Okay, this is a situation that requires careful consideration of the code and best practices. Let's break down the neutral switching and generator grounding.

Neutral Switching

Whether or not to switch the neutral in an ATS is a debated topic and depends on several factors. Here's a breakdown: The Code Requirement

NEC 250.30(A)(5)(b) and 250.36 deals with separately derived systems, which generators often are considered. If the generator qualifies as a separately derived system, then 250.30(A)(5)(b) would require the neutral to be switched to avoid objectionable current.

Why People Switch the Neutral

The main reason to switch the neutral on a generator ATS is to prevent circulating neutral currents. When the generator neutral is connected to the service neutral, there can be parallel paths for neutral current to flow back to the source. This can lead to: Nuisance tripping of breakers. Overheating of neutrals and other conductors. Inaccurate readings from ground fault protection. Increased electrical noise and potential for equipment malfunction.

Why People Don't Switch the Neutral

Cost: 4-pole switches are more expensive than 3-pole. Complexity: Wiring and control schemes are slightly more complex. Potential for voltage imbalances: If the load is highly unbalanced, switching the neutral might (rarely) create a slightly larger voltage imbalance. However, a well-designed system should mitigate this.

Parallel Generators

The situation with parallel generators makes neutral switching even MORE important! Each generator will have its own internal impedance and slight voltage variations. Without neutral switching, you're almost guaranteed to have circulating neutral currents between the generators and back to the service neutral.

Your Specific Case



Review the engineering study that the plans were based on. There is probably a specific reason that the Engineer of Record called out a 4 pole switch. In these cases, it's often safer to just go with what they recommended, as long as it's up to code. If the plans show a 4-pole switch, and you are not sure why, ask the Electrical Engineer who stamped the plans! This is the best and safest course of action. Don't deviate from the plans without their written approval. They likely have a reason for specifying a 4-pole switch.

Recommendation

In your situation, especially with parallel generators,

I would recommend switching the neutral with a 4-pole ATS. The risks of not doing so (circulating neutral currents) are high. Since the EE specified a 4-pole switch, there's likely a valid engineering reason for it.

Generator Grounding

Your memory of the Mike Holt video is generally correct, but there are nuances: Separately Derived Systems

If the generators are truly operated as separately derived systems, which is often the case, then NEC 250.30 dictates how they are grounded. In this case, you would establish a grounding electrode system (ground rod, etc.) at the generator only if you are switching the neutral.

Non-Separately Derived Systems

If the generator is not operated as a separately derived system (meaning the neutral is solidly connected to the service neutral at all times), then you generally do not install a grounding electrode at the generator. This is to avoid creating parallel paths for fault current.

Your Case

Since you have parallel generators and a 4-pole ATS is specified, it's highly likely the engineer intends the generators to be operated as separately derived systems. In this case, a grounding electrode (ground rod) at each generator is likely required (again, verify with the engineer).

Why No Ground Rod (Sometimes)

The concern is creating parallel ground paths that can carry fault current and neutral current. If the generator neutral is bonded to the service neutral, and you drive a ground rod at the generator, you've created a parallel path for current to flow through the earth back to the source. This can interfere with ground fault protection and create other problems.

Why Ground Rod (Sometimes)

When you switch the neutral, you isolate the generator's neutral from the service neutral. In this case, you need to establish a local ground reference at the generator for safety.

Recommendation


Verify with the Engineer of Record

The MOST important thing is to confirm the grounding approach with the Electrical Engineer who designed the system. They have taken into account all the specific details of your installation. They might have seen something like an underground pipe that could have made a local grounding electrode required.2.

If the generators are intended to be operated as separately derived systems (which is likely with a 4-pole ATS), then you probably need a grounding electrode at each generator.3. If you are not switching the neutral (which I strongly advise against with parallel generators), then you probably should not have grounding electrodes at the generators.In Summary



Strongly consider switching the neutral with a 4-pole ATS, especially with parallel generators. The need for ground rods at the generators depends on whether they are operated as separately derived systems (which the 4-pole ATS suggests they are). ABSOLUTELY, POSITIVELY CONFIRM ALL OF THIS WITH THE ELECTRICAL ENGINEER WHO STAMPED THE PLANS. This is the most critical step.

I hope this helps. Be safe and good luck with your project! Flag for review