Growroom Electricity and Wiring

[rives]

You don't want to use a 30 amp breaker unless all of the downstream equipment is rated for 30a or greater, otherwise those components become fuses protecting the breaker. This means that you cannot use standard 15a or 20a receptacles, or the standard cordsets for the ballasts.

What wattage are your ballasts? You also need to stay within the 80% rule, which says that for any continuous load (defined as being greater than 3 hours in duration) you need to stay at or below 80% of the breaker rating.

 

[twist1uc]

You don't want to use a 30 amp breaker unless all of the downstream equipment is rated for 30a or greater, otherwise those components become fuses protecting the breaker. This means that you cannot use standard 15a or 20a receptacles, or the standard cordsets for the ballasts.

Not sure what you are saying.. sorry.

What wattage are your ballasts? You also need to stay within the 80% rule, which says that for any continuous load (defined as being greater than 3 hours in duration) you need to stay at or below 80% of the breaker rating.

Ballasts are rated at 4.375A @ 240V.
I am trying to put 4 ballasts on one 30A 240V double breaker, by using two receptacles.

 

[rives]

What I am saying is that a power cord for a ballast that pulls 4.375a is invariably rated to be powered by a 15 or 20a circuit. The wire size (gauge) and the plug configuration are appropriate only for 15 - 20 amp circuits. Once you step up to a 30a circuit, the plug configuration changes and the wire size has to be increased. If this is not done and you have a problem, a 30a breaker will allow the components to receive 200% of the maximum power that they are designed to use.

This means that you can have a hell of a melt-down going on and the breaker doesn't recognize that there is a problem and will not trip. If it causes a fire, then your fire insurance will not cover an installation that doesn't comply with the electrical code and you could possibly be held criminally liable.

You need to split the circuit into (2) 15a 240v circuits and run two ballasts on each circuit. They will pull slightly under 9 amps together, and the 80% rule says that you can run 12a continuously on a 15a breaker.

If you can't fit two double-pole breakers in your panel, check into "wafer" breakers, which are half the size of conventional breakers.

 

[iTarzan]

Hey rives I have a few questions.

1. If the ballast example you give 4.375a is plugged into a 15-20a circuit isn't that 3 and 4 times what the ballast is capable of handling?

2. I thought a breaker keeps users from overloading a circuit by drawing too many amps. I don't understand how that would work in reverse. Just because it is a 30a circuit it is still 120v. It doesn't deliver extra amps does it? It just can handle more amps being drawn by devices doesn't it?

3. I have a receptacle in my house that is 30a. I have no idea what the other people used it for or why it is there. I was going to use it to power some grow lights in there. The room already has an older (50 years) 15a set of receptacles that was shared by some other rooms. We kept tripping the breaker with the computers and tv. I was actually using it to power a 1000w ballast and big fan with no issues. But I haven't used it in a couple years. So I had electricians come and put in a single receptacle of 20a on it's own breaker and 4 other receptacles on another 20a breaker.

Now I am wanting that 30a circuit to be useful. Is it just as simple as changing the 30a breaker out with a 20a breaker even though the 30a breaker circuit has wire that is heavier gauge? Is there something I can plug into that receptacle that splits it into two 15a circuits.

 

[rives]

1) It is 3-4 times what the ballast will normally draw. However, all of the wiring and components between the wall receptacle and any internal fusing (if present) are all sized to handle the amperage provided by the 15a circuit.

2) Correct. You could hook up the ballast in question directly to the 200a main on your house, and if everything stayed healthy and functioned normally, it would only draw 4.375 amps. The problem comes when something STOPS functioning normally - at that point, the amperage is only limited by the impedance (resistance) of the circuit feeding the device and the overcurrent protection. If the protection is sized incorrectly, then the power will rise to whatever level the protection is sized for, and if the wiring is inadequate for that much power, shit gets ugly.

3) Yes, you can change the breaker out to a smaller size with no problem. The larger wiring will not impact anything other than giving you a little less voltage drop than standard wiring for the lighter circuit would give you. In fact, you oversize the wiring on circuits that run long distances for this very reason.

Another option would be to get a small sub-panel and feed it with the 30a circuit. If it is a 4-wire circuit, then you have the option of using both 120v and 240v. If it is only a 3-wire circuit, then you will have to decide which voltage you want to run. The sub-panel can then accept breakers to reduce the ampacity of the downstream circuits. This could all be set up on a panel of some sort with receptacles fed by the distribution breakers in the sub and a cordset that plugs into your 30a receptacle.

