Disable generator auto-start when emergency disconnect

C

ChasM

Member
Location
North Texas
Occupation
Retired. Electrical System engineer/simulator architect
I understand that NEC 230.85 now requires an emergency disconnect switch (EDS) to be installed on the outside of a house so emergency responders can remove all electrical power from the building. The house is supplied with a 120/240V, 200A split phase electrical service (L1, L2, and N).
However, this requirement becomes somewhat of an enigma when there is a generator with an automatic transfer switch (ATS) at the house with an auto-start capability when utility power is lost. In this situation the generator would immediately try to autostart when the emergency responder opens the emergency disconnect switch, thus energizing the house electrical systems. Not a good situations!
I would like to configure an approach where the emergency responder action does not cause thr generator to autostart. I see several possibilities and would like some feedback back on my preferred solution.
1. Add a second emergency disconnect switch for the generator next to the unity servcoe switch - Not a good situation since the emergency responder must open two switches to remove all power from thr house.
2. Connect the EDS between the house electrical panel and the house output from the ATS - Not a good solution since the ATS and the generator remain have full electrical power with thr house circuits isolated.
3. Preferred approach - Make use of the Generac remote start feature by running the two remote start control wires through the third pole/blade of the EDS. In normal operation, when the EDS is normally closed the generator will automatically startup and power thr house when utility power is lost. When the EDS is opened by an emergency responder, the generator autostart function is disabled preventing the generator from starting and all power is removed from the house by a single emergency responder action. This appears to be the correct solution however does the 2020 NEC allow control wiring to be rooted through one of the poles of a three pole EDS.

I would appreciate any comments on my house requirement so the emergency responder is protected in the best manner possible.
 
You are allowed up to six disconnecting means, so having two is acceptable by code. A labeled EPO switch is also acceptable. You are trying to overthink it.
 
This is actually already handled in the Code and the manufacturers specs.

Labeling is required on the ATS showing the presence and location of the alternative power source, and the generator unit has an external shutdown switch.
 
I understand that several disconnects are permissible. However, I want to have the safest and simplest procedure for an emergency responder to handle. One switch operation is safer than 2 or more.
 
Real issue is related to running generator control wires through the third pole/blade of an external Emergency Disconnect Switch required by NEC 230.85, in conjunction with the phase conductors using the remaining two poles in a three pole switch.

I do not want the generator to even start after the emergency responder opens the emergency disconnect switch.
 
Most/all generators are provided with an emergency disconnect switch loop these days. That is what it does, sets an error that has to be cleared by pushing buttons.

But you can want to integrate it with the main breaker all you want, that still does not mean they make the part you desire. Just go with the flow of what is industry standard. Firemen are not that stupid.
 
ChasM said:
Real issue is related to running generator control wires through the third pole/blade of an external Emergency Disconnect Switch required by NEC 230.85, in conjunction with the phase conductors using the remaining two poles in a three pole switch.

I do not want the generator to even start after the emergency responder opens the emergency disconnect switch.
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Can't you place the emergency disconnect between the ATS and the building?
 
ron said:
If you are thinking of intercepting the auto-start control wires, use an aux contact that is available on most safety switches. That way the control voltage is separate from the line voltage
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You don't intercept the auto start wires, that leaves the generator still able to run in the manual position, and also may run on for many minutes of its own cool down cycle.

You use the emergency shutdown switch loop that is provided on all generators in anticipation of this situation, a separate switch loop from the start/stop loop.
 
Birken Vogt said:
Most/all generators are provided with an emergency disconnect switch loop these days. That is what it does, sets an error that has to be cleared by pushing buttons.

But you can want to integrate it with the main breaker all you want, that still does not mean they make the part you desire. Just go with the flow of what is industry standard. Firemen are not that stupid.
Click to expand...

I had to do an E-Stop on one that was inside an “enclosure”, it was a 5’ high wood fence, but because the gate into the enclosure could potentially be locked, the shutdown switch had to be outside. 445.18(C), new for us here in Cali.

The shutoff switches are all in series, so I just added another and ran it outside the enclosure.

Thats how I would do it in the OP situation. Just mount it next to the emergency disconnect and label it as “generator shutdown”. 👍
 
Birken Vogt said:
You use the emergency shutdown switch loop that is provided on all generators in anticipation of this situation, a separate switch loop from the start/stop loop.
Click to expand...
And it's required by code for generators of a certain size and larger but I can't remember the chapter and verse offhand.
 
Birken Vogt said:
You don't intercept the auto start wires, that leaves the generator still able to run in the manual position, and also may run on for many minutes of its own cool down cycle.

You use the emergency shutdown switch loop that is provided on all generators in anticipation of this situation, a separate switch loop from the start/stop loop.
Click to expand...
Also I think the smaller Generac’s don’t have a connection for a remote e-stop.
 
No, they did not start adding them to the home standby units until the Evolution line came out around 2015 and even then I don't think the switches were in/on the case until later than that.
 
Why wouldn't you just install the ATS on the line side of the emergency disco?
 
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