Protection of electronics from lightning

[thaisail]

I started reading some of the lightning nightmare stories on your electrical forum and I decided it is time to stop taking chances. I am building a new house in Chiang Khan and I have bought a protection device for low voltage, high voltage and high amps. I paid only 350 baht on Lazada and it comes from China. I am a little bit worried about this device for safety because it was so cheap! My building contractor used a Chinese chop saw that was 2300 watts and the device tripped when the amps reached 40 amps during the starting current. So I increased the setting from 40 amps to 45 amps so that he will not trip the device while I am away from the house. In any case the automatic reset worked after 30 seconds and the lights came back on automatically. The circuit breaker for the power receptacle was C16 size and it didn't trip which I guess is normal since it was only starting current.

 

The other concern I have is the heat building up in the plastic box so I removed the clear plastic cover to prevent overheating. I am looking for a small 220 volt fan that I can mount in the bottom of the box so that I can ventilate this box to keep it cool. So far I haven't found a fan that will be around 50 mm in diameter so if you know of one, please let me know. Until then I will have to leave the box with no door. I would also like to hear what you think the settings should be for the low voltage cut out and the high voltage cutout. Also the time settings for shut off and reset.  I have attached the default settings page from the manual but the only one that had been set different was the under voltage reset which had been raised by the factory to 190 volts. 

 

My house originally had a 80 meter length of 16 sq mm aluminum cable that my wife put in when she built a bungalow on her rice farm at New Years and that was good enough for the bungalow. When I went to PEA, they told me that the new house will require 25 sq mm cable because of the all the air cons I will be installing. So while under a two week quarantine in the bungalow in May (we escaped from Phuket when the lockdown ended), I had a 9000 btu double inverter Daikin air con fitted which prevented us from being roasted alive! We started on the new house by June and fitted a new length of 80 meter 25 sq mm aluminum cable to appease the PEA director and I think he was right in the end to require the larger cable. 

 

We built the house and I put in the RCBO panel shown attached and just last week I fitted this Chinese voltage and current protector because where I am living, there is a transient voltage of around 40 VAC when there is a blackout from the PEA. This 40 volts would keep my LED light on the Daikin air con lit up and I was worried about the inverter electronics in the Daikin AC that may not like that 40 volts AC on the power lines during a blackout. I am still waiting for the first black out to see if the 40 VAC is gone after the voltage and current device opens the circuit. I was wondering if someone on the grid is back feeding power from batteries and an inverter somewhere. I asked PEA about this and they just shrugged their shoulders and looked puzzled!

 

I decided to change the  80 meters of 16 mm aluminum line and neutral wires from the electric meter to 25 mm aluminum because my Thai boss told me that in Thailand, if I use copper main cables, they will steal my 80 meters of copper wire if I take a one month vacation. He recommended aluminum for this reason. Where the cable ends at the house, I bought a short section of 25 mm copper wire to run inside the house to the breaker box and used heavy duty clamps to clamp the aluminum cable to the copper cable outside the house under the roofing. 

 

Those cables are then connected to the first 63 amp CB shown in the small box with the din rail. From there, the cables go to the voltage and current protector and then from there they go back to the RCBO panel and connect to the 63 amp main circuit breaker there. I am not sure if this is the right way to wire this voltage protector but it made sense at the time.

 

I was thinking of adding the SPD from Lazada to that DIN rail in the small box and run a second ground wire from that box to same 2.5 meter ground pin that I hammered into the floor of the garage. This ground pin is now being used by the RCBO only. I poured about 20 liters of water today into the small hole that was left by the contractor who poured the cement slab under the garage 2 months ago. I made a classic mistake of not putting the ground pin outside where the earth will remain damp in the rainy season. So I will have to keep pouring water down that hole under the concrete to maintain a good ground on the system especially during the dry season.

 

So, I think there is room for the SPD I found on Lazada seen in the photo attached. My question is: Can I connect this SPD ground wire to the same ground pin as the RCBO panel and also to see if this device is really the right thing to buy since it is only 175 baht which I think might be too cheap to be safe and effective.

 

When my house is finished in two weeks, I will have the following loads.

 

3 x Samsung copper double inverter 12000 btu rated at 960 watt 4.6 amp each

1  x Daikin double inverter 9200 btu rated at 900 watt with 4.2 amp 

1  x York traditional 10,000 btu 13 amp starting current according to my new amp meter built in to the voltage and current protector

1  x shower water heater 3.5 Kw 

1  x 3 Kw deep submersible well pump draws about 7 amps to start and runs about 4 amps 

1  x shallow well pump about 300 watt

33 x LED light 15 watt each

Desktop computer with 20 inch monitor, two laptops, printer scanner

42" flat screen TV, 32" flat screen TV,

medium size microwave and other kitchen appliances

1 big Samsung inverter refrigerator/freezer and one medium size standard type fridge for the bungalow

 

Do you think I will get a big voltage drop with all that running at the same time?

 

I am also planning to add solar water heater and hot water pump and there will one day be about 24 x 330 watt solar panels put in next year

 

Appreciate any help and advice from all of you out there!

 

 

[bankruatsteve]

8 hours ago, thaisail said:

Do you think I will get a big voltage drop with all that running at the same time?

Voltage drop for sure.  How big depends on your supplier.

[Crossy]

Unless you really want fast acting over-current protection I'd wind the current limit to max or disable it if possible, you have plenty of protection from overload with your MCBs.

 

For voltage limits, ours is set to 260V high end and 150V low end but we have an AVR, I would set your low end to 180V. You can tweek it if you find it operating when the pumps start. Our turn-on delay is 5 minutes, we tend to get short blips one after the other. I don't like the juice going on and off rapidly and it upsets the generator.

 

 How hot is the Chinese unit getting? They do run warm but not hot enough to worry about. You could cut ventilation holes top and bottom of your box and try with just convection (put some mozzie screen over to discourage the local wildlife from making a home in there). If you really do want a fan there's loads of small low-voltage fans on the market, add a baby encapsulated or DIN power supply and you're good to go. 

https://www.lazada.co.th/products/flash-saledr-15-12-din-rail-switching12v-125a-15w-i1589700606-s4318498631.html

 

For surge protection I'd go for something like this 

https://www.aliexpress.com/item/1691443754.html 385V 60kA, Tomzn are a well known, medium cost Chinese manufacturer. You may find the same unit on Lazada with cheaper shipping. We have one of these units protecting our solar inverter.

 

We have a 100kA unit similar to this 

https://www.aliexpress.com/item/32867504709.html on our incoming supply but note they are wider than the smaller units so you may need an new box.

 

Run a separate ground wire at least 10mm² directly from the arrestor to your rod by the shortest, straightest route possible.

 

I would also add good-quality plug in arrestors to your valuable technology to mop up any remaining nasties that get past the big boy. As a belt and braces man I've also got a bunch of the little blue 2kA MOVs in all our LED light fittings.

 

The only way to determine just how much drop you're going to get is the try it. If it's too much then it's possibly time for an AVR.

 

[Rmac442]

Meaningless to list all your electrical units and then ask if the electrics can supports them ..

I have got 4 Aircon units ..but 90% of the time use only 1

Also 4 TVs ..same etc.

UK kitchen ..hob, oven, microwave etc ..

Washing machine, pumps etc.. but all short time and highly unlikely to be running at the same time ..