 

[iTarzan]

It is a 3 wire 120v receptacle that has 2 plugs. So that can't ever be 240v could it? It doesn't matter because I don't want 240v. Just interested.

So I would get a small sub panel and feed it with the 30 amp circuit. Then that sub panel would have two 15a breakers and two circuits of wires coming out going to two receptacles.

That is how the garage is wired. There is a 30a breaker and the wire off that goes out the basement wall and underground to the garage where there is a small sub panel that has two 15a fuses.

 

[rives]

Yes, it could be converted from 120v to 240v. The neutral (white) wire would need to be removed from the neutral buss in the load center and paired up with the black wire from the same cable, and the two of them terminated on a double-pole breaker. When done this way, the white wire's insulation should be taped over on each end with "phase tape" (in a color other than white or green - those colors are reserved for neutrals and grounds exclusively) to indicate that it is now being used as a hot wire. Of course, the receptacle would also need to be changed out to get the correct 240v configuration and keep from blowing up 120v gear that was inadvertently plugged into it.

Correct, that is how you would do it. You could actually split it up into 4 breakers or more if you wanted as long as the total load didn't exceed the 30a feed (or 24a for continuous loading). This might be helpful if you wanted to be able to isolate down several lightly-loaded circuits, or keep timer circuits separate from lighting circuits, etc.

 

[Tyga]

Okay, So I have a bathroom on the opposite wall of my growroom. I'm looking to splice the power from the GFI in the bathroom to my room behind it. Im familiar with electrical... The GFI is line only, plan is to snake a 12/2 from the growroom to the Bathroom GFI. Splicing the Black/white/ground with my new 12/2 and Old working a GFCI into my growroom. The GFCI now in the bathroom will be blanked and initially just a splice box.
Anyone see any problems with this considering the GFCI is LINE only? I don't see a problem, but would like to double check...

 

[rives]

First, let's clarify a couple of things. I'm assuming from your description that you have an existing GFCI receptacle (not a circuit from a GFCI breaker) in the bathroom and the only wiring connections go to the line side of it. Correct?

If the above is the case, you can remove the receptacle, splice on your new run to the existing wires, and move the receptacle into the grow room. But, why would you remove the existing receptacle? Code requires that bathroom receptacles be GFCI protected, and you could just as easily attach your new feeders to the load connection on the receptacle and have GFCI protection at both locations. You would have to go into the bathroom to reset the circuit if it tripped on a ground fault, but that shouldn't be much of an issue, and it's unlikely that a convenience receptacle in a bathroom would see much load. If you are concerned about having to go into the other room to reset the GFCI, you could connect in on the line side wiring and go ahead with feeding a new GFCI in the grow room. The breaker feeding the two GFCI receptacles would see the combined load, of course, but you would have local resets at both locations in case they trip.

 

[Tyga]

Thanks Rives,
Not sure why I didnt originally think of that... Stoner moment. This works out well actually because I dont have easy access to the panel. Its in my landlords side of the unit... Hes cool with MMJ but what he doesnt know doesnt hurt him either. So this way I can just trip the GFI and wire my new line to the load part of the GFCI and will be good to go... Thanks brother.

 

[Jhhnn]

Okay, So I have a bathroom on the opposite wall of my growroom. I'm looking to splice the power from the GFI in the bathroom to my room behind it. Im familiar with electrical... The GFI is line only, plan is to snake a 12/2 from the growroom to the Bathroom GFI. Splicing the Black/white/ground with my new 12/2 and Old working a GFCI into my growroom. The GFCI now in the bathroom will be blanked and initially just a splice box.
Anyone see any problems with this considering the GFCI is LINE only? I don't see a problem, but would like to double check...

The GFCI receptacle only has 3 terminals & is not designed to protect other outlets downstream, correct?

That being the case, what you suggest will work, if you're willing to lose the bathroom outlet.

OTOH, you could get a gfci that protects downstream receptacles, install it in the bathroom & a regular (protected) receptacle in the grow room.

Use whatever gauge wire the receptacle currently has, in any case.

 

[Jhhnn]

Thanks Rives,
Not sure why I didnt originally think of that... Stoner moment. This works out well actually because I dont have easy access to the panel. Its in my landlords side of the unit... Hes cool with MMJ but what he doesnt know doesnt hurt him either. So this way I can just trip the GFI and wire my new line to the load part of the GFCI and will be good to go... Thanks brother.

