Two Electric Meters - how to switch between the two?

[mallmagician]

I have to have a second meter installed in order for MG to install my Home Charger for an electric car.  As I only need to do an overnight charge once a week or so - I've opted for a 15/45 Time of Use meter (digital) which has cheaper rates on weekends, and between 10pm and 9am weekdays (But more expensive rates than a regular meter at peak times)

The existing meter for the house is also a 15/45 meter (analogue).  This isn't on a Time of Use plan, just a regular plan.

The new meter hasn't been installed yet, but it will be run over the road to the house in the same location as the existing electric supply, where the existing supply disappears into the roof to the consumer unit, and the new supply with be run to a consumer unit outside the house in the carport.

I would very much like to take advantage of the Time of Use rates when not using the car charger for my main house supply.  Is this possible to install a transfer switch or similar, so that I can manually switch over to the cheaper rates at off peak times, and back to regular rates at other times?  I'm thinking that it could be installed somewhere near where both supplies are attached to the house prior to going off to the consumer units.

Or am I trying to have my cake and eat it too?

[sometimewoodworker]

2 minutes ago, mallmagician said:

I would very much like to take advantage of the Time of Use rates when not using the car charger for my main house supply.  Is this possible to install a transfer switch or similar, so that I can manually switch over to the cheaper rates at off peak times, and back to regular rates at other times?  I'm thinking that it could be installed somewhere near where both supplies are attached to the house prior to going off to the consumer units.

It is extremely doable it can also be automated without much problem. You should be looking for a generator transfer switch as they are designed for the job.

There is one niggle that will almost certainly come into play and that is that it is very probable that mains powered clocks will be useless as the switch MUST disconnect one supply before connecting the other so they will reset twice a day, so microwave etc won’t show the correct time..

[mallmagician]

Great thanks for that.  Now I know I am not barking up the wrong tree - I'll wait until everything is installed, then I'll get a sparky in to do the job neatly/safely.

Thanks for the info.  ????

[Crossy]

15 minutes ago, sometimewoodworker said:

It is extremely doable it can also be automated without much problem. You should be looking for a generator transfer switch as they are designed for the job.

There is one niggle that will almost certainly come into play and that is that it is very probable that mains powered clocks will be useless as the switch MUST disconnect one supply before connecting the other so they will reset twice a day, so microwave etc won’t show the correct time..

 

And your PC etc. will be needing a UPS.

 

[mallmagician]

I've a couple of UPS's knocking around that should do the trick for that stuff.  

Excellent.  ????  

[thaisail]

11 hours ago, sometimewoodworker said:

It is extremely doable it can also be automated without much problem. You should be looking for a generator transfer switch as they are designed for the job.

There is one niggle that will almost certainly come into play and that is that it is very probable that mains powered clocks will be useless as the switch MUST disconnect one supply before connecting the other so they will reset twice a day, so microwave etc won’t show the correct time..

We got our MG ZS EV in December and ordered our TOU meter in January. We thought we were getting a single phase 15/45 digital TOU meter based on what the PEA manager told us but the one we got a few weeks ago was as per the attached photo. We put in our 2 x 25 mm square aluminum core cables 80 meters from the place where the TOU meter was to be fitted on the main road to our garage next to the consumer unit for the house. The TOU meter arrived around Songkran and cost around 4000 baht with 700 baht for PEA to install it. Then, we contacted MG who had a wait list since they have sold a lot of EVs this year. Since we live in Isaan, a company with the name of PRIME was contacted and they set up the appointment to fit the MG home charger. They arrived about 3 weeks later from Ubon Ratchathani. We live in Chiang Khan, Loei about 10 hours drive from there but these guys are going from town to town all over Isaan and they are really good electricians and sometimes they will do jobs outside of their contract for a price. Of course the MG wall box is the olny thing they will do for free. We bought from them that excelet larger box to fit the WiFi breaker and the MOV surge protector. I wanted to put in a low and high voltage cut out switch with high current protection but there was no room in the box. I will modify this later when I start my solar instalation. The guys from PRIME did an excelent job wiring in the gear I bought from Lazada. But a word of advice for someone who wants to copy what I did, please make sure that you have a normal breaker from the TOU meter to the home charger so that you can shut off power to all the things downstream. I made a mistake of running the cables from the TOU meter direct to the WiFi breaker and tonight we got hit by lighting and my WiFi breaker is now a normal breaker with no automation. It worked well for the last few weeks until tonight when we got hit by lightning. Luckily, that was the only thing that got damaged. If I had to do it over, I would run the cables from the TOU meter to normal 64 amp breaker, followed by the MOV surgeprotector and then the high and low voltage cut out along with high currect cut out. This also includes a digital voltmeter and amp meter with all the parameters programable. Not shown in these photos but I have one fitted going into my consumer unit for the house. 

