Bad gen-set install

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goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
The first Generac transfer switch that you've sited is for an Essential Circuits system. This is an indoor transfer switch with a built-in sub-panel. It does not get located between the meter enclosure and the building service disconnect. It allows you to power X # of circuits that must be active during a power outage. The second is a Whole House transfer switch with load shedding. In this case it is service rated because it has a main breaker in it and does get located between the meter enclosure and the existing building service disconnect thereby making it the new building service disconnect. Grounds and neutrals should be terminated here accordingly.

The controversy here is with her interpretation of when neutrals and grounds have to be terminated at the transfer switch. The way I read her statement is that the only time this has to be done is when you have a separately derived system and are switching the neutral OR if the manufacturer states it must be so. I believe the vast majotity of us here in the Forum disagree with that.

If you look at this Kohler automatic transfer switch you'll notice that comes with no service disconnect. This is an outdoor unit that looks like it's designed to go between the meter enclosure and the building service. disconnect.http://www.electricgeneratorsdirect.com/manuals/RXT SPECS.pdf

I hope someone can explain where this might be used. BTW, the reason why my reply sounded like it did was because you cited several Code references and offered no explainations. I wasn't out to insult you or cause you any heartburn.
 
The first Generac transfer switch that you've sited is for an Essential Circuits system. This is an indoor transfer switch with a built-in sub-panel. It does not get located between the meter enclosure and the building service disconnect. It allows you to power X # of circuits that must be active during a power outage. The second is a Whole House transfer switch with load shedding. In this case it is service rated because it has a main breaker in it and does get located between the meter enclosure and the existing building service disconnect thereby making it the new building service disconnect. Grounds and neutrals should be terminated here accordingly.

AGREED

The controversy here is with her interpretation of when neutrals and grounds have to be terminated at the transfer switch. The way I read her statement is that the only time this has to be done is when you have a separately derived system and are switching the neutral OR if the manufacturer states it must be so. I believe the vast majotity of us here in the Forum disagree with that.

If you look at this Kohler automatic transfer switch you'll notice that comes with no service disconnect. This is an outdoor unit that looks like it's designed to go between the meter enclosure and the building service. disconnect.http://www.electricgeneratorsdirect.com/manuals/RXT SPECS.pdf

I hope someone can explain where this might be used. BTW, the reason why my reply sounded like it did was because you cited several Code references and offered no explainations. I wasn't out to insult you or cause you any heartburn.


1) what I have been told is that the TS that is not service rated would need a "disconnect switch added" ... as a seperate piece to buy. inside or outside depending on the actual setup

2) 230.70

3) 230.75 ...... I think this addresses most of the residential issues with the grounded conductor.



Now for me ... there are similar installations .. like a Service breaker that is part of the Meter can ....everything down stream is a sub panel ie meter bank.

the other thing that comes into play IMHO is the "grouping" of the disconnects ..
 
If you look at this Kohler automatic transfer switch you'll notice that comes with no service disconnect. This is an outdoor unit that looks like it's designed to go between the meter enclosure and the building service. disconnect.http://www.electricgeneratorsdirect.com/manuals/RXT SPECS.pdf

I hope someone can explain where this might be used. BTW, the reason why my reply sounded like it did was because you cited several Code references and offered no explainations. I wasn't out to insult you or cause you any heartburn.

yes Generac has that line also RTSN type ...

say that you had al Disconnect already @ the Meter location or had to have installed a Disconnect switch due to the Main Panel was needed to be located else where and not right inside the dwelling ??
 

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
The way I understand this is that an ATS has to contain an over-current device that matches the service it is protecting in order to be considered "service rated". Putting a disconnect "switch" ahead of the ATS doesn't make the installtion Code compliant nor does it make the ATS service rated if my understanding is correct.
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
The way I understand this is that an ATS has to contain an over-current device that matches the service it is protecting in order to be considered "service rated". Putting a disconnect "switch" ahead of the ATS doesn't make the installtion Code compliant nor does it make the ATS service rated if my understanding is correct.

Correct, putting a disconnect ahead the transfer switch does not make the transfer switch service rated, but then it is not the service, so it does not have to be.
 

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
Correct, putting a disconnect ahead the transfer switch does not make the transfer switch service rated, but then it is not the service, so it does not have to be.
So, let me see if I'm understanding you correctly. You're saying if you install a mechanical disconnect switch ahead of a non-service rated ATS then the GEC's can remain inside the existing main breaker panel ? If it's a service rated disconnect it would mean that there is overcurrent protection built in rated to the size service you're protecting and the GEC's would be terminated there. If that's the case why would you do that instead of just using the the service rated ATS that comes with the generator ?.
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
So, let me see if I'm understanding you correctly. You're saying if you install a mechanical disconnect switch ahead of a non-service rated ATS then the GEC's can remain inside the existing main breaker panel ? If it's a service rated disconnect it would mean that there is overcurrent protection built in rated to the size service you're protecting and the GEC's would be terminated there. If that's the case why would you do that instead of just using the the service rated ATS that comes with the generator ?.

Most generators do not come with a service rated transfer switch, you have to order it that way at extra cost. And no, the GEC's have to be moved to the new service disconnect, as they also would if a service rated transfer switch was used. Cost wise you are better off using a separate service disconnect than a service rated transfer switch, along with easier compliance with 70E.
 
