generator wiring and earth

kx3210 · Dec 16, 2024

I have an old Electric Construction generator. There are no markings for the wiring. Putting a meter over the 2 terminals i get 240 volts but connecting the earth comes up with an error connecting to the garage. There is 110 volts between neutral and earth. Should the neutral be connected to the earth. None of the connections as per the photos have a connection to the casing. Can anyone help.

Rockingit · Dec 16, 2024

Sounds as though it’s a CTE arrangement coming off the star point

kx3210 · Dec 17, 2024

Rockingit said:
Sounds as though it’s a CTE arrangement coming off the star point

Hi - What does that mean. Doesn’t really help me solve the problem

James · Dec 17, 2024

kx3210 said:
Hi - What does that mean. Doesn’t really help me solve the problem

Center tapp Earth
2 windings on generator 115v each, coupled in series gives 230v
If you then join the midpoint to earth, you get CTE

kx3210 · Dec 17, 2024

James said:
Center tapp Earth
2 windings on generator 115v each, coupled in series gives 230v
If you then join the midpoint to earth, you get CTE

I checked the generator and it is as per the attached sketch. None of the terminals are attached to the chassis. From your comments I assumed a CTE would have terminal D attached to Earth ? The capacitors are attached on one site to A & C with the third on not attached to anything. The other side of the capacitors are both attached to point D. To connect the generator to the garage when there is a power outage requires the neutral to Earth. So is it acceptable to connect the Earth to point C and have a single phase 240volt output ? Hope that makes sense.

James · Dec 17, 2024

kx3210 said:
I checked the generator and it is as per the attached sketch. None of the terminals are attached to the chassis. From your comments I assumed a CTE would have terminal D attached to Earth ? The capacitors are attached on one site to A & C with the third on not attached to anything. The other side of the capacitors are both attached to point D. To connect the generator to the garage when there is a power outage requires the neutral to Earth. So is it acceptable to connect the Earth to point C and have a single phase 240volt output ? Hope that makes sense.

it may be acceptable, the only thing you can do is try it and test that you have the correct voltages on the correct lines and ensure your safety devices are working correctly by testing them.

freddo · Dec 17, 2024

If you are testing you can link the suspected 'neutral' to the chassis/earth with something like a 100 watt mains filament lightbulb. If the bulb lights you will not be able to make the connection.