My First question is Are Intrinsically safe wiring considered signal ?communication wires? or what? Customer has a gas station that has the intrisically safe wire buried about 6'' below parking lot. Customer claims wire is compromised because everytime a car passes over area it trips alarm in store for probes sensors. Customer wants us to rebury wire same way. First the wire would probably get compromised again over time. Second Belden Cable 88760 is rated for burial rated but it doesnt say DIRECT burial. Is there anywhere other than T300.5 that regulates communication or signal wire burial depth in parking lot. I can find anything in Ch7 or Ch8. 504.20 says I any wire method is suitable including ch7 and ch8 but it just feels wrong to bury wire that shallow.
Communiction wire burial depth
- Thread starter mannyb
- Start date
- Status
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Unless there is a reference to 300.5 in chapter 7 or 8 there is no burial depth requirement. See section 90.3
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
However having said that, I would recommend conduit and 24” cover. 24” is what most would expect when digging
hbiss
EC, New York NEC: 2017
- Location
- Little Falls, New York NEC: 2017
- Occupation
- EC
Actually Belden 88760 is a red high temperature plenum rated cable- two conductor #18 shielded. Nothing is said about burial or direct burial or intrinsically safe so I don't know where you get that from. The jacket is teflon, however I don't know how well it will hold up to moisture or burial. It's not designed for that. It very well may be that the problem they are experiencing is caused by the cable deteriorating, not the burial depth. Because the cable is shielded, if the shield is intact there should be no problem caused by cars passing over it.
I would install conduit buried at 24" and use the proper cable for the wet location which the conduit is.
-Hal
I would install conduit buried at 24" and use the proper cable for the wet location which the conduit is.
-Hal
Fred B
Senior Member
- Location
- Upstate, NY
- Occupation
- Electrician
Here is an odd question and don't know if it possibly applies. I see it odd a vehicle driving over an established buried communication cable would produce enough pressure fluctuation to cause a signal disruption even if buried as shallow as stated.
So can it be close enough to the surface if the cable is not shielded to be picking up induction interference from the vehicle passing over it? Similar effect as that for a traffic light.
I would be interested to know if this is only or mostly happening when hybrid or plug in hybrid vehicles drive over it, this would be more present over time as there has been an increase in the use of these vehicles and their unique electrical RF signatures from their electric motors. If it is from induction getting the wire deeper or shielded would prevent future issues. It would seem if it was every single vehicle or if it was on initial installation the complaint would be immediate and urgent, but it seems this occurred after a period of time had elapsed from original installation.
So can it be close enough to the surface if the cable is not shielded to be picking up induction interference from the vehicle passing over it? Similar effect as that for a traffic light.
I would be interested to know if this is only or mostly happening when hybrid or plug in hybrid vehicles drive over it, this would be more present over time as there has been an increase in the use of these vehicles and their unique electrical RF signatures from their electric motors. If it is from induction getting the wire deeper or shielded would prevent future issues. It would seem if it was every single vehicle or if it was on initial installation the complaint would be immediate and urgent, but it seems this occurred after a period of time had elapsed from original installation.
gadfly56
Senior Member
- Location
- New Jersey
- Occupation
- Professional Engineer, Fire & Life Safety
While Teflon is great for acid and caustic resistance, it's surprisingly not a terrific moisture barrier. I recall a reading a monograph on Teflon in its various flavors and the porosity is something like 0.01%. Not huge by any means, but over 20-30 years?
The problem is how I worded the question. Nothing is said about it being teflon and I got most information from spec sheet. I also agree that it needs to be 24'' but noting in code says it cant be 6'' below finish grade either. The customer is the one who determined its vehicle traffic causing problem. Im just trying to provide a permanent solution. I also want to bury it 24''.
Product Description High Temperature Electronic, 2 Conductor 18AWG (19x30) Tinned Copper, FEP Insulation, Overall Beldfoil® Shield, FEP Outer Jacket, CMP Technical Specifications Product Overview Suitable Applications: extreme high/low temperature environments; chemical resistant; outdoor and burial applications; low voltage analog signals (4-20ma, 0-10v, ...); low voltage digital control (24v, …); line level audio; wet locations; panel wiring Construction Details Conductor Element Number of Element AWG Stranding Material Pair(s) 1 18 19x30 TC - Tinned Copper Insulation Element Material Thickness Color Code Pair(s) FEP - Fluorinated Ethylene Propylene 0.007 in (0.18 mm) Black, Red Outer Shield Material Shield Type Material Coverage Drainwire Type Tape Bi-Laminate (Alum+Poly) 100% 20 AWG (7x28) TC Outer Jacket Material Material Thickness Nom. Diameter FEP - Fluorinated Ethylene Propylene 0.014 in (0.36 mm) 0.146 in Cable Diameter (Nominal): 0.146 in (3.71 mm) Electrical Characteristics Electricals Element Nom. Conductor DCR Nom. Capacitance Cond-to-Cond Nom. Capacitance Cond-to-Other (Conds + Shield) Nom. Characteristic Impedence Nom. Velocity of Prop. Max. Current Pair(s) 5.5 Ohm/1000ft (18 Ohm/km) 51 pF/ft (170 pF/m) 97 pF/ft (320 pF/m) 29 Ohm 69% 5.4 Amps per Conductor at 25ºC Nom. Outer Shield DCR: 7.3 Ohm/1000ft Voltage UL Voltage Rating 300 V (CMP) Mechanical Characteristics Temperature Operating -70°C to +200°C Bend Radius Stationary Min. Installation Min. 1.5 in (38 mm) 1.5 in (38 mm) Max. Pull Tension: 62 lbs (28 kg) Bulk Cable Weight: 23 lbs/1000ft Standards and Compliance Environmental Suitability: Indoor, Outdoor, Sunlight Resistance, Oil Resistance, Oil Resistance, Burial Flammability / Fire Resistance: NFPA 262 Plenum Flame Test (UL 910), FT6, IEC 60332-1-2 NEC / UL Compliance: Article 800, CMP CEC / C(UL) Compliance: CMP CPR Euroclass: Eca European Directive Compliance: EU CE Mark, EU Directive 2015/863/EU (RoHS 2 amendment), EU Directive 2011/65/EU (RoHS 2), EU Directive 2012/19/EU (WEEE) Non-Plenum Number: 8760 Product Notes Notes: For use in indoor plenum environments but also suitable for outdoor and underground applications. Gas/vapor-tight jacket. History Update and Revision: Revision Number: 0.415 Revision Date: 07-02-2021
- Status