we're OK for an electrician, it's the builder, and several other trades, we're short of - credit-crunch BD, who's idea was it to win the Olympics ?
What would be the best way to monitor electric usage over 50 circuits?
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OK - Well I'll be the guinea pig then :-)
I have a question first - in the current configuration setup for the metering there is a 'meter sample period' - which is typically set to 60 seconds. This is how many counts the input must receive before updating the network with its current value. If the counter overflows before that time does Cortex handle sending the packet sooner and updating the meter ? ISTR from another thread that it does.
edit: It seems it does :-) because if I increase the interval to a period when it would overflow then I see in the log reports always with a count of 250 but occurring at irregular intervals which correspond roughly to when I would expect a near overflow.
What would be useful though is to have a way of synchronising your meters displayed value with the software counter held by Cortex and maybe displaying that onscreen against the object. A running total in the daily activity text log would be good too. I think you can sort of work it out by knowing the value at midnight on a certain day and then adding the consumed units eg KWHr as reported by Cortex since then. This for accuracy would require totalling the counts in the daily activity log.
Currently I have only four meters being monitored by Cortex using a QRH - two electric (upstairs and downstairs) and my gas and water. The two electric are also monitored by a Current Cost energy consumption meter in summing mode over the two sensors.
What I see currently however is that CurrentCost is displaying 3.51 KW and Cortex is displaying 2.75 KW + 0.2 KW = 2.95 KW so they don't add up. Now the Cortex sensors are electrically connected and include voltage sensing whereas the CC is a current clamp so I would expect some difference, but it's quite a lot (+19%).
So I'm out to ascertain if that's the different measuring techniques or if the pulse inputs are missing pulses which would make them read low. Tonight at midnight I'll read my two meters and then again tomorrow night and compare that exactly to the values Cortex presents.
More anon...
KLast edited by Kevin; 26 July 2009, 06:37 PM.
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IIUC ... 1.19 power => 1.09 voltage and 1.09 x 230V = 250V ... so, since 250V is not unheard-of our way, the 19% might not be out of court ...
ie: how about tracking voltage for a while ... we find it varies quite a lot with time of day ...
hmm - light bulbs not lasting so long as they used to could be an additional clue - ie: we've had to put-in dimmers to protect lighting circuits where tungsten bulbs are unavoidable & we have to use bulbs optimised for Continental use ...Last edited by chris_j_hunter; 26 July 2009, 06:50 PM.
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Originally posted by chris_j_hunter View PostIIUC ... 1.19 power => 1.09 voltage and 1.09 x 230V = 250V ... so, since 250V is not unheard-of our way, the 19% might not be out of court !
ie: how about tracking voltage for a while ... we find it varies quite a lot with time of day ...
Maybe it's a power factor consideration as the loads are washing machine/dryer mainly but we'll see...
K
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Originally posted by chris_j_hunter View Post
..you've got me worried...
BTW, does anyone know of a way to get multiple meters to provide more information than one per meter would give ... my feeling is that using them in some sort of clever heirachical arrangement ought to be a way of getting more individual things measured, but ... no luck yet !
KLast edited by Kevin; 26 July 2009, 07:30 PM.
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Originally posted by Paul_B View PostCould you also monitor the electricity board meter over the same period? SHould this not be the most accurte metering to act as the baseline?
I'm counting at the moment.... and there's heavy consumption what with washing machines and ovens so we'll see. I'll let it run till just before midnight and see what it looks like - and then I'll run a full days worth from then.
K
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Originally posted by chris_j_hunter View Post>three values from two meters ...
trouble is, one of the three is only the sum of the other two ... so the third is not really new, as it were ... ie: two meters, two items. not three ...
K
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OK - Started running the counters now from a new day... and also had a quick stab at a shorter period over about 4 hours last night. Meter read immediately after time of the Cortex read.
Sum of Cortex counts over period - 6484 = 6.484 KW
(Excel imports and adds these up really easily for you)
Meter Reading change = 40018147-40011603 = 6544 = 6.544 KW
Which on initial observation would indicate some 60 pulses or about 1% were missed . I'll see what comes up from the 24Hr log.
K
(Meter uses 50ms marker pulse and 1 pulse / WHr)
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ok 24 Hours...
Cortex count 29192
Meter Count 40047360-40018147=29213
Difference = 21 = .07% which I think is pretty good.
The last digit is not displayed and the penultimate figure changes about once every 10 secs so that could easily be a reading error as I have to guesstimate when Cortex takes its reading. So I think I'm fairly confident that the QRH sampling period on the inputs is inside of 50ms - and it's not missing any :-) Good stuff.
Now to try the ODI ...
K
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