More Noise, Filtering and Troubleshooting (and let’s get this one done, already)

Which One Should I Use - Part XII

Phil Kingery

kingerly12-01.jpg (9919 bytes)
by Phil Kingery

Is this the real Uncle Phil?

That brings up a very interesting problem. In order for blocking filters to "block", they have to be designed to carry the current of the circuit to which they are wired. Back in WOSIU#10 (August), I spoke of ACT’s AF300 filter. It is a 20 amp, hard-wired filter made to block an entire circuit. But one circuit is a lot different than a whole panel. The AF300 fits into a 3-ganged box. A 200 amp equivalent would have to be 10 times larger. They do exist (although not from us).

Which One Should I Use, Part XII (Preamble)

Did you get that flu bug or whatever it was, that was going around? Boy, I sure got it! I was down for nine days (didn’t take a shower for almost a week) and almost missed Halloween (one of my favorite holidays). I didn’t really start feeling better until just a couple of weeks ago, just in time for my anniversary here at ACT. On November 12th, I started my ninth year at Advanced Control Technologies so either I’m putting up with them or they’re putting up with me, I’m not sure which. We had a party to celebrate. Sorry you couldn’t make it.

Anyway, here we are on the fourth part of what was supposed to be a 3-parter on noise and filtering. This is absolutely going to be the last one on this subject. We are definitely finishing it this time. That’s not to say we won’t come back to it at some distant future date, but as far as THIS one is concerned, this IS IT!!

In WOSIU#9 (or, "Which One Should I Use, Part IX), WOSIU#10 and WOSIU#11 we discussed noise in general, then we talked about basic filtering, then I gave you some basic ideas on troubleshooting. In this last (and I really mean it this time) part, we will talk a little more on troubleshooting plus a lot on the whole-house filter. (If you want to look at any of the previous articles in the series, they are all archived here at HTI, just for you.)

I received a lot of nice comments on the last article. This one was particularly nice plus offered a great troubleshooting idea. I quote (in part):

Dear "Uncle Phil",

As I read your article about troubleshooting, it occurred to me that a general technique I use to find conducted line noise might be very useful for X-10 as well. The technique involves a simple, cheap, portable AM radio. The radio is tuned to an unused frequency near the low end of the dial, say 550 to 650 kHz. It is then used as a sort of probe, bringing it close to outlets to get sort of a "warmer" or "colder" direction. This technique can often lead you directly to the offending source of the noise. Since this portion of the AM band is around the 5th or 6th harmonic of X-10 signals, it should be fairly accurate unless the source is putting out something narrow band.

Keep up the good work,
Bill Whitlock, president
Jensen Transformers, Inc.

I agree!! That is a great idea, especially for the do-it-yourself-er. I have heard of several other people using that same idea. Some HA professionals have even confessed to me that they use the radio trick but only when their customers were not around. They think it looks "unprofessional". Unprofessional or not, if it works, why not use it.

Bill is an expert in his field and will be speaking at the upcoming CEDIA show. I recommend his seminar. (Hey, Bill. Perhaps you would be interested in writing a column for us here at HTI. Maybe you could call it, "What Audio Stuff Should I Use".)

Another comment came from Steven Bloom who brought up a very good point. I will quote (in part from) his email:

In your latest "Uncle Phil - pt 11" you forgot to cover a very important and increasingly common noise problem. What happens when you discover that all breakers … are off and you STILL have interference?

My local electrical provider has begun experimentation with carrier-wave communication on the AC lines and it completely trashes one-half cycle of the X10. I have a bus-bar neutral and unable to use a whole-house blocker. Could you talk to us about alternatives?

Steven Bloom

Well, Steve, I will try. You have brought up two very good points. One is the growing problem of noise coming in from the utility or neighbor, and second, what do you do when you can’t use the whole-house filter. Your email is a great lead-in to this edition. Today, we will talk about those two points plus a lot more. So gather round children and make yourself comfortable. I, the Scheherazade of the HA world will now impart to you all my wisdom and knowledge.

….and now…

More Noise, Filtering and Troubleshooting
(and let’s get this one done, already)

Before I can give Steve Bloom some alternatives, it is important that we discuss the whole-house filter. After we talk about that little gem of a product, we will be in a better position to suggest an alternative for Steve.

