Electronics > Beginners

How do home power monitors work?

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SG-1:
This is the meter you are considering:https://www.amazon.com/Morning-Group-Phase-LCD-Digital-Display-Current-Voltage-Multifunction-Energy-Power-Panel-Meter-RS485-Modbus-Communication-Distribution-Box/dp/B076VKRN4G/ref=cm_cr_arp_d_product_top?ie=UTF8&th=1

Tampering with a revenue meter is a serious offence.  You can check it without buying anything, by controlling your loads. Turn off all loads by unplugging them or with a breaker. Leave everything off for an hour, then read the meter. Now use a known load like a heater that can draw 1KW in an hour. Take the reading on the meter, run the heater for an hour then take the reading again. 

If there is a serious discrepancy call the Power Company. 

Your friend may have a malfunctioning appliance, like a water heater, which is probably his problem to find.

Gregg:
The forum has been down for most of the day, so I might be late to the party.

I personally wouldn’t buy this meter unless I could download a full featured instruction manual and made absolutely sure this device would work for the given situation.  Either my Google-fu has failed or there just isn’t this information available in any language I understand.  I did find a connection diagram that seems to indicate it may not work on split phase or single phase power, but there may be settings to allow it. 
The maximum AC voltage seems to be 265V which may or may not work for you.  It definitely needs line voltage to calculate power as well as input power for the electronics.

If you do end up using this, make sure you get the current transformers to put around the line wires to sense amperage. 

Make sure you fuse it to the line connections with proper fuses

FlyingMoose:

--- Quote from: SG-1 on December 25, 2019, 02:53:52 am ---This is the meter you are considering:https://www.amazon.com/Morning-Group-Phase-LCD-Digital-Display-Current-Voltage-Multifunction-Energy-Power-Panel-Meter-RS485-Modbus-Communication-Distribution-Box/dp/B076VKRN4G/ref=cm_cr_arp_d_product_top?ie=UTF8&th=1

Tampering with a revenue meter is a serious offence.  You can check it without buying anything, by controlling your loads. Turn off all loads by unplugging them or with a breaker. Leave everything off for an hour, then read the meter. Now use a known load like a heater that can draw 1KW in an hour. Take the reading on the meter, run the heater for an hour then take the reading again. 

If there is a serious discrepancy call the Power Company. 

Your friend may have a malfunctioning appliance, like a water heater, which is probably his problem to find.

--- End quote ---

I plan to do that (load testing).

This is in the Philippines.  Here, for example, almost all taxi meters in Manila are tampered and no one does anything about it, despite it being a “serious offense”.  There are people whose career is tampering various types of meters.  It’s very common to illegally tap electricity from your neighbor through a $20 meter from the hardware store.  Grounding is pretty much unheard-of.  I’ve only seen a handful of grounded outlets and I doubt the ground prong is hooked up to anything.

My friend purchased and had a meter installed but then the landlord said it was broken and switched it out with one he provided.  The landlord also wants to add a 30% surcharge which isn’t in the lease.  This is only the problem with the electrical system; there are many other sleazy things going on.

If there is a discrepancy it will need to be handled diplomatically since if you get someone in trouble with the law or the courts you might end up shooting yourself in the back of the head a few times, especially if you’re a foreigner in a dispute with a local, and the police won’t really do anything.  If they can get away with murder, meter tampering doesn’t rate that high.

I measured phase-to-phase at 227v.  This is in a commercial space, not residential (it’s a disco).  There are five 8HP air conditioners so I think that is the majority of the power.

The work done by the supposedly certified electricians here is a dangerous mess.  The main panel has an extra circuit breaker attached below the rest (which are on bus bars) and is tapped off from before the main breaker in the panel.  There are also wires for 2 sub-panels attached on the bus side of two other breakers.  I can see all of this because the cover for the panel is long gone so someone could easily poke their finger into the bus bars.  Thankfully the panel is behind the bar and not where the customers have access to it.

SG-1:
Good hunting Flyingmoose.
Is there any chance the service is a center tapped delta, aka high leg delta.  One transformer is usually larger than the other two.
Then a neutral would be available for the meters power supply.

FlyingMoose:

--- Quote from: SG-1 on December 25, 2019, 03:13:42 pm ---Good hunting Flyingmoose.
Is there any chance the service is a center tapped delta, aka high leg delta.  One transformer is usually larger than the other two.
Then a neutral would be available for the meters power supply.

--- End quote ---

I don’t think so, only 3 wires and equal voltages across each pair.

I wonder if I should run it from an isolation transformer...

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