Subpanel: Multiple outlets on a Single 240v circuit?

[sparkjumper]

5 amps per outlet is news to me bro,I've been running 2 1K's on a 20A 120V receptacle wired for 240 for some years now,thats close to 10A.The third 1k plugs into the other 120V receptacle.I have 2 120V receptacles in a 4 by 4 inch sq metal box.

 

[Schwarzenbart]

Can 2 1000W HPS Ballasts (~20A load) can be plugged into a single duplex 240V 20A Outlet Connected with 12/3 to a 30A Main line?

 

[rives]

Can 2 1000W HPS Ballasts (~20A load) can be plugged into a single duplex 240V 20A Outlet Connected with 12/3 to a 30A Main line?

No, you cannot. The circuit breaker needs to either match or be rated for less current than any downstream device that it is supposed to protect, otherwise the downstream device can burn up in order to keep from tripping the breaker. Bassackwards.

In this case, you have a 20a receptacle and 20a wiring, so the maximum breaker size that you can use is 20a. Also, bear in mind that you are only allowed to draw 80% of the breaker rating for continuous loads (anything over 3 hours in duration), so you are limited to 16a continuous draw on a 20a breaker.

 

[Schwarzenbart]

No, you cannot. The circuit breaker needs to either match or be rated for less current than any downstream device that it is supposed to protect, otherwise the downstream device can burn up in order to keep from tripping the breaker. Bassackwards.

In this case, you have a 20a receptacle and 20a wiring, so the maximum breaker size that you can use is 20a. Also, bear in mind that you are only allowed to draw 80% of the breaker rating for continuous loads (anything over 3 hours in duration), so you are limited to 16a continuous draw on a 20a breaker.

Roger that.

The building is knob and tube with the disconnect, meter, and fusebox all separate boxes.

After checking against this forum and some NEC, Mike Holt, and other sources, I drafted my improvement system a couple of times and speced out the materials. I went and bought the wire and boxes and I had already stripped out and replaced all the wiring in my unit that was 12g soldered to 14g (old knob and tube is stupid) with proper 12g wire and new outlets and put in GFIs in the kitchen and bathroom.

The improvement was I disconnected the power and then disconnected the tar and paper insulated 12g from the meter to the old fusebox and I did a new run of 10/3 straight from the meter to a new breaker panel with a 30A dual pole for line and 30A dual pole for load, and two tandem 15A load breakers.

From the 30A load breaker I wired a sentinel 8 light controller which cannot have more than 2 ballasts plugged in unless it has the full 50A,

From one tandem breaker I wired a single duplex outlet with the jumper snipped which is for the trigger cord and the fans.

From the other tandem breaker I did a new run back to the old fusebox which has the old wiring.

I grounded the breaker box as I am using it as the main panel for the whole house now, but I left the old fusebox in the ungrounded state I found it because it is a subpanel now.

Everywhere says don't ground the subpanel but ground the main because it will energize the box.

I finally got an electrician out to look at it and tell me if it was right and safe and he opened up the boxes I wired up checked the gauges and plugged in his tester and then asked me if I was an electrician.

I told him No and that I needed his opinion even if he wouldn't put his name on it and he said it was to code and safe as long as I don't plug in more than 4 ballasts. He then told me to let him know when we want to actually upgrade the whole place, took the 100 bucks cash, got back into his truck and left. My meter is clocking the increase and the company has already increased my bill but hasn't come knocking or anything so I think I am good. What do you think?

 

[Schwarzenbart]

"which cannot have more than 2 ballasts plugged in" should read "which cannot have more than 4 ballasts plugged in" and I can't figure out how to edit

 

[rives]

Most of it sounds good. However....

Regarding the Sentinel 8 controller, the information that I've found is for a Sentinel BLC-8. It is meant to be fed with a 20a circuit, not 30a. It has (4) 20a duplex receptacles, so the MAXIMUM circuit that can feed it is 20a. I'm not sure if this is the same controller that you have, but it doesn't really matter - if it has either 15a or 20a receptacles, then it can only be safely fed with a 20a circuit unless there is further fuse protection provided inside the controller, breaking the circuit protection down from the 30a-50a feed. I haven't seen any controllers that provide this downstream protection.

You, and apparently your electrician, are a little confused about grounding the sub. The sub should absolutely be grounded - that is what is going to make the breakers trip or the fuses blow if a hot conductor inadvertently comes into contact with the enclosure. Grounding is your first line of defense against an electrical fire.

What you do not want to do is "bond" the neutral buss to the grounded sub enclosure. At the main panel, the neutral buss typically has either a jumper from the box to the buss or an extra-long screw (usually anodized green) that will go clear through the buss and into the sheet metal behind it. At the sub panel, that screw is left out or the jumper left disconnected, thereby isolating the neutral buss from the enclosure. The only place that the neutrals and ground should be bonded together is at the main - if the sub is also bonded, you can get "ground loops" which can electrify your enclosure (usually at a pretty low voltage), cause a terrible hum on stereo equipment, and raise hell with electronics in general.

