air con circuit board fried! surge protection?

[ChiangMai2]

Greetings, I hope I can get some advice here. I'm totally ignorant when it comes to all things electrical so please bear with me.

We recently moved into our new house and have experienced the first heavy rains, high winds and expected power cut. One of our aircon units circuit boards got frazzled when the power came back on. Apparently a "power surge." We are told it will cost 15k to get a new board and a weeks wait whilst it gets shipped from Bangkok. Its not the end of the world but I thought it seemed expensive, the unit itself was (from memory) around 45K. Does this seem like the right price for effectively a pcb with a few bits and pieces soldered on? The aircon is a mitsubishi 24k btu inverter type.

As we have several other aircon units ( not all invertor type ) I would like to avoid this happening again. Not only did one aircon get damaged, also our wifi router and a TV. The same guy that has quoted us 15k for the replacement aircon circuit board said that for a further 15-20k he can install something that will mean this cannot happen again. I asked if it was a surge protector ( not that I really know what these are ) or a type of UPS, sadly with my very basic Thai and his very basic English I don't think either of us had any idea who was talking about what, unfortunately my wife and her guests couldn't really describe what he was offering either.

Google tells me whole house surge protectors are available. Has anyone here got experience of them, can they easily be fitted after a house has had its electrics fitted. Any one have any Chiang Mai contacts to do this work? Or is there a better solution? Does 15-20k sound feasible for a way to protect lots of expensive electrical appliances. Please if anyone has any advice and experience that they can give me in layman's terms please let me know. Much appreciated.

Kind regards

CM2

[Forkinhades]

You can get surge protectors (MOV) for the whole installation, and for individual final circuits, and indeed individual accessories.

They are relatively easy to fit, even after the electrics have been installed.

His prices do seem rather high.

Experts in this field will be along shortly to advise further.

[Rimmer]

I have a three phase supply coming from my own 50Kva transformer, the transformer is just 100 mtrs away from the house so the fault levels are very high.

When the PEA installed the HT lines in the road they did not put in a shield wire above the cables so any lightning strike on the wires comes straight back down the line into the house. This happened once a couple of years back, it blew aircons, cameras, computers and a printer.

One aircon was a Mitsubishi 3KW the main board had to be replaced. The first aircon shop took the unit away and kept it for a number of weeks then quoted 15k to replace the board. We brought the unit back and took it to Numchai in Pattaya, they replaced the board re installed the unit for around 4k.

We subsequently fitted three small surge suppressors on to the transformer tails, they cost around 400 baht each and catch any surge and send it down to two large earth mats they also installed, these things catch around 90% of a surge.

Two weeks back a golden tree snake climbed the transformer pole and shorted out two phases on the HT side of the transformer, the three small surge suppressors on the tails did their job but we still had a surge in the house which blew the same air con plus one more also, CCD cameras and ceiling fans.

I am told that Square D no longer bring in the plug in surge suppressors, which is a shame as they were easy to fit and under 3k per phase to buy. The only domestic units available were ABB which in a three phase plus N configuration cost 22k, I negotiated the price down to 15k.

Fitted the unit last weekend inside a separate box with an MCCB after the board but before the suppressor.

The ABB unit is a one off unit with three indicators on the front, each phase unit is a module and can be replaced.

I will take some pictures of the installation if you want to see what it looks like, you can also search ABB surge suppressors.

[Rimmer]

This is a shot of the small suppressors on the LT side of the transformer, the one that is ringed has blown and the cable connected to the earth matt has come out, the other one you see has the cable intact.

It was a problem to find these units, PEA did not have them and I had to source them in Rayong then get PEA to fit them. as I said they clear 90% of a surge, had I not had these on the snake attack the surge would most likely blown the MCB board off the wall.

The ABB suppressor just fitted I hope will now give close protection to the entire house.

EDIT

A UPS will provide even closer protection to your computer.

You could also check to see if your MCBs are correctly rated for each air con or circuit. Thai electricians like to fit the largest possible MCB in your board which of course gives no protection to your appliance

Despite changing all my MCBs to the correct sizes I doubt it will have much effect in a surge as they will not discriminate and clear fast enough to stop a hit on your air cons. But who knows it might help.

I did two weeks in a classroom discussing discrimination of MCBs Q1 Fuses and MCCB, never understood it back then and have forgotten most of it now

[Gonsalviz]

I had the same problem. Same Air conditioner. 2 months and 16,000 baht to fix it. Also a 50" flat screen and associated satellite receiver. I have had other problems too but cannot pin point them being caused by surges.

I am in the market for a whole house surge protector.

[Forkinhades]

Although good, a whole protector won't protect your satellite cable.

[Rimmer]

One can buy extension cable outlets which cut off under surge conditions, they are not expensive and work well, your TV and sat box will be very happy if you have one of those for them. BELKIN is a well known and trusted brand, the link shows a BS1363 type outlet but they are available here in places like Hardware House with the correct sockets.

The dish and your internet cable is another matter and needs to be disconnected during a storm.

[Forkinhades]

Just to be clear it's the cable from the the sat LNB, that cannot be protected, or from the cable company. Which can be hit, and your tv, and sat equipment will fry.

[Rimmer]

Just to be clear it's the cable from the the sat LNB, that cannot be protected, or from the cable company. Which can be hit, and your tv, and sat equipment will fry.

