Maximum Demand Calculation For Hua Hin House

[elkangorito]

Stgrhe, sorry about the delay but your MD calc was not the easiest.

In order to balance the load across the 3 phases as well as try to sensibly assign circuits, took some extra time.

With regard to your choice of equipment - I have no problem with ABB gear except for their small contactors (which are crap).

It was quite difficult & in some cases impossible, to get all the info I needed from the web. As a result, my conclusions are not based on any particular brand of equipment. I do, however, make the following recommendations;

1] Your Main Switch (Main Circuit Breaker) be rated at 10kA @ 400v. It does not need to be any larger than this (30kA for example).

2] Your Main Switch (Main Circuit Breaker) be 3 pole & rated at 40 amps.

3] Your consumer mains should be no less than 25mm squared copper cable (just to be on the safe side).

4] Your downstream circuit breakers (in your consumer unit) should be rated at no less than 6kA @ 220v.

5] Your RCBO's can be either single pole space (18mm) or 2 pole...the choice is yours. I do recommend the single pole space units. Each of these should also be rated at no less than 6kA. Each RCBO should have a maximum trip current of 30mA. 10mA is not required unless you wish to be super safe. Please bear in mind that 10mA units that protect GPO's may be subject to nuisance trips.

6] Your consumer unit should be metal (not plastic).

7] Other over/under voltage protection equipment, which you are keen on, can be added later for such things as pump protection.

8] Surge diverters & such equipment will need to be mounted in a separate enclosure, which should also be metal & can be mounted on top of or below your consumer unit. Ideally, this enclosure will connect to your consumer unit. The additional size of the enclosure may determine where it is mounted. I hope you have enough space in the small area assigned. Also, be aware that this equipment has specific requirements with regard to cable sizes & lengths. This could be a problem unless the Thai electrician can understand the manufacturers requirements.

9] I recommend ABB Type 2 surge diveters (MOV's as already recommended to you by ABB). These units should be 8/20 micro second rated at 40kA (minimum). These units can be "plug in" devices. Essentially, any surge diveter to this spec should be more than adequate.

10] Ideally, the external guesthouse should have its own consumer unit unit. In your situation (from looking at the drawings you sent me), I don't think this is necessary. As such, I did not allow for this.

11] Unfortunately, I'm unable to offer any recommendations regarding the low voltage lighting transformers. Usually, these devices are sold with the lighting equipment.

12] I do not see any mention of hot water used for the purposes of bathing. Did you forget to include any hot water units for this?

13] I have removed the 1.8kW hot water unit from this calculation.

14] I was not able to find an ABB catalog that listed metal distribution boards (DB's), although I did find some vague information. As such, I am not able to recommend any size of ABB DB.

I shall supply a DB layout drawing tomorrow night (Wednesday night). This drawing will not include the Main Circuit Breaker & will only reference single pole RCBO's (18mm wide).

The attached spreadsheet was made with OpenOffice. Thaivisa does not allow the upload of certain documents with unusual file extensions. If you have OpenOffice, rename the file extension to .ods

If not, it should open ok in Exel.

stgrhe_MD_calc.xls

[stgrhe]

12] I do not see any mention of hot water used for the purposes of bathing. Did you forget to include any hot water units for this?

There is a 150l hot water heater in the system, which is also mentioned in my first post. Originally there were three units, one 150l for the two main bathrooms, one 30l for the kitchen and one 30l for the guest house. The separate kitchen hot water for the kitchen was then removed.

In your MD calculation you have probably deleted the 150l instead of the 30l but as both types use 1.8kW the MD calculation will not be changed.

Can you please recommend a suitable Main Circuit Breaker with current limiter? You mentioned before that a limiter would be recommended as the max current exceeds 100A. Also, can you please explain why you recommend a Main Circuit Breaker rated 40A; shouldn't it be rated the same as the meter, i.e. 100A?

I have no problem converting the Open Office document to Excel but the under laying formulas get lost.

Once again many thanks Elkangorito for your support.

