtalk.com/f170/240v-3-wire-drier-ground-neutral-confusion-287679/#post3577245 which discusses the 3-wire wiring, i.e. that it is the 2 hots and 1 neutral, and that since it is a dedicated circuit it is to code. (Dedicated implying a straight return of the neutral to the mains and then to ground.)

Reading further, if I have downstream 120vAC devices in my control panel, then the neutral between the spa panel to the control panel is carrying load. Thus the neutral potential will be elevated a very small amount above 'earth' due to the voltage drop caused by the current draw on the conductor. But, this is no different than my 50 AMP range or two 20 AMP 240vAC space heaters already existing in my circa 1992 home.

Question: Does the above summarize the pertinent points, or am I still missing things?

 

[lschiavo]

So where is your explanation? The above isn't providing facts.

I posted my original question/comment about using the Spa panel while flying on a plane. Now that I'm grounded (ok, bad pun) I decided to research the following things that kept rattling around my head:

Question: Since neutral and ground are bonded at the main service panel, how could doing the same thing in the SPA panel be an issue (and also since any 3-wire 240vAC appliance (like my dryer) does the same thing?)

Answer: While I'm still not perfectly clear on this, there is plenty of discussion on other forums about sub-panel installs and the neutral to ground bonding. (The NEC code has changed over time and now neutral is not to be bonded to ground unless it is a sub-panel in a building that is physically disconnected from the Mains.) Why? The main reason I've read is the concern that the ground leg not carry current under normal operating conditions, and that If you bond the neutral and ground at the sub panel, then stray currents from the neutral return could go thru the equipment ground on the electrical devices fed from this sub panel.

But then I read this: https://www.homebrewtalk.com/f170/240v-3-wire-drier-ground-neutral-confusion-287679/#post3577245 which discusses the 3-wire wiring, i.e. that it is the 2 hots and 1 neutral, and that since it is a dedicated circuit it is to code. (Dedicated implying a straight return of the neutral to the mains and then to ground.)

Reading further, if I have downstream 120vAC devices in my control panel, then the neutral between the spa panel to the control panel is carrying load. Thus the neutral potential will be elevated a very small amount above 'earth' due to the voltage drop caused by the current draw on the conductor. But, this is no different than my 50 AMP range or two 20 AMP 240vAC space heaters already existing in my circa 1992 home.

Question: Does the above summarize the pertinent points, or am I still missing things?

There may be some technicalities in the code that allow this. Honestly, I have not looked for them. The main issue is that an equipment ground is not intended to carry current. If you are using a 3 wire circuit to ultimately supply a 120/240V system, there is no way to avoid the ground carrying current.

Sure it works. It just does not meet current codes.

From Mike Holt:
To prevent a fire, electric shock, improper operation of circuit protection devices, as well as improper operation of sensitive equipment, the grounding of electrical systems, the bonding of equipment and circuit conductors must be done in a manner that prevents objectionable current (neutral return current) from flowing on conductive materials, electrical equipment, or on grounding and bonding paths [250.6].

This is accomplished by keeping the grounded (neutral) conductor separated from the metal parts of electrical equipment, except as required for service equipment in 250.24(B) and separately derived systems in 250.30(A)(1)] in accordance with 250.142.

Interestingly, the NEC allows the grounded-to-case connections for existing ranges, dryers, and ovens as limited in 250.140 and at meter enclosures located in accordance with 250.142(B) Ex. 2.

 

[copyright1997]

The main issue is that an equipment ground is not intended to carry current. If you are using a 3 wire circuit to ultimately supply a 120/240V system, there is no way to avoid the ground carrying current.

...

Interestingly, the NEC allows the grounded-to-case connections for existing ranges, dryers, and ovens as limited in 250.140 and at meter enclosures located in accordance with 250.142(B) Ex. 2.

Hey, I'm the electrical dummy but I think the difference here is that the 3-wire dedicated appliance circuit (prior to the 2004 NEC changes) consisted of two load lines and a neutral that returned directly to the mains. For some history, I found this quote:

A correct "3-wire" dryer installation has an INSULATED NEUTRAL and does not use the bare ground wire in NM cable as a current carrying conductor.

The only time this is not the case is when SEU cable was used.
The reason SEU was allowed is because the bare wire in SEU cable IS a neutral and IS intended to carry current.

Because this line was grounded to the appliance, and the appliance has 120vAC components, then the appliance could/would have potential > ground.
Another quote (talking about 3-wire appliance):

The wire resistance is low enough that having a neutral grounded chassis for the small 120 V loads (motor and timer typically) does not produce enough voltage drop in the wiring to be detected by people (the chassis has a voltage equal to the voltage drop in the neutral leg present).

The above is likely the reason for the NEC exceptions for existing dryers, ranges, etc. In essence, the spa panel 3-wire setup is treating the downstream (from the 3-wire dryer plug) electric brewery the same way as a dryer or range except that it is also providing GFI protection.

[As an aside I haven't yet decided on whether to piggyback on my existing dryer outlet or run a new circuit...I'm trying to decide whether 30 AMP is enough...if not I may just have a new 100 AMP sub-panel installed.]

 

[lschiavo]

Hey, I'm the electrical dummy but I think the difference here is that the 3-wire dedicated appliance circuit (prior to the 2004 NEC changes) consisted of two load lines and a neutral that returned directly to the mains. For some history, I found this quote:

Because this line was grounded to the appliance, and the appliance has 120vAC components, then the appliance could/would have potential > ground.
Another quote (talking about 3-wire appliance):

The above is likely the reason for the NEC exceptions for existing dryers, ranges, etc. In essence, the spa panel 3-wire setup is treating the downstream (from the 3-wire dryer plug) electric brewery the same way as a dryer or range except that it is also providing GFI protection.

[As an aside I haven't yet decided on whether to piggyback on my existing dryer outlet or run a new circuit...I'm trying to decide whether 30 AMP is enough...if not I may just have a new 100 AMP sub-panel installed.]

You are certainly not a "dummy". You seem to understand the code very well.

If the third wire IS considered a neutral then you are missing an equipment ground which still does not meet current code.

I feel the exception for existing installations is there more for financial than safety considerations. Imagine the uproar if suddenly all of these appliances were wired illegally and had to be re-wired.

"Existing" is the key word. Is plugging an electric brewery into an old dryer receptacle still an existing condition? I don't think many inspectors would think so. As I said before, it will work and the safety issues MAY be minimal.

I fed my brewery panel with 100A. I have all the capacity I will ever need and proper grounding.