 

My Thai wife was told by PEA when we received the new TOU meter, that it was forbidden to connect anything other than the EV charger to the TOU meter. This does make sense because it would easy to buy the units at the off peak rate and then feed it back through the analog meter spinning it backwards during the night and make a profit. The people from "PRIME" will take a lot of photos of their MG installation and if there is any warantee issue with the MG, you may have to allow MG to return to inspect the installation if there is a claim. 

 

The manager also claimed that with the digital meters it was possible for them to see if you are using anything other than charging the EV. For example running your AC at night. I did not really think this was possible, but I noticed that the new TOU meter also measure the "Reactive" power which is used in factories that are running a lot of motors. This may show up when they read the meter if I start using my inverter AC units or fridges or water pumps that have motors on them. The water heater however has no reactive power to speak of so I might get away with that one. 

 

My plan was to install solar panels as soon as the MG home charger was operational and I am starting to do research to buy the equipment so that I can charge my MG in the daytime when there is lots of sun and maybe use the batteries of the MG to power my AC units at night using the V2L cable that supplies 2.2 kW of power all night to my consumer unit from the MG batteries. But any modification that involves solar will get you in trouble with MG if they find out about it. Just make sure that what ever you do, you can put things back to the way they were if there is ever an inspection by PEA or MG warantee claim. I know someone who fought a battle with MG because his house was offgrid capable from solar panels, inverters and huge batteries. When PRIME showed up they refused to give him the waranty but he had them put in his wall box anyway. His solar power is a thousand times cleaner and more stable than any PEA power. 

 

Keep in mind that the price of the units from the TOU meter is going to be a little bit higher than the cost of buying your electricity from PEA and PTT superchargers at the EV stations. This is because the superchargers are feeding DC current at around 50-60 kW rate for about an hour while the home charger will give you only 7 kW AC current which has to be converted to DC inside of the MG EV for 4-8 hours while the cooling systmem is running. There is also a loss of efficiency by having to convert the AC power to DC inside the MG EV. The cost at home will be close to 4 baht per unit when you include FT and VAT, but with those other losses described above, you may end up paying more than the 4.50 + VAT per unit price at the super chargers off peak rate from 2200 to 0600. But for us it is still more convenient to be able to charge at night at home while we sleep than to have to drive 15 km to the closest EV Station. Plus we can charge at home until 9 am instead of 6 am!

 

 

[thaisail]

11 minutes ago, thaisail said:

We got our MG ZS EV in December and ordered our TOU meter in January. We thought we were getting a single phase 15/45 digital TOU meter based on what the PEA manager told us but the one we got a few weeks ago was as per the attached photo. We put in our 2 x 25 mm square aluminum core cables 80 meters from the place where the TOU meter was to be fitted on the main road to our garage next to the consumer unit for the house. The TOU meter arrived around Songkran and cost around 4000 baht with 700 baht for PEA to install it. Then, we contacted MG who had a wait list since they have sold a lot of EVs this year. Since we live in Isaan, a company with the name of PRIME was contacted and they set up the appointment to fit the MG home charger. They arrived about 3 weeks later from Ubon Ratchathani. We live in Chiang Khan, Loei about 10 hours drive from there but these guys are going from town to town all over Isaan and they are really good electricians and sometimes they will do jobs outside of their contract for a price. Of course the MG wall box is the olny thing they will do for free. We bought from them that excelet larger box to fit the WiFi breaker and the MOV surge protector. I wanted to put in a low and high voltage cut out switch with high current protection but there was no room in the box. I will modify this later when I start my solar instalation. The guys from PRIME did an excelent job wiring in the gear I bought from Lazada. But a word of advice for someone who wants to copy what I did, please make sure that you have a normal breaker from the TOU meter to the home charger so that you can shut off power to all the things downstream. I made a mistake of running the cables from the TOU meter direct to the WiFi breaker and tonight we got hit by lighting and my WiFi breaker is now a normal breaker with no automation. It worked well for the last few weeks until tonight when we got hit by lightning. Luckily, that was the only thing that got damaged. If I had to do it over, I would run the cables from the TOU meter to normal 64 amp breaker, followed by the MOV surgeprotector and then the high and low voltage cut out along with high currect cut out. This also includes a digital voltmeter and amp meter with all the parameters programable. Not shown in these photos but I have one fitted going into my consumer unit for the house. 