Most generators do not come with a service rated transfer switch, you have to order it that way at extra cost. And no, the GEC's have to be moved to the new service disconnect, as they also would if a service rated transfer switch was used. Cost wise you are better off using a separate service disconnect than a service rated transfer switch, along with easier compliance with 70E.


and then the automatic Nexus type RTSD200A3 ...( service rated ) which would make the main panel a sub panel ... so the "extra would be to add a ground bar" and seperate the neutrals and grounds, and then making the TS where the grounds land ( water pipe and Ground rod ), instead of in the Main Panel. .... http://www.generac.com/Residential/T..._Smart_Switch/

Generac with the gen "kits" ....5875, 6051, 6052, 6053
 

Jerseydaze

Senior Member
couple more questions how does the load shed get calculated in load calc to me the items that load shed dont count as the system is designed to drop them if the power to run the large loads isnt there 2nd how do you use a utility bill to load calc?
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
You can, of course, omit any "shed" loads when calculating the generator size. For the most part utility bills are worthless for calculating load as they normally own show "usage" (kwh) over an extended period of time ie: month.
If the facility happens to have a "demand" meter it will indicate the highest usage over a mcuh shorter time period (less than a hour) which can be helpful. ( Most facailities that are large enough for a demand meter will have generator systems with engineered loads calculated. )
 

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
I can't speak about larger commercial type generators but I believe the Nexus load shedding systems in the Generac units work as follows (someone please correct me if I'm wrong) :

1) On start-up the (2) n/c contacts that control AC unit activation will open and the (4) 120V outputs that activate relays or contactors will change state
2) Once the generator starts the Nexus will sense the demand and check to see that the current cycles have not dropped below 60 cycles
3) If all is normal it will attempt to start unit # 1
4) If all remains normal it will attempt to start unit # 2
5) If all remains normal it will change state of output # 1 and so on.

The moment the cycles drop appreciably below 60 cycles (I think 57 or 58 cycles) it will start to shed loads in order of importance (i.e load # 4, 3, 2, 1, AC 2, AC 1). If you have no loads connected to the (4) 120V outputs then just the AC loads will be shed.

So, IMHO you'll need to consider those loads when calculation the generator size. Personally speaking, I do not leave my AC unit on when I'm not home so my generator ATS doesn't have to actually make that decision. However, I did have to wire the AC control circuit to the Nexus in order to pass inspection.
 

kwired

Electron manager
Location
NE Nebraska
So, let me see if I'm understanding you correctly. You're saying if you install a mechanical disconnect switch ahead of a non-service rated ATS then the GEC's can remain inside the existing main breaker panel ? If it's a service rated disconnect it would mean that there is overcurrent protection built in rated to the size service you're protecting and the GEC's would be terminated there. If that's the case why would you do that instead of just using the the service rated ATS that comes with the generator ?.

The problem with that is if the mechanical disconnect is disconnecting service conductors, you have other code violations, your transfer switch is still connected to service conductors which it is not rated to connect to. We need to establish where the service equipment ends before we get into where to separate the grounded and grounding conductors.

Bottom line is you are not likely to find a listed transfer switch that is suitable for use as service equipment, that does not contain a service overcurrent protection device.

There are POCO provided transfer switches around here that are a meter and double throw switch in one unit, no overcurrent devices. But I don't think they are listed either, POCO can install them but contractors following NEC can not.
 

jes25

Senior Member
Location
Midwest
On a related note: What about 3 wire range and dryer circuits that come out of the main panel; wouldn't those need to be changed to 4 wire when installing the service rated ATS?
 

John120/240

Senior Member
Location
Olathe, Kansas
On a related note: What about 3 wire range and dryer circuits that come out of the main panel; wouldn't those need to be changed to 4 wire when installing the service rated ATS?

Why would that matter ?

I think jes25's concern is your transfer switch is now the MAIN disconnect & all of your panels are now SUB panels which require

the neutrals & grounds to be seperate. So where would one land the white conductor in a SUB panel; on the neutral bus or the

ground bus ?
 

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
I think jes25's concern is your transfer switch is now the MAIN disconnect & all of your panels are now SUB panels which require

the neutrals & grounds to be seperate. So where would one land the white conductor in a SUB panel; on the neutral bus or the

ground bus ?
If you had any sub panels after your original main breaker panel before you installed the xfer switch then all grounds and neutrals should already be properly terminated. The neutrals in the existing main breaker panel have to now float and the EGC's have to be bonded to the enclosure. In some panels it's an easy fix and some are a PITA.
 

kwired

Electron manager
Location
NE Nebraska
I think jes25's concern is your transfer switch is now the MAIN disconnect & all of your panels are now SUB panels which require

the neutrals & grounds to be seperate. So where would one land the white conductor in a SUB panel; on the neutral bus or the

ground bus ?

You have to land the white on the neutral bus, it is current carrying, but it is also the EGC for a three wire range circuit where permitted.

But the circuit must originate in service equipment.

Check out the exception to 250.140 that tells us where a 3 wire range circuit is permitted. Condition 3 of the exception says the circuit must originate at service equipment. So if you convert your existing service panel to a sub panel when installing a service rated ATS, you can no longer supply the existing 3 wire range circuit from that panel.
 

jes25

Senior Member
Location
Midwest
You have to land the white on the neutral bus, it is current carrying, but it is also the EGC for a three wire range circuit where permitted.

But the circuit must originate in service equipment.

Check out the exception to 250.140 that tells us where a 3 wire range circuit is permitted. Condition 3 of the exception says the circuit must originate at service equipment. So if you convert your existing service panel to a sub panel when installing a service rated ATS, you can no longer supply the existing 3 wire range circuit from that panel.

Yup. I don't think anybody is changing these to 4-wire though. My company does around 400 Generac installs a year and apparently the inspectors aren't citing it.
 
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