It is hard having such a small brain. any help out there

[collier]

Is it possible for a generator to feed the whole load of a house power panel (service panel) thru an automatic transfer switch (ATS) and still meet code?

let me explain

NEC 230.82 does not allow the ATS ahead of the main service equipment
NEC 250.142 does not allow grounding thru the neutral for dryers and stoves

The House power panel will become a subpanel since a new service disconnect will have to be installed ahead of the ATS

The stove and dryer are being served by SE cables with the neutral being grounded to the frames of dryer and stove. This is ok as long as the house is existing and wires are run from service equipment. but this panel will have to be changed and made a subpanel

due to the construction of the house it, it is almost impossible to run new cables with separate neutrals and grounds to the dryer and stove.

All I can think of is to set the new service equipment away from the house, so i can feed the old house power panel and treat it as a separate building.

If you have read this far, can you think of another way. thanks

collier

 

[templdl]

USe a breaker type ATS that is listed for SE.

 

[bob]

Are you planning to use the generator only for emergency conditions?
If so, why would you need to power the whole house. You can make you life simpler by installing an emergency panel and pick off what is necessary. Necessary = Microwave, Lts, Washer, mabe A/C unit, Dish washer.

 

[George Stolz]

Re: It is hard having such a small brain. any help out there

The stove and dryer are being served by SE cables with the neutral being grounded to the frames of dryer and stove. This is ok as long as the house is existing and wires are run from service equipment. but this panel will have to be changed and made a subpanel

Read the exception to 250.142 slower. The branch circuit does not have to originate in the service.

 

[don_resqcapt19]

George,
Look at 250.140(3).
Don

 

[George Stolz]

George, read the exceptions to 250.140 slower, you idiot, you're making a fool of yourself. :roll:



Sad thing was, I didn't even write the section number correctly. :roll:

 

[collier]

Bob,

The problem with a lot of the installations we see is that it is near impossible to pick the circuits you want the generator to run and reroute them to a new panel controlled by the generator. If it wasn't for some code violations with the grounding the neutral in a subpanel, it is much easier to get a transfer switch large enough to run the whole house under normal conditions, and then manually turn off certain loads during an outage

we also want the genertor to exercise on a regular basis, just not transfer the load automatically during an outage - so we don't overload the generator or damage some equipment. not sure that it would - just a precaution...as the generator is not large enough to run the whole house

 

[templdl]

As I stated above "Use a breaker type ATS that is listed for SE (service entrance)." What's nice about a breaker type ATS is that you can get them with OCP.
Because it is listed for SE you can bring your SE to it and feed the main panel with the ATS. Just pay attention to the neutral grounding, and EGC.
Now you've added an "exercising" requirement.
As far as bells and wistles in an ATS I always have recommended that as long as one is paying some big bucks for a Genset and ATS that these options be added:
TDNE, time delay normal to emergency to put a time delay that would prevent immediate transfer to the emergency source should there be a brief interruption in normal source power.
TDES, Time delay engine start warks in concert with TDNE to prevent a genset start due to brief power interruptions.
TDEN, time delay emergency to normal will provide a time delay for retransfer to the normal source to assure as best as you can that the normal source has stabilized.
TDN, Time delay neutral which provides a brief delay in the neutral position do that an out of phase transfer is prevent when transferring from the energized emergency source to the normal source which has been know to put a voltage/current spike on the line that can trip an OCPD.
TDEC, time delay engine cool off which runs the genset a short time unloaded before shutting down.
And a TSS, test selector switch with allows for manually starting and testing the genset either by transferring into the load or no load. The is no problem with no load testing a genset. I haven't picked up upon an ability to program automatic exercising with a time clock but I'm sure there's on available.
There's a boat load of other options available to to fit ones fancy.

Also, with regards to loads, simply comsider what your "normal" loads are. If you have heating loads, range/oven, water, heater, electric heat, etc, those loads have to be removed as they are power hogs. Then consider other unnecessary loads. But as the other guys said if you transfer into the main panel you transfer into any loads that had been energized and would have to be manually removed of shunt trip breallers used which could automatically trip the breakers feeding those loads before transfer but they still must be manually closed after normal source power is restored.

Otherwise your choices are few, to get a bigger genset which can handle the load or install a subpanel and move all the critical loads to it and put your ATS between the main panel and the subpanel and transfer to the subpanel only which is what is normally done.

 

[bob]

Temple Poster

USe a breaker type ATS that is listed for SE.

I do not think that is an automatic TS is it?Is it manual?

George posted

Read the exception to 250.142

This requires that the grounded conductor be inside of the service disconnect. If the TS is installed ahead of the existing disconnect isn't the old SD now a sub panel?

Don posted

Look at 250.140(3).

This exception does not
mention the service disconnect. In the new installation the old SD will have the neutral and EGC isolated. The fault path is back thru the old SD to the transfer switch which is the way it should be.

 

[don_resqcapt19]

Bob,

This exception does not mention the service disconnect. In the new installation the old SD will have the neutral and EGC isolated. The fault path is back thru the old SD to the transfer switch which is the way it should be.

