Help ! Greenhouse wiring

[Stevenfyeager]

I've been asked to estimate re wiring a large greenhouse. 40 yrs old, existing decaying romex. 100' by 150' . He said I could use pvc conduit. Are there NEC wiring conditions for heat, etc ? Your recommendations ? There are fans, thermostat controlled louvers, gas heaters, motors that inflate double plastic roof layers, etc. A lot more than I ever knew of in a greenhouse.
Any help for methods is greatly appreciated. NOT sure where to start estimating. Are there other factors besides conduit fill I need to use ? Thanks so much ! This is new to me.

 

[ptonsparky]

Lots of expansion joints. We used click type pvc straps . Worth every penny. Not greenhouse but a dairy.

 

[Cow]

We did one greenhouse with emt/rt fittings. We are in a dry, hot climate.

Another greenhouse with a lot of humidity, the inspector required us to use pvc flex over pvc conduit, as it has a higher temp rating.

Get all your loads listed out. And what controls them. You need to know how the greenhouse is built to know how you will support your conduits. There are some places I've had to run oversized pvc conduit because the very short spacing requirements for smaller pvc is just not practical.

If you can run underground and do stub ups, that may make life simpler, if that's possible.

PVC coated mc cable may also be an option as long as you can get past the physical damage requirements, it's not cheap and either are the connectors, but the labor savings will probably more than make up for it. Securing and support is 6 feet, so that beats smaller pvc conduit support spacing.

 

[zbang]

Drains- water will condense in the conduits; strategic drain holes in boxes can help the whole system from filling with water.
Depending on how they're operating, it may be a damp, or even wet, environment, so you'll have to work with that.
If any areas are going to have sprinklers or be spray washed, you may need NEMA 3R or 4 boxes stuff.

I'm also a fan of using at least double-gang or deep recepticle boxes wherever possible; they'll hold more longer tails which makes the inevitable rusted device replacement a little easier.

 

[ramsy]

I've been asked to estimate re wiring a large greenhouse. 40 yrs old, existing decaying romex..

Sounds like a job for underground feeder cable (UF).

If old cable was properly sized to handle loads => 40 years, old cable can be used to pull new UF to PVC junctions, & outdoor rated enclosures, properly arranged to drain.

 

[kwired]

Drains- water will condense in the conduits; strategic drain holes in boxes can help the whole system from filling with water.
Depending on how they're operating, it may be a damp, or even wet, environment, so you'll have to work with that.
If any areas are going to have sprinklers or be spray washed, you may need NEMA 3R or 4 boxes stuff.

I'm also a fan of using at least double-gang or deep recepticle boxes wherever possible; they'll hold more longer tails which makes the inevitable rusted device replacement a little easier.

You shouldn't have many rusted in devices if you drilled drain holes. Some areas may not see much watering but will still see daily condensation at times because of temp changes from day to night.