While I await delivery of my 555 PS DR for my NDX2, I was wondering if anyone has measured its power usage when idle, and if possible when active? My XPS DR is 24Watts, and I’ve seen that @Blackbird did quote 30W on 272
I did have a Wattmeter somewhere, but I think I lent it to someone, so wanted to update my Power Usage spreadsheet ready.
35W on an NDS apparently.
Out of interest, to what use do you put a power consumption spreadsheet?
Thanks. Originally it was an interest type exercise to see what was causing the various peak throughout the day. Also with Solar Panels, I wanted to see how low I could get usage during the nights (no batteries you see). It was part knowledge, part environmental, part savings, part liking data.
Ultimately I found the inside Freezer was using twice what a new one would, so I brought a new one, and the old one was passed on via freecycle to someone who’s was desperate after theirs broke (I did make them aware often usage). I also purchased a few Smart Plugs to shut things down at night that were not required 24x7, and the spreadsheet helped to work out the payback time.
Yes, it’s the sort of thing my geeky friend would do. Last week we were away, but took part in the Octopus free hour’s extra electricity. I received an email from them today saying that we hadn’t used more than normal - which we wouldn’t as we were away. Our consumption in the hour was 0.107kw, which covered the fridge-freezer, NAS, router and EE switch. Normally we’d have a 40W bar heater running in the airing cupboard, so our ‘quiescent consumption’ would be about 150W. I’m rather glad my hifi is just a Nova these days, which goes into standby when not being used. A few boxes using 35W is quite a lot.
150W - that’s brilliant. These days I’ve not managed to get the quiescent consumption down much below 250, but at least I am aware why. HiFi in total (e.g. with switches etc) is less than 100W keeping the living room toastie in the winter. The rest is 2 freezers, and various items using 1-6 watts which soon add up.
It’s an interesting one with AC, because actual power, as opposed to approximate power, will depend on your power factor. With DC it’s a lot easier 
I personally think for accurate measurements you need to rely on specifically current and voltage… unless your know your house or circuit power factor.
For very approximate or relative power usage, one can ignore of course.
But for best power efficiency, if you have several highly inductive uncorrected loads (large transformers and motors) is use variable power factor correction in your house.
Whilst PF correction is common in industry, i can’t say i’ve heard of it being used domestically.
Oh yes, I think regulations show power correction must be applied to highly reactive components, like washing machine motors, and large transformers,
… and I believe some switch mode powersupplies. However over time the correction can fail or move out of tolerance.
Now you don’t pay more for poor PF on traditional meters. However on some regulated devices when presented with poor PF they may consume more current to compensate… and you will pay more then.
I believe PF should be between .8 and 1… whether it be leading or lagging.
Haha. Sounds like recap is required.
The meter I had did measure PF, but to be honest I didn’t take much notice of it. It’s not something I looked into much from a household point of view. I do recall from my electrician courses that for fluorescent lighting, industries tend to correct it back at the Consumer Unit end for a given circuit after a measurement then by adding appropriate capacitors. However fluorescent lighting for domestic use, had them inside each tube holder. There were lots of question I wanted to ask about it at the time, but to be honest it was just a matter of getting through the exam with limited teaching time.
Yeah it’s only in these days of cost conscious electricity consumption it is potentially more relevant than previous years. Its not really an electrician thing, they can’t control it, rather its an appliance manufacturing thing,
My 555 has gone straight to be seviced via Class A, so if I can find my watt meter, it will be interesting to see what PF it measures
A minor point and off topic … I’m in the process of changing kitchen lighting to lm & colour variable and noticed PF is spec’d for the SMPS’s in LED arrays.
Yes check whether your power meter read true power which is measured in W or kW or apparent power which is measured in VA or kVA.
Apparent power ignores Power Factor, True power takes the power factor (current voltage phase angle) into consideration and presents the true power than is being consumed or the actual work possible.
So if your power meter is reading true power, you may see the load changing slightly when the washing machine, vacuum cleaner, a large Naim amp or large amounts of led lighting is switched on. If it’s pretty solid the chances are you have either great PF correction on your appliances or it’s measuring apparent power in VA and not Watts.
I take it your 555 is non dr ? I ask as my 555dr will be due a service shortly, but im not sure Darran services dr stuff. I did email him, but didnt get a reply. Didnt chase up as it’s not a priority, and makes my ndx2 sound so much better that the xpsdr that i had before.
It is DR (2014 model), and is with him at the moment. so assuming that it can.
@Simon-in-Suffolk found these in the manual, doesn’t use the word True, but does refer to Actual, and measures in W not VA
Apparent power is measured in VA, not Watts for AC. For DC it’s measured in Watts. My bad the term is ‘Apparent’ not ‘Actual’ for non power factor corrected power as described by the IET.
Curious of what your meter is reading for PF …the ideal 1, .85 is acceptable. But 0.28 would be terrible.
Well that perhaps mean I should go around every device again and measure the PF also. As much as I like data, I don’t think I will be doing that. Hm, or shall I 
When Naim were doing DR conversions they had to go to the factory, not Class A. Perhaps that’s what you were thinking of?
They get their spares supplied from Naim, so if they are sent a DR part I’m sure they could fit it.
Good, thanks for that. My cd555psu is 10 years old, so not quite a now issue and the ndx2 sounds good right now. But, i’ll get a quote from Class A.
