Single phase electricity for a house - 100 amp, possible?

[chrgrims]

Our constructor claims the single phase supply for a house we are building can give up to 100 amp. What he says is that it's graded for 30 amp but can take 100 amp. Is this true?

 

Thanks a lot for any help,

 

chris

[bankruatsteve]

If you are referring to a 30/100 meter, yes.  But actually getting it will depend on grid supply.

[chrgrims]

ok. how can i found out what the grid supply is?

[lopburi3]

The normal house is on a 15/45 amp meter and main breaker is 63 amps so it should not be a problem - but as said the issue will be if the transformer being used can supply to your home - if upcountry it may be an issue and subject to brownouts with major draw.  I would try to limit electric usage as much as possible anywhere - and do your cooking with gas.

[bankruatsteve]

ok. how can i found out what the grid supply is?

 

You could start with your PEA (or whoever supplies the electric).   If you're in a "moo baan" with similarly sized meters, probably not to worry.   If you're the only one with 30/100 and actually use 40 or more amps, you likely to experience "brown outs".  In any case, the PEA can probably advise.

[chrgrims]

Thanks for the feedback guys!

[IMHO]

The MEA/PEA in your area will be reluctant to give you a 30/100 meter if they think the mains to your area is going to struggle to supply it's max. 100A. They might not just come out and say that though - normally you'll find this out because they'll try their best to get you to buy a 3-phase meter instead ;)

[Crossy]

Are you sure you NEED a 100A supply?

 

It's amazing how low the maximum current is even on a big home, you need to do some prospective load calculations, or post here what your major appliances will be.

 

Let us know how many (and how big) water heaters and aircons you are having, will you be using an electric stove, workshop equipment, 3HP water pump etc.

 

We have a 15/45 supply protected by a 50A breaker, it's never opened even with three 15,000 BTU A/C units and two 5kW water heaters running, supply current rarely goes over 30A.

[IMHO]

Are you sure you NEED a 100A supply?

 

It's amazing how low the maximum current is even on a big home, you need to do some prospective load calculations, or post here what your major appliances will be.

 

Let us know how many (and how big) water heaters and aircons you are having, will you be using an electric stove, workshop equipment, 3HP water pump etc.

 

We have a 15/45 supply protected by a 50A breaker, it's never opened even with three 15,000 BTU A/C units and two 5kW water heaters running, supply current rarely goes over 30A.

 

How can you have > 10,000 watts of load and only draw 30A? I wish I had your mains  - mine pulls 100A just to give me 13,000 watts.

[Crossy]

 

Are you sure you NEED a 100A supply?

 

It's amazing how low the maximum current is even on a big home, you need to do some prospective load calculations, or post here what your major appliances will be.

 

Let us know how many (and how big) water heaters and aircons you are having, will you be using an electric stove, workshop equipment, 3HP water pump etc.

 

We have a 15/45 supply protected by a 50A breaker, it's never opened even with three 15,000 BTU A/C units and two 5kW water heaters running, supply current rarely goes over 30A.

 

How can you have > 10,000 watts of load and only draw 30A? I wish I had your mains  - mine pulls 100A just to give me 13,000 watts.

 

Maybe I should re-phrase that IMHO, the 50A incomer hasn't opened with all the load on, at the time I didn't have the mains monitor so I'm not certain of the actual current drawn, probably about 55A, we see little supply droop on load (quite close to a decent Tx).

 

In normal use we rarely see >30A.

 

That mains stabiliser of yours is evidently working well, 13,000W at 100A = 130V, ouch, do the street lights dim?

 

 

 

 

[lopburi3]

You must have some serious power factors to draw 100 amps unless your voltage is very low.  This is an online converter site and if were pure restive at 230v you should only draw about 57amps (real world would be higher but not normally twice.

http://www.rapidtables.com/calc/electric/Watt_to_Amp_Calculator.htm

[Crossy]

You must have some serious power factors to draw 100 amps unless your voltage is very low.  This is an online converter site and if were pure restive at 230v you should only draw about 57amps (real world would be higher but not normally twice.

http://www.rapidtables.com/calc/electric/Watt_to_Amp_Calculator.htm

 

IIRC IMHO has a massive whole-house AVR as he suffers from serious voltage droop on any sensible load, looks like it's getting down near 130V @ 100A from the incoming supply
 

[chrgrims]

Its a two storey house with 5 AC, 5 water heaters, 4 hp pump etc. 11 rooms in total. we did get an offer for 3 phase, but its too expensive (based on the fact that single phase might be enough anyway). so we will follow the advice here and use single phase now. we can always change later if needed.

