Owl or Smart monitor reading - which to believe?

[JohnW2]

This whole discussion started because the OPs Owl was almost 50% higher treading than his smart meter and you are all saying they are accurate?

In my experience, they are ('accurate') so I suspect there is something 'wrong' with what the OP reported, given that it is very unlikely that his whole installation PF could have been as low as ~0.7 and/or that his supply voltage was well under 200V.

I'm not familiar with an OWL which as a 'remote display' (my system is 'web-based') but I suspect that, as with mine, there is a small time lag before data from the OWL appears on the display, and that may possibly be part of this explanation for what the OP observed.

I would suggest that, rather than looking at instantaneous power consumption, the OP should compare the OWL's figure for energy consumption (kWh) over a period of time with what his smart meter says for the same period.

 

[SUNRAY]

This whole discussion started because the OPs Owl was almost 50% higher treading than his smart meter and you are all saying they are accurate?

As I commented before

Yet again it's all down to learning how to use the equipment.

 

[Vicario]

Thanks everyone. I have removed the Owl for the moment as I do believe that the Smart display is more accurate. It is also very useful to be able to see an ongoing cost of electricity used. My OWL left a few indentations on my (previously pristine) 25mm live tail. Only on the surface though so not worried. There's a very useful video on the manufacturer's website. It tells the new user to go round switching things on and off to see how they affect the displayed usage. (Shall I turn off the shower MCB when Mrs V. is in there this morning? Maybe not!). But one appliance that I'm obsessed with is the coffee machine in standby mode. It seems to burst into 1.8KW usage every few minutes. I leave it on from 6 until 7.30 ready for Mrs V's decaff when she emerges.

 

[davelx]

I suspect it's keeping the heater block ready for instant brewing. I've not noticed mine (de longhi) doing that but I only have an owl set to low update rate so am probably missing it.

 

[Vicario]

There is a feature on mine to reduce standby time and then turn off. Trouble is that I couldn't find it when I set it up so haven't bothered. I'll have another look.

 

[Harry Bloomfield]

But one appliance that I'm obsessed with is the coffee machine in standby mode. It seems to burst into 1.8KW usage every few minutes. I leave it on from 6 until 7.30 ready for Mrs V's decaff when she emerges.

Nothing fancy, but my filter coffee maker cuts off after 20 minutes from being started. It cuts in and out constantly on the hotplate state. I don't want to drink coffee after the 20 minutes anyway, it is 'stewed' and bitter. I think the 20 minutes was a new regulation brought in.

 

[JohnW2]

Thanks everyone. I have removed the Owl for the moment as I do believe that the Smart display is more accurate. It is also very useful to be able to see an ongoing cost of electricity used.

Fair enough -although, as I've said and illustrated, the Owl really is pretty accurate, when used properly.

.... It tells the new user to go round switching things on and off to see how they affect the displayed usage.... one appliance that I'm obsessed with is the coffee machine in standby mode. It seems to burst into 1.8KW usage every few minutes.

Well, it has to, if it's going to keep the coffee hot (albeit probably 'stewed' beyond pleasantness!).

However, one needs to keep these things in perspective. How long are these bursts of 1.8 kW usage, I wonder? A usage of 1.8kW will cost roughly 0.5 pence per minute - so, particularly if you are using decent coffee, the cost of keeping it hot (assuming you like 'stewed' coffee!) would probably fade into insignificance in comparison with the cost of the coffee itself

It's very similar to my hot water heating here. Once my (140 litre) storage cylinder is up to temp, then, if I don't use any hot water, it only takes a tiny number of pence per hour to keep all 140 litres up to temp (with very brief bursts of 3kW usage of the immersion) - and I doubt whether you are talking about 140 litres of coffee

Kind Regards, John

 

[aptsys]

Current consumption does not indicate watts. You also need to measure volts and phase angle. The last is important and no clip on device does this. In my opinion Owls are not fit for purpose and should be banned under Consumer Rights Act.

I agree generally. They're useless in the most part and will always over report power consumption.

 

[Harry Bloomfield]

I agree generally. They're useless in the most part and will always over report power consumption.

If they are properly calibrated by the user, as John reports above, they are or can be, pretty accurate.

 

[winston1]

If the users PF is frequently changing they can never be accurate. Let’s face it if they were that good why would the suppliers not use them instead of the expensive meters they use.

 

[JohnW2]

If the users PF is frequently changing they can never be accurate.

That would obviously be true. However, the average PF of a whole installation (or even part of an installation, like one of my phases) over a significant period of time does not change either frequently or significantly - and, as i have said, if my installation is anything to go by (and I see no reason why it it shouldn't) the average PF is never far enough from unity to make any appreciable difference.

However, as I've said, such devices are of no use in relation to a single load which does (or may) have a PF significantly below 1.0 - which is why 'plug-in' ones are needed for such a purpose.

 

[JohnW2]

They're useless in the most part and will always over report power consumption.

... they will if one leaves them programmed with the default PF of 1.0 (which, in my case, would result in "over-reporting" to the tune of about 0.6%).

However, if one programmed it with a PF which was too low, it would always under-report power consumption.

Kind Regards, John

 

[aptsys]

Whole house power factor can change significantly. Things on standby are a typical cause, since the low duty cycle of switch mode supplies gives an extremely low power factor. According to my load meter, the power factor fluctuates anywhere from 0.4 to 0.85 during the day.

 

[JohnW2]

Whole house power factor can change significantly. Things on standby are a typical cause, since the low duty cycle of switch mode supplies gives an extremely low power factor. According to my load meter, the power factor fluctuates anywhere from 0.4 to 0.85 during the day.

As I've explained, I have been talking about the 'average PF' of an installation over appreciable periods of time (which is what matters for my purposes) and I very much doubt that your corresponding figure would vary all that much.

However, I'm rather surprised by the figures you mention. Are you saying that your daytime whole-installation PF is never above 0.85, and that your daytime average is well under 0.85? My 'daytime' (the 17 hours of E7 'day') average PF is well over 0.95, but it would presumably be dramatically lower than that if my figures were anything like you seem to be experiencing.

Is your total load very low?

Kind Regards, John

 

[Harry Bloomfield]

Whole house power factor can change significantly. Things on standby are a typical cause, since the low duty cycle of switch mode supplies gives an extremely low power factor. According to my load meter, the power factor fluctuates anywhere from 0.4 to 0.85 during the day.

Do you not understand what an average is?

Fluctuations matter very little, if your average is reasonably accurately assessed.