Dimmer Neutral Wiring

With respect to the manual for the wiring of the 5504D2A Dimmer Module, I was just wondering if someone could clarify what is meant by the phrase:

"Do not cross Neutral connections" as in:

3. Mains supply to the Control and Switching Stages are NOT internally
connected. Both must be wired from the SAME VOLTAGE PHASE.
DO NOT CROSS NEUTRAL CONNECTIONS.

Cheers, CC&C.

 

It means don't cross the neutrals if your going to be using seperate circuits for the control and load sides. It's sad that it has to be put in writing but some electritions (for want of a better word) think a neutral is a neutral and just grab it from anywhere.

Each electrical circuit must have it's own neutral wired back to the switchboard. Even thou these neutral may be connected back at a neutral bar in the switchboard they still need to be indirvidual cables so that the circuits can be isolated with no chance of any backfeeds!!!

 

I think it is more for installations where individual combination mcb/rcd's are installed per circuit

 

I can't be Neutral on this

There are two seperate issues here:

1. Conformist is right the message about not mixing Neutrals is to guard against installers who take line connections from two different lighting circuits that are protected by RCD's (GFI for the USA) to different C-bus output units. This dimmer here may be controlling two lights in rooms at the front of the house and one up stairs at the back and be supplied by a feed from RCD #1 while this relay just below in the panel may have its feed from RCD #2 and switch power to various lights all over the house. So if to save time/labour the Sparky runs the Neutral return from the load up stairs that controls the light in the main bedroom back via the ceiling rose for the en-suite light that is switched from the relay then he has effectivly saved 10 metres of 1.5mmsq, saved 1/2hr labour and neatly crossed the neutrals of two RCD circuits such that now when ever any one of those two loads are turned on both RCD #1 and RCD #2 will trip off. And when the OZ wiring rules changed in early 2000's to require RCD protection on all lighting circuits there was a spate of such reported problem (as in "this #@%%%&* C-bus, every time I try to turn a light on it trips both the RCD's protecting the lighting circuits")

2. The note about the two Neutral connections on the DIN dimmer not being connected is just to empasise that the installer needs to make connection to both terminals (and also noted somewhare in the text while those two connections can be from 2 different circuits they must be on the same phase. The reason for the two terminals is that you may want to remove the supply to the dimmer channels to isolate the loads while doing maintainence or automatically when the Emergency generator cuts in and you only need to supply a sub set of critical loads but in both cases you probably want to rest of the C-bus network to continue functioning and therefore it needs all of its sourcing C-bus power supplies connected because even though you have isolated some output circuits you stilol have all the C-bus units connected to the bus consuming their 18, 22 or 35mA like the hungry little children they are. By splitting the connections the top left side that feeds the on board power supply can be maintained while the top right hand feed can be removed to isolate the loads and the bus will remain fully powered.

 

Thanks guys for the responses.

I'm certainly aware of the requirement for the neutrals to all go back to the supplying RCD otherwise it obviously won't work correctly. I thought that there may have been another technical reason that I was missing. i.e. If I have a dimmer and relay module supplied by the same RCD I can thus have the neutrals all return to the same point. (I thought the manual might be suggesting that I needed to separate the dimmer neutrals from the relay neutrals).

The reason for my question is that I currently have an issue where lights are instantly going from a dimmed level to 100% for a few power cycles and then instantly back to the dimmed level. The resultant effect is a flash of light across the room. I have a Dimmer and Relay unit protected by the same RCD and the neutrals all return to the same point. I suspect that my dimmer unit may be faulty.

Cheers, CC&C.

 

Would you please expand more on this comment...

Do you mean that when the lights are first turned on, they flash up to 100% then drop down to a (preset) dimming level ?

Or do you mean that you would be sitting there with the lights dimmed, then suddenly the lights flash ON for a split second then return back to dimmed again ?

In other words, is there anything (an event) that triggers the 100% light level ? Does it affect ALL dimmer channels or just one?

Also, is there a PAC or Colour Touch on the circuit? Certain programming methods can cause flashes like you describe, since the Logic can take a split second to realise a dim setting is already in effect (hard to explain here).

