Three Phase Watt To Amps

[Pacificperson]

Three phase electricity is a strange beast to me. I am never quite sure that I have it right. I have a 3 phase heater whose label says 15.000 watts. At 230 volts is this 65 amps? And is this load spread across the three phases at 22 amps per phase? Thanks.

[Crossy]

For a heater yes, treat it as three x 5000W single phase loads, about 23A per phase.

[Pacificperson]

Crossy. Thanks. You should charge consulting fees.

[jombom]

Does the OP have a 3 phase supply ?? --- just wondering.

And why would somebody, need a heater that size in Thailand, just wondering again ??

[Pacificperson]

Yes, I have a three phase supply and the heater is for large volumes of salt water.

[Pib]

So you are the one that keeps the Gulf of Thailand warm .

[Tywais]

So you are the one that keeps the Gulf of Thailand warm .

Sounds like a salt water swimming pool. Either that or he is running Sea World.

[electau]

The heater is rated at 15000 watts total , connected accross three phases and neutral. the individual loads are single phase 5000 watts each. At 230V the current is 22A per phase.

Subject to voltage drop the circuit should be 4.0sqmm minimum and protected by a 25A or 32A MCB. The equipment should be earthed.

As you intend to heat salt water it would appear that you are operating the proposed equipment in a commercial and not a domestic (residential type) environment.

[Pacificperson]

The heater is rated at 15000 watts total , connected accross three phases and neutral. the individual loads are single phase 5000 watts each. At 230V the current is 22A per phase.

Subject to voltage drop the circuit should be 4.0sqmm minimum and protected by a 25A or 32A MCB. The equipment should be earthed.

As you intend to heat salt water it would appear that you are operating the proposed equipment in a commercial and not a domestic (residential type) environment.

It is not residential, not commercial and not in Thailand, but this forum gives me good answers to my questions. Thanks.

Edited July 10, 2012 by Pacificperson

[T_Dog]

The heater is rated at 15000 watts total , connected accross three phases and neutral. the individual loads are single phase 5000 watts each. At 230V the current is 22A per phase.

Subject to voltage drop the circuit should be 4.0sqmm minimum and protected by a 25A or 32A MCB. The equipment should be earthed.

As you intend to heat salt water it would appear that you are operating the proposed equipment in a commercial and not a domestic (residential type) environment.

That's the conservative approximation, correct? The current in each conductor is actually less than 22 amps as it is a three phase connection with the square root of 3 cancellation factor. Still, the 25 or 32 amp MCB or RCBO is appropriate.

[jombom]

The heater is rated at 15000 watts total , connected accross three phases and neutral. the individual loads are single phase 5000 watts each. At 230V the current is 22A per phase.

Subject to voltage drop the circuit should be 4.0sqmm minimum and protected by a 25A or 32A MCB. The equipment should be earthed.

As you intend to heat salt water it would appear that you are operating the proposed equipment in a commercial and not a domestic (residential type) environment.

It is not residential, not commercial and not in Thailand, but this forum gives me good answers to my questions. Thanks.

So, how does your question relate to Thailand, pray tell.

[electau]

The heater is rated at 15000 watts total , connected accross three phases and neutral. the individual loads are single phase 5000 watts each. At 230V the current is 22A per phase.

Subject to voltage drop the circuit should be 4.0sqmm minimum and protected by a 25A or 32A MCB. The equipment should be earthed.

As you intend to heat salt water it would appear that you are operating the proposed equipment in a commercial and not a domestic (residential type) environment.

That's the conservative approximation, correct? The current in each conductor is actually less than 22 amps as it is a three phase connection with the square root of 3 cancellation factor. Still, the 25 or 32 amp MCB or RCBO is appropriate.

It is not a balanced 3 phase load, it is 3 separate single phase loads connected accross a 3 phase and neutral supply. Single phase is 230V to neutral. The elements of the heater are connected in a star configuration with the neutral at the star point.Current in each phase is 5000/230 = 21.73A

The voltage between phases is 400V. With a balanced 3 phase load eg a 3 phase motor the supply voltage is 400V with a load of 15000W the current per phase is 15000/400*1.732 =21.65A.

