Electric schematic help

[JHZR2]

Can anyone help me to decode what is practially being asked of the AC wiring scheme in the following schematic?

My read is that the system is fed with 3-wire 240VAC. That's no big deal. There is a ground on it, great and no big deal.

But, if you look at what goes off of the main feed (labeled TB1) to the inside air handlers (loads labeled TB3), it shows another ground wire there, that is not connected in the one-line as shown.

In other words, it shows continuity of the hot lines in the one-line, but not the ground.

Is it just implied that there will be a ground traveling with the hots, and that it will all be connected one and the same? Or, is it implying that there is another ground, a local ground perhaps, that needs to be supplied.

My read on this (it is a split, ductless system), is that the outdoor unit is fed with 240V 3-wire, and then the indoor handlers are fed with that same 240V over two wires, there is a 12-24V control signal wire and then a ground.

But this seems odd, because would the same ground be used for AC and DC? It looks like only 4 wires transfer from the outdoor unit to the inside...

Im not going to install this myself, if we decide to go this route... but I am trying to figure out the wiring based upon the schematic, so I am savvy.

Thoughts on this?

Thanks!

 

[Dave Sherman]

The ground symbol is indicating that the ground gets passed through. Schematics don't necessarily show the physical location of connections, only what is connected to what, so from that diagram, it is safe to say that the ground from TB1 will be connected to the ground at TB3 at some point. Most likely the two will join at a common grounding screw in a junction box. The DC control can use the same ground, nothing wrong with that.

 

[JHZR2]

OK thanks! Was confused because the hots are shown as continuous while the ground isnt...

 

[HerrStig]

220 circuits shoulld have a ground and a neutral.

 

[JHZR2]

Why? my 220 AC has three connections. I thought 220 does not need a neutral because the two leads are exactly out of phase, so there is always a 220V delta between them.

What am I missing here? Even the wiring schematic I showed does not state a neutral in there...

What I saw and understood was this:

Quote:

Inside main breaker box are Three busbars.
One busbar is Neutral busbar.
Two busbars are Hot busbars.
Each Hot busbar is 'out of phase' with the other.

All residential circuits require Two wires to complete circuit.

120Volt circuit requires 1 Neutral wire and 1 Hot wire.
Hot wire can come from either Hot busbar.
By Code, these wires are Black-Hot and White-Neutral.
If either wire is interrupted, the circuit turns OFF.
By code the Black Hot wire is switched ON-and-OFF.

240Volt circuit also requires 2 wires to complete circuit.
In the case of 240V, the circuit requires 2 Hot wires.
One Hot wire from each 'out of phase' busbar is required to complete 240Volt circuit.
These wires can be Black and White or Black and Red, and with heavier gauge wires, like 6 gauge and 4 gauge, the wires are Black and Black.
If either wire in 240V circuit is interrupted, the circuit turns OFF.
Bare ground wire connects to Neutral busbar as redundant safety.


From:
http://waterheatertimer.org/How-to-install-a-subpanel.html

 

[Dave Sherman]

Originally Posted By: HerrStig
220 circuits shoulld have a ground and a neutral.


Doesn't need the neutral unless it has need for 120 volts. If it's dedicated to one use, like an outdoor 240 volt air conditioning unit, then neutral is not needed.

 

[jaj]

Here's how to read it:

- the precise meaning of the three horizontal lines in the "ground" symbol is that the external ground wire is connected to a bare terminal strip or ground stud that also makes a bond with the chassis. The angled fork symbol attached to "LDE1" also indicates a chassis bonding wire. However, it doesn't go to the ground strip, just to the grounded chassis at a convenient point.

- no neutral is required, provided there are no internal loads that need 120VAC to operate them. If you wire it with 2 legs of a 3-phase service, it will have 208 VAC running it. If you use two legs of a single phase service, it has 240 VAC. The neutral only serves to deliver 120VAC.