How durable is pvc coated MC cable?

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Cow

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Electrician
I looked at a job that requires running a branch circuit 1000' through the ceilings of two different barns. The barns are typical metal buildings with z channels spaced 5' apart. The customer prefers pvc but with the spacing being as far apart as it is, it'd require me to use 1 1/4" pvc for this little 20 amp branch circuit. The load is very small so voltage drop is not an issue, the wire would still be #12 most likely.

That's where I thought 12-2 pvc coated mc cable might work for me since it can be strapped at 6' intervals. My worry is, how well do you think it would hold up in the ceiling of a barn, pigeons landing on it, building nests, etc? Would the birds claws tear the coating? I might be way off base even considering this since I've never used it, it just seems like it'd be a quick way to get a branch circuit across a long barn without resorting to running oversized pvc with expansion joints, etc.

Thanks for the help.
 
What is the use of this "barn"?

I am assuming it houses livestock.

I know what art 547 says, I still have a hard time with conditions being corrosive enough to deteriorate a metal raceway but not the steel building:( 547 IMO is not quite what it needs to be, agricultural things have changed over the years, but 547 hasn't exactly kept up with all the changes. Some areas are not nearly as corrosive as 547 thinks they are, and some are maybe worse then 547 realizes. Anything within reach of 300 pound or more animals is RMC in my book. Sorry but even RMC still will not last long enough from a physical point of view and will need replaced before corrosion becomes the problem. You still try not to run anything within reach of these animals but there are times with something existing that it is harder to avoid.

I don't know how many buildings I wired where I was particular to use all the right stuff to protect the wiring from corrosive elements, then comes the user when you are done, leaving covers off, losing lamp globes, etc. hanging things off your raceways that have plastic straps that maybe have a hard enough time supporting the raceway alone and it and leaves you wondering why you went through some of the effort you did:(

Birds, other then intended poultry of course, in the barn is usually not desired, they bring potential disease with them.
 
1000 ft. That's a long way. Is the attic insulated? Could get warm up there. Or is it all open? I think birds will love perching on it but don't think they could ever damage it cattle on the other hand kwired is right nothing you do will last forever.
 
Cow said:
I looked at a job that requires running a branch circuit 1000' through the ceilings of two different barns. The barns are typical metal buildings with z channels spaced 5' apart. The customer prefers pvc but with the spacing being as far apart as it is, it'd require me to use 1 1/4" pvc for this little 20 amp branch circuit. The load is very small so voltage drop is not an issue, the wire would still be #12 most likely.

That's where I thought 12-2 pvc coated mc cable might work for me since it can be strapped at 6' intervals. My worry is, how well do you think it would hold up in the ceiling of a barn, pigeons landing on it, building nests, etc? Would the birds claws tear the coating? I might be way off base even considering this since I've never used it, it just seems like it'd be a quick way to get a branch circuit across a long barn without resorting to running oversized pvc with expansion joints, etc.

Thanks for the help.
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I have only use coated MC once. The jacket is about the same as TC cable. I don't think birds would tear it up. They might, but your up in the air anyway so no big deal.

Why use coated MC at all? You said the customer likes PVC, does he not like metal?
 
kwired said:
What is the use of this "barn"?

I am assuming it houses livestock.

I know what art 547 says, I still have a hard time with conditions being corrosive enough to deteriorate a metal raceway but not the steel building:( 547 IMO is not quite what it needs to be, agricultural things have changed over the years, but 547 hasn't exactly kept up with all the changes. Some areas are not nearly as corrosive as 547 thinks they are, and some are maybe worse then 547 realizes. Anything within reach of 300 pound or more animals is RMC in my book. Sorry but even RMC still will not last long enough from a physical point of view and will need replaced before corrosion becomes the problem. You still try not to run anything within reach of these animals but there are times with something existing that it is harder to avoid.

I don't know how many buildings I wired where I was particular to use all the right stuff to protect the wiring from corrosive elements, then comes the user when you are done, leaving covers off, losing lamp globes, etc. hanging things off your raceways that have plastic straps that maybe have a hard enough time supporting the raceway alone and it and leaves you wondering why you went through some of the effort you did:(

Birds, other then intended poultry of course, in the barn is usually not desired, they bring potential disease with them.
Click to expand...

The existing conduit in these freestall barns is all done in emt. It's all overhead runs for lighting and rollup curtains on the sides of the buildings. It still looks good from when it was installed probably 14 years ago, but this project manager who came on after the dairies were initially built prefers pvc.

Galt said:
1000 ft. That's a long way. Is the attic insulated? Could get warm up there. Or is it all open? I think birds will love perching on it but don't think they could ever damage it cattle on the other hand kwired is right nothing you do will last forever.
Click to expand...

The barns are all open buildings, it's simply a metal structure with a tin roof. No insulation and no walls.

ActionDave said:
I have only use coated MC once. The jacket is about the same as TC cable. I don't think birds would tear it up. They might, but your up in the air anyway so no big deal.

Why use coated MC at all? You said the customer likes PVC, does he not like metal?
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No, he does not care for emt. Even though everything existing is ran in emt and IMO still looks good, he just doesn't care for it unless it's in a totally dry environment away from cows. Ooops, I almost missed your first question Dave, I was planning on coated MC because this branch circuit will be feeding a mister system for the cows.

It looks like you guys don't think it's such a bad idea, anyone else have any input before I approach the customer with this idea?
 
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This type of cable is permitted to be embedded in concrete, which is pretty corrosive, or directly buried in the earth so it would probably be suitable for this environment.
 
domnic said:
How many amps does the mister system pull?
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It may just be a timer and a solenoid.

For what it is worth, for a 1,000 long, 12 AWG, 120 volt circuit I come up with the following voltage drops.

  • 1 amp load = 3.3% drop
  • 2 amp load = 6.6%% drop
  • 3 amp load = 9.9% drop


Even 10% drop may be fine for the equipment.

I might consider feeding it at 240 and installing a small 240/120 transformer to provide a bit more power.

You could even use two small transformers one raising the voltage to 600 volts the other dropping the voltage to 120.
 
You guys are on the right track. I have four cow alleys, I'm figuring each with two wet location rated occupancy sensors driving a single solenoid. I expect the load to be just a few watts per cow alley and probably not much higher overall for the whole circuit since not all cow alleys will be showing occupancy at the same time.

I'm leaning towards these occ. sensors. Has anyone used these? I've had good luck with Wattstoppers in office buildings but have never used a wet location style yet:

http://www.wattstopper.com/products...occupancy-sensors/hb3x0w-lx.aspx#.U8vnieLn-M8

Thanks.
 
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