3 Phase

[offset]

After thinking about it I have decided to have a 3 Phase 30amp connection and I was wondering about balancing the phases what is the maximum amps per phase that a 30 amp supply will take (is it like the normal 30amp supply which gives you much more than 30amps) because I would like to keep one phase for my bore pump and split the rest between the other 2 phases which might be a problem as I have 3 air con units of a total of 45amps, 4 water heaters plus the other usual electrical items I know that they will not be all on at the same time. The PEA area manager has guaranteed that a will not get a voltage drop but we will have to wait and see about that

[InterestedObserver]

I assume we are talking a four wire connection here. In that case you treat it as three separate single phase supplies, line to neutral. The meter will accommodate more than 30 amps per phase as is normal practice around these parts. The actual limit would be determined by the main circuit breaker size. Make certain the contractor installs a full sized neutral wire.

Edited July 11, 2010 by InterestedObserver

[offset]

<BR>I assume we are talking a four wire connection here. In that case you treat it as three separate single phase supplies, line to neutral. The meter will accommodate more than 30 amps per phase as is normal practice around these parts. The actual limit would be determined by the main circuit breaker size. Make certain the contractor installs a full sized neutral wire.<BR>

<BR><BR>When the man from the PEA visited he told me that it was going to be 3 wires so I guess that i will have to wait and see <BR><BR>

[InterestedObserver]

Yup, either something was lost in translation or terminology (such as 3 wires + neutral) or you are getting a 3 wire delta installation. The answer to your original question remains the same; namely, meter current will be limited by the main circuit breaker (MCB) and not the actual meter rating. I'd be interested to know where PEA is getting this 3-phase from and the distance run.

Edited July 11, 2010 by InterestedObserver

[offset]

<BR>Yup, either something was lost in translation or terminology (such as 3 wires + neutral) or you are getting a 3 wire delta installation. The answer to your original question remains the same; namely, meter current will be limited by the main circuit breaker (MCB) and not the actual meter rating. I'd be interested to know where PEA is getting this 3-phase from and the distance run.<BR>

<BR><BR>The only thing I am sure about is that it comes from the main road where there are a few factories the cable run that I have to pay for is about 500mtrs they are going to use aluminium cable why I ask about power at the moment we have got used to a low power usage at the moment and the voltage is pretty stable (due to the rain not many people using there pumps) and I was hoping to connect the house supply to one phase and the bore hole pump another phase to test to see what the voltage drop was like before completely changing the house wiring so if there was a voltage drop I would ask to revert to the single phase setup and try to get my money back for the 3 wire job <BR><BR>Where will the MCB be situated will I be able to find out what current I can use per phase

[electau]

Supply 3 phase 4 wire 220/380V.

Loading (a guide only)

Phase A. A/C, HW, HW.

Phase B. A/C, HW, Lights, Pump.

Phase C. A/C, HW, Power.

All load is single phase in this example.

Voltage drop should not exceed 5% to any point in the installation.

You will need to carry out a max demand calculation.

Edited July 11, 2010 by electau

[offset]

Supply 3 phase 4 wire 220/380V.

Loading (a guide only)

Phase A. A/C, HW, HW.

Phase B. A/C, HW, Lights, Pump.

Phase C. A/C, HW, Power.

All load is single phase in this example.

Voltage drop should not exceed 5% to any point in the installation.

You will need to carry out a max demand calculation.

The 5% voltage drop is that a Thai standard for 3-phase or the norm in the western world only on my single phase suppy I got a 24% voltage drop under full load (tested by the PEA) on a supply voltage that was already 5% below the 220 volts

[bankruatsteve]

Are you saying that you get a noticeable voltage drop when you run your bore hole pump? That doesn't sound right. You sure everything hooked up properly?

[offset]

Are you saying that you get a noticeable voltage drop when you run your bore hole pump? That doesn't sound right. You sure everything hooked up properly?