The current differential is negligable and may be disregarded for practicable purposes in the selection of a protective device eg a 3 pole MCB in this case.

　

[Pacificperson]

Jombom - the answer to this particular question is the same inside or outside Thailand. I read this forum and in particular this topic and the others are kind enough to give answers.

Electau - the "star" configuration is also called a "wye" while the phase to phase is called a delta?

[electau]

Jombom - the answer to this particular question is the same inside or outside Thailand. I read this forum and in particular this topic and the others are kind enough to give answers.

Electau - the "star" configuration is also called a "wye" while the phase to phase is called a delta?

Yes the star configuration has the star point connected to the neutral, 230V L to N. 400V L to L.

The delta configuration has no neutral connection, 400V L to L.

The resistance of each heater element is 10.6ohms. These must be connected in a star configuration not a delta one. Elements are rated at 230V not 400V.

[Khonwan]

The heater is rated at 15000 watts total , connected accross three phases and neutral. the individual loads are single phase 5000 watts each. At 230V the current is 22A per phase.

Subject to voltage drop the circuit should be 4.0sqmm minimum and protected by a 25A or 32A MCB. The equipment should be earthed.

As you intend to heat salt water it would appear that you are operating the proposed equipment in a commercial and not a domestic (residential type) environment.

That's the conservative approximation, correct? The current in each conductor is actually less than 22 amps as it is a three phase connection with the square root of 3 cancellation factor. Still, the 25 or 32 amp MCB or RCBO is appropriate.

It is not a balanced 3 phase load, it is 3 separate single phase loads connected accross a 3 phase and neutral supply. Single phase is 230V to neutral. The elements of the heater are connected in a star configuration with the neutral at the star point.Current in each phase is 5000/230 = 21.73A

The voltage between phases is 400V. With a balanced 3 phase load eg a 3 phase motor the supply voltage is 400V with a load of 15000W the current per phase is 15000/400*1.732 =21.65A.

The current differential is negligable and may be disregarded for practicable purposes in the selection of a protective device eg a 3 pole MCB in this case.

　

Electau, I’m a bit confused. I have two 3-ph showers (12kW and 13.something kW). They appear to me to have only one element inside (though I appreciate that the copper “element” could be an envelope for 3 elements). More crucially, there are no neutral cables. I thought that indicated a 400V element. Please clarify.

[Murtle71]

The heater is rated at 15000 watts total , connected accross three phases and neutral. the individual loads are single phase 5000 watts each. At 230V the current is 22A per phase.

Subject to voltage drop the circuit should be 4.0sqmm minimum and protected by a 25A or 32A MCB. The equipment should be earthed.

As you intend to heat salt water it would appear that you are operating the proposed equipment in a commercial and not a domestic (residential type) environment.

That's the conservative approximation, correct? The current in each conductor is actually less than 22 amps as it is a three phase connection with the square root of 3 cancellation factor. Still, the 25 or 32 amp MCB or RCBO is appropriate.

It is not a balanced 3 phase load, it is 3 separate single phase loads connected accross a 3 phase and neutral supply. Single phase is 230V to neutral. The elements of the heater are connected in a star configuration with the neutral at the star point.Current in each phase is 5000/230 = 21.73A

The voltage between phases is 400V. With a balanced 3 phase load eg a 3 phase motor the supply voltage is 400V with a load of 15000W the current per phase is 15000/400*1.732 =21.65A.

The current differential is negligable and may be disregarded for practicable purposes in the selection of a protective device eg a 3 pole MCB in this case.

　

Electau, I’m a bit confused. I have two 3-ph showers (12kW and 13.something kW). They appear to me to have only one element inside (though I appreciate that the copper “element” could be an envelope for 3 elements). More crucially, there are no neutral cables. I thought that indicated a 400V element. Please clarify.

The element may be labelled as to the internal wiring. If the element is for heating then 3 phase load would normally be balanced. Meaning very little current in the neutral if connected in star "Y". the star point could be left off.

