Generator X-fer switch question

Status
Not open for further replies.
T

tango2echo

Member
I came across a house in the field this week that had a full-load generator. The service was 200 amps. On the side of the house they had the meterbase, then the transfer switch, then a 200 amp MLO panel. The transfer switch enclosure had an interlocked main breaker and load side breaker, which supplied the lugs in the MLO panel. My question is this: You cannot manually throw the breakers in the generator transfer panel when this panel is NOT energized. Therefore, there is no main breaker on the house. Is this legal? Is my logic on this correct? Shouldn't there be a main breaker panel downstream of the transfer switch?
 
The breaker should be on the generator. You may encounter lively discussion as to whether this meets the requirements. I say under most conditions it does. Many transfer switches up until a few years ago did not have a main at the ATS.
 
tango2echo said:
Shouldn't there be a main breaker panel downstream of the transfer switch?
Click to expand...


Actually, IMO, a more likely set-up, if required, would be a disconnecting panel for the generator leads right before they land in the ATS.
 
In order to come from the meter base or the generator to a transfer switch the transfer switch is required by 230.66 and 225.36 to be rated as service equipment.
 
If the house looses power the ATS switches to GEN and isolates the service.

If the GEN looses power, it switches back to service, and then locks in this position and displays "fault with system".

If the Service power comes back online you still cannot manually throw the main breaker in the ATS panel until the system resets. (about 10-15 minutes) And the ATS powers up the panel before it finishes resetting.

So, the house has no true "main" and to disconnect power at this point you would need to throw every breaker in the main lug only panel to disconnect power in the house. (rule of 6) Plus the panel itself is live should work need to be done in this panel at this point.

So, is this system in compliance with the NEC? Would you consider it safe?
 
tango2echo said:
If the house looses power the ATS switches to GEN and isolates the service.

If the GEN looses power, it switches back to service, and then locks in this position and displays "fault with system".

If the Service power comes back online you still cannot manually throw the main breaker in the ATS panel until the system resets. (about 10-15 minutes) And the ATS powers up the panel before it finishes resetting.

So, the house has no true "main" and to disconnect power at this point you would need to throw every breaker in the main lug only panel to disconnect power in the house. (rule of 6) Plus the panel itself is live should work need to be done in this panel at this point.

So, is this system in compliance with the NEC? Would you consider it safe?
Click to expand...
Safe yes compliant No. Whiskey Tango ............ There is usually a main on the Genset or an epo pushbutton.
 
jwelectric said:
In order to come from the meter base or the generator to a transfer switch the transfer switch is required by 230.66 and 225.36 to be rated as service equipment.
Click to expand...

I think he means there is a service disconnecting means ahead of the ATS and MLO panel when on utility power but no disconnecting means at the service location when on generator power.

Edit it to add: I reread the OP and it does not mention a separate disc. I am assuming he is speaking of an ATS with one it.

tango2echo said:
So, the house has no true "main" and to disconnect power at this point you would need to throw every breaker in the main lug only panel to disconnect power in the house. (rule of 6) Plus the panel itself is live should work need to be done in this panel at this point.

So, is this system in compliance with the NEC? Would you consider it safe?
Click to expand...

It depends on whether you count the OCP on the generator as the single disconnecting means. As I mentioned earlier, there has been much discussion over that.
 
tango2echo said:
You cannot manually throw the breakers in the generator transfer panel when this panel is NOT energized. Therefore, there is no main breaker on the house. Is this legal? Is my logic on this correct? Shouldn't there be a main breaker panel downstream of the transfer switch?
Click to expand...
There should be a manually-operable main breaker (or switch) upstream of the ATS. Doesn't sound compliant to me.
 
Although this is not like the installation in the original post it will give an idea of what is required when making a gen-set installation.

In this first picture the service comes from the main disconnect to the transfer switch and the gen-set comes to the transfer switch. This is in violation of Article 225.

nodisconnect.jpg


In the second picture the electrical contractor has installed a disconnect on the feeders from the gen-set and now is in compliance with Article 225

withdisconnect.jpg


In order for the service to land in the transfer switch or the feeders from the gen-set to land in the transfer switch the transfer switch will be required to be service rated.
In order for a transfer switch to be rated as a service disconnect it will have an absolute off where it is not connected to either the service or the generator.
 
