When calculating loads, how do halogen 50w LV recess cans figure into play? Do I just treat it as I would a 50w incandescent? Same question for neon...
TIA
Mike

If it's 50 watts, it's 50 watts..

Halogens are a form of incondescent suspended in a halogen gas. It rates the same.

If there is a 12V transformer allow 10% for transformer losses. Also check the type of the transformer and make sure it is compatible (dimmable - leading edge e.t.c).
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In Vantage using the DIN-EDS dimmer module where there is a LV magnetic load the dimmer only allows 70% max watts compared to a normal load.

Is this a Homeworks system? Which dimmer module, HWPM, HRPM, GXI?

The transformer loss should be part of the 50w rating for the pot light. Most if not all recessed pots lights, that support a MR16 bulb, are magnetic transformer based. In the case of a Lutron Homeworks system it doesn't matter if it's Magnetic or electronic transformer.

If it's 50w it's 50w.

Neon? I would have to assume that is some sort of old term for fluorescent lighting? If so, these are typically switched devices (i.e. on or off) even though there are some dimmable ballasts available for fluorescent fixtures.

If it a real NEON tube, it will have a transformer/ballast, but should be treated as a non-dimmable device.

If the transformer is Electronic Low-Voltage then you typically derate the dimmer 50%. This goes for wallbox dimmers or dimming modules.

Keeping that in mind a dimmer specifically listed for Electronic Low-Voltage is generally a standard dimmer derated 50% and priced at a premium. Some low voltage dimmers simply don't like dimming and will respond irradically to amy dimmer.

As for neon, read the power supply. Neon is more like fluorescent so dimming may be a challenge.

Is such the case for the RA ELV's?

Neon tubes are commonly used nowadays for setting a specific color temprature of lighting for specialty displays. They can Absolutely be dimmed (And most even require it) as you need to mix the 2 colors of neon to acheive the output you desire to properly light you artwork.

50watt LV may still be 50w, but you really need to pay atention tot he wattage rating of the Transformer. Especially with Track type Fixtures. just bcause there are 3 50watt Fixtures onthat Track the day you set the system up doesnt mean some lighting person (Or even the homeowner) wont throw another fixture (or 5) on that track sometime inteh future. (Its happened to me)

I believe there has only been one correct answer here, at least technically. If you pay attention to the software utility, in preferences, under load, you will see something called transformer VA derating. Any transformer will do work. In the case of a MLV transformer it will turn 120v into 12v. In the process of doing that step down energy will be lost, used by or lost in the process of the transformer doing its work, turning 120v into 12v.

For the purposes of the load schedule you should just enter 50w and multiply it by the number of fixtures. But the program will add on to that number some constant, usually 20% or an other if you've entered a different value in load preferences, and make the correct load calculation. You may not see that value entered in the load schedule but try this: Try and attach 3 incandescent loads that add up to 1200w. Assuming a 20A lighting circuit try and drop a 400w MLV load on to that module and see what the software does. You will see a GRX-PB added automatically even through you have 1600w total on that module. The software is accounting behind the scenes for the transformer's energy and it knows that you have exceeded 16A and adds the power booster.

I believe the correct value, in absence of a specific transformer VA rating for the fixture being used, is 20%.

Yes, Alan is of cource once again right.

Lutron estimates 20% for transformer loss (MLV)
Vantage estimates 30% (for MLV)
Another system we do advices us for 10% (for ELV)

Alan do both kind of transformers (magnetic and electronic) waste energy? Aren't the electronic ones a bit more efficient?

Advice on electronic transformers:
First check if the transformer is dimmable.

Then check if it is dimmable by leading or trainling edge dimmers- usually good transformers indicate this on their casing: dimmable by leading and trailing edge dimmers.

If you only see on the case "dimmable" there is a big chance the transformer is not very good and of questionable (not good quality) origin.

If there is nothing written on the case about dimming, change transformer. You will almost certainly have problems if you try to dim this.

Connect the transformer and see if the buzzing is bearable. If there is a lot of buzzing from the transformer or the dimmer this probably means that the transformer is not good and that it will fail after a few months (this really happens). Also obesrve the lamp when you dim and fade up and see if the process is natural.

Do not use trailing edge transformers on a leading edge dimmer. They will gradually fail or even not work at all.

Homeworks is a leading edge system but there are modules (HRPM4A, GXI3504, NGELVI) that can be used with trailing edge transformers.

The best transformers we have tried and the most silent ones are the Lutron ones, but they are quite expensive.

This thread has reminded of an excellent paper on transformers by Lutron:

[Link: lutron.com]

Application Note 19: Guide to Dimming Low-Voltage Lighting

Work requires energy. If you recall you basic high school physics, matter cannot be created or destroyed, only changed from one form to an other. Boil water and you will lose some of that water -- a licquid--into air in the form of steam. A transformer will "waste" some energy in the form of heat and some more energy in the process of generating a magnetic field ( in the case of a magnetic transformer ). I'd not call this waste as the cost of the work the transformer is doing. Every transformer has a VA rating and you can substitute the specific, accurate VA rating for the specific transformer rather than use the generalized, assumed value of 20%

I do not know much about the relative efficiencies of electronic vs magnetic transformers. Electronic transformers are smaller and so very popular with many fixture designers. They cause less lamp buzzing issues as the transformer itself does not make any noise. On the other hand electronic transformers are typically much less reliable, especially as 98% of them are made in China for the least amount of money. They are much more difficult to dim, typically due to the reverse phase dimming and capacitive load they present to the dimmer.

I simply do not know the aswer to your question though if you look at the VA rating on the transformer you can make your own determination. My gut guess would be that electronic transformers are more efficient and require less energy to the work of transforming 120v to 12v than a magnetic transformer.

Another FYI on magnetic transformers: If a magnetic transformer is used to supply a one-lamp fixture and that lamp burns out, you do not want to keep turning that fixture on before the lamp is replaced. Operating a magnetic transformer with no load on it will burn out the transformer.

Another caution regarding track lighting installs: Fixtures are available for line-voltage (120 V) track that can utilize incandescent, fluorescent (compact or T5), magnetic low-voltage, and electronic low-voltage. Be careful about mix & match of these fixtures when connecting to dimmers both at the time of installation and as a warning to the client for future adds and changes.

GFood stuff, fellas. Keep it coming...

Very true.. However I have yet to work on a house where the client changed anything like this after moving in on their own.. They usually call you to change the light bulbs, and with specialty fixtures that come from designers you could never find the stuff in Home Depot to do yourself..