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Daikin Inverter AC in IT System (No Netural)

03/13/2018 9:29 PM

Hi,
Would like to check, we have one project which is for ship/vessel with Daikin inverter unit.
we are planning to supply Daikin Inverter unit for Vessels which is unearthed system ( 3 wire system, No Neutral).
The Daikin unit is commercial usage one and designed for Line and Neutral (230V, L+N), however the vessel voltage is Line to Line(L1+L2) , but the voltage is same.
My service person is saying that, the system need neutral otherwise system will not function.
Now, We are worrying that the inverter unit might not work in L1 + L2 supply.
Any one having this experience?.

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#1

Re: Daikin Inverter AC in IT System ( no Netural)

03/13/2018 11:10 PM

If it is not obvious it is best to ask Daikin directly as it is possible that it will work but it really depends on the electronics inside, and the last thing you want is any exposed metalwork becoming live potentially causing an electric shock.

Does the Daikin unit in question have an earth and/or exposed metalwork that a user could touch without the use of a tool?

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#4
In reply to #1

Re: Daikin Inverter AC in IT System ( no Netural)

03/14/2018 8:32 PM

Hi,

Daikin simply replied ,"only standard power incoming is suitable for our product. Other than that kindly cover by your own risk."

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#5
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Re: Daikin Inverter AC in IT System ( no Netural)

03/14/2018 11:35 PM

Thought that would be the case, but you never know unless you ask.

If you have access to an electrician (or similar) and a sample of the AC inverter you could carefully partially disassemble it and perform some basic checks to see if there is anything inside that could be a safety issue if unearthed, then if that looks good plug it into a IT system and carefully check it works and is not electrically unsafe.

You don't have much option except to assess it and try it out or look for another supplier. It may be fine, but as it is outside what the supplier has designed it originally for they won't take responsibility.

Let us know what you find.

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#2

Re: Daikin Inverter AC in IT System ( no Netural)

03/14/2018 3:46 AM

You say the 230v is line to line, Is it coming from a delta connected output or a star connected output?

If Delta then the 230v L-L will be a single sine wave at the line frequency and would be acceptable for a single phase device at the same voltage and frequency.

If Star, then it is a combination of 2 sine waves 120° apart. The resultant waveform will be a single sine wave at the same frequency reaching the same voltage peak as, but midway between those of the 2 phases, this would also be acceptable for a single phase 230v device.

All outputs from a generator are live until one of them is connected to earth, this makes it a neutral, the earthing is not necessary for the function of the device, but it may well be necessary for safety reasons.

Many vessels use either insulated neutral (not really a neutral as it is not at earth potential) where no live conductors are connected to earth. The frames of individual equipment are connected to the general earth/hull of the vessel. a first earth fault will normally go undetected unless some dedicated detection equipment is used, and will present no personal danger (bird on a wire). A second fault in a different conductor will create a short circuit and cause protection devices to operate. The more equipment that is connected to this system, the less safe it becomes.

Another common system employs a more standard earthed neutral much like standard onshore systems.

Many use a combination of both systems, insulated neutral for essential services such as steering etc, and earthed neutral for general power.

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#3

Re: Daikin Inverter AC in IT System ( no Netural)

03/14/2018 4:44 AM
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#6
In reply to #3

Re: Daikin Inverter AC in IT System ( no Netural)

03/15/2018 6:56 AM

Yeah, he did. See their reply! (#4)

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