Well, yeh, except that the wiring at the gfci will still be hot. Def tape the terminals to protect yourself, if you don't pop the breaker in the panel getting it out. Better to work with your landlord if possible.

Arcy-sparky!

 

[Tyga]

As far as I know (correct me if Im wrong) anything you load off a GFCI is protected... Thats why in bathrooms if there is more than one receptacle there is only one GFCI, because any receptacle loaded off that is already protected..?

 

[Jhhnn]

As far as I know (correct me if Im wrong) anything you load off a GFCI is protected... Thats why in bathrooms if there is more than one receptacle there is only one GFCI, because any receptacle loaded off that is already protected..?

Correct. The way you described it at first, I thought you might have an older GFCI that doesn't have load terminals.

 

[HenDokuYaku]

Question for you gurus out there. Please and thank you.

If a transformer for 5 houses has been substantially upgraded, does that mean that the 5 houses should be able to pull more juice or does the individual service still need to be upgraded without just upgrading the panels and breakers? This is residential, as I mentioned.

 

[Jhhnn]

Question for you gurus out there. Please and thank you.

If a transformer for 5 houses has been substantially upgraded, does that mean that the 5 houses should be able to pull more juice or does the individual service still need to be upgraded without just upgrading the panels and breakers? This is residential, as I mentioned.

It depends on the existing wire size & material from the pole to the panel.

Chart-

http://inspectapedia.com/electric/Electrical_SEC_Sizes_Amps.htm

 

[rives]

The service entrance cable should already be matched to the main breaker in the load center. If it is an overhead service, the wire coming from the pole to the weatherhead will normally be much smaller because it is in free air, and the utility frequently uses smaller-than-normal feed wire even if they run underground - the NEC doesn't apply to them, and they play pretty loosely with the amperage tables. They will sometimes go as small as 2/0 aluminum for an underground 200a service, which according to code is only good for 135 amps.

In theory you should be able to pull up to the full ampacity of your service for short periods and 80% of the main breaker capacity for continuous (over 3 hours) loads. In reality, if all of the houses are doing it at the same time, there will undoubtedly be a problem because the utility sizes it's transformers based on average utilization, not maximum capacity. Pole-mounted transformers bigger than around 75kva (312 amps @ 240v) are very rare and require more elaborate support than the typical pole-mount. My local utility usually uses a 50kva (208 amps @ 240v) transformer normally to feed multiple houses.

 

[Jhhnn]

^^^

Kinda-sorta. Around here, Xcel & their predecessor, PSC, standardized service drops a long time ago. Whatever size wire they use, it's good to 200A per the electricians who upgraded our service from 100A when we put on an addition. They do go larger on McMansions, obviously special order at extra cost.

I'm sure that varies locally & by age of the service.

 

[rives]

Kinda-sorta?? I would bet you a significant sum that the service drop is undersized per the NEC.

This is the 200a service on my house. The wire coming out of the weatherhead is 2/0 copper with THHN insulation, which is rated at 195 amps and is approved for a 200a service. Notice how much smaller the service drop is, and that is aluminum which will drop the rated ampacity by roughly 25%.

This is a picture of the secondary wiring on the transformer feeding my house and 4 others (total of 5). The triplex at the bottom of the picture feeds 3 houses. The two exiting to the left feed one house each. The wire from the transformer to the splice connection is actually smaller than the wiring in my service entrance.

Larger picture of the above.

This transformer is rated at 25kva, or 104 amps of 240v. Again, it feeds 5 houses.

 

[Jhhnn]

Please, rives. I'm not arguing with that. I'm just saying that the drop is usually standardized, not really sized to the panel on a particular house unless the builder specifies otherwise. They don't care if your panel is 100, 150 or 200A- they hook it up using standard hardware. Your pics illustrate that entirely.

When we moved in here 20 years ago, the house next door still had a very old service- 3 separate solid copper wires set ~1' apart & a fuse panel rather than a breaker box. I can still find that in the neighborhood when I look around. Some services are intermediate in age, don't have wire as heavy as ours which appears to be the same as new construction. Seeing any of that, an electrician like you would tell the homeowner that they need to upgrade to standard if they want a higher capacity panel. That's why I said it depends.

As you say, actual capacity of the neighborhood system to deliver power is another kettle of fish entirely.