Are these generator switches OK?

[Michael Thellend]

Hi Paul,

I envy that you found the time to acquire such a vast level of certification regarding electrical systems and the field in general.

I too know a bit about electrical, generators and installations. I'm a master electrician in the province of Ontario with 30 years of experience in the electrical industry, and I've installed over 50 generators in recent years. I also have a diploma in electronic controls. I was offered a chance to teach ESA (Electrical Safety Authority) inspectors and master electricians regarding installation of alternative power systems from generators, solar, grounding to bonding and I chose not to as I had a busy life with 6 children.

The topic here started with "Are these generator switches ok?"

As an electrician I don't need to look at the switches up close to see that this is not an approved transfer switch system, therefore the answer to his question is no.

I agree that most fixed 3 phase standby generator installs do not switch the neutral and it's not mandated by the NEC except in special circumstances. This type of 3 phase system can use a 3 pole MTS or ATS to break the lines. One instance where the game changes is with portable generator systems, 3 phase or single phase. Many people use portable generators and manual switching in an emergency power outage, this I assumed was the case here. A portable generator supplying 120/240 Vac power from a cord and plug connected to a transfer switch to feed a premise wiring system (say via a male flanged inlet receptacle outside or too the three ways in this system from a junction box) is considered to be a separately derived system. This is what most people do in an outage as many don't have fixed stanby systems with automatic transfer. They put the generator outside on the ground and connect to a 3 pole transfer switch (3 poles 3 throw for L1-L2-N) using the methods I mentioned earlier to feed circuits in a emergency circuit sub panel. When 3 wire 120/240 Vac generators are of a portable nature, and most are, a load neutral along with its phase conductors when transferring loads between power sources must be switched. If ground fault protection is not required, the portable generator is not connected via a cord and receptacle attached from it, and the generator is fixed the generator neutral can be solidly connected to the service neutral. In this case a 2 pole (DPDT L1-L2) transfer switch can be used.
So if you use a portable generator, 3 phase or single phase, it has to be converted to a fixed system bolted to concrete (isolated from earth ground) have no generator frame bonding and no ground fault system to make it a non SDS. A 120/240 Vac portable generator should have a 3 pole MTS or ATS as it is a separately derived source and the neutral is grounded at the generator. The same holds true for a 3 phase 4 wire system having to use a 4 pole MTS or ATS. A neutral conductor shall be bonded to the generator frame if the generator is a component of a separately derived system (portable).

please read the definition of a SDS in the National Electrical Code and understand that while some transfers switches will switch the grounded conductor ( a true SDS ) some transfer switches do not and they are no more dangerous.

A four-pole ATS is better than a three-pole switch from a maintenance and safety perspective. With the 3 pole ATS, if the main service is taken offline for maintenance or any other reason and the standby generator is running to serve the critical and life safety loads, the standby generator is still relying on the main service ground connection to the neutral for the return path of any ground fault. If somebody is not aware of this grounding configuration, and maintenance is performed on the main service ground when the service is offline and the standby generator is running, the standby generator would no longer be properly grounded. This could be a serious safety concern and could potentially allow fault currents to flow without tripping the over current protective device.

Mike

My last generator install this winter.

A non SDS. I do have pics of an SDS using a portable generator, with manual transfer and flanged inlet receptacle to supply the transfer switch from a generator outlet that I will post here soon. The wiring of the system may be useful to someone in the forum.

[Paul W. Abernathy]

Mike,

Keep in mind my responses are general in nature based on the reply to the question involving a comment made by marc and answered by others. There are complex issues when dealing with generators as a whole. I did not address the switches is because others have addressed them.....I was dealing more with responses to marc's statement which is correct in nature.

In a feedback type senerio you will always be safer in theory by removing the ability for the grounded conductor to connect back to te system.....but the NEC does not prevent this situation for the most part in normal applications....

Lets remember now that HI's do not extend into the level of this knowledge under their SOP....but I guess some will disagree.

[Michael Thellend]

Hi Paul,

I get the plan on the HI-SOP and you're right.

I need to bring this up.

I was dealing more with responses to marc's statement which is correct in nature

• Marc is 1/2 correct in nature.

• Randall is 1/2 correct in nature and his post was not utter and complete nonsense.

Mike

[Paul W. Abernathy]

Nonsense is a BROAD statement. If someone wishes to be precise with the statements then we can lay a claim on real nonsense. My experience is in the NEC and the NEC does not have a problem with either application and since HI's dont deal in rhelms they should not dabble in I would prefer to tell the HI's to walk away from the situation.
Also...don't envy me.....my wife and child are the ones who have suffered from my selfish adventure into the National Electrical Code.

[Terry Clayton]

The picture looks to be a two position switch, Middle NO contact, Up current flow from Generator, Down current flow from power company. As Paul stated using a approved transfer switch you do not break grounded conductors.

[Paul W. Abernathy]

Terry,

Remember now they do make transfer switches that do switch even the grounded connection which would constitute an SDS. But I only really see them on plans that I have done for larger companies and so on. I would venture to say 90+ % of transfer switches I see are Non-SDS and a small fraction are truly SDS's.

IE: SDS = Seperatly Derived Systems - No direct electrical connection between the utility power source and other source of power or equipment, which translates to switching the grounded conductor or not on an ATS when speaking of generators.