Edited due to spelling error

Edited December 8, 2009 by stgrhe

[stgrhe]

Elk, I have some follow-up questions related to the balance load calculation:

1. You suggest CB's for the A/C's, hob and oven circuits. Does that mean you propose separate RCD's to these circuits in addition to the CB's, or if not, how would you propose I handle the ground fault issue?

2. You do not suggest separate circuits for the two water pumps. Would it not be better to keep those two units on a separate circuit since I eventually will install high- and low voltage protection at a later stage?

3. I have also noted that you recommend GPO's and lights respectively be grouped together for the indoor store, laundry, external store, carport, pump room and pool equipment room. However, as the carport/laundry/external store is on the complete opposite side of the plot to the pump room/pool equipment room this would mean a rather odd and very long cable run. I would suggest they be split-up. Your comments please.

[stgrhe]

I realised I had yet another question related to the Main Circuit Breaker Elk:

You recommend a three pole breaker. This must mean that you recommend the neutral to be connected directly from the meter to the DB's neutral bar, right?

Would there be any technical draw-back of using a four pole breaker except that I suppose it is more expensive?

[david96]

Just as a matter of interest I did a MD calculation based on your prospective load and came up with the following, This does not include the airconditioning load.

A phase. 53A + airconditioner load.

B phase. 54.5A + airconditioner load.

C phase. 46.5A + airconditioner load.

Allowing for 30A per phase for airconditioning (FL Amps of airconditioners not supplied) the estimated MD would be:

A phase. 83A

B phase. 84.5A

C phase. 76.5A

The permissible MD 100A per phase, 25sqmm minimum.

Voltage drop calculations on the consumers mains should be carried out using 100A.

What is the proposed route length of the consumers mains in meters?

With the TN (MEN) system the incoming neutral is not switched. However if the TT system is used the incoming neutral may be switched.

[stgrhe]

Just as a matter of interest I did a MD calculation based on your prospective load and came up with the following, This does not include the airconditioning load.

A phase. 53A + airconditioner load.

B phase. 54.5A + airconditioner load.

C phase. 46.5A + airconditioner load.

Allowing for 30A per phase for airconditioning (FL Amps of airconditioners not supplied) the estimated MD would be:

A phase. 83A

B phase. 84.5A

C phase. 76.5A

The permissible MD 100A per phase, 25sqmm minimum.

Voltage drop calculations on the consumers mains should be carried out using 100A.

What is the proposed route length of the consumers mains in meters?

With the TN (MEN) system the incoming neutral is not switched. However if the TT system is used the incoming neutral may be switched.

Thanks for your comments David.

The air conditioners have not yet been selected but it now looks like I will go for the Mitsubishi "City Multi" system using inverters both for the outdoor and the indoor units. There will then be three outdoor units and probably six, or possibly seven, ceiling consealed indoor units.

The outdoor units will be the Mitsubishi PUMY-P VHMB(-BS) series using R410a refrigerant (I prefer not to use R22):

2 x 15.5kW (52,900 BTU) for the main house; Power consumption: 5.35kW or 24.7A each; and

1 x 11.2kW (38,200 BTU) for the guest house; Power consumption: 3.34kW or 15.4A

The indoor units have still not decided upon as MELANS (Mitsubishi Electric Air-conditioners Network System) have not yet finished their calculations of the exact requirement. One or their engineers has been on site and so far they have acted very professionally, something I regrettably cannot say about Siam Daikin, which originally were my first choice. Also the local major A/C company here in Hua Hin had really no clue how to properly design an air conditioner system so I simply walked out of his office.

The indoor units are likely to be the Mitsubishi PEFY-P VMA(L)-E series (there are 10 models) and and their power consumptions are between 60W (0.53A) for the smallest unit to 360W (2.21A) for the largest unit.

Thus, it appears that your assumption for 30A per phase for the air conditioners is about right given the new air conditioner data.

I estimate the length of the mains cables from the transformer to my meter to be between 60 to 100 metres. It will depend on how the cables will be run but I can clear that tomorrow when I next meet with the construction engineer. The meter will be installed indoor next to consumer unit.