[Crossy]

In that case wire it so you can easily change to 3-phase later, nothing to stop you having a 3-phase incomer wired for single-phase.

[chrgrims]

yes, that sounds like a good idea.

[JesseFrank]

Its a two storey house with 5 AC, 5 water heaters, 4 hp pump etc. 11 rooms in total. we did get an offer for 3 phase, but its too expensive (based on the fact that single phase might be enough anyway). so we will follow the advice here and use single phase now. we can always change later if needed.

 

When i build my house I was told that I need a 3 phase transformer or I couldn't handle the power supply.

I have 5 AC, 5 waterheater with the biggest ome 12000W, 12,5 Hp in pumps installed and a 30kVa single phase transformer with a 30/100A meter. Split up in 3 circuits with each a 63A RCBO, and a 100A breaker at the supply, never had one trip for overload.

 

You don't use all these appliances at the same time.

Edited August 3, 2014 by JesseFrank

[Naam]

Its a two storey house with 5 AC, 5 water heaters, 4 hp pump etc. 11 rooms in total. we did get an offer for 3 phase, but its too expensive (based on the fact that single phase might be enough anyway). so we will follow the advice here and use single phase now. we can always change later if needed.

in what way "too expensive"? please define

[bankruatsteve]

If you can get what you need on single phase, sounds good to me.  Just wondering... why would 3-phase supply be that much more expensive if it's already there?  I like Crossy's idea to distribute circuits to easily change over to 3-phase b/c if you are the lonely home needing that much power - you just won't get it.

[JesseFrank]

If you can get what you need on single phase, sounds good to me.  Just wondering... why would 3-phase supply be that much more expensive if it's already there?  I like Crossy's idea to distribute circuits to easily change over to 3-phase b/c if you are the lonely home needing that much power - you just won't get it.

 

Never seen 3 phase available anywhere in Thailand. It will cost you a 300K transformer and an extra wire.

[chrgrims]

3 phase must be taken from the main road, its not available on our road now. the offer was 50000 baht.

[Naam]

3 phase must be taken from the main road, its not available on our road now. the offer was 50000 baht.

understand.

[Naam]

 

If you can get what you need on single phase, sounds good to me.  Just wondering... why would 3-phase supply be that much more expensive if it's already there?  I like Crossy's idea to distribute circuits to easily change over to 3-phase b/c if you are the lonely home needing that much power - you just won't get it.

 

Never seen 3 phase available anywhere in Thailand. It will cost you a 300K transformer and an extra wire.

 

in my moo baan each of the 43 homes has a three-phase connection. of course my home has one too and i did not pay for a transformer. only additional cost was a few thousand Baht for the wiring from the meter to the distribution panels of my home which i paid to the electrical contractor.

 

i'd be lost with a single-phase connection!

 

[attachment=277778:3-elc.jpg]

[JesseFrank]

 

 

If you can get what you need on single phase, sounds good to me.  Just wondering... why would 3-phase supply be that much more expensive if it's already there?  I like Crossy's idea to distribute circuits to easily change over to 3-phase b/c if you are the lonely home needing that much power - you just won't get it.

 

Never seen 3 phase available anywhere in Thailand. It will cost you a 300K transformer and an extra wire.

 

in my moo baan each of the 43 homes has a three-phase connection. of course my home has one too and i did not pay for a transformer. only additional cost was a few thousand Baht for the wiring from the meter to the distribution panels of my home which i paid to the electrical contractor.

 

i'd be lost with a single-phase connection!

 

3-elc.jpg

 

 

But I assume that is because the management of the moobaan invested in 3 phase transformer for the community.

 

Is there a public 3 phase power grid available in Thailand ? My understanding is that if you need 3 phase you need to invest in a 3 phase transformer and connect to the high voltage grid.
 

[Naam]

If you can get what you need on single phase, sounds good to me.  Just wondering... why would 3-phase supply be that much more expensive if it's already there?  I like Crossy's idea to distribute circuits to easily change over to 3-phase b/c if you are the lonely home needing that much power - you just won't get it.

i [not so] humbly beg to differ. a 3-phase connection has a big advantage, e.g. when one or two of the phases have a brown-out or fail completely you still have power and cooling in 2/3 or 1/3 of your home.

