Is is Possible To Get An Electric Shock From TV Aerial/ Sat Cable?
If you want to splice/ cut your coax cable that is feeding your TV or satellite receiver and wanted to know if you are going to get an electric shock or if it is safe to do so, read this blog for some help and advice. I think that most of use have had some sort of electrical shock at one time or another so you’re right to do some research before playing you’re your TV cables.
Before I proceed any further I just want to get a general disclaimer out of the way. There is no substitute for safety, so if you’re concerned about cutting into a cable that may or may not feed your TV you should test that it’s live first and/or shut of the electricity to be safe. You should consult a competent/ qualified electrician or installer if you’re concerned about this. I accept no responsibility whatsoever for any loss, harm,damage or injury that may occur from any interpretation of the content of this article.
Do TV/ Radio Aerial Cables Carry Current?
The way that TV aerials and satellite dishes work by their very nature carry current. A TV aerial will capture radio-waves that are in the air and transfer them onto the coax cable that feeds your TV positions. The“signal” on a cable is in fact alternating current electricity, which is of a much, much higher frequency than that of your mains electrical supply. This doesn’t mean that you can’t cut into the cable as the voltage induced onto a coax cable from a TV aerial is very, very low. To give you an idea TV signal level of around 60dBµV is equal to 1mV. This is one thousandth of a volt which you’re not going to feel if you touch it and will not cause you any harm. Even if you have a very strong signal at your TV position of 80dBµV, this still only equates to 10mV which is 100th of a volt. You’re unlikely to have a signal strength of much more than 80dBµV as to be any higher you would likely overload, you’re TV tuner and cause poor TV reception. Yes, too much signal is a thing!
Systems With Masthead Amp/ Sky Remote Eyes/ Line Power
It is common with certain types of TV aerial system to have a DC line power being delivered down the coax cable at the same time as the signal to power line powered equipment. Common examples of where this may be this case is with a power supply unit providing power for a masthead amplifier and line power from a Sky box or something similar powering a line powered amplifier and/ or remote magic eyes that will allow you to control your equipment from another room. In situations like this you are still going to have a small amount of current coming down the coax cable. Most power units for masthead amplifiers will be something like 5-12V DC, but some are 18-24V DC for communal TV systems. Most Sky playback, remote eye systems will only be 9-12V DC.
Do Satellite Dish Coax Cables Carry Current?
Satellite dishes in essence work very similar to TV aerials,they pick up signals that are beamed to earth from space and deliver these to your satellite receiver. This is usually something like a Sky/ Freesat box or TV with an integrated satellite TV tuner. The difference with satellite dishes in terms of current is that as the signals are beamed down to earth and received at such a low level the signal needs to be really amplified by the satellite LNB before it can be delivered to your satellite receiver. To do this a continuous DC voltage is supplied by the satellite receiver to power the LNB. This is usually 13V DC but switching LNB’s like universal Quad LNB’s also use 18V DC to switch between horizontal and vertical polarised signals. Although this is considerably higher than passive TV/Radio cables it is still well below anything that is likely to ever cause you harm. This doesn’t mean that you won’t feel it. I really DO NOT ADVISE THIS but I used to work with a guy that used to put cables in his mouth on his tongue to see if they were connected!
If you’re connecting cables at the satellite dish and you can feel a current, this is a lot more common as typically you would be standing on a metal ladder or holding a metal scaffold pole etc. You may noticed that this increases in wet weather. This is not likely to ever cause you harm but you wouldn’t want it to catch you off guard make you jump and fall off your ladder (which you should be harnessed to). In situations like this it is advise to switch off/ or disconnect the satellite cables from the satellite receiver so that no current is being delivered to the satellite dish whilst you work on it.
Communal TV Systems
Communal TV systems are different to conventional TV systems in the sense that potentially the system could be feeding 100’s of flats which in turn could be feeding 100’s of connected TV equipment. All of this together with all the amplifiers and equipment that are required for the TV system in first instance has an accumulative affect and the voltage could build up on the cables. It’s still unlikely that this will ever be anywhere near causing harm but you shouldn’t take this for granted. TV systems that feed multiple dwellings should always be connected to an earth connection for electrical safety, but this isn’t always the case. Particularly with old TV systems. I warn you when working on TV systems which and disconnecting cables or powering down equipment you're going to get lots of residents come out and tell you that their TV has gone off. It's not uncommon for them to try retuning in this time when the signal is down and deleting all of their stored services, expect them blame you for it not working when you leave. Tuning the TV again should resolve this issue.
