As I prepare to attend the American Society for Healthcare Engineering (ASHE) annual conference in Boston, I thought I would share some thoughts — and some Code references — with you regarding ground fault protection and how it applies to a health care facility. But before we talk about what is required for ground fault protection, we first need to understand what a ground fault is.
“Ground fault” is defined in NFPA 70 (Art. 100) as: “An unintentional, electrically conductive connection between an ungrounded conductor of an electrical circuit and the normally non-current-carrying conductors, metallic enclosures, metallic raceways, metallic equipment, or earth.” Wait, what? Basically, a ground fault is when the electricity goes rogue and finds its own easiest (shortest) path to ground — typically with catastrophic results. The typical outcome of an unrestrained ground fault is equipment damage, an explosion, a fire, or electrocution (worst-case scenario) — none of which is a desired outcome.
So how do we address a ground fault? Well, with ground fault protection, of course. We all have seen the GFCI receptacles in our bathrooms, which consistently trip when we use our hairdryers. However, this is just a small event. I’d like to focus on the big stuff — electrical distribution equipment. So get ready because here comes the nerd Code speak.
Section 230.95 of the 2014 NEC requires ground fault protection of equipment as follows: “Ground fault protection of equipment shall be provided for solidly grounded wye electric services of more than 150V to ground, but not exceeding 1,000V phase-to-phase for each service disconnect rated 1,000A or more……” Article 100 defines “Service” as: “The conductors and equipment for delivering electric energy from the serving utility to the wiring systems of the premises served.” This seems pretty straightforward, right? If you have a utility service (incoming power) that falls within the parameter of 230.95, then ground fault protection is required on the service disconnecting means.
Here is where health care design starts to add on additional requirements beyond other types of construction. Section 517.17 indicates that two levels of ground fault protection are required in a health care facility “with critical care spaces or utilizing electrical life-support equipment…”. Once again, this requirement seems pretty straightforward. When ground fault protection is required on the service disconnecting means, a second level is then required in a health care facility that uses life-support equipment.
Now that we’ve addressed the utility (normal) source in a health care facility, are the rules the same for the emergency (essential) distribution system? Nope!
Section 700.27 states: “The alternate source for emergency systems shall not be required to have ground fault protection of equipment with automatic disconnecting means. Ground fault indication of the emergency source shall be provided in accordance with 700.6(D) if ground fault protection of equipment with automatic disconnecting means is not provided.” This requirement just wants to make sure someone will know if a ground fault has occurred in the equipment, so it requires some type of ground fault sensing for the equipment if ground fault tripping is not installed. Note that Art. 700 [Emergency Systems] is applicable to both “those systems legally required and classed as emergency,” as indicated in Sec. 700.2.
Section 701.26, legally required standby systems (which are what we typically have in health care facilities) indicates: “The alternate source for legally required standby systems shall not be required to have ground fault protection of equipment with automatic disconnecting means.” Articles 700 and 701 are in alignment that ground fault tripping is not required on generator distribution equipment, which is why it typically is not installed in a health care facility.
But if a ground fault situation is so catastrophic, then why wouldn’t we put ground fault protection on our emergency systems in a health care facility? To answer this question, we have to think about the damage that a ground fault can produce. Yes, it can start a fire, make things explode, or kill someone who is the path of the fault. But in a health care facility, your generator is the last line of defense to maintain power in the event of a utility outage. Damage of the generator and associated distribution equipment is much preferred to a complete facility outage where you may risk the safety of patients who are dependent upon electricity to sustain their lives.
