Electric system

[Rothrock42]

My new greenhouse is built in my backyard -- I hired somebody, I don't have construction skills. It is 15x11 feet. I also had water, natural gas, and electric services run to the side of the building.

But I'm trying to figure out what to do with the electrical.

I had an electrician setup a sub panel at the building. But since I'm not sure exactly what I'll need and where it should go, I was hoping to do some of the circuits on my own.

What I have:

• At the main panel in the garage a 60 A breaker feeding the subpanel
• A subpanel with an unusual breaker with a 40A shut off and two 20A breakers
• One 20A breaker goes to one GFCI outlet inside and one 20A breaker is free.

What I want:

• A circuit for my exhaust fan and ambient air intake
• A circuit for my air circulation fans
• A circuit for my misting system pump and maybe a wet wall pump.

Here are my questions and concerns:

The fans are all variable speed and some are controlled with a thermostat. Will that cause a problem with using GFCI outlets?

Also some of the plugs for fans are up high and if the GFCI outlets trip I'll have to get a ladder out. Would it be better to have AFCI/GFCI breakers?

If I go with AFCI/GFCI breakers will the variable speeds for the fans cause problems on those circuits.

Is a building shut off at the subpanel a good idea?

Does anybody have any resources? Or experiences they can share with AFCI/GFCI circuit breakers or outlets?

BTW: I know that I should have an electrician do this, but that will cost as much as the rest of the building and I can't afford that. And even if it ends up being to complicated have to find somebody I'll need to be able to explain exactly what I need.

[rbarata]

Here, to build a gh like yours, you would need a permit. And to get it you would need to present a project covering not only the building but also all the systems (water, gas, electricity).
Even though, many times it is not allowed based on arquitecture or security. Needless to say that all the projects must be done and signed by a qualified engineer
Are you sure you can do it by yourself?

[Ray]

GFCI's (GROUND Fault Circuit Interrupters) trip when the two "sides" of the alternating current curve become suddenly unequal, which is what happens if you, or part of the structure become a short to ground. Being a wet environment, all electrical equipment should be grounded.

They should not be affected in the least by variable-speed devices or those with automatic controls like thermostats, humidistats, or timers.

AFCI's (ARC Fault Circuit Interrupters) trip when an arc - across two conductors, or along one - is caused by damaged, overheated, or stressed electrical wiring or devices. Arc faults can occur when older wires become frayed or cracked, when a nail or screw damages a wire behind a wall, or when outlets or circuits are overburdened. It is that last item that is likely of interest with the automated controls, but if you use wire that is of the correct current-carrying capacity, and all connections are solid, that shouldn't be an issue.

My greenhouse in PA had a cutoff switch in my main panel in the basement of the house, which disconnected all electricity from the structure.

I ran 220 to the GH - 2 "hot" legs, one common, and one ground. In the greenhouse, I split that into two, 110V circuits - 1 hot+common+ground on each. I also added another ground stake just outside of the back of the structure to be safe. In other words, that 220V line ground was attached to both the house ground and the greenhouse ground.

What you need to do is look up the maximum current ratings of every device you want to operate in the greenhouse, making sure that the sum does not exceed the 60 amp service you currently have.
The smart thing to do would be to have a breaker in the subpanel for each device, and have each of them connected via a GFCI.

[Rothrock42]

rbarata -- because it is less than 200 sq ft (18.5 sq m) the building itself didn't need to be permitted. Homeowners are allowed to do their own electrical work which I've done before -- just not in a damp location.

ray -- Yeah the sub panel has two grounding rods more than 6 feet apart at the building (and the main panel in the garage is also grounded. I'm using flexible non-metallic conduit, so I be running an actual grounding wire to each fixture and box.

There isn't enough space in the panel for each device to have its own breaker. The subpanel specification says it has 4 spaces and can support 8 circuits, but I haven't been able to locate half-height breakers that are compatible, so I assume I'll just be able to fit 4 at most.

The winter heat is natural gas, so there isn't a lot of electric demand

I have totaled it up and I'm a bit over 12 amps for everything I'm currently planning. If I go with 3 circuits for now -- air circulation, heat exhaust, and mist/water pumps -- that ends up 3 to 4.5 amps on a circuit and I think I should be fine and have some room to grow.

All the outlets I have are gfci and have the in-use all weather covers. I just wasn't sure if the gfci would have issues with the additional controls.

[Ray]

I went far more "laissez faire"....

My "electrical panel" was a water-tight electrical box, similar to the attached picture, but considerably larger and with three vertical terminal strips plus a fourth across the bottom for the ground.

The 220 came in through the back, with the two "hot" strips on either side of the central "common". My various GFCI outlets were mounted through the sides (silicone-sealed) and wired to the bus bars. No individual breakers.

[Rothrock42]

lol...yes that looks a bit more "laissez faire"!

Thanks for the thoughts. I think I'm going to get this done pretty soon. Awesome.

[Roberta]

I did have my GH wired by an electrician. One thing he did, very important, is somehow the GFCI on each outlet is independent of the others... so if one blows, it doesn't take the others down. (It's all once circuit, but each outlet can do its thing independently) I don't know how it was done (that's why I hired a professional), but clearly it is do-able. And it wasn't prohibitively expensive.... for someone who knows what they're doing it apparently is pretty easy. (In general, since I know very little about construction matters, I discuss with the professional what I want to accomplish, but let them figure out how to do it. I have gotten some very creative, functional solutions that way)