live condenser without earth

[casino]

Hi

one of our lads installed a daikin ftxs42 the other day and found himself getting shocks from the system, after i had checked his electrical connections (should of done this first i know) i found he had wired the earth in the neutral block at the side of the isolator instead of in the earth block where the actual earth was connected.
no neutral cable was connected there so basically the unit was not earthed and the unit was giving off 105volts AC.
i didn't check if any amps were coming from the unit but my question is why would the unit do this.

i have since tested this with another small daikin system we have set up in our factory (by disconnecting the earth and running) and found this to do the same. tried disconecting the earth from a daikin ftxs50 and this unit did not liven up.

anyone help me understand this as it seems quite bizzare to me.

Daikin say yes it would do this but could not give me a reason why.

thanks for any replies.

chris

[NoNickName]

It's not bizzare. It's quite normal. Neutral is not necessarily at earth potential. This is only true on PEN systems, where the Potential Earth is Neutral (acronym of PEN).
Everywhere else Neutral may have a floating potential to earth which can well be few dozen volts or even 100 as in your case.

Whether the distribution system is PE or PEN very much depends on the building and on the utility company.

[casino]

thanks for the reply nonickname

so your saying some condensers use the PEN system?? combine earth and neutral.

and also i think you are saying depending if the incomming to the building uses the tnc or tncs earthing system.

i see you are from italy, i'm from the UK so your PEN system may be our TNCS system, if this is the case ignore the above but it does not explain why 2 of our condensers livened up and one didn't.

chris

[NoNickName]

Yes, TNC+PEN requires three pole switches, while TNS+PE requires four pole switches. Why the unit livened up? Well, maybe the motor or the fan, or even maybe the transformer was not perfectly insulated and few mA or uA escaped...

[paul_h]

A lot of electronics bleed excess voltage to neutral/earth when they are filtering mains, it's normal for them to do so. There's no bad effects if the neutral and earth conductors are good.
Not having a proper neutral can be bad. I've heard of situations where if a house loses neutral to the street, people get shocked when getting water out of a tap. Here they hook up the earth to the water pipes, if there's no neutral, all current goes through the earth, so any copper water pipe carries current and the water coming out gives you a boot.

[Thermatech]

Always remember to check power supply before exposing the system to a faulty power supply otherwise all the circuit boards can be dammaged & the manufacturer can void warrantee due to incorrect power supply.

Earth to Neutral measurment is very important to make sure the Neutral is connected, any voltage reading will indicate poor Neutral connection.
Then check earth to each phase & N to each phase.
Also phase to phase to ensure correct 3 ph.

Then make final power connection to outdoor unit only if all ok.

Manufacturers assume that the installer will check that the power supply is correct before connection to the system.
They know exactly which components will fail on each circuit board if there is a power supply problem.

[NoNickName]

A lot of electronics bleed excess voltage to neutral/earth when they are filtering mains, it's normal for them to do so. There's no bad effects if the neutral and earth conductors are good.
Not having a proper neutral can be bad. I've heard of situations where if a house loses neutral to the street, people get shocked when getting water out of a tap. Here they hook up the earth to the water pipes, if there's no neutral, all current goes through the earth, so any copper water pipe carries current and the water coming out gives you a boot.

Earthing via water pipes has been banned for ages, here in the EU.

[casino]

Hi
Referring to one of my previous posts I’ve had a thought on why I had one unit not give the voltage when the earth was disconnected and that was because another unit that was earthed was on the same set of wall brackets.

I put this down to the incoming earth to our factory being linked to the neutral (tncs) as opposed to separate (tns).

I know the effects from these kind of systems when the neutral becomes loose or disconnected as we had a customer who had a routine yearly check on one of there distribution boards and the sparky forgot to connect the neutral resulting in the amps going down the earth blowing a capacitor on every ac unit and air handling unit that was on the distribution board.

All power supply is ok to the unit as this has been checked over.

I understand what paul_h is saying and as far as I’m aware all new houses in the UK are built with the tncs system where the earth is connected to the neutral at the CCU which in my opinion is a danger to people just as he explains. That and most of the equipment in the house.


chris