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leebut

Regular EF Member
hiya chaps


I did a City and Guilds course, practical assessment and exam for the CG2919 on Monday and Tuesday, we were told about the difficulties with ensuring the safety of the charging equipment especially regarding the earthing in domestic properties, lots of discussions were about using the isolating transformer instead of converting the existing property to a TT system.


My question is which isolating transformers do you EV guys use typically looking at supplying a 7 Kw charging unit, where do you get them from and what is the cost of them.


Regards


Lee
 

freddo

Regular EF Member
Plenty of companies sell isolation transformers, for 7KW it will be large, heavy and expensive.
 

leebut

Regular EF Member
Bill01803


The issue isn’t conversion of the clients property to a TT system, if there is any class 1 light outside fittings or bonded pipes to gas or water within 10 metres of the charging point you have the risk of dangerous touch voltages under earth fault (possibly from neighbours property etc) it’s part of the risk assessment you have to carry out prior to installation.

EV installation not straight forward external influences play a big part of installation, if you change the property from a PME to TT there’s always a risk of another electrician who doesn’t know the legislation on EV installation puts the PME connection back.

Also some ground conditions you would struggle to get the earth potential acceptable for the EV installation, hence why in the installation it’s easier and straight forward to install an isolating transformer.


Lee
 

bill01803

Regular EF Member
“Puts the PME back”

I don’t think you should be concerned about what another electrician may do in the future, as long as it is correct when you have completed your work.
 

Jim_e_Jib

Regular EF Member
Unfortunately I’m in the UK so postage would be expensive, there are units available in the UK that are fitted to a standard din rail
I don't think units that fit to a standard din rail would be 7KW isolation transformers.
 
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Reactions: DPG

spinlondon

Forum Mentor
Electrician's Arms
Trainee Access
I was not aware the requirement is to change an existing installation from PME to TT?
I thought the requirement is to make just the EV charger TT?
 

bill01803

Regular EF Member
I think he is concerned about touch voltage between the class 1 fittings so considering TTing the whole installation
 

dmxtothemax

Regular EF Member
I can understand not wanting to get involved with checking and changing electrical instalations and then being responsible for that instalation to some degree. but it;s not that easy with a 7kw load involved, that's not exactly a trivial load, and any transformer of 7kw capacity will be large and expensive, so there is NO easy way out. I say forget the trasformer idea ! it's just not practicle.
 

DPG

Respected Member
Electrician's Arms
DIY
OP, could you clarify - were you meaning make the whole house electrical system TT?
 

leebut

Regular EF Member
I can understand not wanting to get involved with checking and changing electrical instalations and then being responsible for that instalation to some degree. but it;s not that easy with a 7kw load involved, that's not exactly a trivial load, and any transformer of 7kw capacity will be large and expensive, so there is NO easy way out. I say forget the trasformer idea ! it's just not practicle.


Check out the wiring regulations on EV charging it’s the only sensible way to go with PME unless the DNO can guarantee that there will never be a damaged cable to the neutral you need to carry out a risk assessment on the installation, I did my City and Guilds 2919-10 on Monday and Tuesday this week and going through the regs the only solution is to go down the isolating transformer (been told there’s a small unit that does 7Kw that fits a din rail unit ( not in a CU) that’s around the £200 +Vat price range just trying to find who sells it)
 

DPG

Respected Member
Electrician's Arms
DIY
I'd like to see a 7000 watt transformer that would mount on a DIN rail. Not saying it's impossible but can't imagine it
 

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