Also can you please explain what these acronyms stands for:

FL

MEN

TN

TT

Göran

[david96]

The acronyms, yes, one should have been clearer.

FL. Full Load in amps.

MEN. mutiple earth neutral, the main neutral bar is connected to the main earth by a link.

TN. An IEC term. the neutral at the star point of the transformer is earthed and the neutral is earthed at the consumers installation, referred to as the MEN system in AS3000.

TT. An IEC term. the neutral at the star point of the transformer is earthed. The neutral is not earthed at the consumers installation. The earthing systems are separate and are not bonded. TT systems require RCDs to be fitted to give earth fault protection.

But remember in Thailand TT is the norm and RCD protection is very often not installed.

You will most likely be using the MEN system.

,

[david96]

It looks like your consumers mains will be 70sqmm for a 60M run and 95sqmm for a 100M

run based on 100A per phase and a voltage drop of 2.5%.

[stgrhe]

It looks like your consumers mains will be 70sqmm for a 60M run and 95sqmm for a 100M

run based on 100A per phase and a voltage drop of 2.5%.

You mean by this 4 x 70sqmm or 4 x 95 sqmm cables right?

[elkangorito]

My comments in blue.

12] I do not see any mention of hot water used for the purposes of bathing. Did you forget to include any hot water units for this?

There is a 150l hot water heater in the system, which is also mentioned in my first post. Originally there were three units, one 150l for the two main bathrooms, one 30l for the kitchen and one 30l for the guest house. The separate kitchen hot water for the kitchen was then removed.

In your MD calculation you have probably deleted the 150l instead of the 30l but as both types use 1.8kW the MD calculation will not be changed.

This is correct.

Can you please recommend a suitable Main Circuit Breaker with current limiter? You mentioned before that a limiter would be recommended as the max current exceeds 100A. Also, can you please explain why you recommend a Main Circuit Breaker rated 40A; shouldn't it be rated the same as the meter, i.e. 100A?

Sorry, that should've been a 32 amp breaker.

You indicated that you have a 3 phase supply. This breaker will limit each phase current to 32 amps (approx). Your load is single phase, spread over 3 phases.

I have no problem converting the Open Office document to Excel but the under laying formulas get lost.

Once again many thanks Elkangorito for your support.

Edited due to spelling error

[elkangorito]

My comments in blue.

Elk, I have some follow-up questions related to the balance load calculation:

1. You suggest CB's for the A/C's, hob and oven circuits. Does that mean you propose separate RCD's to these circuits in addition to the CB's, or if not, how would you propose I handle the ground fault issue?

This equipment is typically "leaky". The problem is not so much with new equipment.

If you wish to use RCBO's with this equipment, you may.

If this equipment is the "plug in" type & the socket cannot be easily accessed for a use other than that of its intended use (supply for the hob, oven etc), an RCBO need not be installed.

If this equipment is NOT the "plug in" type, AS3000 states that an RCBO must be used.

I personally think that this rule is a tad over the top.

2. You do not suggest separate circuits for the two water pumps. Would it not be better to keep those two units on a separate circuit since I eventually will install high- and low voltage protection at a later stage?

The pumps you indicated are small (less than 2.2kW) & are "plug in" devices. If you wish to put these on separate circuits, you have space on the DB to do so.

3. I have also noted that you recommend GPO's and lights respectively be grouped together for the indoor store, laundry, external store, carport, pump room and pool equipment room. However, as the carport/laundry/external store is on the complete opposite side of the plot to the pump room/pool equipment room this would mean a rather odd and very long cable run. I would suggest they be split-up. Your comments please.

This circuit has the pump equipment on it. When pumps start, the voltage will drop slightly & can cause lights to temporarily dim. Some people find this annoying. For this reason, I included the pumps with other rooms that people don't normally habitate.

[elkangorito]

I realised I had yet another question related to the Main Circuit Breaker Elk:

You recommend a three pole breaker. This must mean that you recommend the neutral to be connected directly from the meter to the DB's neutral bar, right?

Would there be any technical draw-back of using a four pole breaker except that I suppose it is more expensive?