No what happens is that we have the bore hole pump on a control circuit so any noticeable drop in volt increases the amps and it cuts out to protect the pump and the supply here is normally below 205 volts so it is already on the low side if I was to turn my large air con unit (25amps) or a hot water tap on the bore pump cuts out sometimes when it is hot and dry I cannot even use the pump. When I turn on the pump the voltage drops by about 5 volts which is about the same as my small air con unit (both 10amps) so I think that is ok

[bankruatsteve]

Is that pump over 2000 watts? Otherwise, it shouldn't be tripping a 10a breaker. you might want to check out the connection to that. If it's buried, the cable should be in proper sheathing or conduit and no pvc tape connections. Do you see a lot of dead worms around.

[Crossy]

Is that pump over 2000 watts? Otherwise, it shouldn't be tripping a 10a breaker. you might want to check out the connection to that. If it's buried, the cable should be in proper sheathing or conduit and no pvc tape connections. Do you see a lot of dead worms around.

I think offset is saying his pump controller cuts off the pump to protect it under low-voltage conditions.

[Naam]

Yup, either something was lost in translation or terminology (such as 3 wires + neutral) or you are getting a 3 wire delta installation. The answer to your original question remains the same; namely, meter current will be limited by the main circuit breaker (MCB) and not the actual meter rating. I'd be interested to know where PEA is getting this 3-phase from and the distance run.

interesting! i was always wondering why the cable diameter seems to be nearly triple of the one going to my home.

question: i have a 3 x 30 amp connection and was told i could continously 'overload' by 100% which would only be the case of a total power cut when all aircons plus some other gadgets are running and power coming back. does the meter itself have no internal "breaker" if a certain nominal load is exceeded?

[InterestedObserver]

Nope, the meter works until it burns up. The cables will be protected from overload/short circuit and that also protects the meter, sort of.

Edited July 12, 2010 by InterestedObserver

[elkangorito]

In order to find out the specifications of a meter, the model number must be known. I have specs for many of the meters used in Thailand.

[bankruatsteve]

Is that pump over 2000 watts? Otherwise, it shouldn't be tripping a 10a breaker. you might want to check out the connection to that. If it's buried, the cable should be in proper sheathing or conduit and no pvc tape connections. Do you see a lot of dead worms around.

I think offset is saying his pump controller cuts off the pump to protect it under low-voltage conditions.

What's a "pump controller"? I have both a bore hole pump (the two pipe kind that sucks) and a normal pressure pump for top side but neither have a controller that I'm aware of. And neither draws 10 amps. Why would you consider 200v to be "low" for (let's say most) things to work?

[InterestedObserver]

What's a "pump controller"? I have both a bore hole pump (the two pipe kind that sucks) and a normal pressure pump for top side but neither have a controller that I'm aware of. And neither draws 10 amps. Why would you consider 200v to be "low" for (let's say most) things to work?

"I got a 24% voltage drop under full load (tested by the PEA) on a supply voltage that was already 5% below the 220 volts" Under full load the OP is down around 160 volts, not 200 volts.

[bankruatsteve]

What's a "pump controller"? I have both a bore hole pump (the two pipe kind that sucks) and a normal pressure pump for top side but neither have a controller that I'm aware of. And neither draws 10 amps. Why would you consider 200v to be "low" for (let's say most) things to work?

"I got a 24% voltage drop under full load (tested by the PEA) on a supply voltage that was already 5% below the 220 volts" Under full load the OP is down around 160 volts, not 200 volts.

Oh, OK - I missed that. Well anyway, my point was that MAYBE the connection to the pump might be the problem. ?? (and I would still like to know what a pump controller is - maybe I need one?)

[offset]

The PEA came today and run a third cable which is what the man said he would do so it is still single phase but it has increased the voltage to 225 but the voltage still drops when I use anything powerful I tested the volts  with 1 small air con, 1 large air con and the large hot water unit (which drops the voltage the most) and it ended up at 185 volts so i am not sure what I should try next  

[Crossy]

The PEA came today and run a third cable which is what the man said he would do so it is still single phase but it has increased the voltage to 225 but the voltage still drops when I use anything powerful I tested the volts  with 1 small air con, 1 large air con and the large hot water unit (which drops the voltage the most) and it ended up at 185 volts so i am not sure what I should try next  

I don't know if we've been down this route before (time blurs the memory) but:-

How far are you from the transformer?

