Emergency Generator Installation

[Tom Anderson]

We are having an emergency generator installed for our Community Center. The electrician plans to install the whole house transfer switch in the attic between the meter and the the circuit panel and locate the generator behind the building.
The interior circuit panel does not have a emergency (on/off) switch, as it is incorporated in the meter (main) inlet box on the outside of the building.
I asked the electrician if the outside switch is turned off will the generator come on and continue to supply the panel? He said yes. I said that does not seem safe, if we had a smoking interior panel and came out and turned off the power at the meter the generator would come on and continue to supply power. The Electrician said you would have to go to the generator and turn off the generator behind the building. He said it was code to do it the way he is wiring?
Seems wrong to me.
Thanks

[Rick Bunzel]

Tom,

Basically there needs to be a switch that disconnects the power from the power company and switches over to the generator. Once the power company is locked out there is usually a "main breaker" for the generator source. In most systems the lock out prevents both of these breakers from being on simultaneously. I believe this is what you are describing as the transfer switch.

You did not mention if the generator is automatic start but most generator I am familiar with also have a breaker on them to protect them from an overcurrent. You could isolate the generator from the interior panel with this breaker or as I described the breaker on the transfer switch.

If in doubt ask the electrician to diagram the system and take it to the local building department for an opinion.

Happy Holidays!

//Rick

[Jerry Peck]

The intent is that when utility power is lost, the generator *automatically* comes on to replace the lost power.

So, yes, if you had a problem with an interior panel and turned off the utility main, the generator would automatically start up - just as it is designed to.

The solution, then, would be to install another disconnect next to or near the utility main disconnect so that, if you *did not want* the generator to automatically start up when you turned off the utility power, you could turn *both* the disconnects off - the utility power disconnect and the automatic standby generator disconnect.

Another solution would be to replace the exterior disconnect with a service equipment panel with a main breaker to the service equipment panel and another breaker to the interior panel(s) and another breaker to the generator transfer switch feeders.

That way you would turn off power to the interior panel(s) without interrupting power to the generator transfer switch, which would not call for the generator to automatically start up, yet allowing for the loss of utility power to cause the generator to automatically start up - perceived problem solved.

[John Kogel]

The intent is that when utility power is lost, the generator *automatically* comes on to replace the lost power.

So, yes, if you had a problem with an interior panel and turned off the utility main, the generator would automatically start up - just as it is designed to.

The solution, then, would be to install another disconnect next to or near the utility main disconnect so that, if you *did not want* the generator to automatically start up when you turned off the utility power, you could turn *both* the disconnects off - the utility power disconnect and the automatic standby generator disconnect.

Another solution would be to replace the exterior disconnect with a service equipment panel with a main breaker to the service equipment panel and another breaker to the interior panel(s) and another breaker to the generator transfer switch feeders.
How about a kill switch for the generator, just a simple toggle switch that grounds the ignition? You can wire it with bell cord, and any savvy volunteer can do it.

Happy Holidays to all! :D:D

Edit - of course, the switch would kill the starter solenoid as well.

[Jerry Peck]

How about a kill switch for the generator, just a simple toggle switch that grounds the ignition? You can wire it with bell cord, and any savvy volunteer can do it.


Because the transfer switch, which no longer has utility power, is going to crank, and crank, and crank the generator ... and crank it until its battery runs down, and properly damage the battery, and maybe overheat the starter, and ... why not do it the right way? Install the new panel with the two breakers, one which shuts the building panel down but leaves the transfer switch energized, and the other which shuts the generator supply down from the structure's panel.

Remember, I said "perceived problem" ... and that would be the way to rectify the "perceived problem".

[John Steinke]

I hear all manner of marvelous thoughts, but not one is coming from anyone who is actually competent. This is a design issue for the EE, EC, or ME to submit to the towna and the AHJ, and for them to approve, inspect, and sign off on.

We're not there, and it's not our call to make. Period.

[Jerry Peck]

I hear all manner of marvelous thoughts, but not one is coming from anyone who is actually competent. This is a design issue for the EE, EC, or ME to submit to the towna and the AHJ, and for them to approve, inspect, and sign off on.

We're not there, and it's not our call to make. Period.

John,

He is not actually asking a design question, but a hypothetical 'What if.' question, and that can be answered with 'If you do this, or this, or this ... '

The reality of it is that very few, and possibly none, generator installations address the hypothetical 'What if.' question he is asking.

