TVSS at Transfer switch
- Thread starter jgriffin
- Start date
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hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: TVSS at Transfer switch
I would think this would not be a good loaction in a circuit as it would not provide any protection when the panel is supplyed by the utility. and it would increase the load on the generator to boot. Maybe somone got in a hurry and connected it to the wrong source as I think it should have been connected to the utility side of the transfer switch. Also how is it connected as most terminals are only rated for one wire. Doesn't sound like a compliant installation to me. Maybe Derrek will jump in here, he knows his stuff when it comes to TVSS systems.
I would think this would not be a good loaction in a circuit as it would not provide any protection when the panel is supplyed by the utility. and it would increase the load on the generator to boot. Maybe somone got in a hurry and connected it to the wrong source as I think it should have been connected to the utility side of the transfer switch. Also how is it connected as most terminals are only rated for one wire. Doesn't sound like a compliant installation to me. Maybe Derrek will jump in here, he knows his stuff when it comes to TVSS systems.
ron
Senior Member
- Location
- New York, 40.7514,-73.9925
Re: TVSS at Transfer switch
First suggestion is to relocate the existing TVSS to the load side of the transfer switch.
If you cannot do that, then add another TVSS to the Gen supply side of the transfer switch to offer protection when in that power connection position.
First suggestion is to relocate the existing TVSS to the load side of the transfer switch.
If you cannot do that, then add another TVSS to the Gen supply side of the transfer switch to offer protection when in that power connection position.
Re: TVSS at Transfer switch
RON and WAYNE , They installed a 12"*12" hoffman enclosure on the POCO side of the ATS (200 amp) with a TVSS connected at that Hoffman Enclosure by a keytap .....and another 12"*12" on the Generator side of the ATS with a keytap and NO TVSS at this point.The Customer Asked about ADDING another TVSS at the Generator(20kw Diesel) side Hoffman Enclosure. It seems like a BAD DESIGN but He wants it DONE. I think his INTENTIONS are to protect the circuitry of the ATS as well.
[ February 28, 2004, 08:45 PM: Message edited by: jgriffin ]
RON and WAYNE , They installed a 12"*12" hoffman enclosure on the POCO side of the ATS (200 amp) with a TVSS connected at that Hoffman Enclosure by a keytap .....and another 12"*12" on the Generator side of the ATS with a keytap and NO TVSS at this point.The Customer Asked about ADDING another TVSS at the Generator(20kw Diesel) side Hoffman Enclosure. It seems like a BAD DESIGN but He wants it DONE. I think his INTENTIONS are to protect the circuitry of the ATS as well.
[ February 28, 2004, 08:45 PM: Message edited by: jgriffin ]
Re: TVSS at Transfer switch
I have done it two different ways in industrial settings. First method, install a TVSS on the POCO line side and another on the Genset line side. Second method, is one TVSS on the load side of the ATS.
For a residance I would probably just install one unit on the POCO line side. But if you got the budget go ahead and install a second on the genset line side. But I think it is a waist.
I have done it two different ways in industrial settings. First method, install a TVSS on the POCO line side and another on the Genset line side. Second method, is one TVSS on the load side of the ATS.
For a residance I would probably just install one unit on the POCO line side. But if you got the budget go ahead and install a second on the genset line side. But I think it is a waist.
Re: TVSS at Transfer switch
BENNIE ,if I'm understanding you correctly you're suggesting a SDS setup once I ADD TVSS on Genset side of the ATS. That's how I read your post. Considered as much,Will inform customer of required changes.Thanks,Griff.
[ February 29, 2004, 09:15 AM: Message edited by: jgriffin ]
BENNIE ,if I'm understanding you correctly you're suggesting a SDS setup once I ADD TVSS on Genset side of the ATS. That's how I read your post. Considered as much,Will inform customer of required changes.Thanks,Griff.
