1st vs 2nd point of disconnect in an older house with 3 wire service (2 hot and 1 neutral/ground)

[inplainview]

TLDR: In a 3 wire service are the ground and the neutral always bonded, in all subpanels?

House made in 1970 has the meter and a 150 amps breaker outside the house, on the east wall. There are two hot wires and one neutral, which is clearly bonded/grounded with the enclosure.

Through the attic this feeds a main lug (sub)panel inside the garage (same structure on the west side of the house). The neutral and the ground in this (sub)panel are also clearly bonded. All services in this house connect to this main lug (sub)panel. As far as I can tell, some are only 2 wire service, hot and neutral, no ground.

I am supposed to replace this main lug panel with a bigger panel to create space for an instant electric water heater (3 x 40 amp double poles) and an electric car charger (1 x 50 amp double poles), plus a couple small 20 amp single pole services.

I bought a 200 amp 40 circuit main breaker plug-on neutral and a 125 amp 16 circuit load center, both from Siemens. I will be using the main breaker to replace the older main lug panel. I will be using the load center to connect the instant water heater.

After doing a lot of reading on this forum and others, I am still not sure if I am supposed to separate the ground and the neutral in all of these new panels that I will be installing, in none, or maybe only the one for the instant hot water heater.

Most of the comments I read say that any panel after the 1st point of disconnect has to separate the ground and the neutral.

Some comments, few, said that it depends if there is a 3-wire service or a 4-wire service. Apparently, if it’s a 3-wire service then all (sub)panels in the system have to bound the neutral and the ground.

This reflects the reality in this house as far as I can tell, although I am still confused why some of the services (outlets) that I found have only two wires, hot and neutral.

I would truly appreciate your feedback on all these.

 

[Megawatt]

TLDR: In a 3 wire service are the ground and the neutral always bonded, in all subpanels?

House made in 1970 has the meter and a 150 amps breaker outside the house, on the east wall. There are two hot wires and one neutral, which is clearly bonded/grounded with the enclosure.

Through the attic this feeds a main lug (sub)panel inside the garage (same structure on the west side of the house). The neutral and the ground in this (sub)panel are also clearly bonded. All services in this house connect to this main lug (sub)panel. As far as I can tell, some are only 2 wire service, hot and neutral, no ground.

I am supposed to replace this main lug panel with a bigger panel to create space for an instant electric water heater (3 x 40 amp double poles) and an electric car charger (1 x 50 amp double poles), plus a couple small 20 amp single pole services.

I bought a 200 amp 40 circuit main breaker plug-on neutral and a 125 amp 16 circuit load center, both from Siemens. I will be using the main breaker to replace the older main lug panel. I will be using the load center to connect the instant water heater.

After doing a lot of reading on this forum and others, I am still not sure if I am supposed to separate the ground and the neutral in all of these new panels that I will be installing, in none, or maybe only the one for the instant hot water heater.

Most of the comments I read say that any panel after the 1st point of disconnect has to separate the ground and the neutral.

Some comments, few, said that it depends if there is a 3-wire service or a 4-wire service. Apparently, if it’s a 3-wire service then all (sub)panels in the system have to bound the neutral and the ground.

This reflects the reality in this house as far as I can tell, although I am still confused why some of the services (outlets) that I found have only two wires, hot and neutral.

I would truly appreciate your feedback on all these.

the first panel outside where the meter is located has a 3 wire service coming from the power company. You probably only have 1 ground rod at the main panel and a #6 bare wire going from the neutral bar to the ground rod. Yes they are all mixed up in the first panel with the neutrals and grounds. Any sub panel after the main panel you are required to isolate the neutrals from the ground wires. You have to pull 4 wires from your main panel to your sub panels (no 3 wire). You will probably have to go to Lowe’s or Home Depot to purchase a ground bar to install in your sub panels. Now you know how to properly install sub panels. Good luck

 

[inplainview]

the first panel outside where the meter is located has a 3 wire service coming from the power company. You probably only have 1 ground rod at the main panel and a #6 bare wire going from the neutral bar to the ground rod. Yes they are all mixed up in the first panel with the neutrals and grounds. Any sub panel after the main panel you are required to isolate the neutrals from the ground wires. You have to pull 4 wires from your main panel to your sub panels (no 3 wire). You will probably have to go to Lowe’s or Home Depot to purchase a ground bar to install in your sub panels. Now you know how to properly install sub panels. Good luck

Thank you for your reply.

But isn't the first panel the one that sits next to the meter and has a big 150 amp breaker in it as the first point of disconnect?

Or does this panel not count?

There is a big panel in the garage were all the circuits are terminated, and that's were all the neutral and ground are connected to the same bar. So, this panel is actually a sub-panel and the 2nd point of disconnect. Shouldn't this panel have separate ground and neutral bars and unbounded?

Or maybe this is how they built home bake in the 1970? I guess the ground is represented by all the steel conduits the wires are running through. The thing is, I found newer circuits added later that are Romex. They too connect to this subpanel and have the ground and the neutrals connected to the same bar.

Just trying to understand why the wiring has been done like that, and wondering if I should just replicate what exist at the moment as I don't really have a neutral coming from the first panel by the counter, there are just two hot wires and the ground.

 

[Megawatt]

Thank you for your reply.

But isn't the first panel the one that sits next to the meter and has a big 150 amp breaker in it as the first point of disconnect?

Or does this panel not count?

There is a big panel in the garage were all the circuits are terminated, and that's were all the neutral and ground are connected to the same bar. So, this panel is actually a sub-panel and the 2nd point of disconnect. Shouldn't this panel have separate ground and neutral bars and unbounded?

Or maybe this is how they built home bake in the 1970? I guess the ground is represented by all the steel conduits the wires are running through. The thing is, I found newer circuits added later that are Romex. They too connect to this subpanel and have the ground and the neutrals connected to the same bar.

Just trying to understand why the wiring has been done like that, and wondering if I should just replicate what exist at the moment as I don't really have a neutral coming from the first panel by the counter, there are just two hot wires and the ground.

What you currently have will work but 30, 40, or 50 years ago houses was wired the way your sub panel is now. The NEC changes every 3 years but what I’ve told you is the correct way to add or repair your panel. Yes by code on sub panels you always isolate the neutrals from the grounds and have a 4 wire service. The way your sub panel is wired it gives it a undesirable path to ground. The main panel at the meter is the only panel that you can mix the grounds with the neutrals on the same neutral bar.