 

My Thai wife was told by PEA when we received the new TOU meter, that it was forbidden to connect anything other than the EV charger to the TOU meter. This does make sense because it would easy to buy the units at the off peak rate and then feed it back through the analog meter spinning it backwards during the night and make a profit. The people from "PRIME" will take a lot of photos of their MG installation and if there is any warantee issue with the MG, you may have to allow MG to return to inspect the installation if there is a claim. 

 

The manager also claimed that with the digital meters it was possible for them to see if you are using anything other than charging the EV. For example running your AC at night. I did not really think this was possible, but I noticed that the new TOU meter also measure the "Reactive" power which is used in factories that are running a lot of motors. This may show up when they read the meter if I start using my inverter AC units or fridges or water pumps that have motors on them. The water heater however has no reactive power to speak of so I might get away with that one. 

 

My plan was to install solar panels as soon as the MG home charger was operational and I am starting to do research to buy the equipment so that I can charge my MG in the daytime when there is lots of sun and maybe use the batteries of the MG to power my AC units at night using the V2L cable that supplies 2.2 kW of power all night to my consumer unit from the MG batteries. But any modification that involves solar will get you in trouble with MG if they find out about it. Just make sure that what ever you do, you can put things back to the way they were if there is ever an inspection by PEA or MG warantee claim. I know someone who fought a battle with MG because his house was offgrid capable from solar panels, inverters and huge batteries. When PRIME showed up they refused to give him the waranty but he had them put in his wall box anyway. His solar power is a thousand times cleaner and more stable than any PEA power. 

 

Keep in mind that the price of the units from the TOU meter is going to be a little bit higher than the cost of buying your electricity from PEA and PTT superchargers at the EV stations. This is because the superchargers are feeding DC current at around 50-60 kW rate for about an hour while the home charger will give you only 7 kW AC current which has to be converted to DC inside of the MG EV for 4-8 hours while the cooling systmem is running. There is also a loss of efficiency by having to convert the AC power to DC inside the MG EV. The cost at home will be close to 4 baht per unit when you include FT and VAT, but with those other losses described above, you may end up paying more than the 4.50 + VAT per unit price at the super chargers off peak rate from 2200 to 0600. But for us it is still more convenient to be able to charge at night at home while we sleep than to have to drive 15 km to the closest EV Station. Plus we can charge at home until 9 am instead of 6 am!

 

 

If could be that with 3 phase power, you may get a 15 (45) meter instead of the 5 (100) meter that I got because with single phase I am running more than 32 amp continuous which may overheat the single phase circuit. Out here in the countrysize, we all have use single phase power unless you live in town. 

[bluejets]

20 hours ago, mallmagician said:

Or am I trying to have my cake and eat it too?

I'd be checking with PEA.....many countries this sort of thing is highly illegal.

If it is illegal, you might get away with it for a while but eventually they'll smell a rat and you could be up for whopping great penalty fees.

[mallmagician]

Yeah, looks like it's a no go. I don't want to do anything illegal/risky for penalties. 

 

Thanks everyone for the input. 

[digbeth]

We've seen case where people install sockets along with their charger behind the TOU meter and the power company is fine with it.

Only MEA in Bangkok makes you switch your whole house over to TOU before giving you a separate meter for EV

 

before you automate everything, make sure the clock on the meter itself is set to the correct time, there has been case where the TOU meter's time is off and incorrect rates applied even while charging on off-peak times

[thaisail]

On 6/2/2023 at 12:08 PM, Crossy said:

 

And your PC etc. will be needing a UPS.

 

I am trying to find out how much I can get away with to mofify my TOU meter with the free MG home charger instalation. A few weeks after PEA installed the TOU meter, a private company called PRIME arrived to install the MG home charger for free in my garage. They removed my 60 Amp knife switch that had been placed temporary in the garrage while waiting for PRIME to arrive. The cables were live from the TOU meter to the knife switch. They just wrapped electrical tape around the cables and cut them with insulated cutters while they installed the MG provided electrical boxes. Then they connected the live cables carefully to my new WiFi 30 amp two pole breaker. After that there was a MOV surge suppressor and followed by a single pole 40 amp breaker with the phase wire connected through it. From there, there were three cables (Phase, Neutral and Earth) that went into the separate MG breaker box that had the Chinese breaker with earth fault protection on it. From there to the MG home charger. 

