<div class="bbWrapper">How would you approach the following (I'm interested both from a theory and practical point of view as I'm studying for 2382 and working out an actual design spec prior to LAB submission right now):<br />
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Lighting circuit with mixture of <br />
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6 x GU10 w. 11WCF<br />
3 x GX10 HID (Britespot 35w Metal Halide).<br />
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Ususally I understand (irrespective of the lamp holder and ignoring diversity for now (see last questions below)) a minimum of 100W per lamp should be assumed i.e. 9 x 100w = 900w / 230 = 3.91A. <br />
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What happens when you mix in HID though? <br />
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I think I am right in saying that (assuming power factor is not <0.85), the guideline is to assume a 1.8 correction for transient load i.e. on the 35w/ 100v HIDs above this would be (3 x (35w*1.8))/100 = 1.89A.<br />
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However, when you think about it, the 100w guideline assumes 230v i.e. 0.43A per lamp. At 100v (which is what the balasts run at), the same calculation produces 0.63A - a 43% difference.<br />
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I've searched everything I can think of, but can't see a guide on this. <br />
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I suppose a second related question is whether the Design Current for a lighting circuit can take account of the type of lamp holder in use (for example, while a GU10 can take anything upto a 100W GU10, a GX10 can only take a 35W Sylvania HID. If this was the case then the Design calc could use the actual I guess.<br />
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Also, if this is a single radial supplying all of these lights in the same room, am I right in saying that it is not appropriate to apply 66% diversity guideline as it is likely they will be used simultaneously.<br />
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Apologies for the long post, hopefully someone will have experience on this.</div>
Calculating Design and Estimated for mixed Lighting Circuit
- Thread starter benstoneham
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<div class="bbWrapper"><blockquote data-attributes="" data-quote="benstoneham" data-source="post: 819759"
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However, when you think about it, the 100w guideline assumes 230v i.e. 0.43A per lamp. At 100v (which is what the balasts run at), the same calculation produces 0.63A - a 43% difference.
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</blockquote>100W is 100W is 100W.<br />
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If the lamps were ELV, you'd have a figure of 5.25A <b>for the lamp</b>, but it would still only be 0.27A <b>for the circuit</b>.<br />
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I've searched everything I can think of, but can't see a guide on this.
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</blockquote>Try <a href="http://en.wikipedia.org/wiki/Ohms_law" target="_blank" class="link link--external" rel="nofollow ugc noopener">this... <img src="https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f606.png" class="smilie smilie--emoji" loading="lazy" width="64" height="64" alt=":lol:" title="Laugh :lol:" data-smilie="18"data-shortname=":lol:" /> <img src="https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f606.png" class="smilie smilie--emoji" loading="lazy" width="64" height="64" alt=":lol:" title="Laugh :lol:" data-smilie="18"data-shortname=":lol:" /> </a><br />
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I suppose a second related question is whether the Design Current for a lighting circuit can take account of the type of lamp holder in use (for example, while a GU10 can take anything upto a 100W GU10, a GX10 can only take a 35W Sylvania HID. If this was the case then the Design calc could use the actual I guess.
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</blockquote>Isn't the whole point of the 100W rule that anyone could come along and change the luminaire or fit a different lamp? I know it's hopelessly outdated though, as it harks back to the time when all there was were 40/60/100W GLS...<br />
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Also, if this is a single radial supplying all of these lights in the same room, am I right in saying that it is not appropriate to apply 66% diversity guideline as it is likely they will be used simultaneously.
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</blockquote>In any diversity calculation the designer must be guided by his knowledge and expertise. If you judge that they'll all be on then you can't use diversity....</div>
<div class="bbWrapper">The 100W rule only applies to lamp holders which take standard GLS lamps. Any fitting with a fixed wattage (such as flourescent tubes) can be counted as it's rated wattage.<br />
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You design a circuit for what you put in, not to what it might be altered to.</div>
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The 100W rule only applies to lamp holders which take standard GLS lamps. Any fitting with a fixed wattage (such as flourescent tubes) can be counted as it's rated wattage.
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</blockquote>That makes a lot more sense.</div>
<div class="bbWrapper">OK, that makes sense... always seems obvious when someone points it out.. I'll re-read wikipedia as pennance! thanks for the help.</div>