Below is a drawing of how the neutrals are bonded at the main and floated at the sub.

 

[Jhhnn]

Well said, rives. If the neutral is bonded to the subpanel then an open neutral between it and the main panel can allow seemingly normal operation at 120v thru the ground when it shouldn't.

Similarly, the subpanel must have an earth ground only back at the main panel.

 

[rives]

Similarly, the subpanel must have an earth ground only back at the main panel.

The exception to this is if the subpanel is located in a separate structure, like a detached garage or the increasingly-required separate structure for growing. A second ground rod is required in that instance, but the neutral is still isolated.

 

[Jhhnn]

Makes sense, rives. Years ago a friend lived in a ramshackle sort of place that had been added onto repeatedly. Lightning hit the pole in his backyard. Unbeknownst to him the heavy earth ground at the main panel had become disconnected & there was an improper earth ground at a subpanel in the house. The lighting strike turned the relatively small gauge ground wire between the panels instantly to smoke & started the house on fire. At least, that's what fire investigators told him after the fire was put out. Three other houses hooked to that pole & none suffered fires.

 

[Schwarzenbart]

Not surprised. Like I said I am not an electrician and he probably didn't look close enough and just wanted my money.

This is the one. https://growgps.com/products/hph8/

It's discontinued and the one I have are North American 240

Supposed to have 50, only has 30 feeding it.

For sure, I just double checked the setup and I misspoke I meant to say unbonded, it is grounded with a ground bar I put in it but the neutral isn't tied to the ground, and the old fusebox is grounded and unbonded as well.

From that diagram and above condition I should bond the neutral and ground at the main panel, leave it unbonded at the fusebox, and add a ground rod because the water pipe isn't enough.

 

[rives]

That controller uses "universal" receptacles that accept either 120v or 240v plugs and are, at best, rated for 15-20 amps. My above statements about the level of protection stand, and the internal wiring is also going to be too light for anything above a 20a feed - receptacles struggle to accept a #10 wire, and anything larger simply won't fit.

How many lights are you going to run? A 20a breaker will give you 16a continuous, and on 240v that is 3800 watts.

Be aware that "universal" receptacles are junk. They break every electrical code and standard by being able to accept both voltages, and no reputable manufacturer is going to make them.

It sounds like you have a good plan with the grounding.

 

[Schwarzenbart]

That controller uses "universal" receptacles that accept either 120v or 240v plugs and are, at best, rated for 15-20 amps. My above statements about the level of protection stand, and the internal wiring is also going to be too light for anything above a 20a feed - receptacles struggle to accept a #10 wire, and anything larger simply won't fit.

How many lights are you going to run? A 20a breaker will give you 16a continuous, and on 240v that is 3800 watts.

Be aware that "universal" receptacles are junk. They break every electrical code and standard by being able to accept both voltages, and no reputable manufacturer is going to make them.

It sounds like you have a good plan with the grounding.

Please don't go by the one in the picture. I have the 6-20R side prong only outlets on mine. Also it says right on the front of the controller and in the wiring instructions to use a 50A breaker. I have it wired to a 30A breaker and am using it for 2 mag ballasts only (~18A+firing spikes to ~20A) instead of the 8 ballasts it says it can supposedly run with the 50A.

I am trying to be as safe as I can rather than jumping head first into stupid like most people when confronted with electrical problems.

I used to do it too!

I want to build a hood flip flop relay so I can use two ballasts for four hoods and split the room in two, so and I am saving up for that, but it's just a little old 2K single room right now.

I don't have room for all 8 hoods (area is only 10x13) and I wouldn't dare push harder than safe. It took me almost 4 months of calling every single electrician and grower I know to find one that wasn't a methhead and spoke english to even come out!

I have to put the ground rod in and tie the neutral to ground in the main panel like you said.

The controller and panel are cold and haven't tripped and the lights don't dim when the ballasts fire up or the dryer is started like on the old 110V K&T now, so yay!

 

[rives]

Ok, good on the receptacles.

A 30a feed is too much for 20a receptacles regardless of what the directions say. All of the manufacturers of the low-end controllers use an exception to the NEC that allows up to a 50a feed for HID lighting. The problem is that the exception is accompanied by a number of stipulations, all of which have to be met or the exception cannot be used. It is meant for warehouse lighting, and the stips cannot be met in any grow that I've ever seen. They include: the fixture must hang directly below the receptacle; the cord cannot be more than 18" long; the cord must be made by the same manufacturer as the fixture and it has to be listed (tested and certified) for this application; the cord must be visible over it's entire length.

