Greenhouse wiring

[arnettda]

I have searched old posts and found most people use PVC to wire a greenhouse. I have a customer who saw one wired in NM and wants me to wire it that way. I told them no as it would be a damp location. Now they want to know If I can use UF? I am not sure about this. Can I? 340.10(4) says used as NM follow 334. To me I am not using it as NM as Nm can not be used in wet or damp locations. But if I need to follow 334.10(3) The building type and it needing to be concealed by a thermal barrier would stop me from using it?
Thanks.

 

[hurk27]

I have searched old posts and found most people use PVC to wire a greenhouse. I have a customer who saw one wired in NM and wants me to wire it that way. I told them no as it would be a damp location. Now they want to know If I can use UF? I am not sure about this. Can I? 340.10(4) says used as NM follow 334. To me I am not using it as NM as Nm can not be used in wet or damp locations. But if I need to follow 334.10(3) The building type and it needing to be concealed by a thermal barrier would stop me from using it?
Thanks.

Interesting dilemma that I have not run across yet?

340.10(4) states:

4) Installed as nonmetallic-sheathed cable. Where so installed,
the installation and conductor requirements
shall comply with Parts II and III of Article 334 and
shall be of the multiconductor type.

And 334.10(A)(1) state:

(A) Type NM. Type NM cable shall be permitted as
follows:
(1) For both exposed and concealed work in normally dry
locations except as prohibited in 334.10(3)

Part II of 334 includes 334.10

So it does seem if you use UF in place of NM it requires it to be a dry location:?

Never ever run in to this before?

Wonder what determines when it is used as NM and when it is used as UF?

 

[gndrod]

I have searched old posts and found most people use PVC to wire a greenhouse. I have a customer who saw one wired in NM and wants me to wire it that way. I told them no as it would be a damp location. Now they want to know If I can use UF? I am not sure about this. Can I? 340.10(4) says used as NM follow 334. To me I am not using it as NM as Nm can not be used in wet or damp locations. But if I need to follow 334.10(3) The building type and it needing to be concealed by a thermal barrier would stop me from using it?
Thanks.

UF-B is qualified for both wet or damp locations.[310.104] The cable can be direct burial but the stub up must be protected by PVC or 'listed' tubing. Not sure where thermal barriers (ambient correction factors?) would come into play since all the circuits would normally be in an interior location. If not, further description on how the electrical is routed would be helpful.

 

[blargh]

Whether you use NM or UF in this greenhouse, how are you going to make connections to fixtures, receptacles, and junction boxes? Surely those would have to be set up for damp or wet locations as well. If you have to use cable glands or something at every junction, it hardly seems worth it.

 

[iwire]

In my opinion 334.10(3) will require the UF to be behind at least a 15 minute wall finish.

334.10(3) Other structures permitted to be of Types III, IV, and V
construction except as prohibited in 334.12. Cables
shall be concealed within walls, floors, or ceilings that
provide a thermal barrier of material that has at least a
15-minute finish rating as identified in listings of firerated
assemblies.

 

[gndrod]

Whether you use NM or UF in this greenhouse, how are you going to make connections to fixtures, receptacles, and junction boxes? Surely those would have to be set up for damp or wet locations as well. If you have to use cable glands or something at every junction, it hardly seems worth it.

Even if the greenhouse is a permanent closed-in solarium structure...NM can not be used. Any UF cabling that is direct buried must emerge conduit protected into the greenhouse. All interfacing outlets would be watertight enclosed and most likely THWN interconnected through conduit or equal raceways.

 

[gndrod]

In my opinion 334.10(3) will require the UF to be behind at least a 15 minute wall finish.

Interesting that a thermal barrier is mentioned in the OP statement. Maybe it is being used as a firewall adjacent to a heater. In residential attached greenhouse solariums I have installed zero clearance or freestanding fireplaces that indeed require a 15 minute sheathing barrier at framed wall structures.

 

[iwire]

Interesting that a thermal barrier is mentioned in the OP statement. Maybe it is being used as a firewall adjacent to a heater. In residential attached greenhouse solariums I have installed zero clearance or freestanding fireplaces that indeed require a 15 minute sheathing barrier at framed wall structures.

I don't think you really read the first post.

 

[Dennis Alwon]

I have always used emt, not pvc. I can't imagine using UF and as stated , IMO, it is not compliant.

 

[gndrod]

I don't think you really read the first post.

Tx Bob, I did and a second time also with glasses on. Confusion abounds in trying to interpret what 340.10(4) has to do with UF once it emerges above ground into a JB? Does 334(3) really require UF to be behind a thermal barrier at that point? Maybe I need find clarity in how this greenhouse is structured and if it is attached to a first floor residence or on top of a 4 story penthouse.

Any help is welcome in setting me straight here.

 

[hurk27]

Tx Bob, I did and a second time also with glasses on. Confusion abounds in trying to interpret what 340.10(4) has to do with UF once it emerges above ground into a JB? Does 334(3) really require UF to be behind a thermal barrier at that point? Maybe I need find clarity in how this greenhouse is structured and if it is attached to a first floor residence or on top of a 4 story penthouse.

Any help is welcome in setting me straight here.

Me either, around here when a green house is mentioned a picture of a building made out of poles with plastic covering that has sprinklers systems, air movement and maybe heaters which are commonly operated by manual or PLC systems, along with vent panels and shades that control humidity and sun light, not much to have a rating on in my opinion?

 

[ceb58]

Me either, around here when a green house is mentioned a picture of a building made out of poles with plastic covering that has sprinklers systems, air movement and maybe heaters which are commonly operated by manual or PLC systems, along with vent panels and shades that control humidity and sun light, not much to have a rating on in my opinion?

I agree with the description and wonder why 547.5 (A) is not being looked at. It list UF as one of the wiring methods that SHALL be used.

 

[gndrod]

nitro

nitro

I agree with the description and wonder why 547.5 (A) is not being looked at. It list UF as one of the wiring methods that SHALL be used.

Good point, especially if the fertilizer is being used inappropriately. I am not sure if a greenhouse qualifies as agricultural in the context used in [547] overall.

 

[ceb58]

Good point, especially if the fertilizer is being used inappropriately. I am not sure if a greenhouse qualifies as agricultural in the context used in [547] overall.

Do not see why not. Look at 547.1 (B) (2)&(3)
The use of liquid fertilizer sprayed onto the plants. When a greenhouse is emptied, it is washed down with chemicals to kill any bugs or disease before new plants are brought in.
Here in NC we are a agricultural state,so if I put up a greenhouse and produce and sell plants then I am a farm and it would be an agricultural building.