I really don’t want to get into the "physics" of how X-10 signal and noise is referenced, so let’s just say that most of the time, they both (the good signal and the bad noise) are referenced to neutral. (For all you engineers out there, we will keep the technical definitions of common mode and differential mode noise to ourselves, shall we?) We are also going to assume that everything on my side of the meter is perfect. I don’t have any noise problems inside my house. Unfortunately, I happen to live next door to a guy who belongs to the Welding-of-the-Month Club and his big arc welder puts out a bunch of electrical noise. (Or it could be another X-10 system which uses nearly all the available addresses. Or it could be situation where a neighbor, metaphorically speaking, uses variable speed drives, often called "VFD’s", which generate a high amplitude interference spectrum.) Whatever the source of the interference, I have discovered that it is coming into my house and I need to block it.

Of course, sometimes it may be the other way around. Perhaps I have a large X-10 installation and I need to be a responsible neighbor. Therefore, I want to keep my X-10 signals from interfering with my neighbor’s system. A third possibility is that I have a home theater system with a "kick-butt" sound system but I have discovered that all those audio amplifiers and all that video stuff is killing my X-10 system. Fortunately, all of my home theater equipment is one sub-panel.

We now have at least three examples when it would be nice to be able to block noise and/or X-10 signals on a large scale. This is one way we can do it.

dec9801.gif (6916 bytes)Since the noise from the neighbor comes into my house by way of the main power, I could stop that noise by simply cutting those cables (fig. 1), right? Well, that would work, but it is obviously impractical. Okay, since that is not a sensible solution, what about putting a filter at that same location?

That brings up a very interesting problem. In order for blocking filters to "block", they have to be designed to carry the current of the circuit to which they are wired. Back in WOSIU#10 (August), I spoke of ACT’s AF300 filter. It is a 20 amp, hard-wired filter made to block an entire circuit. But one circuit is a lot different than a whole panel. The AF300 fits into a 3-ganged box. A 200 amp equivalent would have to be 10 times larger. They do exist (although not from us).

dec9802.gif (6444 bytes)Let’s say that I went ahead and bought one (at great expense, I might add) and decided to put it between my main panel and the meter (fig. 2). Well, that would work, but it would be difficult to install since the lines would be "hot" (can you say "electrocution"?). That’s because they are upstream from the main breakers in my panel. That also means that I am going to have to pay the utility company to come out and remove the meter so I could install the B.A.F. Of course, that is when the electrician informs me that my installation is against the NEC.

dec9803.gif (6806 bytes)Since I am forced to have some major wiring done to conform to the National Electric Code, I might as well have an entirely new enclosure installed (fig. 3).

Now I have spent a small fortune to have an new box installed and a R.B.A.F. wired into it. Now, my electrician can remove the B.A.F. and reroute my power cables into the new panel (with its new main breakers) and then back to my old panel (fig 4).

dec9804.gif (7274 bytes)Now I have a wonderful, whole-house blocking filter. My neighbor’s noise can’t get into my house and my X-10 signals can’t get out. (Actually, there is no such thing as a perfect filter, so it will most likely be about a 40:1 reduction factor.) The only problem is that it cost me so much money that I had to sell my big screen TV, all my stereo equipment, my furniture and my X-10 system to pay for it. Hardly seems worth it, does it.

Well, children, there is an alternative. Let’s go back to my regular breaker panel before I paid to have all that other stuff added to it. Remember I said that I could block outside noise by cutting the cables? It also stands to reason that I could do basically the same thing if I cut the main neutral wire, right? (Yes, I know that I am over simplifying this, but play along, okay?) dec9805.gif (5411 bytes)Let’s take this one step further. Instead of "cutting": the neutral wire (which is somewhat impractical), what if we could make a small section of that neutral wire have "frequency selective reactance"? (Fig. 5.) What that means is that the neutral wire would be just a regular neutral wire for all my power (at 60Hz), but as the frequency went higher, the resistance would increase. Finally, at the frequencies near that of the X-10 signal, the neutral wire would appear to be a big fat resistor.

dec9806.gif (5676 bytes)That is exactly what I have here (fig. 6). The CP303 is the ACT part number for the "whole-panel" filter. (Leviton and X-10 Pro have the same thing but since I have 12 children to feed, I would prefer that you buy it from one or our distributors.) We call it a whole-panel filter since we use it in a lot of industrial / commercial systems to isolate sub-panels. You will notice that it has screw terminals for L1, L2 and L3 so it is obviously made for a 3-phase panel. Since it will also work quite nicely on a 120/240v residential panel, you can call it a "whole-house" filter if you like, I don’t mind.