There are quite a few veru good reasons why the nuetral in the Consumers Mains must not be broken. Without going into these reasons, I highly recommend that you do not switch this neutral. Use a 3 pole breaker.

[stgrhe]

My comments in blue.

Elk, I have some follow-up questions related to the balance load calculation:

1. You suggest CB's for the A/C's, hob and oven circuits. Does that mean you propose separate RCD's to these circuits in addition to the CB's, or if not, how would you propose I handle the ground fault issue?

This equipment is typically "leaky". The problem is not so much with new equipment.

If you wish to use RCBO's with this equipment, you may.

If this equipment is the "plug in" type & the socket cannot be easily accessed for a use other than that of its intended use (supply for the hob, oven etc), an RCBO need not be installed.

If this equipment is NOT the "plug in" type, AS3000 states that an RCBO must be used.

I personally think that this rule is a tad over the top.

2. You do not suggest separate circuits for the two water pumps. Would it not be better to keep those two units on a separate circuit since I eventually will install high- and low voltage protection at a later stage?

The pumps you indicated are small (less than 2.2kW) & are "plug in" devices. If you wish to put these on separate circuits, you have space on the DB to do so.

3. I have also noted that you recommend GPO's and lights respectively be grouped together for the indoor store, laundry, external store, carport, pump room and pool equipment room. However, as the carport/laundry/external store is on the complete opposite side of the plot to the pump room/pool equipment room this would mean a rather odd and very long cable run. I would suggest they be split-up. Your comments please.

This circuit has the pump equipment on it. When pumps start, the voltage will drop slightly & can cause lights to temporarily dim. Some people find this annoying. For this reason, I included the pumps with other rooms that people don't normally habitate.

Thanks Elk, all understood!

[stgrhe]

I realised I had yet another question related to the Main Circuit Breaker Elk:

You recommend a three pole breaker. This must mean that you recommend the neutral to be connected directly from the meter to the DB's neutral bar, right?

Would there be any technical draw-back of using a four pole breaker except that I suppose it is more expensive?

There are quite a few veru good reasons why the nuetral in the Consumers Mains must not be broken. Without going into these reasons, I highly recommend that you do not switch this neutral. Use a 3 pole breaker.

So a 3-pole breaker it will be!

Many thanks

[elkangorito]

Sorry. I forgot to post your DB layout. See attached PDF.

DB_layout.pdf

[stgrhe]

Sorry. I forgot to post your DB layout. See attached PDF.

DB_layout.pdf

Thank you!

[david96]

It looks like your consumers mains will be 70sqmm for a 60M run and 95sqmm for a 100M

run based on 100A per phase and a voltage drop of 2.5%.

You mean by this 4 x 70sqmm or 4 x 95 sqmm cables right?

Yes, that is correct, 4 x 70sqmm or 4 x 95sqmm copper conductor PVC insulated PVC sheathed (PVC/PVC).

Just as a matter of interest 95sqmm appears a large conductor it actually has a nominal diameter of approx.11mm,a 70sqmm has a diameter of approx. 9.5mm. (With allowance for the multi stranding). It is sometimes easier to compare conductors by their diameter.

[stgrhe]

...copper conductor PVC insulated PVC sheathed (PVC/PVC).

It this cable type what one refers to as double insulated?

I have also another question, which might sound silly and obvious to many, but what exactly is the definition of the figures 30/100 in a meter?

[longball53098]

...copper conductor PVC insulated PVC sheathed (PVC/PVC).

It this cable type what one refers to as double insulated?

I have also another question, which might sound silly and obvious to many, but what exactly is the definition of the figures 30/100 in a meter?

This is not silly as I started a whole topic about meters a few years ago because of my lack of knowledge about meters.

According to a data sheet from Mitsu that makes these types of meters the 30 refers to the basic current for this meter and the 100 refers to the maximum current that this meter can safely pass and meter.

Here is a copy of a data sheet

MF220_30A100_3E.pdf

See the notes on the bottom for the 30/100 explanation

[stgrhe]

...copper conductor PVC insulated PVC sheathed (PVC/PVC).