[Khonwan]

Murtle71, thanks for this. Based on my interpretation of your reply (note: I’m not an electrician), the absence of a neutral cable does not signify that there is only one heating element operating on 400V but neither does it preclude that possibility, i.e. there could be three elements inside the visible copper cylinder each operating on 230V or only one element operating on 400V. Please correct my conclusion if incorrect.

[electau]

The heater is rated at 15000 watts total , connected accross three phases and neutral. the individual loads are single phase 5000 watts each. At 230V the current is 22A per phase.

Subject to voltage drop the circuit should be 4.0sqmm minimum and protected by a 25A or 32A MCB. The equipment should be earthed.

As you intend to heat salt water it would appear that you are operating the proposed equipment in a commercial and not a domestic (residential type) environment.

That's the conservative approximation, correct? The current in each conductor is actually less than 22 amps as it is a three phase connection with the square root of 3 cancellation factor. Still, the 25 or 32 amp MCB or RCBO is appropriate.

It is not a balanced 3 phase load, it is 3 separate single phase loads connected accross a 3 phase and neutral supply. Single phase is 230V to neutral. The elements of the heater are connected in a star configuration with the neutral at the star point.Current in each phase is 5000/230 = 21.73A

The voltage between phases is 400V. With a balanced 3 phase load eg a 3 phase motor the supply voltage is 400V with a load of 15000W the current per phase is 15000/400*1.732 =21.65A.

The current differential is negligable and may be disregarded for practicable purposes in the selection of a protective device eg a 3 pole MCB in this case.

　

Electau, I’m a bit confused. I have two 3-ph showers (12kW and 13.something kW). They appear to me to have only one element inside (though I appreciate that the copper “element” could be an envelope for 3 elements). More crucially, there are no neutral cables. I thought that indicated a 400V element. Please clarify.

What is the voltage rating of the elements 230V or 400V.? If 230V they will have a neutral connection and be connected in star configuration.

If they are 230V there will be a neutral connection. If they are 400V they will not have a neutral connection and will be connected in delta configuration.

Based on a 3 phase connection and 3 elements.

Edited August 12, 2012 by electau

[Khonwan]

Ok, so in the absence of a neutral cable and with no sign of three elements (both units have only two heat settings and only one copper whatever) I am continuing to conclude I have a 400V element. It was only the fact that you, Electau, have posted more than once that 3-ph shower water heaters here consist of 3 elements each powered by 220V that caused me to question what I had.

Thanks for clarifying.

[electau]

Ok, so in the absence of a neutral cable and with no sign of three elements (both units have only two heat settings and only one copper whatever) I am continuing to conclude I have a 400V element. It was only the fact that you, Electau, have posted more than once that 3-ph shower water heaters here consist of 3 elements each powered by 220V that caused me to question what I had.

Thanks for clarifying.

The individual heater elements are combined into one unit ie 3 elements, ie 6 terminals. An individual element will have 2 terminals. What are the connections at your cable connection point at the appliance? L1, L2, L3 and N plus E ( 3 phase connection) or L, N, E. ( single phase 230V connection).

Never assume, visually check and confirm ratings and phase connections first.

[Khonwan]

Electau, you’ve done it again. You’ve ignored the other possibility: L1, L2, L3, E, i.e. no N. This is what I have in both units. Only 3 connections on the copper element: L1, L2, L3. If you doubt this (no offense taken) please ask me for photos of the open units. I’m the one who personally installed both units; I’ve been using them every day.

[electau]

Electau, you’ve done it again. You’ve ignored the other possibility: L1, L2, L3, E, i.e. no N. This is what I have in both units. Only 3 connections on the copper element: L1, L2, L3. If you doubt this (no offense taken) please ask me for photos of the open units. I’m the one who personally installed both units; I’ve been using them every day.

L1,L2,L3. a 3 wire three phase 400V heaters connected in delta configuration.

Edited August 16, 2012 by electau

[electau]

Heater elements made in Germany often have a 3 phase 3 wire connection only.

Heaters designed for single or three phase connection will have a neutral terminal. (ie Australia, UK etc.)

A schematic drawing of the equipment would be useful in determining the connections and control of the heater.

Edited August 16, 2012 by electau

[Khonwan]

Yes, my showers are German made and are only for 3-phase. I managed to find the wiring diagrams (attached).