How to wire and test an isolation transformer

[s/v Jedi]

Originally Posted by freeden

Hi Jedi thanks so much for the detailed reply, I found your blog "sv Jedi" and added myself, your electrical work looks amazing, if you looked at mine you would have convulsions and horrific nightmares ha ha.

Re; the other jumper wires supplied by victron, why would you put them on the 110v or 240v input and output if the transformer is auto switching? shouldn't the transformer know what voltage is coming in?

another question I have single pole RCBO's, one next to the shore power inlet plug and now one straight after the transformer, but you recommend double pole so should I change them or use the jumper wire supplied by victron?

My earth wire comes from the shore inlet and terminates at the transformer input E,
then my earth wire from the output goes directly to my inverter AC IN then to a bus bar which has the negative from house bank batteries attached to it as well and all my outlet power points are earthed from there, does all of that sound right.
thanks Den

The auto-switching model only switches the input side between 120 and 240V. The output side you still have to set manually to either 120V or 240V and this is done with the jumper wires. They may have thrown in the same kit as for the manual model so that you have extra wires.

You must use double pole breakers. Normally you must also use an expensive ELCI breaker at the inlet but for an isolation transformer they made the exception that you can use a simple double pole breaker.

The breakers have no relation to the jumper wires.

To test your installation: switch everything off and disconnect shore power cable at the inlet. Now with a multimeter measure at the transformer terminals. Use the resistance or continuity mode and do three measurements: input ground to output ground, input neutral to output neutral and input phase/hot/L to output phase/hot/L (I think the terminals are marked G, N and L). None of these should have continuity, meaning that the transformer does complete galvanic isolation.

You electrical installation was not for an isolation transformer. I hate to see DC and AC interconnected but it’s how it is done in the US without isolation transformers. Also, you probably have single pole AC breakers on the distribution panel and 120V only.

Assuming the above, if you want to change as little as possible then the simplest thing to do is to jumper transformer output ground to transformer output neutral (both on the output side). Check with the multimeter because this jumper may already be somewhere in the installation.

Disconnecting DC from AC can be difficult when the engine block connects to both. Leave that for now unless you want to study this further.

[freeden]

many thanks Jedi I very much appreciate you taken time to reply, I owe you a beer or 3.
Den

[s/v Jedi]

Originally Posted by freeden

many thanks Jedi I very much appreciate you taken time to reply, I owe you a beer or 3.
Den

Wait, are you in Melbourne Australia? I thought you were in the US so I posted about US code, ABYC etc. I don’t even know what they use in Australia… British system 230V?

You can buy small DIN rail boxes and put terminals and breaker on the DIN rail; should be easy to source in Australia

[freeden]

Hi Jedi, yes I'm I Australia 240v, I thought you may have missed that minor detail,
I don't think it makes much difference, because I mainly wanted to know why you (hid the jumper wires never to be found again) supplied by victron,
And I also wasn't sure about the other jumper wires supplied as the installation brochure is very vague but you cleared that up for me.
I have checked the resistence with my multimeter on all input and output terminals and they have no readings so the install is good,
I haven't changed to double pole breakers yet and I also need to ground the transformer enclosure as victron state to do,
those two things will finish the install.
I haven't gone with the DIN rail box as the only thing there is the breaker because I'm on a catamaran all my electronics are on the other side 25 feet away from shore inlet, so I have busbars to distribute live and neutral and earth.
did you check my location to see if you could access those beers I promised you I know I would have ha ha.
thanks again
Den

[s/v Jedi]

Originally Posted by freeden

Hi Jedi, yes I'm I Australia 240v, I thought you may have missed that minor detail,
I don't think it makes much difference, because I mainly wanted to know why you (hid the jumper wires never to be found again) supplied by victron,
And I also wasn't sure about the other jumper wires supplied as the installation brochure is very vague but you cleared that up for me.
I have checked the resistence with my multimeter on all input and output terminals and they have no readings so the install is good,
I haven't changed to double pole breakers yet and I also need to ground the transformer enclosure as victron state to do,
those two things will finish the install.
I haven't gone with the DIN rail box as the only thing there is the breaker because I'm on a catamaran all my electronics are on the other side 25 feet away from shore inlet, so I have busbars to distribute live and neutral and earth.
did you check my location to see if you could access those beers I promised you I know I would have ha ha.
thanks again
Den

Be careful grounding the case… you may create a wrong connection! I think the case is connected to output ground terminal. Check this because you probably already have the case grounded that way.