It is wired in such a way as to sample the signal (or noise) on the panel and then use that signal on itself. The small voltage is inverted and fed into a tuned circuit which contains a coil which induces a reverse potential onto the neutral wire. It’s like a small transformer which uses any incoming high frequencies to create a high impedance to block its entry, and/or it uses any outgoing high frequencies to create a high impedance to block its exit. Stuff in my house stays in my house. Stuff outside, stays outside.

The advantages are obvious. It is much lower in cost compared to that heavy R.B.A.F. and does not require its own enclosure. It can be installed in about 10 to 20 minutes without the need for removing the meter. Another advantage is that it also acts as a passive coupler for leg-to-leg signal coupling. It’s not quite as good as a dedicated passive coupler (the ACT part number CP000) but it is close. There are a few disadvantages. If you already have a coupler/repeater in place (CR230, for instance) then the passive coupling nature of the CP303 will degrade the effectiveness of the repeater. They tend to work against each other.

There are also some limitations. While most inspectors will allow it, there are some who will not let you install the CP303 inside your panel. Installing it outside the panel would render it completely ineffective so there seems to be no alternative. Another limitation is that the hole through which the neutral wire must pass is only big enough to handle the neutral wire used on 200 amp panels. If your service is larger than 200 amps, the CP303 will not work.

There also seems to be another limitation but it is really simply a misunderstanding. Often, an inexperienced installer will attempt to use a whole-panel filter when he really has no clue where his noise problem is originating. He may think that "a filter is a filter", so any filter will help. In this case, he may be completely wrong. If the noise is coming from inside the residence, he has now "trapped the skunk inside the house". Not a good idea. In these situations, his problems may increase dramatically. Where he had a moderate problem with his X-10 system, he may now have a complete failure of the system. (Of course, he calls me and complains that we sold him a defective CP303 and I try to explain….)

dec9807.gif (8135 bytes)Another misunderstanding is in the way this blocking filter works. Look back at figure 6. At the bottom of the graphic, you will notice a little symbol like an upside down tree connected to the neutral bus bar. That is the symbol for a "ground" connection. In my own house (where one of the very first whole-panel filters was tested) my grounding wire is a long, flexible, bare copper wire that goes up and out of the panel along with all my other power wires. That ground wire may give the X-10 signal an alternate pathway to get out, or noise to get in, while bypassing the filter. My experiments showed that I could increase the effectiveness of the filter simply by feeding that ground wire through the hole in the filter, along with the neutral wire (fig. 7).

You may not be so lucky. You may find that your neutral wire is not flexible enough to wiggle it through the hole. You may find that the ground wire goes out to the grounding rod through another pathway. You may find that you can’t even use the whole-panel filter, just like Steven Bloom did. That is the other limitation to which he referred in his email. He said: I have a bus-bar neutral and unable to use a whole-house blocker. Could you talk to us about alternatives?

Many residential electrical panels do not look like the ones I have pictured in this article. Instead of a panel inside the house, many houses have "load centers" where the meter and breaker panel are in one large enclosure, mounted on the outside of the house. In those cases (as Mr. Bloom can surely attest), there is no "neutral wire". Instead, the load center has a solid, welded bus bar. There is no way to detach one end and feed it through the hole in the CP303. Do we have plans for a "wrap-around" unit? No sorry, we don’t.