It doesn't?

Exception No. 1: The frames of ranges, wall-mounted ovens, counter-mounted cooking units, and clothes dryers under the conditions permitted for existing installations by 250.140 shall be permitted to be grounded by a grounded circuit conductor.

One of those conditions is that the circuit originates at the service equipment.
Don

 

[collier]

Maybe I am still missing something. A service entrance rated transfer switch with overcurrent protection becomes the new service. Since I want to be able to have back-up power available to all the circuits in the house (although not all at one time, because a generator that large is too expensive), the old service panel will become a subpanel. Herein lies the problem. I understand the old service panel will have to be changed out or modified to separate the equipment grounds and neutrals with the neutral not bonded to the enclosure. But the code still doesn't allow SE type cables without an equipment grounding conductor in a subpanel if it is serving a dryer or stove ---so I can't see what the service rated transfer switch has to do with it. I am still trying to transfer the load of the new subpanel (which was the old service panel)

I am assuming the "breaker type ATS" mentioned by someone is just to meet NEC 230.82.

If you are going to spend the money on a good generator, there ought to be a way to use all the circuits in your house, not just a limited few - without have to rip out half the drywall in your house to run new 4 wire circuits for the stove and dryer with a neutral and equipment ground . I went thru Katrina. After a while you want to wash and dry your clothes. It would be nice to turn off some loads while you did this, then when you are thru, turn the A/C back on.

 

[bob]

Don
What I was saying is that 250.142 said "within the enclosure of the ac service disconnect" 250.140 did not say this. However I overlooked
exception #3 that the "branch circuit originates at the service disconnect."
If thats so, then the circuits must go back the the Transfer Switch.
Is that correct?

 

[ramdiesel3500]

Wow, this is a real problem! I would think that in this case, most inspectors would understand the circumstances and accept the arrangement as is. Here locally, we have installed several transfer switches and service disconnects for whole house generator systems in existing homes. The inspectors do not require us to separate the grounded and grounding conductors in the panels nor do we have to worry about any of the existing branch circuit arrangements. The treat the modifications similar to the way they deal with an outbuilding.
In your particular case, if the AHJ won't allow it, then reroute the service to the generator and install a service disconnect and ATS (both 3R rated) at the generator and then treat the house as an outbuilding!

 

[templdl]

Bob,
The original post referred to an ATS and not MTS some my reply was base upon that.

collier,
Unless I'm missing something as I understand it, yes, the original panel becomes a subpanel and the neutral and EGC have to be insulated and isolated from one another which would require a separate isolated neutral bar if there isn't one or removing the green bonding screw is there are (2) bars. The you must assure that all of the EGCs terminate on the ground bar and the neutrals on the neutral.
If the SE cables now terminate at the ATS then don't understand where the SE connection to panel comes into play. Also note that the panel does not need to be replaced but just the neutral and ground reconfigured.
There should be not be issues with the range and dryer connections either other than they would be unnecessary loads on the generator when used during power outages.

 

[iwire]

I can not see anyway out of running new circuits to the stove and dryer is he goes the SE type ATS route.

There is not always an easy way to meet code.

 

[collier]

templdl,

you throw me off when you say

"If the SE cables now terminate at the ATS then don't understand where the SE connection to panel comes into play."

The SE cables still need overcurrent protection and originate at a breaker in the subpanel. If I got a service entrance rated transfer switch, it would just have one main breaker or set of fuses to be used as a new service disconnect switch which is require to be upstream/ahead of the transfer switch to meet code. To my knowledge there is no transfer switch that is service rated with a bunch of smaller breakers in it -- to terminate the SE cables

collier

 

[jwelectric]

One thing that needs to be thought out is that the use of an automatic transfer switch and the load being served. If the ATS is energizing the whole panel the feeders from the gen-set would be required to be the same size as the SE conductors.

The use of a ATS in a dwelling needs to be thought through completely in order to keep the conductors sized correctly.

 

[ramsy]

I need pictures to understand you guys,

So I found the difference between templdl's suggested "breaker type ATS" and a "conventional ATS installation" illustrated here:
http://www.eatonelectrical.com/unsecure/html/101basics/Module29/Output/SwitchConfigurations.html
Scoll down to the "Service Entrance" section.

Nevertheless, without modifying the wash/dryer circuit ramdiesel3500's idea seems the most economical to me.

"reroute the service to the generator and install a service disconnect and ATS (both 3R rated) at the generator and then treat the house as an outbuilding!"

 

[templdl]

collier
You appear to mbe making this a bit more somplex than it should be.
The SE will be at the ATS and not the panel. The SE drop is relocated to land on the ATS and not the panel so I can't understand where this protection that you are referring to is required.
The SE drop must be relocated to the ATS normal side.
The SE drop is rermoved from the original SE panel and is now terminated on the ATS which now makes it the service entrance. The load side it connected to the panel which has been reconfigured as a sub panel.
The genset feeds the emegency source.

Again, I fail to understand where this SE cable protection comes if you simply relocate them to terminate in the ATS.
Dave