I'm a little confused as why the second disconnecting means was added to the generator? Even if the T-switch is not service rated, There is a service disconnect on the utility side, and the service disconnect on the generator side is inside the generator enclosure. The only purpose for another disconnect would be if the generator main is of a higher rating than the switch or panel feeder, or if it is required by local fire code for the firemen to turn off power, which would be fire code, not electrical.
 
hillbilly1 said:
I'm a little confused as why the second disconnecting means was added to the generator? Even if the T-switch is not service rated, There is a service disconnect on the utility side, and the service disconnect on the generator side is inside the generator enclosure. The only purpose for another disconnect would be if the generator main is of a higher rating than the switch or panel feeder, or if it is required by local fire code for the firemen to turn off power, which would be fire code, not electrical.
Click to expand...

ARTICLE 225 Outside Branch Circuits and Feeders
II. More Than One Building or Other Structure
225.31 Disconnecting Means.
Means shall be provided for disconnecting all ungrounded conductors that supply or pass through the building or structure.

Being that the conductors are not service or branch circuit conductor they must be feeders. They are on the outside therefore must comply with 225.

702.11 Outdoor Generator Sets.
Where an outdoor housed generator set is equipped with a readily accessible disconnecting means located within sight of the building or structure supplied, an additional disconnecting means shall not be required where ungrounded conductors serve or pass through the building or structure. The disconnecting means shall meet the requirements of 225.36.

Under the Optional Standby Systems rules the disconnect in the generator must comply with two things that this generator disconnect does not comply with.
1- it must be in sight of
2- it must be service rated
 
The generator that is setting in the foreground is not the one feeding that transfer switch? Looks like that would be "in sight of", Must be Mecklinberg county, or is this 2008 code? Have not had an inspector bring this up in any of the states that I have done them in east of the Mississippi. But I can see how it can be interperted this way.
 
jwelectric said:
[/SIZE][/FONT]
In order for a transfer switch to be rated as a service disconnect it will have an absolute off where it is not connected to either the service or the generator.
Click to expand...


If I am reading you correctly I think I would have to disagree. I have installed countless ATS that were service entrance rated with a service disconnecting means but no generator disconnecting means. If there were no disconnecting means or OCP at the genset then field installed means would be required to be compliant.
 
360Youth said:
If I am reading you correctly I think I would have to disagree.
Click to expand...

Mike is correct, it is not optional. UL requires a service rated transfer switch to be cable of disconnecting both sources.

From the UL white book

TRANSFER SWITCHES (WPTZ)

Transfer switches are required to be designed so that the load cannot remain simultaneously disconnected from both the normal and alternative sources when either or both sources are available, except that transfer switches marked ??SUITABLE FOR USE AS SERVICE EQUIPMENT?? are provided with externally accessible means to independently disconnect both the normal and alternate sources.
Click to expand...
 
hillbilly1 said:
The generator that is setting in the foreground is not the one feeding that transfer switch? Looks like that would be "in sight of", Must be Mecklinberg county, or is this 2008 code? Have not had an inspector bring this up in any of the states that I have done them in east of the Mississippi. But I can see how it can be interperted this way.
Click to expand...

Yes the generator is in sight of the transfer switch but the disconnect for the generator is not nor is the disconnect for the generator rated as service equipment.

I just picked up the 1996 edition of the NEC and in 702-3 it states that all applicable articles of this Code shall apply which would include Article 225 so the disconnect at the building is not new.

What is new is the influx of generators being installed at dwelling units that both inspectors and electricians don't understand.
 
iwire said:
Mike is correct, it is not optional. UL requires a service rated transfer switch to be cable of disconnecting both sources.

From the UL white book

TRANSFER SWITCHES (WPTZ)
Click to expand...

I just know the switches that come through the door with UL listings on them and only one disconnecting means. I may have to go read some old paperwork and stand corrected, but I have installed quite a few and did the start up on many others installed.
 
360Youth said:
I just know the switches that come through the door with UL listings on them and only one disconnecting means.
Click to expand...
I'm sure you're correct, but I've seen some residential Generac T/S's that had a main breaker for the utility input and a bat-handled toggle switch, and not a breaker, for the genny input. What that switch controlled, I'm not sure.
 
The bat toggle that I have seen on Generacs locks out the automatic transfer only, it does not send the switch to neutral. On the larger motorized breaker type transfer switches, such as those made by CH have a key switch inside the cabinet that opens both sides, utility and generator. Have had inspectors call for this switch to be moved to the outside of the enclosure, because it is behind two doors. Talked to the manufacture about making this the standard, as firemen don't know to open the doors to cut building power.
 
Status
Not open for further replies.
Top