What size cable have PEA installed (the cable will be marked)?

Steve. The 'pump controller' being referred to as well as controlling tank level also incorporates an under-voltage cutout to protect the motor. If you suffer from frequent under voltage supply you would do well to install one to prolong the life of your pump.

[InterestedObserver]

You need to find out exactly what connection type you have now, measure the voltage between all three wires at no load. It all boils down to load, wire size and material, distance run, and transformer size. Didn't PEA guarantee no voltage drop. What happened to the three phase?

[offset]

The PEA came today and run a third cable which is what the man said he would do so it is still single phase but it has increased the voltage to 225 but the voltage still drops when I use anything powerful I tested the volts  with 1 small air con, 1 large air con and the large hot water unit (which drops the voltage the most) and it ended up at 185 volts so i am not sure what I should try next  

I don't know if we've been down this route before (time blurs the memory) but:-

How far are you from the transformer?

What size cable have PEA installed (the cable will be marked)?

Steve. The 'pump controller' being referred to as well as controlling tank level also incorporates an under-voltage cutout to protect the motor. If you suffer from frequent under voltage supply you would do well to install one to prolong the life of your pump.

Yes we have been through this before and that is why I have tried this new supply I am now worried about over voltage I have just check the voltage and get a reading of 238 volts what voltage range is safe for my electrical equipment

[offset]

You need to find out exactly what connection type you have now, measure the voltage between all three wires at no load. It all boils down to load, wire size and material, distance run, and transformer size. Didn't PEA guarantee no voltage drop. What happened to the three phase?

I must be fair the man only said 3 wire connection and when I asked him about the voltage drop he told me that it would be no problem I do find it difficult to get my other half to help deal with problems I think she is like most Thia's and manage with what they have than get it fixed properly when I asked her to tell the man that it was no good she just said that we should not use the air con when we use the water pump

[InterestedObserver]

1. 238 volts is on the high end of the normal range for 220 volt equipment, it will be ok. Your lights will be a tad bright.

2. PEA still has an unresolved voltage drop/regulation problem, 238 volts down to 185 volts..

2. Of more immediate concern is exactly what 3-wire connection you have. Measure between all three wires and record the reading at no load:

Wire 1 to wire 2 =?

Wire 2 to wire 3 =?

Wire 3 to wire 1 =?

3. There is no need to explain the idiosyncrasies of a Thai wife, most of us have learned first hand.

Edited July 13, 2010 by InterestedObserver

[bankruatsteve]

Just b/c I find some of these issues interesting...

offset = you said the PEA supplied a 3rd cable for your single phase service. Do you know what that is?

Where are you measuring your voltage? IE: at your CU? an outlet somewhere?

As an aside (perhaps good for a new topic: "The way things are sometimes". I could load that up with LOTS of my experiences). Anyway... relevant or not I'm in the middle of a project where I just tore down the old electric installation From the meter to the main breaker/fuse had the blue AL wire (don't know the size). And I don't know what size fuse there was (it was inside a round ceramic thing). But, from there was a patchwork of maybe 8-10 PVC taped connected cables of various size (maybe 30 meters total) that serviced a bore pump, refrig, TV, numerous lights, fans, and the occasional construction equipement (cutters, welders, etc.). After seeing some of the cable being no more than lamp cord (like 2-3 strands of copper) I have to wonder how nothing ever melted!! And this was in place for maybe 4-5 years!! I do recall measuring the voltage once when my drill just didn't seem "zippy" and got 180v (although I didn't know the wiring situation at the time). Anyway... now after new installation (although not yet totally completed) the voltage is running about 230 at all points and with the normal stuff turned on (no big loads yet though).

So, back to the topic... it seems to me if you (the OP) are getting votage drops when you run the A/C, heaters, etc. then so should everyone on your link (ie: the neighbors). does that happen? If not, maybe something in your installation is suspect (like improper size cable?).

[electau]

You need to find out exactly what connection type you have now, measure the voltage between all three wires at no load. It all boils down to load, wire size and material, distance run, and transformer size. Didn't PEA guarantee no voltage drop. What happened to the three phase?