 

A few weeks after the install, we had a similanious lightning and thunder strike and the WiFi smart programable breaker was turned into a dumb 32 amp breaker. I did not like the way that PRIME installed the live cables from the TOU meter direct to my WiFi breaker but rather than complain, I decided to just let them do it the way they wanted knowing that when they were gone, I could make it the way I wanted. Unfortunately they did not want to put back the 60 amp knife switch between the WiFi breaker and they TOU meter. So now I have ordered a new WiFi breaker and I have no way to isolate the power to the damaged Wifi breaker because the cables are now live going into the terminals of the WiFi breaker. I want to install the old knife switch breaker into the circuit and mount it above the new home charger boxes so that I can de-energize the circuit and work on all the componants down stream without being energized.

 

I also want to be able to open the knife switch during lightning storms to protect all the items downstream. 

 

We also wanted to find out how to check the "clock" on our TOU meter to be sure that the time is set properly as we hear on this forum that some people have been charged the peak rate even though the charging was done during offpeak hours. So, my wife called the PEA office to ask how we can verify the clock on the TOU meter is set properly because we have lots of blackout these days. Also, it would be nice to see how to read this digtal high tech meter to make sure that we are not being cheated. The guy at PEA took offence about us questioning the clock on the meter and did not want to continue the conversation with my wife, so I will have to try to get the manual for that meter on the internet.  

 

So, my questions are:

 

1. Can I have someone install the 60 Amp knife switch back into the circuit above the home charger boxes while the cables are live? I can get PEA back out here to inspect afterwards if needed. 

 

2. Is 60 Amp the correct size fuse for the home charger? My amp meter reads 33 amps continuous at 230 Volts single phase when the battery of the MG is below 75%. However, I noticed the cooling system on the car starts up occasionally during the charging cycle. I haven't been able to get an amp reading while the cooling systems is running. I could also be that the cooling system is running on 400 volts from the batteries. In this case the amps will remain at maximum 33 amps. When charging, the voltmeter on the MG App is reading 400 Volts at 14 amps. 

 

My plan now is to fit the MOV surge suppressor after the knife switch followed by the new WiFi multi function C-63 amp protector, followed by the single pole ABB breaker on the phase cable only (MG required) followed by the second box with the 30 mA earth fault protector C-50 amp breaker that was delivered with the car from China. 

 

Further down the road, I will be working on a solar planel instation so I may need to tap in to the home charger as soon as I am able to produce power from the sun. My wife is telling me that PEA is going into the Solar power business and will not allow home Solar installations done by others. Has anyone heard about this new requirement?

 

Today, my wife called the PEA boss in Chiang Khan and asked him how we can check the clock on the TOU meter and he got offended that we would doubt them so we may have to wait for the bill to come to see if the clock is set right. We also noticed that when the car is charging the "Active" red light is flashing on the TOU meter. We are also wondering what purpose the measure of "Reactive" power will serve for battery charging. 

 

Any advice or inputs will be appreciated. 

 

 

[asf6]

Ref: checking the clock on the TOU meter. 

 

Do you know what the specified times are supposed to be for off peak for your meter? If so, you could go and stand in front of the meter for about 15 minutes, starting 10 minutes before the time and click through the display. At the appointed time see if anything on the display changes. There will probably be something, a symbol or something, you just have to figure out what it is/they are. 

[asf6]

A bit more about that^ 

 

Apparently Peak times are 9am to 10pm on weekdays.

 

About 15 minutes before the change time (say 8.45am), check your current usage of both on and off peak (scroll through the display to find them). Monitor it until just before the time change. Take a note of both readings. Then half an hour later check both readings again (assuming you are using electricity at that time). One reading should have changed, the other should have remained the same.

 

If, for example, at 9.30am, your off-peak reading has remained the same as at 9am and your on-peak reading has increased since 9am, your meter "clock" is correct.

 

You should be able to easily check the current time on your meter by scrolling through the display settings. A few YT videos say the first thing shown on the display is the current date and the second thing shown is the current time. 

 

Whether that clock affects the on-off peak charge, I don't know. It's quite possible that that is set centrally somewhere. 

 

Just my thoughts and 2 baht's worth. 

 

.

Edited June 7, 2023 by asf6