Measure everything against upon finishing the install. Such last things can potentially defeat the isolation.

[freeden]

Hi Jedi OK I will double check the case ground.
thanks again.
Den

[freeden]

Hi Jedi I apolagise for bothering you again but I have a minor problem,
After connecting the transformer with the shore supply on,
My victron display is now only showing the inverter light on, which is the same on my actual multiplus, its no longer showing grid input or bulk, absorption or float lights on? and is showing battery full which I know cant be correct??
any Ideas ???
thanks
Den

[s/v Jedi]

Originally Posted by freeden

Hi Jedi I apolagise for bothering you again but I have a minor problem,
After connecting the transformer with the shore supply on,
My victron display is now only showing the inverter light on, which is the same on my actual multiplus, its no longer showing grid input or bulk, absorption or float lights on? and is showing battery full which I know cant be correct??
any Ideas ???
thanks
Den

Can’t help with that from a distance, but the first thing to do is take the multimeter in AC voltage mode and measure transformer output, then multiplus input. I am still puzzled by the single pole breakers in that circuit, never seen that so I am suspicious of it.

[freeden]

Hi Jedi I have changed to double pole breakers as you suggested, just not sure what is going on now with the multiplus is not registering as being in a mode ie; bulk absorption etc. I can understand the display not showing grid input as the transformer has isolated the grid but turning everything off has done something to the multiplus??
thanks
Den

[s/v Jedi]

Originally Posted by freeden

Hi Jedi I have changed to double pole breakers as you suggested, just not sure what is going on now with the multiplus is not registering as being in a mode ie; bulk absorption etc. I can understand the display not showing grid input as the transformer has isolated the grid but turning everything off has done something to the multiplus??
thanks
Den

Measurements?

[freeden]

Hi Jedi I took the multimeter and checked the double pole breakers and they are correct at 240v and then checked the terminals on the input side of the transformer and that is also showing 240v but the output side is not showing any voltage at all,
so that is the problem why the inverter is not registering bulk etc because no voltage is going over to the inverter, I am going to look for a way to kick start the transformer as the wiring is as per the instalation brochure but nothing is happening.
thanks
Den

[freeden]

Hi Jedi
I downloaded the PDF from victron and found out that both the input and output terminals of the transformer need to have the jumper wires installed,
I thought that auto switching model wouldn't need that,
So I put that on and hey presto everything is up and running, the inverter display is showing grid input and mains on and bulk on all back to normal but now isolated, yippee!
the battery is showing 100% but before installing the extra jumper wire the battery was at 46% so I know it cant charge that fast, so I will let it go into float and see if that corrects the battery % readout.
many thanks for taking the time to help.
long live the JEDI ha ha
Den

[s/v Jedi]

Originally Posted by freeden

Hi Jedi
I downloaded the PDF from victron and found out that both the input and output terminals of the transformer need to have the jumper wires installed,
I thought that auto switching model wouldn't need that,
So I put that on and hey presto everything is up and running, the inverter display is showing grid input and mains on and bulk on all back to normal but now isolated, yippee!
the battery is showing 100% but before installing the extra jumper wire the battery was at 46% so I know it cant charge that fast, so I will let it go into float and see if that corrects the battery % readout.
many thanks for taking the time to help.
long live the JEDI ha ha
Den

Good news! You need to get the charger settings right and also the battery monitor settings. If this is a Victron BMV, check the manual about “charged voltage”