Part 2 - Energy-saving debate

Thank you Dynalite for your civil debate on power-saving methods.

Let's continue with some rebuttal and a quick look back to the original points. We will start off by looking into your solution.

I will try to detail some issues that need to be taken into account when deploying this solution and why in some cases I find it hard to justify. There may be some cases where the savings can work, but it is not a simple open and shut case.

Let's consider the wiring diagram above that you presented. This at a glance may look correct, but it misses the mark on what is actually required. Below I have put together what I would consider to be a compliant design. Note, The subcircuit circuit breakers can be replaced with RCD's ( or protection devices)

You see, as I tried to point out in my previous discussion, to be compliant you need to be able to detect a mains failure on the final subcircuit after any protection device and switch on the emergency lighting. Note: The subcircuit is that last circuit on a bigger circuit as per AS2293.1 2.3.3 (See below) and includes the protection device(like a RCD).

I used Contactors in the last analysis as I assumed I was making a compliant design and a contactor is not a protection device, but changed where the final subcircuit circuit breaker was located. Due to this, I foolishly added the Contactor power loss into my equation.

Edit: I forgot one really important point. Even if you put the monitoring on the subcircuit as shown, the system still doesn't work as the Emergency lighting will be triggered every time the system disables the lighting. It would need more logic to make it work. (how did the sites get around this?)

In reply to this comment:

As you can see, there is no extra field cabling required for network lighting control to manage the emergency lighting that would not already be required for a standalone system." - Quote Dynalite.

I have highlighted the additional cable in red. Later in the document, you will be able to find the alternative layout to compare to. Typically wired in 2.5mm2 three core cable (up to 2-300 meters?), unless used in a 6 wire harness, which would wire 6 wires to every device adding cost and waste.

Let's also now understand the inrush current of this design and how it applies to limit the design.

As we all know, when we turn the lighting on we will experience a inrush of current for a short period of time. This current needs to be designed for, and most LED driver manufacturers will list it on their datasheet. Now, in this application, all three subcircuits are wired through and switched via the DDBC120-DALI. This means, that when the DDBC120-DALI turns the lighting back on, we have a large inrush. Looking at the maximum stated inrush for the latching relay (yes, you are correct a good-designed one) the inrush current cannot exceed 500Amps. That is, the total load after this switching device shall not have an inrush current larger than 500A.

As we take the inrush current into consideration, we now have a look at a number of DALI drivers.

Firstly, yes there are some poor drivers on the market and as good advocates for quality, we steer our customers away from inferior devices. The DALI standard is not a MEPs standard but has defined a maximum standby power and many manufactures have chosen to provide better solutions. I decided to find the first three drivers I could google for this example from Tridonic, Osram and Philips to demonstrate the power consumption (and I included our smart driver which includes the standby power of the emergency charger and plug in DALI sensor (active, but not detecting) which is not powered from the driver). It must be noted that OEM's can purchase Tridonic, Osram and Philips drivers at very similar and competitive price points and arguable would be within the top 5 DALI drivers sold within Australia (by unit quantity).

Now, calculate the standby power. Firstly, how many devices can I use in this installation based on the inrush current? Can I safely derate the drivers inrush current, do I know the design of all DALI drivers to know under which circumstances the inrush current could be less? Most likely not, so we will need to use the data provided by the manufacturer and provision the system to meet those requirements.

It might spring to mind that this is nowhere near the maximum capacity of a DALI line, but we are limited by the latching relays' maximum inrush current and the information provided by the driver manufacturer. On a side note, because of this application I need more controllers and DALI lines to be able to deliver my building which adds to the total power consumption.

So we end up with the following standby power (per device), which can be saved by this system (7am–7pm 5.5 days per week).

But what were the costs to get to this result?

• More controllers were needed to complete the building, with additional power consumption (looks to be up to 25W? 2 controllers are needed per DALI line)

• The addition of a contactor for the emergency lighting, which adds 2.755W *24 hours. this will only be off when there is an emergency = 462.84Watts / week (standards requirement).
• The addition of circuit monitoring, which can add 6-10W/hour or 1008-1680 Watts/week (standards requirement)

The savings before adding the power consumption of the second controller and more circuit monitoring on the second set of controllers (due to inrush current limitations) show negative savings when Osram and Tridonic drivers are used with this technique. However the Philips driver, due to its idle power provides a net saving before adding a second controller.