This is so true, the only solution is to un plug all, I once had un plugged all the computer stuff but forgot the internet cable, a surge came back from a strike on the internet line, it blew the computer mother board and a printer which was not plugged to the electric but had a USB link to the computer so that went as well..

[Crossy]

Ah, the advantages of WiNet or fibre internet, no surges up the line

OK, for those on a bit of a budget who want to protect their aircon, go and buy a bag of these chaps, the ones you want are s20k250 varistor :-

http://www.mynpe.com/mynpe/more.php?data=116450101022&quantity=1&c=class2



They're 11.25 Baht each at NPE.

Connect three at the incoming supply terminals of your aircon (actually at the aircon, long supply cables can pick up nasties), please sleeve the leads to prevent excitement.

Connect-
L-N
L-E
N-E

They are much bigger than the ones usually found in the surge arresting adaptors so can absorb more nasties.

If you also have a whole house unit you'll be pretty safe from anything but a direct hit.

[bankruatsteve]

While those will protect transient surges, a direct - or close to direct - lighting hit will fry though any MOV and destroy whatever. The best protection from lightning is to unplug/disconnect.

[Crossy]

While those will protect transient surges, a direct - or close to direct - lighting hit will fry though any MOV and destroy whatever. The best protection from lightning is to unplug/disconnect.

Indeed, but since the majority of damage to electronics is via induced transients the use of MOVs liberally scattered throughout your installation is a sensible and inexpensive precaution, with a big bu99er on the front end you're protected from 99.9% of the nasties.

How many of us unplug our aircon when the lightning starts? Or for that matter, have aircon that we can unplug?

[Rimmer]

The old window mounted aircons used to have if I remember correctly a 15a round pin socket feeding them, I wonder if the newer Belkin surge arrestor sockets sold here would be continually rated for 15a, if so that could also be an easy solution for the odd air con.

Or what about those tiny DP so called safety switch MCB things that come in all sizes, easy to install close to the aircon for someone that wants to turn it off.

Rather strange the OP seems to have gone to ground, please excuse the pun

[Crossy]

India still use 15A UK (BS 546) plugs/sockets to supply aircons, with a locally mounted AVR being standard equipment, never bothered unplugging them mind. Could be an idea for new installs.

One of those safety breakers would give some peace of mind, but their contact gap is only about 3mm when 'off', any surge worth its salt would be doing the long jump.

Our A/Cs are all wired direct back to the distribution board, a 60kA whole-house MOV lives there. I will be following my own advice and dropping a few of those 8kA beasties around the place before the wet starts properly.

[Crossy]

And now, by popular demand (OK 1 PM), how to connect up the blue chaps in post #10.

First the diagram:-

Now the photo, sorry about the crumby connector strip, all I had available:-

Please sleeve the wires even if you think you've got them far enough apart. most aircons should have room in the connector to slip these chaps in, if they don't then make up a jobbie like the photo with some flexible cable and slide it in anywhere it will fit.

The circuit is completely symmetrical, so it matters not a jot which wire goes where.

[Forkinhades]

Silly question Xy how do you know when one has popped?

[Crossy]

Silly question Xy how do you know when one has popped?

It goes black and the magic smoke comes out

Seriously, if you've had a big surge you'll know about it, if it's big enough to wipe out a MOV it will have killed off other stuff.

They're cheap enough to replace the lot even if showing no signs of stress.

[JDGRUEN]

Power surge protection being a subject of its own... I recently had a Air Con unit with a Dead Circuit board repaired in a novel way... The Air Con Tech went and got a Generic Controller box containing a circuit board- very small box with a LCD displayed -- took the old circuit board out -- and plugged in several wires were the original circuit with a connector for the generic circuit board in the small box... The unit came with a new remote ... works perfectly -- 2500 Baht. I can send a photo of the unit if you wish ... The little circuit board box is mounted below the Air Con Unit and works better than the old one ever did ... Totally compatible 3rd party solution

[Forkinhades]

Silly question Xy how do you know when one has popped?

It goes black and the magic smoke comes out

Seriously, if you've had a big surge you'll know about it, if it's big enough to wipe out a MOV it will have killed off other stuff.

They're cheap enough to replace the lot even if showing no signs of stress.

The answer was aimed at the guys that do not have a whole system MOV

[Crossy]

Whole house units usually have an indicator of some sort to show when it's died in the line of duty and should be replaced.

The blue chaps aren't really intended as primary defence, they're there to finish off the remains of the enemy and handle the smaller surges that don't awaken the big beastie.

[Forkinhades]

ok, just being devils advocate here, if the blue chaps handled a surge that did not awaken big beastie, i take it they just go black? and you would have a burning electronic smell lingering.

[Crossy]

ok, just being devils advocate here, if the blue chaps handled a surge that did not awaken big beastie, i take it they just go black? and you would have a burning electronic smell lingering.

A surge that caused one to fail catastrophically should have awakened any front end unit, they'll happily clamp many surges that are within their rating. All MOVs wear out over time, not sure how to tell the blue ones are actually life expired, as noted earlier the big units have life indicators.

I don't recall seeing one go bang as the result of a surge (they do if you connect a 115V one to 220V). And yes, they give off that lovely "burning electronics" aroma that pervades any lab where electronics students are operating (and their experiments aren't).

[Crossy]

We have two closely related threads running here, it's splitting the good information so let's continue our discussions in this one http://www.thaivisa.com/forum/topic/812868-power-surges/

For now this thread is closed, but please PM myself or Forkinhades if you have information best served here.