CAI – 6 Pieces Of AV Equipment Disclaimer
The CAI has interpreted electrical safety in the domestic environment as being safe up to be point of 5 pieces of equipment connected to your TV system. If you have 6 or more then the system should be earthed or the customer should be made aware of this situation and a disclaimer signed to waiver any liability on the installers part. The theory behind this is with 6 or more pieces of AV equipment connected your system there is a potential for the touch current to build up which could cause injury if you were to touch it,not necessarily from the current itself but by potentially cause you to fall over or something similar which could cause an accident. Please note that this is not regulation, I have yet to meet a single company that does this with domestic systems religiously but in their opinion these measures would be enough to limit legal liability. I advise that you contact them direct for more information as this could have changed at the time of you reading this.
Electrical Shock Safe Apparently Up To 50V (Not My Words)
It is said that a human being can absorb an electrical voltage of up to 50V without injury or harm. For this reason, many systems will operate up to 50V. Systems like Power over Ethernet (POE) are 24-48V, the ring circuit that comes down your telephone line (probably soon to be defunct) that makes your phone ring is 50V. A lot of electrical transformers will deliver voltage below 50V for this reason. To make it clear that this isn’t my interpretation but by others.
Fault Conditions/ Poor Electrical Installation Could Carry High Currents
In situations of fault conditions it is possible that there could be a high voltage/ current present on the coax cable that feeds your TV aerial or satellite dish. You may find this hard to believe but many of the old style Cathode Ray Tube TV’s (CRT) has voltages around 25,000V inside of the TV.As TV’s are not “White Goods” like Freezers, Fridges, Washing machine etc and do not have a metal outside shell. They often do not have an earth connection in the mains plug. This means that the only exposed piece of metal on the outside of the TV is usually the aerial plug itself, it’s not impossible that there could be an unwanted voltage here. Fortunately most new LED/ LCD/ OLED style TV’s do not reach voltages anywhere near this high.
Also it’s not beyond the realms of possibility where a poor electrical installation could cause an unwanted high voltage on the coax TV cable. This is really not common and it’s only likely that you will ever encounter a situation like this on very old electrical installations. I will add I visited family in Ireland a few years back and whoever had installed their electrical cabling had by passed the fuse board altogether! This really was not safe. Fortunately most new systems incorporate RCD’s and MCB’s that will immediately cut of the electric supply if something is not safe.
Safety Measures That You Can Take
I appreciate much of this article has been written in a worst case scenario as I want to make sure that you’re safe and that nobody comes back to me and says that they had electrocuted themselves and that I’m to blame (please read disclaimer at top again.) Baring all this in mind there area few safety measures that you can take.
-Switch off all TV equipment when working on TV cables.
-Switch off electric supply.
-Use cutters/ hand tools that have appropriate electrical insulation – Most electricians sets will go up to around 1000V.
-Earth TV systems for electrical safety. You could use temporary earth bonding whilst working on the TV system.
-Employ a professional if in doubt.
TV Cable Questions - In Blog Comments Section Only Please
I hope that you have found this article helpful, please note it is safe to work on TV coaxial wiring but you should always take safety precautions. If you have any comments or questions please feel free to post them in the BLOG COMMENT SECTION BELOW and I will get back back to you as soon as I can. I thank you in advance for your patience. Please do not:
Call out telephone lines with your questions - these are intended for customers only and we are a small company that operates in Sussex/ Kent only and do not have the resources to offer over the phone technical support.
E-mail your questions - I do not have time to privately answer questions on a one by one basis in private. By posting your questions in the blog comment section below it gives me a central location to answer of the questions as efficiently as I can.
Fill out out website contact forms - These again are intended for customers only, if you do post your question here it's very likely that you will not receive a response. By posting your comments in the blog comments section below everyone reading the blog will get the benefit of the question asked and the answer given.
Thank you and until next time.
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