On my property I have a mains transformer 50 KvA. 3 Phase. The main breaker is 80 Amp. I do have 13 air-cons, not running all at the same time mostly. Besides, the air-cons, 4 80 liter hot water tanks, fridges, fans, lights etc. I am wondering if the 50 KvA transformer is sufficient to power all this, as sometimes (for no reason and at that moment consumption super low) the breaker trips? Thank you.

Can you post photo of your box panel off? 

50kVA 3-phase is about 80A per phase so you breaker is correctly sized for the transformer.

 

Do you know what value the "super low" consumption actually is? Is all the load on one phase?

 

Does your incoming panel have volt and amp meters as many seem to?

 

Assuming your A/Cs are 12,000 BTU, 13 of them will draw about 15kW spread between the 3 phases, only about 20A per phase even with them all at full chat!

 

This the main meter box. I also have like a "surge protector" against lighting installed.

Do you know what value the "super low" consumption actually is? Is all the load on one phase?

 

Sorry, don't understand this. Maybe clear from the pictures?

3 hours ago, JAN said:

Sorry, don't understand this. Maybe clear from the pictures?

 

Set your meter switches to each position and record the result. Post here.

 

Which of those breakers is actually tripping?

This the voltmeter high voltage

 

This the normal 230 V. The "TN" is showing 0........??

This the Ammeter; which in all positions shows "0"

Thanks for looking into it. Really appreciated!

The breaker tripping is the actual main breaker. The one with the blue, red and black wires. 

Of note to me in the above images:

 

- Firstly, that EasyPact looks like might have residual current leakage detection built in. I can't really see the model number clearly, but if so, this is more likely to be the root of your trip issues rather than over-current.

- Secondly, the phase guards are missing from one of those incomers, the one with the MOVs below it. This is hazardous.

- Thirdly, those improvised bus bars sticking out above the phase guards of the EasyPact. That's really disgraceful. I suspect whoever did that couldn't make the cable terminations fit in the breaker, and so kludged it. A 50KVA transformer will be capable of producing a very serious and dangerous arc flash event, and that kludge is on the transformer side of the breaker. I would personally condemn this installation until this is remedied.

 

It looks like the installation has been modified by 'someone' ???

 

To see how much current each phase is drawing, change the ammeter selector to something other than the 0 point, you can go switch everything on and do a load test.

 

 

 

Further to the above, this is a 480 volt arc flash. You DO NOT want it to happen, believe me. You should ALWAYS be cogniscent of the possibility this might occur when working on live panels downstream of a transformer like that. . .

 

 

Something decidedly odd going on here. Can you post a better image of the main breaker showing the model number etc.

 

Also, where do those thin grey wires from the left side of the main breaker go? How about the thin black wires from the top of the main breaker?

 

Do all three lights light up?

 

I also see a phase-loss / under voltage / over voltage cutout unit (orange thing to left) but I don't see any contactors for it to operate. Could it be tripping the main breaker via control wires (the grey ones)?

 

I don't suppose any drawings came with the panel? Do you still have contact with the installer?

 

EDIT Do you have any actual 3-phase appliances?

 

EDIT 2 Is that the PEA energy consumption meter top right?

NE bond also appears to be missing but it's hard to tell, maybe the one under the same screw as the Neutral incomer. It's debatable if it should be present here without knowing more about the site.

 

 

 

 

 

 

What the hell is this? Red wire spliced into a blue wire with a wrap of PVC tape, looks like the local Somchai the know it all has been busy here...

 

 

What's going on here? Two phase conductors appear to be missing...

Also, the breaker opposite this one has secondary wires that are obviously too small for this breaker and they seem to go to a wire nut kludge. You've had the clowns in for sure.

 

 

1 minute ago, Led Lolly Yellow Lolly said:

What's going on here? Two phase conductors appears to be missing...

 

Single-phase supply to "House 2 & 3" perhaps?

 

It would be useful to have clear photos of each of the breakers, MCCBs all look alike from a distance.

Count the wires on the neutral bus. The count is wrong for the downstream supplied buildings unless they used microscopic neutral conductors.

 

 

 

 

20 minutes ago, Led Lolly Yellow Lolly said:

... maybe the one under the same screw as the Neutral incomer.

 

I reckon you're right with that without actually seeing the physical beast "reckon" is as close as I'm going to go ???? 

13 minutes ago, Led Lolly Yellow Lolly said:

Count the wires on the neutral bus. The count is wrong for the downstream supplied buildings unless they used microscopic neutral conductors.

 

Oh good god, can't be sure but it looks like the ground bus is being used as the neutral bus!

 

 

 

1 minute ago, Led Lolly Yellow Lolly said:

Oh good god, it looks like the ground bus is being used as the neutral bus!

 

At least it has a nice meaty wire to the "real" neutral.

 

In our old condo all the A/C units took their neutrals from the ground bar, system was TNS so it worked just fine until I wanted to install an RCBO. 

... which would explain the erroneous neutral count...

 

 

@JAN Do those individual breakers actually control separate buildings or are they sub-mains in one building?

 

I can work out what the one marked "Swimming Pool" does ???? 

I think @JAN needs to get a "professional" in with a specific brief:-

• Sort out why one P-N voltage reads zero.
• Sort out why all the ammeter settings read zero.
• Identify what's causing the main breaker to open. I very much doubt it's actually over-current and is something to do with whatever is on the other end of those small grey wires (possibly the orange beastie).

There's really too much lethal stuff in there for an amateur to be poking around ???? 

 

Is that meter the one the PEA/MEA comes to read? If so, it's possible this installation might be directly connected to the transformer unfused (I've seen it done). This would be bad, very very bad. Do yourself a favour and get a pro on site to assess things. A pro doesn't cost 300 Baht per day and make everything safe with reassuring words.