Fuses, Breakers, Amps, Max Load... Crossy!

[Mudcrab]

Another thought - you said a fuse holder melted and had to be replaced. It will be worth checking (or getting someone to check) the tightness of each terminal. A molten fuse holder is usually the result of a high load and a high resistance connection usually from a loose connection. A high load in itself should be within the capability of the fuse holder....a very high load should blow the fuse.

[sandrabbit]

Crossy, on 10 Apr 2013 - 12:21, said:

Welcome to the mad world of Thai electrics sandrabbit

As an industrial sparky I would welcome your thoughts on the inrush current of contactor coils. Naam's panel has under-voltage sensors driving slave relays which in turn drive the contactor coils. It seems that the fuses are only feeding the sensors etc, the load current is not does not appear to be passing through them.

There is a problem with the 30A fuses popping, would you think that a single contactor coil is likely to pop a 30A fuse?

it is a mad world here, I bought a condo which had been refurbished to a high standard but when I checked the sockets about 90% of them were wired live and neutral reversed which is not normally a problem as most electrical equipment now are 2 wire devices without earths although I did have to open up my distribution board to make sure it wasn't reversed there which would make things still live if a mcb tripped.

Contactor coils of the size in the pictures would have a negligible inrush current, their resistance would be in kilo ohms although they usually have a suppressor or capacitor across them to prevent a voltage surge. A contactor coil would have to have a short in it somewhere to blow 30A fuses and it wouldn't be an intermittent fault, it would be permanent.

The only thing that concerned me on reading the post the first time was about having a 3 phase supply in a domestic environment which means you could have a very nasty 400V shock if you managed to get across 2 phases, you have to be qualified in the UK to work at or above mains voltages. When I reread it seems more like a commercial installation than domestic but my previous advice is still the same, leave it to a qualified guy ( I mean practically not just on paper)as 3 phase will really bite you in the arse and the current available to the circuits could certainly start a fire instantly in a fault condition. If the a/c units can be programmed set them not to restart after a blackout might be a good idea or have the circuit modified so it doesn't reset.

p.s. don't trust a cheap digital multimeter to say the circuit is voltage free and put your fingers in, in work I usually find a voltage source to check my multimeter before my fingers go anywhere near any electrical equipment and my personal meter is a Fluke.

[Naam]

picture: the upper row cables right side "in", left side "out". the "in" cables are in an integrated channel on the right side, go all the way down and then through the varies thingies up again.

Good Naam, where is the other end of the 'IN' cables, the MCBs perhaps?

Things are becoming clearer through the haze

the end are the contactors. from there they cables go to the distribution boxes which hold 50 fuses/breakers/MCBs or whatever you call it. there's also a sub-panel in my "pumphouse" and a small panel in the little staff house.

[Naam]

Hi Naam, Thanks for an interesting thread.

Nice to see some neat and tidy Electrical wiring in LOS for a change.

I agree that a wiring diagram would be an excellent idea. You really should have one posted on the inside of the cabinet for the Sparky.

I'm an Electronic Engineer, and although Electrical Diagrams are quite different to Electronic Circuit Drawings, I can probably figure one out.

Can't be much help without a diagram.

One Comment, you mentioned that multiple Airconditioners starting together will sometimes trip a Breaker.

Are you aware that there a Delayed Start Timers available to fix this very problem?

You wire one in series with each Air Con, and after a black-out they wait a random time to re-engage so that you don't get such a big spike of start-up current.

The destructive failure of the fuse assembly is definitely a worry. The only thing which should be able to do this is a nearby lightning strike,

or a 22KV line dropping onto the 240V lines after a traffic accident, etc.

Perhaps a big surge has caused the Spike Supressors to conduct, thus taking out the fuses catastropically, but the surge suppressors somehow survived

(assuming they are not now open-circuit).

i'm aware that delayed start gadgets are available but the chance is extremely low that it will happen again.