It this cable type what one refers to as double insulated?

I have also another question, which might sound silly and obvious to many, but what exactly is the definition of the figures 30/100 in a meter?

This is not silly as I started a whole topic about meters a few years ago because of my lack of knowledge about meters.

According to a data sheet from Mitsu that makes these types of meters the 30 refers to the basic current for this meter and the 100 refers to the maximum current that this meter can safely pass and meter.

Here is a copy of a data sheet

MF220_30A100_3E.pdf

See the notes on the bottom for the 30/100 explanation

Thanks for that Longball.

I note from the data sheet that the meter's data refers to an ambient temperature of 23 deg. Here in Thailand we mostly see a much higher temperature than that. Does any one know how the data, the current rating, is affected by a 10 degree increase?

[stgrhe]

Gentlemen electrical gurus,

The estimated cable length from the 3-phase transformer to the house's distribution board is 100 metres (95 to be more precise). I plan to limit the current to maximum 100A. Using data from a Swedish cable manufacturer's calculator it says I shall use a minimum of 40mm2 cable. I also tried Crossby's calculator but that one didn't come up with any result.

I have three questions:

1) Does 40mm2 seem reasonable and if so how much voltage drop would it mean?

2) What is the resistance (impedance) per metre cable length per mm2 cable thickness?

3) The cable will be drawn underground in conduits, which cable type shall be used for best insulation and lowest voltage drop?

[powderpuff]

you are in good hands with ElKangorito BUT i doubt that the 52,000 btu unit is single phase and i strongly doubt that you need a 52k unit. please reconsider, plan smaller units instead, have a better airflow and save energy by using only the capacity you need.

Yes, he is very good and indeed a true gentleman, I take of my hat and bow.

I know something is not right with the A/C and I have therefore asked another company to estimate the need in the applicable area. The 52,000 BTU figure was actually suggested by an engineer from Siam-Daikin in Bangkok after I had given him all relevant parameters and a layout of the house. Sadly he wouldn't reveal the formula he used. I am not a fully novice in this department but my knowledge is very dated and I simply do not remember how to carry out the calculation properly. My intuition tells me that something around 36,000 BTU or even less is probably more realistic.

I remember though that volume, insulation types (U-values), outdoor temperature and humidity, number of sunny hours per day, window sizes, glass thickness (single / double / triple), direction North / South etc. all matters but not their relation to one another.

Unless you have massively high celings - like 20 foot - I use 1,000 btu per sq/m floor space. Some on here will say that's too much. I don't think so, better to have a little bit excess.

I agree that 52,000 sounds a bit excessive. As an aside an aircon that size would be cheaper to run in 3 phase.

Your overall requirements are not beyong a normal house ( I have 4 bedroom/4 bath) but your run from the street to load center is LONG. Hopefully someone will chime in soon with wire diameter. It's a pretty straightforward calculation.

[david96]

Gentlemen electrical gurus,

The estimated cable length from the 3-phase transformer to the house's distribution board is 100 metres (95 to be more precise). I plan to limit the current to maximum 100A. Using data from a Swedish cable manufacturer's calculator it says I shall use a minimum of 40mm2 cable. I also tried Crossby's calculator but that one didn't come up with any result.

I have three questions:

1) Does 40mm2 seem reasonable and if so how much voltage drop would it mean?

2) What is the resistance (impedance) per metre cable length per mm2 cable thickness?

3) The cable will be drawn underground in conduits, which cable type shall be used for best insulation and lowest voltage drop?

1. 35sqmm cable for 6% voltage drop over that length.

2. 35sqmm = 1773 Am per%Vd single phase at (230V) circuit.

50sqmm = 2377. 70sqmm = 3342. 95sqmm = 4445.

Calculation. (A x L) / %age voltage drop. You need to maintain the max voltage drop to any part of the electrical installation to less than 5%. A =Amps, L length in meters.

Source, AS3000/2007 Table C7 Voltage drop- Simplified Method developed from AS3008.