[ February 29, 2004, 09:15 AM: Message edited by: jgriffin ]
Re: TVSS at Transfer switch
JGriffin: This is my opinion. Choosing my suggestion is at your own choice. There is many who do not agree with my perception of a separately derived system.
With the utility MGN disconnected, I can not see any purpose for transient suppression on a generator. I have scoped many of them and have not observed any garbage on the sine wave.
Transients are created by two situations, lightning flashes, and capacitor bank switching. Neither condition is present in a generator when operating as the power source for a separately derived system.
[ February 29, 2004, 10:21 AM: Message edited by: bennie ]
JGriffin: This is my opinion. Choosing my suggestion is at your own choice. There is many who do not agree with my perception of a separately derived system.
With the utility MGN disconnected, I can not see any purpose for transient suppression on a generator. I have scoped many of them and have not observed any garbage on the sine wave.
Transients are created by two situations, lightning flashes, and capacitor bank switching. Neither condition is present in a generator when operating as the power source for a separately derived system.
[ February 29, 2004, 10:21 AM: Message edited by: bennie ]
Re: TVSS at Transfer switch
BENNIE, I'd rather have ALL CONDUCTORS disconnected from POCO at the ATS. I'M thinking it Should be SDS for safety reasons as well,(local lightning strikes) I just try to AVOID jobs where I have to EXPLAIN having to fix or modify improper installations or correct code violations. Griff
BENNIE, I'd rather have ALL CONDUCTORS disconnected from POCO at the ATS. I'M thinking it Should be SDS for safety reasons as well,(local lightning strikes) I just try to AVOID jobs where I have to EXPLAIN having to fix or modify improper installations or correct code violations. Griff
Re: TVSS at Transfer switch
JGriffin: I agree that all utility lines should be disconnected during a power outage. The results of many outages are broken power lines and transformer faults. Both events often energize the MGN for a period of time. This will wipe out the generator logic and shut down all power.
I do not want to be on life support in an ICU that is powered by a generator connected to the utility MGN.
JGriffin: I agree that all utility lines should be disconnected during a power outage. The results of many outages are broken power lines and transformer faults. Both events often energize the MGN for a period of time. This will wipe out the generator logic and shut down all power.
I do not want to be on life support in an ICU that is powered by a generator connected to the utility MGN.
Re: TVSS at Transfer switch
Bennie have you ever installed or seen the meter sections that have ATS built into them for Residential Services? These are Manufactured by Electro-Industries about 16" high * 32" long and have a 200 amp,220 volt, single phase meter socket on the left half and a 200amp power transfer switch on the right half.They are non-SDS and Permitted for Use by some POCOs.
[ February 29, 2004, 11:10 AM: Message edited by: jgriffin ]
Bennie have you ever installed or seen the meter sections that have ATS built into them for Residential Services? These are Manufactured by Electro-Industries about 16" high * 32" long and have a 200 amp,220 volt, single phase meter socket on the left half and a 200amp power transfer switch on the right half.They are non-SDS and Permitted for Use by some POCOs.
[ February 29, 2004, 11:10 AM: Message edited by: jgriffin ]
- Location
- Illinois
- Occupation
- retired electrician
Re: TVSS at Transfer switch
Bennie,
How do we get this seperation from the utility? Even if the transfer switch switches the grounded conductor, the generator and utility are still connnected via the grounding system. The only way that I can see is to have the transfer switch on the utility side of the main bonding jumper and use nonmetallic service raceway. I'm not sure that there is a code compliant way to put the transfer switch on the line side of the main bonding jumper.
PS...great to see you back here
Don
Bennie,
How do we get this seperation from the utility? Even if the transfer switch switches the grounded conductor, the generator and utility are still connnected via the grounding system. The only way that I can see is to have the transfer switch on the utility side of the main bonding jumper and use nonmetallic service raceway. I'm not sure that there is a code compliant way to put the transfer switch on the line side of the main bonding jumper.