I must be fair the man only said 3 wire connection and when I asked him about the voltage drop he told me that it would be no problem I do find it difficult to get my other half to help deal with problems I think she is like most Thia's and manage with what they have than get it fixed properly when I asked her to tell the man that it was no good she just said that we should not use the air con when we use the water pump

Is your supply 3 phase 4 wire 220/380V or 3 phase 3 wire 220V ?

[offset]

Had a good look at what they have done it seems like they have just run a clean line from the transformer the pole outside which just means that there is not draw down of volts by other users which is giving me more volts to start with it does prove that the transformer is not big enough While I was sitting here she run the hot water the lights dimmed and the fan slowed down so I will have to disconnect the hot water again and not use the big air con unit then we can manage until I can talk her into complaining again

[InterestedObserver]

Not entirely correct. PEA only ran one new cable, you had two wires and now you have three wires. So you are still sharing half the single phase circuit with other users (the neutral or return line), assuming it is still single phase. Your service has improved, it now only drops to 185 volts instead of 160 volts. I would like to know just what a 3-wire connection means to PEA.

Edited July 14, 2010 by InterestedObserver

[elkangorito]

This is what I think the situation is:

a] The OP has a single phase supply & therefore a single phase Distribution Board (DB).

b] The PEA have not added a phase. If they did, the OP's DB would need to be changed to accommodate the extra phase. Of course, I'm assuming that the OP has a single phase DB.

c] The likely cause of the OP's problems probably relates to the following:

The only thing I am sure about is that it comes from the main road where there are a few factories the cable run that I have to pay for is about 500mtrs...

The length of the cable (500m) is the probable cause of the problem.

Obviously, the original cable size is now too small with respect to the demand & so voltage drop is evident. The PEA have solved half of the problem by adding an extra cable to the existing phase. What they haven't done is add an extra cable for the Neutral, which would probably provide a complete fix.

What they should've done is either:

1] Add 2 extra cables - one Neutral & one Active of the same size & type or,

2] Remove the existing cables & install larger cables to handle the load.

With regard to 2], the load must be known. Essentially, a Maximum Demand calculation must be done (there are 4 ways to do this calc).

I don't think that the Tx is overloaded.

[offset]

Not entirely correct. PEA only ran one new cable, you had two wires and now you have three wires. So you are still sharing half the single phase circuit with other users (the neutral or return line), assuming it is still single phase. Your service has improved, it now only drops to 185 volts instead of 160 volts. I would like to know just what a 3-wire connection means to PEA.

It dropped to 180 with only 3 items on I would guess that if I put it on full load (another 3 water heaters, a air con unit and the bore pump ) I would guess that it would be no better it was also the hot dry period when I carried out the test that gave me 160volts at the moment it is not very hot and with the rain that we are having nobody is using there bore pumps around here and I do not know what voltage I would get when they do I seem to get a drop of about 10 volts during the day

[offset]

This is what I think the situation is:

a] The OP has a single phase supply & therefore a single phase Distribution Board (DB).

b] The PEA have not added a phase. If they did, the OP's DB would need to be changed to accommodate the extra phase. Of course, I'm assuming that the OP has a single phase DB.

c] The likely cause of the OP's problems probably relates to the following:

The only thing I am sure about is that it comes from the main road where there are a few factories the cable run that I have to pay for is about 500mtrs...

The length of the cable (500m) is the probable cause of the problem.

Obviously, the original cable size is now too small with respect to the demand & so voltage drop is evident. The PEA have solved half of the problem by adding an extra cable to the existing phase. What they haven't done is add an extra cable for the Neutral, which would probably provide a complete fix.

What they should've done is either:

1] Add 2 extra cables - one Neutral & one Active of the same size & type or,

2] Remove the existing cables & install larger cables to handle the load.

With regard to 2], the load must be known. Essentially, a Maximum Demand calculation must be done (there are 4 ways to do this calc).

I don't think that the Tx is overloaded.

The new cable that they added was is the same size has the existing cables the new cable has just been run from the transformer not the main road that I was hoping for (problems not understanding Thai)