Electrical, Power

Q&A about hospital backup, standby, emergency power

Your questions about power in hospitals are answered here

By Richard A. Vedvik and David Stymiest August 24, 2021
Courtesy: IMEG Corp., Smith Seckman Reid

When designing backup, standby and emergency power systems for hospitals, there are several considerations. Read this Q&A with the two expert presenters.

Answered by:

  • Richard A. Vedvik, PE, Senior Electrical Engineer/Acoustics Engineer/Senior Associate, IMEG Corp., Rock Island, Ill.
  • David Stymiest, PE, CHFM, CHSP, FASHE, Senior Consultant, Smith Seckman Reid, New Orleans

Amara Rozgus: Is CMS the agency that is responsible for recognition of reliable natural gas as a bona fide reliable on-site fuel and if not, where does it come from?

David Stymiest: From what I’ve seen so far, CMS is not taking position on that. I heard that at least one state has taken a position. The state of Florida, I believe, has taken a position. They’ve determined whether or not it’s reliable and the degree to which natural gas has to be on-site. I’m not aware of other states, but I believe it would probably be a state or local decision making.

Amara Rozgus: We’re talking about hospitals and the whole hospital is backed up by a diesel generator, can all of the utility power and all the generator power be applied to the ATSs and then distributed? Or is redundant power?

Richard Vedvik: We get this question a lot. If you’re looking at the resiliency of a hospital system, maybe you’re doing a Greenfield standalone hospital and you get to build this thing from scratch and the utility says we can give you two feeds coming in. Well, that’s great. I would like to have two feeds coming in, but maybe they say, “I can only give you one feed and I can’t guarantee it’s going to be up all the time because we like to have tornadoes here.” In that case the facility might say, “Well, let’s go ahead and do some tier four big 15 kV say gensets that just take over for the utility.” Now, what does that do for the rest of your discussions that we’ve been talking about on what kind of transfer switch branches you’ll have?

Well, remember that we’re still looking at resiliency. If you’re going to have just one or two or single pathways, you’re going to do that common mode failure analysis and what things can fail. The one thing I have experienced is that it does ease the conversation sometimes on does it have to be on all emergency or can we actually put some more of this stuff back on normal? So sometimes there’s actually a cost savings that can happen when you’re doing the 15 kV utility backup, because you feel like your normal is now more resilient than it would be otherwise. And you can go to maybe a more code minimum approach for normal and critical instead of critical one, critical two. But it depends because you’re going to have to perform the risk analysis to find within NFPA 99.

Amara Rozgus: Which code mandates the length of time a generator is required to run without refueling and very specifically, can you discuss the class X designation?

David Stymiest: The codes, for example, the life safety code has two chapters that invoke NFPA 110 and at least one of those chapters, it talks about how many hours the generator needs to operate for that particular type of load, which I believe was the means of egress, that’s diversity lighting means of egress. There are different requirements in different codes and standards and those requirements they’re not the same. Basically, you have to look at what applies to the facility that you are concerned with and what are the rules and follow those rules. In the event of two different rules with one big more restrictive than the other, you must always go with the more restrictive.

Amara Rozgus: We’re talking about limited care facilities, such as hospice facilities. Do I have to sort out the branch circuits like critical equipment and life safety?

Richard Vedvik: Now when you look at, say 517.40, when you start getting into essential electrical systems for nursing homes and other limited care facilities, you’re going to see that it actually changes the figures. The figures show two switches instead of one. It’ll show a life safety and an equipment branch switch and it doesn’t necessarily show a critical switch and so three, it shows two. Now of course, this comes back to risk assessment and just determining how many of those equipment branch “switches” you’re going to have in your limited care facility and if you’re actually going to treat some of them more like critical and equipment or just go minimalistic. And I see both approaches being used.

It does also depend on the acuity of those patients within there and what the staff is used to seeing. You’ll have some staff that’s just used to seeing all three branches and wants them, in which case that’s a labeling issue, but pay attention that 517.30 and 517.40 and those sections that follow are different because they apply to those different facilities.

Amara Rozgus: Would you please tell us the difference between NFPA 110 class and the requirement or recommendation for on-site stored fuel run time?

David Stymiest: The on-site stored fuel run time that’s determined by the code and the class. Basically, the amount of fuel that is toward on-site is determined by what the code says for how many hours you have to run the generator at full load. In most cases, it’s at full generator load and that’s the criterion. It’s determined by the codes and standards. It’s determined by the authorities having jurisdiction. In some cases, it’s determined by the state. In a lot of cases, there’s no particular requirement for so many hours of run time having the national documentation, but different states have different requirements.

Amara Rozgus: Can you please provide some examples when ground fault protection not required by code could benefit critical power supply system?

Richard Vedvik: Now, we want to be careful because when we’re doing ground fault, yes, that’s a requirement on the normal side. And if we’re talking health care facilities, then we’re looking at selective coordination requirements. So that means we’re going to have the main and the branches. Now, NFPA also explained and NEC does that, that’s not two in series. It’s not two main breakers in series. It’s the main and the branches because the intent of selective coordination. We want to maintain select activity so a ground fault and a branch doesn’t take out the main.

Now what we’re looking on the emergency side, we’re interested in knowing do we have a ground fault, but we’re not required to trip on that, instead we would like to get an alarm. So, your LSIG right, your G is your ground fault. Your LSIA is going to be your same breaker, except I’m alarming instead of providing an actual trip. And that’s important, because we’re considering that we want to know we have a problem, but if we just shut the generator off, because it has a ground fault, we could actually be doing more damage than what we would if we were to try and save it.

Imagine shutting down the generator on the entire hospital campus while that’s the only power source and the hospital goes completely dark. So, we want to know… it’s a good question, because we want to know if we have a ground fault, but we want an alarm in that condition. We don’t want to trip the entire system in that condition. Any individual ground fault requirements are also listed in NEC and those would be at the branch circuit level, but not shutting off the entire facility.


Richard A. Vedvik and David Stymiest
Author Bio: Richard A. Vedvik, PE, Senior Electrical Engineer/Acoustics Engineer/Senior Associate, IMEG Corp., Rock Island, Ill. David Stymiest, PE, CHFM, CHSP, FASHE, Senior Consultant, Smith Seckman Reid, New Orleans