PS...great to see you back here
Don
Re: TVSS at Transfer switch
The original post indicates that the ATS is after the meter. I assume it is ahead of the first service switch, and the generator supplies the entire premises wiring system.
Switching to generator power is the same as switching to a backup transformer fed by a separate feeder. The neutrals are switched by the ATS, the premises grounding remains the same.
When operating on the generator power, or on the backup transformer, the power sources are not electrically connected even by a ground conductor.
Each source is electrically isolated.
When ATS is after the service main, a separately derived system bond must be established either at the source or the first switch.
The original post indicates that the ATS is after the meter. I assume it is ahead of the first service switch, and the generator supplies the entire premises wiring system.
Switching to generator power is the same as switching to a backup transformer fed by a separate feeder. The neutrals are switched by the ATS, the premises grounding remains the same.
When operating on the generator power, or on the backup transformer, the power sources are not electrically connected even by a ground conductor.
Each source is electrically isolated.
When ATS is after the service main, a separately derived system bond must be established either at the source or the first switch.
Re: TVSS at Transfer switch
Bennie & Don,... there's a 200 amp fused Service disconnect between the POCO meter and 1st TVSS on PoCo Side of ATS. At this disconnect THERE is a Main bonding jumper,GEC,EGC and what appeared to be 2 -8' copper clad ground rods about 10' apart on other side of the cinder block wall connected together by a continuous #8 solid Copper back to Main Service disconnect. The PoCo MGN is common with the GenSet and bonding Strap is currently removed at GenSet.The panel(s) inside the residence I didn't get to see........From the notes I took....Just noticed the GEC is too small,But IT COULD HAVE BEEN #6 Solid if I'm mistaken. (I previously typed EGC was too small,It was a TYPO)
[ February 29, 2004, 05:37 PM: Message edited by: jgriffin ]
Bennie & Don,... there's a 200 amp fused Service disconnect between the POCO meter and 1st TVSS on PoCo Side of ATS. At this disconnect THERE is a Main bonding jumper,GEC,EGC and what appeared to be 2 -8' copper clad ground rods about 10' apart on other side of the cinder block wall connected together by a continuous #8 solid Copper back to Main Service disconnect. The PoCo MGN is common with the GenSet and bonding Strap is currently removed at GenSet.The panel(s) inside the residence I didn't get to see........From the notes I took....Just noticed the GEC is too small,But IT COULD HAVE BEEN #6 Solid if I'm mistaken. (I previously typed EGC was too small,It was a TYPO)
[ February 29, 2004, 05:37 PM: Message edited by: jgriffin ]
- Location
- Illinois
- Occupation
- retired electrician
Re: TVSS at Transfer switch
Bennie,
If the conduit is metallic, then the equipment grounding systems will be tied together and this will provide a connection to the utility neutral at the meter. Most meter cans have a neutral to case connection. Even without metallic conduit there will be a bond. The transfer swicth enclosure must be connected to an EGC from both the utility and generator sources. I see no way to eliminate a connection to the utility grounded conductor.
Don
Bennie,
If the conduit is metallic, then the equipment grounding systems will be tied together and this will provide a connection to the utility neutral at the meter. Most meter cans have a neutral to case connection. Even without metallic conduit there will be a bond. The transfer swicth enclosure must be connected to an EGC from both the utility and generator sources. I see no way to eliminate a connection to the utility grounded conductor.
Don
Re: TVSS at Transfer switch
Don: Complete isolation of neutrals can be obtained by careful design to eliminate multiple grounding connections.
I have made drawings, but can't display them. I will have to learn how to post them.
I may enroll in a training class at Gateway computer store, if I survive surgery.
Don: Complete isolation of neutrals can be obtained by careful design to eliminate multiple grounding connections.
I have made drawings, but can't display them. I will have to learn how to post them.
I may enroll in a training class at Gateway computer store, if I survive surgery.
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