The weekly power consumption for the additional controller can be up to 4200 Watts (taken from the DDBC120-DALI datasheet) which makes even the best scenario provide negative power savings.

Power savings summary (based on the wiring provided by Dynalite)

• To comply the design needs to add circuit monitoring which adds additional power
• To design within the limits of the DDBC120-DALI's inrush parameters the down circuit loading has to be limited to 500A (good safe design, with edge-case protection), this provides fewer power savings and increased deployment costs significantly.

We now compare this wiring to one which does not need to switch the standby power off.

This design

• Doesn't require circuit monitoring as the emergency devices (DALI, HIVE, Axiom or another monitored system) will activate if the circuit fails.
• Has no inrush limitations and can comfortably accommodate 64 devices.
• Doesn't require a large amount of additional cabling to power the emergency devices as they are wired in the same system as the standard lighting.
• Reduces the space needed in the distribution board
• Allows for significant luminaires to come on in the event of a system failure and covers all edge cases (some presented previously) including the safe egress of people who enter the building after failure, who for whatever reason decided they needed to get back into their office. (Something the energy-saver schematic does not achieve)

• Has a faster and possibly more comfortable first activation time as it doesn't go into power-saving mode.
• Increases the reliability of the total system as it reduces dependent and interconnected parts.
• Cost significantly less to deploy
• Contrary to the remark (below), the installation could have used the savings from the less complex design and purchased the correct driver (although low cost, low standby drivers can be found without the additional cost).

It would be nice for our competitors if drivers consumed less power in standby mode, but in a world where price sensitivity means installers often select the most cost-effective driver, this is not the case. -Dynalite.

• Additionally, the customer could use the savings (the actual argument which was not addressed) to purchase more energy-efficient lighting as 2% better efficiency at the driver level could return 3-6.5x the energy savings. For customers who are cost/price sensitive, I think my argument makes a lot of sense - remove all the ambiguity of the complex design, remove potential edge case issues and use the money you have saved to give you the best environmentally friendly savings as not only have you saved on energy costs (and as a result produced less carbon), but you have also reduced the amount of raw materials and consumed energy needed to manufacture, ship and install the additional parts.

Energy efficiency needs a smart approach to get the best results, but it also needs to consider the circular economy and reduction. A solution that reduces consumption (i.e. the parts required to achieve the solution) while delivering better energy efficiency surely is a better overall solution.

With regards to the example of reactive power, a site like you describe tends to have active power correction installed. Sometimes it becomes more cost economical (or mandated) than dealing with the installation of larger supply transformers and cabling. Additionally, it becomes a moot point in this argument as the power factor changes on many drivers as they are dimmed and is a much bigger problem when they are Active due to the magnitude. A bigger-picture solution that covers the entire building's power and all modes of operation will effectively become the most cost effective solution.

I agree with you that some competitors outsource (or divert attention away or focus in on specific areas) from their responsibility for sustainability. When looking at lighting control people need to look at the full picture. We included emergency lighting here, but what about the other auxiliary items like controller power, onsite PCs, switch, sensor, and other items that make up the total installation?

Now just remember this discussion wasn't a marketing contest for those that can hide the most amount of insults or political wins, rather this was me making the discussion point about the best way to make energy and environmental savings. My point was;

1) I don't think the costs stack up when delivering a standards-compliant installation. It would be at least $500 / Line to add the required parts and you are getting a $14/ year saving (a 35-year payback when using a driver that has a 0.5 Watt standby power). You could double the savings and still be at 17+ years payback. We know you can fiddle some maths, choose different drivers, maybe even wire it differently, but the outcome is very similar.

2) The complexity and edge cases that need to be considered becomes higher

3) Customers can get a better bang for their buck and faster environmental wins by concentrating on driver efficiency (as an example)

4) There is no argument about energy efficiency and the need to deliver savings, the argument is about what is the best savings to be had and how best to spend your money to achieve it.

Last thoughts -another example of why I think it doesn't stack up

If a customer spent the same amount of money installing solar power as needed to make this method a compliant design, then for every ~12 lines, they would have a 10kW solar installation. This installation could produce 280kW power a week and is the equivalent of 109 DALI lines of standby power. Make better decisions for faster results as we are running out of time.

We are all passionate about energy efficiency and lighting control and as such, we value your input.

Josh

(BTW, you might not have seen that the original article was updated early in the week, this update addressed some of your points)