Prev Page 3 of 3 1 2 3 Please log in to reply 72 replies to this topic

[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]

stgrhe, on 2009-11-30 19:23:08, said:

Naam, on 2009-11-30 17:05:50, said:

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]

stgrhe, on 2009-12-14 06:43:53, said:

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 by david96, 2009-12-14 07:04:24.

[stgrhe]

david96, on 2009-12-14 06:59:20, said:

stgrhe, on 2009-12-14 06:43:53, said:

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 by stgrhe, 2009-12-14 08:28:05.

[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]

powderpuff, on 2009-12-14 18:35:50, said:

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 by stgrhe, 2009-12-15 07:03:49.

[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

[stgrhe]

powderpuff, on 2009-12-16 02:30:30, said:

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

                                    
I suppose it will be one cable with four cores PVC insulated and single or double sheeted like e.g. Thai-Tazaki's cable type                                      NYY-GRD, MEA TYPE C-GRD or similar power cable.

THIS SPECIFIC CABLE'S                                           SPECIFICATION

                                          NUMBER OF CORE : 2 - 4 cores plus earth
                                          CONDUCTOR : Solid                                                                                                                       and stranded                                           annealed copper, sizes 1 mm2 up to 300 mm2; Earth conductor size 1 mm2 up 35 mm2
                                          INSULATION : PVC
                                          COLOUR :
- 2 cores – Light gray and Black
                                          - 3 cores – Light gray, Black and Red
                                          - 4 cores – Light gray, Black, Red and Blue
                                          - Earthing core - Green/Yellow
                                          SHEATH : PVC
                                          UNDER SHEATH Color: Black
                                          CLASSIFICATION : Maximum                                           conductor temperature 70 °C Circuit                                           voltage not exceeding 750 V
                                          TESTING VOLTAGE : 2,500 V

http://www.thaiyazak...ndex_power.html

[stgrhe]

The exercise with the MDC is now almost done and I like to express my thank to all Thai Visa members who have contributed and especially I like to thank Elkangorito and David96 who both have provided advice by PM. I am ever so grateful, many thanks.

The next step will be to select the consumer unit and its equipment. I a looking at two solutions, 1) to go for a more industrial type cabinet and fit the units on DIN-rails linked together with bush-bars; or 2) go for the more common cabinet type.

The advantage with special designed cabinet is that it will allow me to fit other units I need in the same cabinet, but I suppose it will be a more costly alternative. I will chose the equipment from ABB's product ranges.

[David006]

Just a thought..have you checked with your friendly power company as to the availability of the required service.
I just paid to have our meter changed to permanent from temp building and asked for 30amp.. "No Can".. "only have 15amp here..most people have 5amps" ...sigh! I wrote down potential load of about 16AMPs...to no avail....TIT ( I guess 5A is enough for a big screen TV, fridge and a fluorescent strip or two).
Oh ...and the site inspection consisted of holding a clipboard staring at the house, glancing at the domestic box and asking if we had a ground rod..lol


Okay sorry... just read you are in a development etc. with three phase   ..disregard

Edited by David006, 2009-12-17 07:55:43.

[powderpuff]

If you are willing to pay (I guess around 8000 baht) I'll bet you can get 15/45 amp meter. Go back to PEA office & ask them again. Speak to the manager if necessary.

[stgrhe]

powderpuff, on 2009-12-18 03:52:37, said:

If you are willing to pay (I guess around 8000 baht) I'll bet you can get 15/45 amp meter. Go back to PEA office & ask them again. Speak to the manager if necessary.

The meter will be a 30/100 amp meter for 3-phase so there is no need to pay any money. The developer has already paid for the transformer and it will be installed before the end of the month. The poles and the insulators are already there.

[david96]

elkangorito, on 2009-12-16 01:35:58, said:

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.

What value of MD in amps per phase and route length in meters did you use on the heaviest loaded phase?

[stgrhe]

david96, on 2009-12-18 07:06:33, said:

elkangorito, on 2009-12-16 01:35:58, said:

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.

What value of MD in amps per phase and route length in meters did you use on the heaviest loaded phase?

