Dimmer Neutral Wiring

Thanks for the suggestion Nick, that had certainly crossed my mind. As the "events" could be a month apart, and then every night for a week, I was thinking about how I could achieve both. As the sprinklers are only in the period 8-9am on various days and the water hammer is only at night and the sprinklers are all attached to the one C-Bus relay unit, I'll connect the supply of that C-Bus unit and the 24VAC Txfmr to another C-BUS relay unit (via an interposing relay) and put a schedule on the relay so "the system" is only ever active for the period that is required and isolated for the rest. As you say, it will certainly give me an answer. Cheers, cc&c.

 

Flash in the pan

From the colective responces and incident reports I can see 3 distinct possibilities for these lights flashing to full brighness then back to their original setting (and also for the apparent flickering of lights at certain times of the day)

Let's start with the flickering: in NSW, parts of NZ, parts of Southern Queensland, most of South Africa the generating authority send a (relativly) high frequency pulse down the mains usually for 5 to 10 minuites every 15 to 20 minutes at around 10 - 12 at night and again at around 4 - 6 in the morning. This pulse is to signal the meter to start the off peak or 'j' tarriff meter that is pumping up the emersion heater and the storage radiators etc.

The Dimmers have filter circuitry to minimise the effect of this pulsing on the load brightness but the authorities between countries and states and even local areas use different frequencies (in particular in adjascent areas they will transmmit at one frequency for a period to turn on some meters and then issue a different frequency to turn on others so they don't load the system too much by turning all the 'j' tariff loads at the same time).

So the filters work with some frequencies better than others and some units in some areas will exibit more 'flickering' than others in other areas. Also in any system the 'flickering' is more perseevable (if that is a real word) when the light level is low and that is because your eyes are more sensitive to changes in light levels when the light level is low, the same amount of 'flickering' can happen at 100% brightness and your eye may not 'see' it.

While some replies on this page have mentioned this effect it is quite different to that reported by CC&C

Don's explanation of dv/dt is comprehensive and undoubtedly can cause the effect that was reported. However it is unlikely that this effect would occur in a house unless the source of the interference was very close (ie in the house itself),

The third possibility is the frequency tracking circuitry of the dimmers. as reported before the C-bus dimmers will track the mains frequency, and if it sees it changing at a rate of more than 10Hz per minute (from memory) it will go to full brightness untill the frequency settles and then it resumes the set level.

There are a couple of reasons that I think #3 is the prome suspect in CC&C's case, firstly the observation fits the mechanism like a glove, but also because historically there have been more reports of this behaviour from Tassie and NZ and guess what is the connecting factor between Tassie and NZ? Most if not all power in those two areas is generated by Hydro, now I don't pretend to understand how they bring generators on and off line to cope with changes in demand in power stations but it seems more than a coincidence to me that these reports more often come from these two spots. In fact the early DIN and PRO dimmers could only stand 3Hz per minute rate of variation but they were modified to the more robust level primarily because of reports of this type of behavior form tass and NZ (as well as a couple of Islands and outback towns that were running on generators that groaned under heavy load changes) It may well be that for what ever reason Hydro generated power is more prone to frequency variation (you wouldn't think so during its normal running but may be when the loads change and more/less capacity is required there could be frequency pertibations (and boy do I love that word, thanks to Ashleigh for injecting it into the debate, I first heard it from the mouth of Don many years ago with regards to a different product and I had to go and look it up!)

 

Uncle Sam

First it is nice to from you over there in the land of Stars and Stripes.

On your point of frequency variation 10Hz or more over 1 minute (I think these were the specs you mentioned) is this the spec for DIN and Pro dimmers alike.

PS. Do you miss me ?

 

My memory tells me that the 10hz over a minute is for both DIN and PRO is correct (but I may be wrong ADL could confirm), on earlier units there was a difference in the rate change that either model could cope with and in the behaviour of the two models when a too rapid change was detected but this was reglarised back in 2002 or so and the two models effectivly react the same the frequency changes.

Miss you? of course I do but let's keep that just between us ok?