3. 1. Copper conductors, 2. Insulation does not affect voltage drop. 3. Single conductor configuration will give the highest current rating. 4. Use PVC/PVC 75C temp rating would be recomended.

Edited December 14, 2009 by david96

[stgrhe]

Gentlemen electrical gurus,

The estimated cable length from the 3-phase transformer to the house's distribution board is 100 metres (95 to be more precise). I plan to limit the current to maximum 100A. Using data from a Swedish cable manufacturer's calculator it says I shall use a minimum of 40mm2 cable. I also tried Crossby's calculator but that one didn't come up with any result.

I have three questions:

1) Does 40mm2 seem reasonable and if so how much voltage drop would it mean?

2) What is the resistance (impedance) per metre cable length per mm2 cable thickness?

3) The cable will be drawn underground in conduits, which cable type shall be used for best insulation and lowest voltage drop?

1. 35sqmm cable for 6% voltage drop over that length.

2. 35sqmm = 1773 Am per%Vd single phase at (230V) circuit.

50sqmm = 2377. 70sqmm = 3342. 95sqmm = 4445.

Calculation. (A x L) / %age voltage drop. You need to maintain the max voltage drop to any part of the electrical installation to less than 5%. A =Amps, L length in meters.

Source, AS3000/2007 Table C7 Voltage drop- Simplified Method developed from AS3008.

3. 1. Copper conductors, 2. Insulation does not affect voltage drop. 3. Single conductor configuration will give the highest current rating. 4. Use PVC/PVC 75C temp rating would be recomended.

On an internet cable manufacturer's site I found this statement:

Cupper's resistance at 20°C is approx. 0,018 ohm/mm² per metre cable. For aluminium it is 0,028 ohm/mm².

It also states that for both cupper and aluminium the resistance increases with 0.4% per °C temperature increase.

Using a 40mm² cable over 100m means that the resistance is 0.045 ohm at 20°C and for 33°C after adding 0.4% per °C I get an added resistance of 0.052 ohm, and thus a total resistance for the 100m cable of 0.097 ohm. This gives a voltage drop of 9.7V equals to 4.4%.

Is this calculation correct?

Edited: Spelling error corrected

Edited December 14, 2009 by stgrhe

[powderpuff]

Forgot to mention. Since your cable is buried inside conduit I would go copper - not alum. That's because weight is not an issue. I suppose you cab use either PVC or that galvanized stuff. I would dig a channel, concrete it & then fabricate a cover - that way if you have to dig it up someday it's real easy & less corrosion problems on the conduit.

[stgrhe]

Forgot to mention. Since your cable is buried inside conduit I would go copper - not alum. That's because weight is not an issue. I suppose you cab use either PVC or that galvanized stuff. I would dig a channel, concrete it & then fabricate a cover - that way if you have to dig it up someday it's real easy & less corrosion problems on the conduit.

Yes, the cable will be copper and the conduit will be PVC. The conduit itself will run in a U-shape channel beam an then the top side covered with a fabric. There is a kind of fabric one uses for drains but I cannot remember the name right now. The depth of the channel will be 1m+ to

keep the cables cooler

[powderpuff]

Excellent plan. btw - do you have to run 4 strands from the street to account for NEUTRAL?

[stgrhe]

Not actually from the street as the 3-phase 11kV transformer is privately funded and inside the development. It has been fully paid for by the developer.

I yesterday once again measured the distance for the cable run to my house's DB, and the 100m from my estimate stands. I have requested 50mm2 PVC insulated and sheeted cables to be used.

Edited: Typing error corrected

Edited December 15, 2009 by stgrhe

[elkangorito]

The method I used to come to a figure of 25mm squared copper cable for the Consumer Mains was derived from AS3008. AS3000 gives a very conservative figure (very safe) whilst AS3008 provides a safe but more cost effective cable sizing calculation.

If you want to make sure that everything is ok, go with 35mm squared copper cable. It is more than ample for your situation (buried in conduit). I recently did the same calc for zapatero.

[powderpuff]

Let me ask it this way. How many wires do you run from the meter to the DP? 3 or 4 ? Thanks