What are some alternatives for Mr. Bloom? Unfortunately, they’re not many. In his email to me, he describe a situation where the "noise" appeared to be a deliberately transmitted signal originating from the electric utility itself. This is very unusual. I have worked with a lot of electric utilities and although there are many power line carrier protocols (usually of lower frequency and higher power so that they will migrate more easily through the utility transformers) they are never "on" all the time, at least not the ones I have seen. They also operate at a frequency, typically below 10kHz, so that they don’t interfere with residential X-10 systems. If you are an electric utility representative and would like to offer any information on this subject, please email me. I would be very interested in hearing about what is being used by the utilities around the country.

Steven Bloom also said. "My local utility did not offer a filter (I did not ask, though) plus they implied that it may be my responsibility to compensate for it." Although it is not a daily occurrence, all the incidents in which I have been involved, it was made clear that the utility is responsible for providing clean, interference free, power to its customers. In those cases where a filter (or in one case, an expensive isolation transformer) was needed, the utility put it in without cost to the customer. I suppose that they could also turn it around (although I'm not going to bring up the subject) that if they are going to provide clean power to its customers, the customers must also keep their signals (X-10) from getting on the utility's lines.

There are companies who specialize in cleaning up dirty power. One company in Milwaukee gets a lot of referrals from me.

TCI - Trans-Coil, Inc.
7878 North 76th Street
Milwaukee, WI 53224  
Phone (414) 357-4480 * Fax (414) 357-4484  
Helpline 800-TCI-8282

They sell the "HarmonicGuard K-Series" isolation transformers and have representatives all over the country.

Another company with whom I am just starting to investigate is:

Filter Concepts, Inc.
2624 South Rousselle Street
Santa Ana, CA 92707
Phone (714) 545-7003, Fax (714) 545-4607

For a long time, I stayed away from companies like this because most of my experience had been with filters that suck up the noise plus all the X-10 signal at the same time. Now, it appears that this company is also designing some high current blocking filters.

I also would like to hear your experiences. Please send me an email if you know of a source for blocking filters that can be used in a similar fashion to the CP303, or perhaps a ferrite core choke. Let me know and I will include it in the next issue.

We have come to the end of yet another episode in this series. I told you that this was going to be the end of this sub-series and by jiminy, I am sticking to my word. I will leave myself an escape route, however. I will ask that, once again, you vote on what you want as the subject of our next meeting. Over the last several months, these subjects have been suggested:

  1. An in-depth explanation of the standard X-10 binary code structure with an introduction to the X-10 Extended Code set. This one may be a little boring to the do-it-yourself-ers out there, but to the professionals, it could be very enlightening and would explain a lot of the "why does it do that" questions.
  2. A discussion of preparing a new house for home automation "before" it is built. What to tell your electrical contractor to do while your new house is being built so that you are well prepared for all that new home automation, home theater, phone system and home office equipment you want to install later. Since I do not consider myself an expert on this subject, I would have to rely on a lot of ghost writers to help me (any volunteers?).
  3. A discussion of complex coupling situations not previously covered. For instance, what if your house has two 200 amp panels side-by-side and you need to install a CP303 on each one. How to you couple the two panels to each other. This is a common question in my emails.

Send me your votes on 1, 2 or 3, or come up with your own subject. (If you want a discussion on Audio-Video Grounding and Interfacing, I know just the guy to ask to be a guest columnist.)

I also want your vote on one more thing. For the last year and a half, Bob has used the picture of "me-in-the-oscilloscope" at the top of my articles. You no doubt noticed (which might have been quite a shock) that the picture was different this time. Vote on going back to the old "o’scope" picture, or staying with the new "line-up" shot. We could even do a completely different one. My friend, Dave Rye (VP at X-10) also writes articles for this web site and his picture also accompanies all of his articles. If you have ever met Dave you know that his picture is most definitely "him". He is always impeccably dressed, ever the professional and ever the gentleman. (I suppose my picture says something different about me.) If you really want, I will do a picture of me with a "tie" (but I won’t shave off my beard).

Like they say in politics, vote soon and vote often.

Is this last we have heard of Captain Coupling?
What’s this we hear about the new A10?
Stay tuned, children! Same Bat Time, same Bat Channel!

Phillip Kingery is a representative of Advanced Control Technologies, Inc. and teaches X-10 related classes around the country. Email him at

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