A surge suppressor (the term that has been used here) usually can (should) handle multiple voltage spikes before total failure. Each spike will degrade the internals until the end of the devices life. They should not fail on the first voltage spike. Are the neighbours experiencing similar issues...this could point to a supply authority issue. If not then you need to look closely at he actual wiring in your home, its hard to determine if the board is correctly wired from photos.

to the best of my knowledge i never had a voltage spike in the electrical system. had there been a spike not detected by the surge suppressors the sensors would have shut off the phase via the conductors, i.e. discussing the surge suppressors is in my [not so] humble opinion irrelevant.

once there was a spike, caused by lightning strike, coming through one of my phone lines frying two modem/routers and two motherboarda. also, i don't think it's a matter of correctly wiring. one incident in over five years.

[Naam]

The only thing that concerned me on reading the post the first time was
about having a 3 phase supply in a domestic environment which means you
could have a very nasty 400V shock if you managed to get across 2
phases, you have to be qualified in the UK to work at or above mains
voltages.

yawwwnnnn... here we go UK again as so often. no offence meant! how would you suggest to supply a domestic environment with 19 airconditioners, 7 pumps, not to talk about fridges, freezers, cooktops, 4 females washing hair using 4 instant water heaters? single phase?

[Naam]

»any objection for any reason to "upgrade" to 40amps?«

Your +/-10% devices are there to to protect your electronics for voltage deviations – an often used and good solution in Thailand. Looks like it has been installed correctly.

When upgrading fuses, you may need to check and eventually upgrade the cables, running from the fuses to the ourlets. If your cables are to small (thin), they will get warm or even hot – and can cause fire. 32A to 40A is +25%.

I am using the same kind of system to protect my electronics, but splitted with voltage detectors for each outgoing cirquit; as there may be areas you wish a higher protection for, like Aircons and waterpumps, and cirquits you don't need the same protection level, like light. The protection devices are not that costly, about 2,000 baht each set. Sometimes the selenoids (magnetic switches) do wear out and need to be replaced, but normally the shall last for many years.

actually i installed the protection devices only to save on burned aircon and pump relays which i had to replace frequently in olden times due to brown-outs.

all our electronics are additionally protected by 3 inverters (not UPS toys but 320A each) which kick in when voltage deviates too much.

even though i am a "sparkie apprentice" i have a hard time not taking your advice of upgrading the cables to the outlets as a terrible insult. this time i will overlook the remark. next time expect my seconds to knock at your door and challenge you for a duel, "heavy sabres sine sine" on sunday morning at dawn in my front garden

320A inverters? You sure? Not 320 Watts? if they are 320A UPS then they will be very large.

i forgot to type the "h". the output capacity of each inverter is 2,000W, input is 24V supplied by 2 batteries each 160Ah (amphours) = 320Ah.

[Crossy]

the end are the contactors. from there they cables go to the distribution boxes which hold 50 fuses/breakers/MCBs or whatever you call it. there's also a sub-panel in my "pumphouse" and a small panel in the little staff house.

Hi Naam, I meant where do they go inside the box, left cables go to the contactors, right cables go to?

[XINLOI]

@Naam, do you have access to a clamp on amp meter? It will tell you why you keep blowing a fuse on one leg. I would suspect a very imbalanced panel for starts with the entire house load on one leg, again, the clamp on will tell you this. If you have 30 amps on L1 and 5 amps on L2and 3 amps on L3, your problem is solved. Balance the panel by moving wires connected to the L1 to the L3, as well as the L2 and get it to where the phases are drawing the same amount of current. Don't understand all this stuff in a panel though. What are you trying to accomplish? An OLD "Sparky"

[Forkinhades]

it is a mad world here, I bought a condo which had been refurbished to a

high standard but when I checked the sockets about 90% of them were

wired live and neutral reversed which is not normally a problem as most

electrical equipment now are 2 wire devices without earths although I

did have to open up my distribution board to make sure it wasn't

reversed there which would make things still live if a mcb tripped.

Really?

I would have thought measuring the currents would have been a first move as suggested post38

Interesting thread, need some time to look over properly

[Crossy]

Gentlemen and sparkies, am I the only one to notice that the fuses (far left) appear to be feeding only the control gear?

There is (should be) no load current passing through them, so why are 30A fuses fitted, and why do they pop?

Or am I missing something?

[Forkinhades]

I wasn't suggesting that I had any answers, but it looks more like an in/out relationship rather than parallel feeds to me.