[Darrell Cummins]

It sounds like your electrician might consider putting the transfer switch at the beginning of the original service ie next to the meter. The transfer switch becomes the first disconnecting means in both systems(normally powered and emergency powered). I do think the attic might not be the best place and the electrical inspector probably will agree. Darrell

[Darrell Cummins]

Also your main disconnects need to be in the same location. Since your meter has a disconnect I would think it needs to be next to each other...humm your generator probably has a breaker in it i wonder if it should be located in close proximity ? Jerry?

[Jerry Peck]

The transfer switch becomes the first disconnecting means in both systems(normally powered and emergency powered).

The typical transfer switch is not also a disconnect as it does not disconnect both service sources, it simply "transfers" from one source to the other.


Also your main disconnects need to be in the same location. Since your meter has a disconnect I would think it needs to be next to each other...humm your generator probably has a breaker in it i wonder if it should be located in close proximity ? Jerry?

The generator is a separate source of power, and when it is on the utility power is already disconnected, thus the two disconnects do not need to be next to each other as there is but one source at a time.

However, as I stated in a previous post, the perceived problem can be alleviated by installing a disconnect for the generator in a new service equipment panel which has a main service disconnect for the utility service and breakers feeding the interior panel and the generator transfer switch - if there is a problem inside, simply turn off the breaker going to the inside panel, the utility service stays on, and is still powering the generator transfer switch so that the transfer switch sees utility power and does not automatically start the generator. Yet when utility power is lost, the transfer switch automatically starts the generator which energizes all the circuits from it (which could include the entire interior panel if the generator is of sufficient size).

[John Steinke]

One of the subtle points about generator installations ... or, for that mattter, installing any manner of secondary power source, be it a UPS, transformer, solar panel, wind turbine, or hamster in a wheel ... is that your 'service point' is no longer at the meter. Now the service point becomes the transfer switch, and you have two services to that point.

Considering all the issues that already arise regarding when and where you bond the neutral to the ground, adding a sendary power source really opens the bonding discussion up.

At any event, it is at the transfer switch that you can now disconnect the building from all power sources. Therefor, the transfer switch needs to be accessible, and not tucked away in an attic.

As a community center, exactly what manner of generator instal is required becomes an AHJ decision. The NEC has three separate sets of generator rules, so all bets are off.

Since the NEC has fractured 'separately derived systems' into at least half a dozen unrelated sections, the rules are a mess, a mess even worst than Article 250. The easiest way to keep things sane is to consider each source before the transfer switch as though it were another 'power company.'

That's why I consider the transfer switch the key to the system, and far more important than the brand of generator. It's also why I have such a strong preference for switching the neutral at the transfer switch - so there is no doubt that we are dealing with a separately derived system.

It may seem simple, but that transfer switch, especially if it is an automatic one, really complicates things. The result is that the testing and 'exercising' of the entire system become a critical part of the installation.

[Bruce King]

We are having an emergency generator installed for our Community Center. The electrician plans to install the whole house transfer switch in the attic between the meter and the the circuit panel and locate the generator behind the building.
The interior circuit panel does not have a emergency (on/off) switch, as it is incorporated in the meter (main) inlet box on the outside of the building.
I asked the electrician if the outside switch is turned off will the generator come on and continue to supply the panel? He said yes. I said that does not seem safe, if we had a smoking interior panel and came out and turned off the power at the meter the generator would come on and continue to supply power. The Electrician said you would have to go to the generator and turn off the generator behind the building. He said it was code to do it the way he is wiring?
Seems wrong to me.
Thanks


I have seen placards at commercial shut off locations warning about the presence of an automatic backup power source. I would think code has this placard requirement in there somewhere or they made a huge mistake and left it out.

[Kenneth Bauer]

NFPA 37 guidelines are required to be followed as well as the NEC, which calls for signs at service entrance equipment indicating the presence of the standby source of electrical power.

[Rick Bunzel]

Jerry,

90% of the generator panels I see are not for automatic generators. They are usually 6 breaker panels such as here Transfer Switches, Reliance Controls, Pro/Tran Indoor Manual Transfer Switches, Indoor, Pro/Tran Indoor, ProTran (http://www.generatorjoe.net/product.asp?0=289&1=466&3=1055)

They do not control the generator and require manually intervention before they power the home. The fully automatic system are typically on larger homes so in my area they are the exception not the rule.

//Rick

[David Bell]

Any distribution panels, disconnects, that are fed by auto transfer switchgear, or a manual transfer must be clearly tagged as such.

[Darrell Cummins]

The typical transfer switch is not also a disconnect as it does not disconnect both service sources, it simply "transfers" from one source to the other.

I see.:) I was thinking of a specific model of switch . It was a gernerac 200amp ATS and it included an Open position to disconnect both emergency and normal power.