POWER, TELEPHONE AND CABLE, ALL IN ONE CONDUIT 2

[EEAOC]

I would like to know whether I can run power [208 v], telephone and cable TV in one conduit for a private home/vacation home project. It is 350 feet run. I don't see any code violation in doing this, however will there be any interference or cross talks?

Please advise.

Thanking you in advance

 

[resqcapt19]

Look at 800.52(A), 820.52(A) and since communications cables are not marked with a voltage rating also look at 300.3(C)(1).

 

[DougMSOE]

This is a very bad idea. Cross talk and computer interference will be a big problem.

 

[itsmoked]

Yes DougMSOE is correct. Whether or not it is "allowed" it is BAD, BAD, BAD. It is a poor idea. It should not be done. Bad ju-ju will be present.

Yes there will be crosstalk you may have hums and buzzes in your phone. Your DSL can have problems. Your TV cable may give you bars. A serious fault in the power may actually damage something.

It is also kinda strange to be running 208V into a "house' of any kind too. Your 240V range will have troubles as the elements will only get 75% as hot. Your A/C unit may burn out if not truly rated for 208V. Your water heater, if electric, will be abysmal.

 

[resqcapt19]

itsmoked,
Actually 208 to a dwelling unit is not all that uncommon. Many large apartment buildings are fed from a 208 wye system. There are also subdivisions in some areas where the utility supplies houses with two hots and a grounded conductor from a 208 volt wye. You are correct that the appliances have to be designed for this voltage to work correctly.
Don

 

[itsmoked]

Ah yes, but I said "house" resqcapt19. Does indeed make sense for apts though.

 

[rbulsara]

even for house 208/120V, 3 wire is pretty common now..

 

[lengould]

Just from memory, but doesn't the code require that all conductors in a conduit must be insulated with a rating equal to the highest voltage in the conduit? Will be very difficult to find TV cable with any voltage rating, therefore the electrical run should fail inspection.

For 208V residential, the apartment developers usually purchase all heavy appliances and heating equipment with element manufactured specially for 208 V rather than 240V, eg. lower resistance higher amperage for a given rating.


Pechez les vaches.

 

[mc5w]

A lot of electric ranges are dual rated 120/240 and 120/208 volts and just simply have the thermostats and controllers throttle the heating elements differently.

Also, on some utilites here in the U.S. REQUIRE larger houses to have 3 phase power and 3 phase air conditioners. One of then is Duquesne Light Company.

Just this past Thursday I ran into another house in Cleveland Electric Illuminating Company territory that has 120/240 4-wire delta 3-phase to run the central air. A lot of these house date to before 1967 when a house with central air had to have 3 phase power. I even ran into the housewife this time and she told me that the previous owner was an HVAC guy.

I told her about how the original way that noise abatement was done along Interstate 71 in Columbus, Ohio was to stick 3 phase air conditioners into all of the houses. In the kind of climate that Columbus has household A/C does need to be 3 phase - one time when visiting Ohio State University my urine turned brown even though I was drinking about a quart of water an hour. I also told her that I get a kick every time that I see a house that has 3 phase power in it.

Actually, geothermal heat pump neighborhoods would work a lot better using 6 wire services that are both 120/240 single phase and 277Y480 three phase. All of the power quality problems from the heat pump compressors would be isolated from the lighting. The safety difference between 120 volts and 277 volts is like the safety difference between a 0.22 firearm and a Colt 0.45. Both guns will kill you just as dead if not handled correctly. For that matter, the Ohio legislature reclassified air rifles as firearms after someone was killed or seriously assulted with an air rifle and the prosecutor could not attach a firearm specification and extra jail time.

 

[itsmoked]

Well By geebers I stand korrekted!

 

[mc5w]

US rules in National Electrical Code are that CATV and telephone conductors cannot be in the same conduit. The same trench but not the same conduit. NEC 725.55, 800.47, 800.133, 820.47, and 820.133 effectively prohibit this. Also, the electrical utility would want to put antitampering seals on any pull box that is on the supply side of a meter and they would object to giving permission to break seals to maintain anything other than the electrical service conductors, meter sockets, and so forth. There are just too many safety and practical considerations.

In actuality, putting 2 or 3 different kinds of electrical conductors in the same conduit would prevent withdrawal and replacement of broken conductors or doing an upgrade. What you need to do is to install 3 conduits and 2 sets of handholes.

You need 1 conduit ( about 4 inch ) and 1 set of handholes for the power condutors. Because of your distance from the power source you need 400 amp service conductors to get adequate voltage drop performance when starting a central air conditioner or subersible well pump. ( 4 inch well pump motors are up in the code S starting current range. ) You need at least 500 KCM copper or 750 KCM aluminum for your distance. You might need to instead use 2 smaller power conduits using 2 conductors in parallel per phase and neutral. Using an oversize conduit will make wire pulling a LOT easier and will save on screaming as well as wire pulling labor. Stuffing a conduit to only 3/4 of what NEC allows almost always pays because of lower wire pulling labor.

You would then need two 1 inch conduits for the telephone and CATV. Telephone and CATV can share the same handholes and pull boxes unless there is somehow a major amount of labor friction. Communications Workers of America, Utility Workers, and Teamsters happen to like each other as opposed to how UAW has blacklisted everybody who has a Teamsters card.

The telephone and CATV companies around here never object to using the same trench as a power service if the power service is in PVC conduit.

Modern underground telephone service cables have a copper clad steel foil shield that is grounded at the protector block so you should not have too many problems with noise frommthe adjacent power lines.

Where you must have lots of separation is between natural gas lines and anything with electricity in it. In the early 1980s 2 feet of vertical or horizontal separation from natural gas and electrical stuff was required but since then the separation distance is more like 3 feet. You will have to ask each utility and the building inspectors how much they want between natural gas and electrical stuff.

Spearation from water services and sanitary sewers is also a consideration. In the case of water services a water main break could force its way into electrical stuff. In both cases they usually want a certain amount of horizontal separation from electrical and natural gas line so that they can dig up the water and sewer lines for replacement.

 

[advidana]

Where did you get the idea that all these systems could be run in a common conduit?

 

[stevenal]

Lots of citations for classified areas that wouldn't normally apply to the residential system described. The other citations specifically allow the communication conductors in the same raceway provided a "suitable" barrier is used. With no further explanation of "suitable", I guess it's up to the AHJ what will be allowed. The sheathing enclosing an NMC cable is certainly a barrier, don't know if it's "suitable".