I am helping a friend get a greenhouse wired for electricity.

No worries I will have a licensed electrician do the work but I need advice for the plan.

It is a prefab greenhouse which came pre-wired with four 20 amp circuits.

It is on a farm and a barn that has electric service which is about 130 feet away from the circuit breaker box on the back of the greenhouse.

The electric power pole with a transformer is about 40 feet from the circuit breaker box. You can see it in the distance of the picture.

They called an electrician and he wants to dig a trench from the barn to the back of the greenhouse and tap into the barn service. Big $$$

I was thinking it would be cheaper to put a weather-head/service entrance on the back of the green house with a meter and tap the transformer on the pole. I know it will be another electric bill. They are OK with another electric bill they have multiple barns with multiple meters on the farm already.

I realize that the greenhouse may not be strong enough to support the weather-head and meter box so as an alternative I was thinking of a pole near the circuit box and wires run to the pole (with the meter box) from the greenhouse.

I am checking with the greenhouse manufacturer to see if the green house is strong enough to support the weather-head. It does not appear like it to me.

Here is the questions.

If we go with a pole and meter box near the greenhouse can I run external conduit (i.e. flex conduit) to the greenhouse from the pole or do I need to bury it in a conduit and short trench? We are talking a few feet about 3 to 5 feet.

Is there a better plan?

Thanks in advance.

No neighbor or someone else with a backhoe who can dig a trench?
Id do the math first, between the extra cost of another bill and the post with the meter and all that it might be cheaper in the long run to connect to the barn.

I wish that they had another farm neighbor. That whole area is being bought up by developers and turned into sub divisions. They are one of the only farms left around there.

PVC conduit from the green house box to ground, trench, PVC conduit from ground up pole with weather head at top of conduit. USE cable.

Conduit in trench is important within the greenhouse no pvc or flex plastic. Make sure to not undersize the circuits (add up anticipated loads) and install a disconnect at the greenhouse before the branch circuits..
Make sure all the runs are thwn in conduit and carry a ground. Needs to be designed for "wet locations" and gcfi's..
Insure electrician properly grounds and does not energize the frame of the greenhouse. Additionally any cable used to lighting or equipment should be rated sjoow.

I thought the OP said the greenhouse was "pre-wired" and only needed the service entrance?

Thank you all for the information.

It is exactly what I needed to know.

I am looking at getting a pole installed and will call an electrician for the hookup. I will dig the trench over to the greenhouse for the conduit.

The idea the current electrician has of trenching to the barn is going to hit a snag because there is a water main crossing between the two. I know for a fact that the main is not as deep as it should be and it will be a problem I don't' want to address.

Thanks again

Prewired only indicates it's there. No indication of code or suitability. The "cable" pertains to that used from gcfi to fixture or appliance.
Greenhouses degrade due to exposure, UV and moisture. Locally there are lots of greenhouses, some done right, some are shocking experiences.

"some are shocking experiences"..................


one of my first jobs in life was in the 7th grade.
a few of us kids would ride ride the school bus that went to the outskirts of town where a greenhouse was located, that was owned by the parents of another kid we knew in school.
i'll never forget the pay scale quote : "5 cents for the little boxes and 10 cents for the big boxes. the more ya do, the more ya make. and if you do good during the week, you can work saterday with Ears...." [that was a grownup doofus that tended the coal furnace and did repairs to the greenhouse structure]
some, or should i say MOST of the wiring in that place, was done using the "best" cheapo extension cords and multi-plug adapters the local 5&10 store had to offer.

A product for sale to the general public with pre-wired electrical that doesn't meet the NEC? Hmm.

Plot thickens.

I looked at the service box on the barn today and found a 2 pole 50amp circuit that luckily connects to an RV plug just a few feet from the greenhouse. Woo hoo.... Maybe.
The greenhouse has four 20 amp circuit breakers


Correct me if I am wrong.

I know that the double pole means there are two separate power wires each 120v in separate phases to make 240v service.

My questions are this.

Can I split the 50amp two pole breaker into two 50 amp circuits One for two of the 20 amp circuit breakers and one for the other two?

I think I would seal that box up a lot better than it has been to prevent a fire from one of the Wasp touching the power close to a ground when making their nests

Yep I do need to seal it up when the job gets done but for the short term at least I did evict the paper wasp squatters. I need to go after the mud dobbers with insulated tools and not just my hands.

That 50A breaker looks like it already is 2 single 50A breakers tied together. If for some reason you can't split it you could always replace it with 2 single pole 50A breakers.
But is what you described the way those 20A breakers are supposed to be wired?

Currently the box on the greenhouse has a single bus bar for power to all 4 breakers and one connection for ground/return.

I will have to replace the box with one that has 2 power buses and one ground/return.

I may be using the wrong terminology but hopefully that makes sense.

Do you have a picture of the internals of the greenhouse service entrance? Having four, 20 ampere breakers on a single 110 volt feeder seems odd.

You are correct, I was wrong.

After looking at the box diagram from the manufacturer I realized that there are 2 buss bars. One connects at the top and one in the middle.

I only saw the middle buss connector when I first looked but it does have 2.

My concern is if I can split the 240v 50amp dual pole breaker into two 120v 50amp circuits?

All you need to do is run 1 leg off the 50amp breaker to each terminal lug on green house box. ( one wire from each screw on 50 amp breaker to green house main lug connection) No need to chance it to 2 single 50's. Double breakers will both trip even if only 1 side is overloaded. You must run wire rated for 50 amps between boxes. The 50amp breaker is to protect the feed circuit. I bet that's at least a 60 amp rated box on green house. As it's wired you need 40amp per leg. The 20 amp breakers protect the load.

And be careful the service coming out the bottom isn't really fused. The 200 amp main is it's only protection and that looks like 2agw which is only good for 100 amps. Needs reattached and a bushing installed too.

Awesome that is what I was hoping.

The saga continues....lol

As for the service out of the bottom I think it goes to another barn which has 1 light and maybe 2 fans. It has a breaker box on that barn for those circuits.

After I resolve the electrical to the greenhouse I will have to address the wiring to the breaker box. It is really installed poorly. As you can see the conduit wasn't even attached to it.

Thanks for letting me know about the bushings, I will make sure they are addressed when the box gets fixed.

There is a basic question that only the electrical inspector (Authority Having Jurisdiction) can answer.

Is the green house a feeder circuit or a service entrance?

The answer will determine what kind of underground wire is permissible and how many conductors you will need. As to your feeder breaker sizing, that is dependent on the wire size or vice versa, the feeder breaker size is dependent on the wire size. As has been mentioned, determine what the current rating of the greenhouse entrance box and size the wiring and breaker accordingly. It is a common misconception that a distribution panel has to be fed at the panel rating. You can feed a 60 ampere panel with 20 amp breakers but obviously that would be a questionable thing to do.