Does that describe your installation? If not, then to be code-compliant (and fire insurance....) then you can have a maximum of a 20a breaker.

If you are running 1000w fixtures on 240v, with ballast losses they are pulling roughly 4.5 amps each. The 9 amp figure is when running them on 120v. If you are running 2kw at 240v, you can easily run the controller on a double-pole 20a breaker, or even a 15a (a 15 will give you 12a (2880 watts) continuous duty). Volts x Amps = Watts, or Watts / Volts = Amps.

Glad to hear that the grounding is worked out.

 

[Schwarzenbart]

Alright. I'll switch the 30 for a 15 and see if it does it when the light go off in the morning. If not I'll use a 20.

Also, I have seen the flipbox and horticontrol prefab units, and the threads on here for diy flip flops, but they are all for ballasts, not hoods.

What is the safe gauge wire and relay for a hood flip flop? I have a powder coated steel enclosure and strain relief nuts, 10 and 12g wire nuts and the tools but I want to operate 4 hoods from 2 ballasts operating 24/7, and switch which hoods are illuminated with a trigger wire or single gang timer.

Is there such a thing as a safe DIY hood relay?

I have read that the same NTE R04-11A30-120 relay guys are using in their DIY ballast relays can be used it just needs to be wired differently, can you confirm this?

Thanks again for all your advice and sorry to hijack this thread, I hope my learning and evolving helps others as they follow our dialog.

Peace

 

[rives]

I'm not sure what you are talking about with a "hood flip-flop", or a hood relay.

A flip needs to go between the ballast and the two lamps that it feeds at some point. All of the installations that I've seen have the flip mounted near the ballast for ease of centralizing the controls, but it could really be anywhere in the circuit.

That relay would work fine, but the one in the following link is rated for more current and appears to be a good bit cheaper. The supplier has some of the best pricing for electrical components that I've found. http://www.automationdirect.com/adc/Shopping/Catalog/Relays_-z-_Timers/Electro-Mechanical_Relays/Power_Relays,_Open-Style,_40A_%28AD-PR40_Series%29/AD-PR40-2C-120A

Glad I could help.

 

[Schwarzenbart]

I dunno, for some reason all the flip flop controllers I have seen are like an 8 light controller but 4 always on and 4 always off, with a ballast per hood, and they switch the ballasts on and off.

The one I am talking about reproducing, not reinventing, is like the horticontrol or flipbox.

Kind of like madpenguins
https://www.icmag.com/ic/showpost.php?p=3165155&postcount=494 or any standard 4 light controller but where I can run 4 hoods from 2 ballasts on 24, with each set of 2 on for 12, and hook it up between hood and ballast instead of 4 ballasts on at same time or 4 total ballasts and 2 on at a time.

I am confused on how it's wired. Two relays for the ballasts, and one for the trigger, but can the relay switch dc from ballast using an ac coil?

 

[rives]

Madpenguins is a light controller, not a flip box. A simple controller with a relay that has (2) NO/NC contacts could be used to control opposing rooms, with one set of ballasts controlled by the NO contact and one set controlled with the NC contact. This way, one or the other would always be powered, but it would still take one ballast per lamp. I don't recall ever seeing a setup like this, but it could be done.

A flip box uses a relay with the same Double Pole, Double Throw (DPDT) NO/NC contact configuration, but the Common contacts are fed by the ballast, one lamp is hooked up to the Normally Open contacts and the other lamp is hooked to the Normally Closed. This way, when the relay coil is unpowered, the ballast output power flows from the Common contacts through the Normally Closed contacts and powers up the 1st lamp. When the relay coil has voltage applied, the contacts close and now the power flow from the ballast goes from the Common contacts through the Normally Open contacts and powers up the 2nd lamp.

On a hot-switched flip, the ballast stays on all of the time. On a cold-switched flip, the ballast is shut off, the flip takes place, and the ballast is powered back up. Some electronic ballasts aren't compatible with a hot flip, and a hot flip is always harder on the relay contacts because current is flowing and arcing takes place when transitioning from one lamp to the other.

A relay can have a coil that is either AC or DC, and of a different voltage than the contacts are switching. The contacts can switch DC, but it requires a different design relay for good service life. This is irrelevant for our purposes, because there is no DC in the light circuit - the lamps are powered by high voltage AC provided by the ballast.

 

[Schwarzenbart]

Oh wow man, I thought ballast to hood was DC.

Thanks for clarifying and the terms.

Do you know what those SS plugs and sockets are called formally?
and
What relay would you recommend for a hot-switched flip box?

 

[rives]

SS plugs & sockets? I don't know what you are referring to.

The relay that I linked up above in post #35 will work fine for both the light controller and a flip box.

 

[Schwarzenbart]

Ok thanks.

I guess I just have to take a bunch of sunlight supply hood extension cords and cut them up to provide the female sockets for the male ends from the hoods.