Adding Home Generator Transfer Switch, question on Neutral

[etbrown4]

Adding a 6 circuit 30a transfer switch, connecting to main panelboard.
Requires a 12g thhn out to the transfer switch and back to main panel for each circuit.
Plan to run those 12 conductors in one conduit.
Plan to run 10g neutral and ground in a separate cable from main panel to transfer switch.
Nec typically requires current carring conductors and neutrals to run in the same raceway.
Transfer switch manufacturer says conductors and neutrals not required to be in same raceway, but they are not the Nec!
Mfg says this setup will work properly so long as there is a 10g neutral connecting transfer switch and main panel.
Can the conductors and neutral be safely be run separately?

 

[waross]

Follow the NEC.
It will work, until it doesn't.
Wait until that neutral is damaged.
I have more than once had to do repairs after a neutral went open.
It's not pretty.

 

[etbrown4]

As a practical matter, if I follow the manufacturer instruction using the single separate 10g neutral should that function properly with that neutral connected to the tsf switch annd to the main panelboard?

 

[TugboatEng]

I think this is a very good question to explore. At these power levels were probably talking cheap import generators that are generally meant to be standalone sources. In that case, they likely have their neutral and ground connected in the generator enclosure. If you're powering a home you may want to consider disabling the outlets on the generator and lifting this bond in the generator enclosure. Your ground neutral bond is already likely in your main panel.

 

[waross]

Don't ask us.
Ask your insurance underwriter.

 

[waross]

If you're powering a home you may want to consider disabling the outlets on the generator and lifting this bond in the generator enclosure. Your ground neutral bond is already likely(edit) in your main panel.

This also.

 

[etbrown4]

Sounds right. The transfer switch mfg says the ground neutral bond is in the main panel as prior poster mentiomed.

Mfg says with one #12 over to the switch, and one #12 back to main panel for each circuit, in Util mode, the main panel breakers provide circuit protection, and in Gen mode, the transfer switch provide protection. There is no main breaker in the transfer switch. Transfer switch is 4' from main panel.

Just wanted to see if folks on this forum agree this setup should perform ok, with no overheating of conductors etc

 

[waross]

with no overheating of conductors etc

Did you ever tell us the ratings of the breakers?

 

[etbrown4]

6 Breakers in tsf switch panel are 15a.
6 breakers in main panelboard are 15a

 

[waross]

It will work electrically, but working electrically is not the only factor addressed by the NEC.
If you have a fire, even if not caused by the ATS, your insurance adjuster may void your policy.
But hey, do what you are going to do.

 

[etbrown4]

The purpose of the question is simply to verify if the information provided by the transfer switch manufacturer, i. e. that running the 15a circuits in one conduit and and a #10 neutral and ground separately will operate properly and be safe.

It seems clear that if a neutral is not connected or becomes loose there will be a problem, but that's not the question or the situation today.

 

[3DDave]

Always good to hear from someone who isn't sure about what is going on and have to ask, when they turn and are hostile to expert information that is intended to keep them safe. There is only a minor difference between "will work" and "is safest" and it may not matter, but no need to lash out at advice intended to prevent burning your house down.

 

[LionelHutz]

n Util mode, the main panel breakers provide circuit protection, and in Gen mode, the transfer switch provide protection.

I have never seen a transfer panel that worked this way. Each circuit should have one breaker. The main panel powers the transfer panel through a single circuit and then the transfer panel switches between either using the utility power from the main panel or the generator power. The selected source then powers all the circuits connected to the transfer switch panel.

 

[waross]

I have never seen a transfer panel that worked this way.

You can see similar sets in agricultural supply outlets.
They come pre=wired.
The sets on floor display will have a length of armoured cable and a combination transfer-switch/sub panel pre wired and coiled up on top of the set.

Standby sets marketed to the residential market are designed for cheap installation.
I have done a lot of residential standby with the conventional transfer switch.
This is a major project involving cutting into the main feeds and a utility outage.
It is often difficult to get a utility outage without pulling a permit.
However I see quite a few residential standby packages offered with a sub panel that includes a transfer switch.
The installation is quite simple.
1. Instal a sub-feed breaker in the existing panel to feed the new transfer-switch/sub-panel.
2. Instal a cable from the new breaker to the new transfer-switch/sub-panel.
3. Decide which circuits are to be powered by the standby set and transfer the circuits to the new panel, one wire at a time.
These installations are much more DIY friendly than a full on conventional transfer switch instal.
I'll make an exception here and and suggest that this system uses a cheap, 15 Amp, multi-pole, double throw relay to transfer each individual 15 Amp circuit.
This will be very DIY friendly.

 

[etbrown4]

Appreciate all the comments!

We have multiple applications in several properties with generator or battery backup and some use automatic transfer switches, some manual.

Described above, a manual transfer switch, with 6 breakers in the main panelboard supplying 6 circuits in the transfer switch panel is more cumbersome and requires twice the wire because those 6 circuits passing through the transfer switch return to the main panel, powering the outgoing wires for the original 6 circuits.

The way this switch works is you manually select Gen and the 6) 15a transfer switch breakers provide overcurrent protection. Switched to Util, the original 6) 15a breakers in the panelboard provide overcurrent protection. Perhaps more complicated but seems to work properly.

Electrician went ahead and installed a #10 neutral in each conduit carrying half of the circuits out and back, each. Where this gets unusual again, there is no neutral bar or buss in this manual switch. The manufacture shows the neutrals run from the main panelboard neutral buss, and connection to the incoming
twistlock male receptacle which receives power from gen or battery pack.

We have this Reliance transfer switch and panel installed exactly as specified by the manufacturer. It's an unusual setup for many folks I think, however Reliance says they've sold tens of thousands of them.

If this had been an ordinary setup with a neutral and one set of circuits going to an automatic transfer switch, the connection would have been routine and we wouldn't have needed help. Thanks to all those offering suggestions!

 

[waross]

Described above, a manual transfer switch, with 6 breakers in the main panelboard supplying 6 circuits in the transfer switch panel is more cumbersome and requires twice the wire because those 6 circuits passing through the transfer switch return to the main panel, powering the outgoing wires for the original 6 circuits.

the transfer switch panel is more cumbersome and requires twice the wire because those 6 circuits passing through the transfer switch return to the main panel.
That may not be as bad as the alternative.
I had to correct the wiring on a transfer-switch/sub-panel installation originally done by others.
First issue was space to mount the new equipment.
Then the Romex for each circuit had to be removed from the existing panel and re-installed in the new sub panel.
Almost all of the existing Romex was too short to reach the new panel.
That meant a couple of junction boxes to splice extension wires.
The job ended up with a lot more labour than just running a few extra wires.
DIY friendly.