The contacts have been linked on the double pole contactors

[Crossy]

I wasn't suggesting that I had any answers, but it looks more like an in/out relationship rather than parallel feeds to me.

The contacts have been linked on the double pole contactors

I thought that, but apparently only the top terminals are linked according to Naam's inspection. Seems odd if so.

[Forkinhades]

^ok crossy

Need a clearer picture, and diagram

So its the 30Amp control fuse thats is blowing?

[Crossy]

^ok crossy

Need a clearer picture, and diagram

So its the 30Amp control fuse thats is blowing?

Agreed, and yes, it's my understanding that the control fuses (the only fuses in the box) are popping. One wonders (worries) why the panel builder used 30A fuses.

No diagram is available, I asked earlier

@Naam, can you get better photos of the wiring around the top of the fuses / MCBs and the bottom of the contactors.

[doglover]

Gentlemen and sparkies, am I the only one to notice that the fuses (far left) appear to be feeding only the control gear?

There is (should be) no load current passing through them, so why are 30A fuses fitted, and why do they pop?

Or am I missing something?

No you are not. They are only feeding the control circuit.

Line side of mains comes in at top right of terminal strip and then feeds

43 or 45 amp (hard to see) MCB's which then,

Reverse feeds T1 of contactors.

L1 of contactors feeds load side at top left of terminal strip feeding main CU and sub-CU.

Mains at L1 are jumpered over to L3.

T3 has two wires terminated and feeds fuse holders and surge arrestors.

Hence my comment of an in\out relationship.

So why indeed do the 30 amp fuses have those big line feeds and tiny little yellow wires on the load side?

[doglover]

Was the fuse type info provided? That could also be helpful.

[Crossy]

Was the fuse type info provided? That could also be helpful.

Post 1

Going back to Naam's original request, I believe he already has 'the amps he's paying for' because he has 45A MCBs on his 15/45 3-phase meter.

He's asking if he can replace the fuses with MCBs, that would be a yes. BUT it's still worrying why these 30A fuses (or future 30A MCBs) need to be that big and why they blow or overheat (although I suspect that was a one-off loose connection), ever.

[Forkinhades]

^ok crossy

Need a clearer picture, and diagram

So its the 30Amp control fuse thats is blowing?

Agreed, and yes, it's my understanding that the control fuses (the only fuses in the box) are popping. One wonders (worries) why the panel builder used 30A fuses.

No diagram is available, I asked earlier

@Naam, can you get better photos of the wiring around the top of the fuses / MCBs and the bottom of the contactors.

Indeed

[Forkinhades]

Was the fuse type info provided? That could also be helpful.

Post 1

Going back to Naam's original request, I believe he already has 'the amps he's paying for' because he has 45A MCBs on his 15/45 3-phase meter.

He's asking if he can replace the fuses with MCBs, that would be a yes. BUT it's still worrying why these 30A fuses (or future 30A MCBs) need to be that big and why they blow or overheat (although I suspect that was a one-off loose connection), ever.

Sounds like to me its a control side issue, and not a load side issue. If so I would change the fuses to 2 amp, certainly would not upgrade.

So we are thinking that the supply comes in the right hand side, through to the contactors. Then from the live side feed the control fuses, which in turn supply the monitoring equipment? through some relays, which hold the coils in the contactors?

So ok Naam a couple of questions

Do you have any 3 phase equipment installed to the house (pumps?)

Does the coil on the contactor (same phase as 'control' fuse) drop out when the fault happens?

[Forkinhades]

^ Just seen post 45, and still digesting that, before anyone jumps on me.

[Forkinhades]

Taking a closer look at the picture.

I assume the red wires from the live side of the 45amp mcbs go to lamp indicators on the front of the panel?

[jbrain]

»any objection for any reason to "upgrade" to 40amps?«

Your +/-10% devices are there to to protect your electronics for voltage deviations – an often used and good solution in Thailand. Looks like it has been installed correctly.

When upgrading fuses, you may need to check and eventually upgrade the cables, running from the fuses to the ourlets. If your cables are to small (thin), they will get warm or even hot – and can cause fire. 32A to 40A is +25%.