 

Thanks for your interest JohnC. The above statement is correct. It is all very randomn, sometimes even in the early hours of the morning (we leave the hallway lights dimmed low overnight for our young child). I've got a B&W C-Touch with some scenes programmed in, however, this fault has only occurred over the past month and I haven't touched the C-Touch for around 6 months. I turned on toolkit the other night just before going to bed and I checked the "last known to set" in the morning to see if there were any C-Bus events. Nothing showed up for the lights in question. In order to totally eliminate the C-Touch I will disconnect it for a few nights and see what transpires.

When the event occurs, the lights that it happens to is all randomn. I thought that the lights in question were all on the same dimmer, but I've just checked and they're spread across 2 different dimmers. I have previously checked all the wiring for a loose wire, but didn't find anything. Hence my original question about crossed neutrals and whether there was something technical that I was missing.

Probably a question that I should pose in a separate post, but do you know the tolerance limits on the voltage supply for C-Bus units? The manual simply states 220-240V. Do you know if these are absolute limits? The reason I ask is that I was wondering if it is something on the supply side. I live right next to the neighbourhoods supply txfmr and if this is a possible cause, I've got no problems with trying to track down a power analyser and eliminating that as an issue as well.

Thanks again, CC&C.

 

Do you have three phases on the supplies or just a single phase? What your relay is connected to? Any Fluorescent Ballast? Is the dimmer the Din Rail ones? While dimmer is sensitive to the "zero" level of the supply, any feedback from Neutral or cross talk between wires could confuse the dimmer, I think. So it is important to trigger the fault. Switch on the affected load at a low dim level, switch on and off, one by one, all other lighting in that night scene until you can see flashes on the dimmed load. If you can, you then find the affecting load. If not, really you need a scope to look at the waveform.

 

Take that to the next level too... run toolkit and turn on the Application Log and leave it running. That'll catch ALL events, not just the LAST one to set.

Please note that I am officially out of my depth answering this problem... I actually asked the questions because I saw that the other replies missed the real problem (flashing lights).

I have had faulty dimmers that have done wierd things like this, but since your's are across different dimmers I reckon that it's something on the Bus. There will be a reason it's happening, but I have absolutely no idea what that might be

JC

 

Thanks for the response Wanricky.

Single phase, relay is connected to incandescent lights, no fluros on the dimmers or relay, yes it is the din rail.

Because the flashes are completely randomn then I haven't been thinking along the lines of other loads causing the flashing. (i.e. I didn't experience anything last night, only once the night before and above 7 times the night before that). You have a good suggestion though in that there could be a source even though to it appears randomn. I'll keep a closer scrutiny on what could affect this. You've got me thinking and this could be temperature related, but at the lower end. I just checked the specs for the dimmer and it says a minimum of 0 degrees. The unit has probably been as low as say +3 degrees but certainly not below 0 degrees. I'll keep a note though to see if there is any correlation.

Thanks again, cc&c.

 

Thanks I'll certainly do that and see if something turns up. It does become quite annoying to be sitting in a dim lit room and all of a sudden a flash of light goes across the room like lighting. Does tend to get the heart skipping a few beats. I'll post separately about the max. voltage.


Thanks again, cc&c.

 

Don't know if it affects Cbus or not (and as I'm off-grid I can't check it here), but some equipment (particularly dimmers from memory) were badly affected by various tone injection systems. (The ones used to turn on and off off-peak water and heating systems etc). Is there any chance its that?

Another thing I had quite some years ago (and it too a lot of hunting down!) was a similar experience with ordinary triac-based dimmers that did strange things at irregular times. Usually a few hours apart. Generally only one flash, but sometimes two or three. Turned out to be a really noisy (dirty) thermostat on a cheap bar fridge that arced and sparked and introduced a heap of crap on one phase only.

 

I have 2 other ideas - probably wrong, but might give a clue perhaps.

The first one is a story about a brand new Osram SwitchDim installation we just did. This is DALI ballasts run without DALI controllers, but instead uses a pulsing of 240V across the ballast control terminals to make it do things (dim, toggle power, set scene, etc).

