MI Cable through a teldata room

[mshields]

In demoing the area around where we will be putting in a new teldata room, it was discovered that there was some pretty good size (I would say maybe as large as 500's) MI cable feeders running through the space. These are at ceiling level although now tight up against the deck. i.e. I haven't seen it yet, but it appears to me that these could be a foot or two away from teldata racks (based on the pictures I was sent).

Moving these and the shut down it would require (its a hospital by the way) will be a major pain in the *&%* not to mention expensive, but I'm inclined to require it given the concern for interferance that could be caused by these conductors. Would be interested in your collective opinions.

thanks,

Mike

 

[ron]

I bet they are just copper water pipes .....

I would bet that the metal jacket will reduce EMI transmission.
Are the IT racks copper or fiber transmission?

 

[mshields]

Fiber or Copper

Fiber or Copper

mix of copper and fiber Ron

So how much faith would you have? If for example they are a foot away from my Cat 6 cable?

 

[ron]

I guess it would be an owners call.
Is it a change order? That will also 'cloud' the answer.
We run AC power all the time near Cat 6. Sometimes in a busy data center it is unavoidable.

 

[mshields]

You hit the nail on the head

You hit the nail on the head

It will be a change order. So yeah - I don't want to be so conservative as to shoot myself in the foot.

I think the shut down required would also go over like a fart in church.

But all that aside, thanks for the excellent input as usual.

 

[petersonra]

mix of copper and fiber Ron

So how much faith would you have? If for example they are a foot away from my Cat 6 cable?

Ethernet has a lot of inherent noise resistance.

The MI cable conductors have a pretty good Faraday cage around them.

A foot is a pretty long way.

My guess is that whatever noise might be generated would be no worse than if the MI was not there.

Why not put some kind of noise monitor in place for a while and see what kind of noise you get? You might be surprised at how little there is.

You might be able to box in the MI with some kind of sheet steel shield a foot or so from the MI if it still bothers you.

 

[ghostbuster]

We have measured the 60 hz. magnetic fields radiated from MI cable(many,many times).The copper does absolutely nothing w.r.t. attenuating these 60 hz. fields.We are currently working with a specification calling for mag fields to be less then 5 mg. around all communication cabling.

 

[LarryFine]

We have measured the 60 hz. magnetic fields radiated from MI cable(many,many times).The copper does absolutely nothing w.r.t. attenuating these 60 hz. fields.We are currently working with a specification calling for mag fields to be less then 5 mg. around all communication cabling.

Have you measured how much of that 60Hz (a) get's into UTP, and (b) affects ethernet throughput?

 

[rcwilson]

IMHO, MI cable is used on critical circuits where its fire rating or higher ampacity is a benefit. If this circuit falls in that category, an outage and relocating it may be a major issue. If the interference is a concern, could a steel plate or mu-metal shield be installed under the MI cables to attenuate the magnetic fileds and protect your communications? That way no outage is needed and your communication circuits are protected.

 

[petersonra]

We have measured the 60 hz. magnetic fields radiated from MI cable(many,many times).The copper does absolutely nothing w.r.t. attenuating these 60 hz. fields.We are currently working with a specification calling for mag fields to be less then 5 mg. around all communication cabling.

You would need something magnetic such as a piece of sheet steel to deal with the magnetic fields. The copper will reduce radiated RF though.

I am curious where they came up with the 5 mg number.

How far away from the MI do you typically have to go for various current levels to get to 5 mg. Can't be real far.

 

[ghostbuster]

You would need something magnetic such as a piece of sheet steel to deal with the magnetic fields. The copper will reduce radiated RF though.

I am curious where they came up with the 5 mg number.

How far away from the MI do you typically have to go for various current levels to get to 5 mg. Can't be real far.

Single conductor:

10 amps

generates approx. 5 mg. field at a distance of approx. 12 ft. away from conductor

 

[LarryFine]

How about a pair of such conductors in a cable?

 

[petersonra]

Single conductor:

10 amps

generates approx. 5 mg. field at a distance of approx. 12 ft. away from conductor

why would you ever run a single conductor like that? it would not appear to be even code compliant.