I am using the same kind of system to protect my electronics, but splitted with voltage detectors for each outgoing cirquit; as there may be areas you wish a higher protection for, like Aircons and waterpumps, and cirquits you don't need the same protection level, like light. The protection devices are not that costly, about 2,000 baht each set. Sometimes the selenoids (magnetic switches) do wear out and need to be replaced, but normally the shall last for many years.

actually i installed the protection devices only to save on burned aircon and pump relays which i had to replace frequently in olden times due to brown-outs.

all our electronics are additionally protected by 3 inverters (not UPS toys but 320A each) which kick in when voltage deviates too much.

even though i am a "sparkie apprentice" i have a hard time not taking your advice of upgrading the cables to the outlets as a terrible insult. this time i will overlook the remark. next time expect my seconds to knock at your door and challenge you for a duel, "heavy sabres sine sine" on sunday morning at dawn in my front garden

320A inverters? You sure? Not 320 Watts? if they are 320A UPS then they will be very large.

i forgot to type the "h". the output capacity of each inverter is 2,000W, input is 24V supplied by 2 batteries each 160Ah (amphours) = 320Ah.

2 x 12V 160Ah batteries in series to feed a 24V inverter deliver 24V 160 Ah.

[Forkinhades]

So it seems the monitoring equipment is holding in the coils, which is holding in the supply to the control fuses? As the supply from the load side of the contactors is feeding the 30Amp control fuses?

[Forkinhades]

^ that cannot be right?

surely the supply to the 'control' fuses is coming from the live side of the contactors?

picture not very clear, and think that goes against post 45?

so can we have confimation please what side of the contactor the control fuses are fed from.

[Forkinhades]

^ might seem silly questions, but just need to get things clear in my head

[Naam]

Gentlemen and sparkies, am I the only one to notice that the fuses (far left) appear to be feeding only the control gear?

There is (should be) no load current passing through them, so why are 30A fuses fitted, and why do they pop?

Or am I missing something?

please define "control gear" Crossy.

[Naam]

^ that cannot be right?

surely the supply to the 'control' fuses is coming from the live side of the contactors?

picture not very clear, and think that goes against post 45?

so can we have confimation please what side of the contactor the control fuses are fed from.

please read what i wrote before. nothing, zilch, nada, rien, niente, nichts, muffat, mafeesh is coming from the contactors except uninterrupted power to the distibution panels if the solenoids close the contacts.

[Forkinhades]

^ that cannot be right?

surely the supply to the 'control' fuses is coming from the live side of the contactors?

picture not very clear, and think that goes against post 45?

so can we have confimation please what side of the contactor the control fuses are fed from.

please read what i wrote before. nothing, zilch, nada, rien, niente, nichts, muffat, mafeesh is coming from the contactors except uninterrupted power to the distibution panels if the solenoids close the contacts.

So can you advise where the supply is coming from that feed the 'control' fuses

Sorry but I have jumped in on this thread, and not read all the posts thoroughly, I am trying help. Will reread all the posts

[Naam]

i forgot to type the "h". the output capacity of each inverter is 2,000W, input is 24V supplied by 2 batteries each 160Ah (amphours) = 320Ah.

actually i installed the protection devices only to save on burned aircon and pump relays which i had to replace frequently in olden times due to brown-outs.

all our electronics are additionally protected by 3 inverters (not UPS toys but 320A each) which kick in when voltage deviates too much.

even though i am a "sparkie apprentice" i have a hard time not taking your advice of upgrading the cables to the outlets as a terrible insult. this time i will overlook the remark. next time expect my seconds to knock at your door and challenge you for a duel, "heavy sabres sine sine" on sunday morning at dawn in my front garden

2 x 12V 160Ah batteries in series to feed a 24V inverter deliver 24V 160 Ah.

advice from experts is always highly appreciated even if totally irrelevant to the thread

[Crossy]

If I read Naam's earlier post correctly, power enters the board via the right hand contacts of the terminal strip, proceeds down the trunking on the right to the MCBs, from where it goes to the T1 terminal of the contactor, the load is fed via the L1 contactor terminal and exits via the left hand end of the terminal strip..

I think the fuses are fed from the T3 terminals and it still looks like T1 and T3 are linked on each contactor.

Please can Naam confirm these assertions?