David,

Elkangorito has informed me that he will now focus on another forum, the Generator Solution Forum, so you may not get a reply on here to your post.

G.

[stgrhe]

This is the final result of this exercise, which was started in order to establish the maximum demand, and balancing of the load over the three phases, for our Hua Hin villa that is currently under construction. As earlier said a combined input from Elkangorito and David96 has been used to arrive at the figures below.

My apology for the poor resolution.


MDC - Page 1


MDC - Page 2


Load Balance - Page 1


Load Balance - Page 2


Load Balance - Page 3

[stgrhe]

The second MDC page has been updated.

[stgrhe]

Just an update on this project. The design of the distribution board has now been set and the unit ordered on PMK Industry in Nonthaburi for production. PMK is ABB's main distributor in Thailand and I found this company very prompt and skillful for a Thai company.

The DB will comprise two section of which one has the form of a standard layout for RCBO fittings, the right section of the cabinet drawing below, while the left section is specially designed.  

The standard right section will hold 33 ABB DS271 type RCBO with three sockets in spare for eventual future expansion. The left specially designed compartment will hold the main incoming terminals, the main circuit breaker (ABB MCCB type T2max), surge arrestor, a panel volt meter, a panel ampmeter plus selector switches and fuses.

Photos will be posted once the unit has been designed and put into operation.



Layout drawing



Electrical drawing of the specially designed left compartment



Distribution board configuration.

[stgrhe]

Yesterday I went up to PMK in Nonthaburi, the manufacturer of the distribution board, to fetch the distribution board. It consists of one cabinet with dimensions 120 x 100 x 20 cm (w x h x d) with two separate compartments.  

The left compartment holds the terminals for the incoming mains, the main circuit breaker, a surge arrester with HRC fuses, neutral and earth bars, current transformers and shortening links for an ammeter, and fuses for a volt meter. Both meters are panel mounted with individual selector switches.

Each phase current can thus be measured whereas the voltage can measure each phase to neutral and each phase to another phase. PMK also fitted three panel mounted indicator LEDs, one for each phase.

The right side compartment hoses 33 RCBOs, one for each circuit with three slots in spare for future expansions.

The products are:

1. MCCB - ABB T1maxB160 16kA

2. Distribution Board - ABB 3-phase, 4-wire, 36 CCT, main lug, bushbar 200A

3. RCBOs - ABB DS271 1P, 30mA

3.1 1 x 32A

3.2 11 x 25A

3.3 10 x 20A

3.3 11 x 16A

4. Control Fuse - ABB E931-32 with fuse base rail mounting

5. HRC Fuse Link - ABB 125A, size 00

6. HRC Fuse Base - ABB OFAX 00 P3, 3-pole, 160A, size 00

7. Voltmeter - Crompton E244-02V, 0 - 500V, scale 90 degree, class 1.5

8. Ammeter - Crompton E244-022A, 0 - 50A, scale 90 degree, class 1.5

9. Current Transformer - Crompton CI-MSQ-30, 50/5A, burden 3VA, class 3

10. Volt Selector Switch - Salzer SA16-7-3, 7 positions, 16A, 660V

11. Amp Selector Switch - Salzer SA16-4-3, 4 positions, 16A, 660V (O = off will not be used)

12. Surge Arrester Class II - DEHN 952310, DG M TT 275 40kA (8/20)

13. Shortening Links 

Separately supplied:

14. Surge Arrester for Satellite TV Antenna - DEHNgat 909705, DGA GFF TV 2.5kV (10/350)

15. Surge Arrester for Telephone Line - DEHN Blitzductor, BXT ML4 B 180 10kA (10/350) + BXT BAS



Distribution Board front view



Left side compartment



Left side compartment close up



Right side compartment holding the RCBOs

[david96]

A very well designed Main Switchboard and of a high standard of workmanship by the contractor.

[stgrhe]

david96, on 2010-04-01 09:52:28, said:

A very well designed Main Switchboard and of a high standard of workmanship by the contractor.

Thank you David!


I am very pleased with PMK's work and it was surprisingly cheap too. The total price including VAT came to 137,000 baht only.