Anyway, the system was acting totally ape-**** whenever a large DMX-controlled 3-phase stage lighting Dimmer Rack was in use and large loads were being dimmed by it. Use the fade controls and the DALI ballasts went completely crazy, some switching on and it was completely random. It was not coming over the the control line (Bus), because it didn't affect all the ballasts at the same time.

After hours and hours of testing we discovered that there was heaps of harmonics and RFI being generated by the Dimmer Rack. This was putting a heap of wierd noise onto the Neutral. The DALI ballasts were picking up this neutral current and thinking that it was a control signal. The dimmer was made by a very well-known Lighting Control Supplier that specialises in that kind of product, and it was producing enough noise to also make the inhouse audio system completely unusable as well !

OK - C-Bus is completely different... but don't discount interference from other devices. For example, off-peak hot water signals happen at night (probably isn't that, but mentioning it as an example). I dunno what I am trying to say here, except that our company lost about 100 man-hours tracing the cause of what appeared to be faulty DALI ballasts, when the real cause was a completely unrelated product.

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Second suggestion is the TYPE of loads. Are these incandescent lamps? If they're LV then are they wire-wound or electronic transformers? And you are dimming to a VERY LOW level (as a night light for your kids)?

a) With electronic transformers that have very low input capacitance (eg: Atco Possum/Speedy) the Leading Edge dimmers tend to be unstable at low levels. I have heard reports (but not seen evidence) that the light level wavers around quite a lot in this situation.

b) In my son's bedroom we have a Clipsal (non-c-bus) dimmer that flashes and farts around at low dimming settings. There is no logic to it and it only happens when I am NOT watching it... kind of like what you describe but not as radical. This is with a 60W incandescent load.

**********

So, try the troubleshooting as we have mentioned above. But also try changing the Minimum Dim setting in toolkit and see if that fixes the problem. It may not do anything to solve it, but it's not going to hurt to try it out.

I realise I am clutching at straws here, but there is definitely some reason for this psycho flashing wierdness.

John

PS: What is the toolkit Application Log reporting each morning ?

EDIT : I could have saved a fair bit of typing if I had read what Ross wrote before I posted this But I guess that since we both say the same kind of things, then it might be more likely than I have initially considered.

 

Flashing

This is a very interesting subject, similar to the dimmer protection threads. Anyway, I have also come across flashing dimmer channels.

The type of flashing is mostly a fast continuous flashing, in most cases at low settings (<10%), but there is also one occasion of a dimmer flashing at a setting around 70%. What is common to all of them, as far as I could establish, is that this phenomenon occurs in the evening into the night, and affects certain channels of different dimmers.

This leads me to believe that the tone signals mentioned earlier are good candidates for this. The question would be why it would only be certain channels?

Another type of flashing which I have come across is a single flash at switch-on of a light circuit. That, however, occurs anytime that the circuit is switched on.

It has to be mentioned that the type of loads in question are incandescent, low voltage and in one instance electronic trannies (Osram mouse 2x). The load as such also ranges from minimal (relative to the channel capacity) to 90% of the rated capacity.

Now if the cause for the mis-behaviour of the dimmers is a tone signal, is there no filter which can be used to get rid of that?

 

I know for a fact that those cheapo crappy (please forgive me for saying the following 3 letters) HPM remote-controlled touch-plate dimmers (2-wire kind) almost always have a problem with the hot water switching signals at night, usually between 10pm and 6am, when dimmed to levels below about 40%

Although I would assume that Clipsal and CIS, seeing as that they are far smarter, and build much better quality gear than that OTHER company..., would have a higher immunity to those other pieces of junk I have sadly installed in the past when some consumers like their "wow" factor... (then again, they cost about $70, so u get what you pay for...)