 

[Naam]

 

 

 

If you can get what you need on single phase, sounds good to me.  Just wondering... why would 3-phase supply be that much more expensive if it's already there?  I like Crossy's idea to distribute circuits to easily change over to 3-phase b/c if you are the lonely home needing that much power - you just won't get it.

 

Never seen 3 phase available anywhere in Thailand. It will cost you a 300K transformer and an extra wire.

 

in my moo baan each of the 43 homes has a three-phase connection. of course my home has one too and i did not pay for a transformer. only additional cost was a few thousand Baht for the wiring from the meter to the distribution panels of my home which i paid to the electrical contractor.

 

i'd be lost with a single-phase connection!

 

3-elc.jpg

 

 

But I assume that is because the management of the moobaan invested in 3 phase transformer for the community.

 

Is there a public 3 phase power grid available in Thailand ? My understanding is that if you need 3 phase you need to invest in a 3 phase transformer and connect to the high voltage grid.
 

 

i think your assumption is correct and the moo baan has its own transformer. but even the high voltage public grid must be 3-phase because i don't think you can convert any single phase, no matter what voltage, into 3-phase.

 

let's have Crossy's comments before we jump to conclusions.

[bankruatsteve]

I thought 3-phase was the 'normal' distribution just about everywhere in the world.  (?)  How the power company breaks out to single phase is the challenge for them.  Or what???

[lopburi3]

Three phase transformers are normal here in Bangkok - but if you only have a single phase your voltage drops to about 140-160 when one of the other two phases are out in our mooban so don't believe three phase is going to be a Savior for running the Naam cooling machine in 2/3 of the house (and it happens too often at start of rainy seasons here with limbs falling but normally fixed within an hour or so) - although it will allow most lighting and fans to run..

[Pib]

I thought 3-phase was the 'normal' distribution just about everywhere in the world.  (?)  How the power company breaks out to single phase is the challenge for them.  Or what???

In my Bangkok moobaan three phase is used to distribute power around the sois.  Some large houses have 3 phase meters/hookups (that most really don't need because the most Thais don't use many "power-hungry" appliances like A/Cs...they got A/C but don't use them much), but most homes have single phase 30/100A hook ups like my home.  The 30/100A meter means 100A service with the meter calibrated at 30A at the factory since a properly sized meter to service will normally draw around 1/3 of capacity most of the time/on the average.  The electric company will simply split the load among the three lines for single phased homes...like my home on the first phase, my neighbor on the second phase, and the next neighbor on the third  phase.  

 

My meter/service is a 30/100A service and my main circuit box has a 80A main breaker.  My voltage is very stable at around 225V night and day.   I have 7 A/Cs in my home but 3 is about the max that would run at once, bunches of electronics/appliances like two 30A water heaters, clothes drier, 3 frigs always running,  etc...etc.  With one 18K BTU A/C running, a couple of TVs running, a fan or two on, some lights on, 3 frigs running, I'm pulling around 12A on the average...turn on another 18K BTU A/C and I'm up around 20A....turn the clothes dryer on and its up to around 45A...washing machine running to and you are up to around 50A.  This is just a couple of examples.

 

Like mentioned earlier a 100A service should be plenty except maybe for the big homes with some serious electricity usage/power hungry electrical items.   

[IMHO]

 

You must have some serious power factors to draw 100 amps unless your voltage is very low.  This is an online converter site and if were pure restive at 230v you should only draw about 57amps (real world would be higher but not normally twice.

http://www.rapidtables.com/calc/electric/Watt_to_Amp_Calculator.htm

 

IIRC IMHO has a massive whole-house AVR as he suffers from serious voltage droop on any sensible load, looks like it's getting down near 130V @ 100A from the incoming supply
 

 

 

You recall correctly :) 

[Naam]

Three phase transformers are normal here in Bangkok - but if you only have a single phase your voltage drops to about 140-160 when one of the other two phases are out in our mooban so don't believe three phase is going to be a Savior for running the Naam cooling machine in 2/3 of the house (and it happens too often at start of rainy seasons here with limbs falling but normally fixed within an hour or so) - although it will allow most lighting and fans to run..

i never experienced and actually can't experience a voltage drop when only one phase remains because my "protective thingy" shuts down any phase completely if the voltage drops below 200.

 

but i can monitor whether the phase from the grid is missing or whether it was shut down by my afore-mentioned thingy because of low voltage.

 

these are the indicators. "on" means voltage ≥200, "12" means low voltage checking every 12 seconds for variation, "--" means grid phase completely down.

 

[attachment=277806:indic-phase.jpg]