Darpa

 

I have one of those in our Master Bedroom - bought it in about 1980 when they were first released. Haven't had any problem with ripple signals. One thing about that HPM device is that the IR signal is so crude that the TV remote turns it on and off (hmmm... dunno if that is good or bad -we find it handy)

JC

 

Lots of ideas, thanks to everyone, some quick simple answers:

1. Lights are all incandescent, hence, no issues with LV txfmrs. Lights can be dimmed anywhere between 10-70%, hence, doesn't appear to be due to a specific level.
2. My experience with this problem is the same as Thomas, i.e. only at night (I know that sounds logical, but we leave our young childs light on sometimes during the day and it hasn't exhibited the same symptons.)
3. I haven't enacted the toolkit application log yet as I haven't experienced any incidents over the past few nights. This is starting to create a pattern though where it may be related to external ambient temperatures. I have a couple of CBus units located external to the house (in a weather proof metal enclosure) which would experience temperatures down to say +3 degrees.
4. Harmonics is another good suggestion. I've been racking my brain as to why this has all of a sudden stopped, what have we been doing differently the past few days.
5. I'm not exactly sure whether "off-peak" signals are used in our area (hot water, heater, etc. is wired to a separate meter on a different tarrif). This wouldn't explain why it is intermittment though.

Thanks for all the comments, I've certainly got a lot of suggestions as to what the problem could be and now it is a matter of following them up.

Thanks again to everyone, cheers CC&C.

 

In Hobart we used to have a few problems exactly the same as you. In fact I had the same problem in my own house. (not that clipsal would admit a problem, however they did change a whole apartment blocks dimmers free of charge years ago.)

It related to a 'dirty supply'. The power would brown out ( either low voltage or fequency change) and c-bus would think the power went completely off. It would then do a system check for a split second then the lights that were on would go to full brightness then back to the level they were set at. (note the dimmers were set to NC at power fail). This happened mostly later at night and if there was a storm somewhere it would be terrible

I believe Clipsal changed the dimmers to be more tolerant. You can check the dimmer version by looking through the vent slots on the bottom side of the dimmer. There is a sticker on one of the chips from memory that may start or end in 6. If it does, then you probably have a less tolerant dimmer. I think the good ones had a number nine.

Sorry I am so vague but it was ages ago I had the problem.

How new are the dimmers.

Chris.

 

Thanks very much for your response Nobes. You post has helpd to preserve some of my sanity ...

I'm in Hobart as well, however, my dimmers are relatively new (MFG Date Nov 2004). I've checked the chip that you mention and all the dimmers end in a 9, so they are of the newer type. I had about 10 months of worry free dimming and then the last 6 months the flash events (as described).

I had made the basic observation that this phenoma was occurring when ambient temperatures were cold which could be related to all the electric heaters, hot water cylinders and heat pumps switching on/off around the state. I also had this first occur in about March so the cold temperatures didn't fit but certainly the storms observation does.

A few more ideas that I've had but didn't air earlier as my understanding is basic and didn't think many here would be able to help, but that is the effect of BassLink and BPL on the incoming supply (not to mention Zinifex, Comalco, Temco and the mines of the West coast). The former two are recent additions to the supply system.

Just another thing, have you ever experienced a "flash event" on a relay unit? I've got solenoids for my sprinklers connected to a relay unit. I've been randomnly experiencing water hammer for the past two years which is unrelated to anything happening inside our house. I'd been blaming our neighbours (our lines are joined before connecting to the mains) but when it occurs on randomn nights and at randomn times, i.e. sometimes can go weeks, then sometimes 4 events in the space of 5 minutes at 3am; then it must be something else. The penny is now dropping that the water hammer is quite possibly because of a "flash event" on the relay unit. There hasn't been a strong correlation between a flash event on the dimmers and the water hammer, however, the water hammer only occurs at night .....

Can you confirm for me that the flash events that you experienced generally occured only on 1 (or possibly 2) channels at a time, not all channels that were dimmed. I believe that this is generally my case but as it occurs so fast and so randomnly, I'm not sure how many channels this happens on at once.

Thanks again Nobes, you've certainly given me some hope that I might be headed towards finding a solution (for both my problems).

 

Flashing lights

Check the compatability of your LV transformers. I have had exactly the same problem occur months after completion. I discovered that we had installed the wrong Tx to the lights. Every now & then the lights would flash to 100% & back off for no reason