Power, electrical equipment for hospitals
Electrical systems, including batteries, are touched on in this hospital electrical systems discussion
When designing backup, standby and emergency power systems for hospitals, there are several considerations beyond NFPA 70: National Electrical Code and other building code requirements that must be addressed. Engineers need to be mindful of the construction process, and ensure equipment replacement is coordinated, temporary power strategies are identified and phasing concepts are developed.
- 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
Richard Vedvik: Now, batteries are another concept with the advent of electric vehicles and lithium-ion making a pretty strong play. We’re seeing 15, 20-year lifespans with batteries. So, is that allowed when NEC 517 30B3 does specifically with batteries and references NFPA 111? Another question I get is, can I use a natural gas generator? Well, remember that there’s going to be standards and codes applicable for run time and on-site storage. If I have a natural gas line break because of saving earthquake, national disaster or even construction activities and I lose my power source, what can I do about a backup or on-site fuel? Now, maybe it’s propane. The takeaway I have in this bottom image is that keep in mind your generator, regardless of natural gas or diesel, fuel oil, might actually share some of that with boilers, for example.
So, when you’re citing your run time and calculating your volumes, it’s not just the generator you need to be concerned about, you might also have to take into account mechanical systems. Now, when we’re loading, you’ve heard the term 30% minimum, right? And that’s something that, as David mentioned NFPA 110 says comply with manufacturers’ testing. So, we look at, are we’re getting enough load? And we’ll talk about load banks on the slide here. But from a minimum size, I want to make sure that anything that has to be on in say 10 seconds is going to be able to fit on the smallest genset. So, I’m going to size if I’m doing parallel gensets the smallest one, any one of them, to make a point, to handle all of the 10 second load that can include medical, air and back pumps and the elevators use for fire rescue, fire pumps, critical transfer switches, et cetera.
So, you want to make sure you’re taking that sizing into consideration. And if you have a lot of extra capacity, because you’re doing parallel gensets, if you want to back feed normal, A, take into consideration that you might have an Environmental Protection Agency tier four situation on your hands, if the client wants to use that for load shedding or peak shaving, if they’re going to receive financial incentives from the utility, that’s usually what’s going to trigger NFPA, sorry, tier four. And whatever your strategy for back feeding normal, ensure that the facility actually understands how that system works and that they feel comfortable using it.
Now, if we’re going to do supplemental generator connections, i.e., an external load bank or an external generator connection, like you see images in the bottom left, it can look at a variety of ways. And one of which is you could actually put a transfer switch that allows for those external connections to be either attempt genset or a load bank. Now, David, what are your concerns associated with using equipment like this?
David Stymiest: The only concerns I would have of an equipment like this requires basically human action. And it generally occurs at a time when there is an emergency in place at the health care facility. Several years ago, during one of the major natural disasters that was affecting the Eastern Seaboard. There were health care facilities that had a range for portable generators and the portable generators arrived. And the staff has never really trained on what to do and connect them and to get them operating properly, as a result, there was a delay in getting backup power to those particular facilities. It’s really important anytime you have human interaction that needs to occur, it’s really important to make sure that the people who have to do the work are able to do the work at the instance they need to do the work. Back to you Rich.
Richard Vedvik: I agree 100% and that also relates to onboard versus just traditional external paralleling gear. Your staff might be very comfortable with external paralleling gear and the big sections, but now they might want to save some space and move to onboard paralleling. Well, that’s what’s the controllers themselves to have the logic on the gensets and maybe that’s not where they want to stand or where they’re used to standing to operate systems. So, you might need an alternate display or a copy of the engine generator controller inside a location, like I show on the bottom right.
Just because we’re doing onboard paralleling doesn’t necessarily mean that we’re going to eliminate all of the gear and eliminate a whole electrical room. It just means we’re shifting some of that location and how big some of that gear is. I love transfer switches. They were one of my favorite parts of the whole system. They are what define each of those individual branches and they do a lot of work, but there’s a lot of options. One of the things I’d like to discuss with you is planning for space.
Bypass isolation adds a lot of physical space into that electrical room. It sometimes doubles the size of the switch. So, in your sizing of space, whether or not the client says, “I’m on the fence on bypass isolation and close transition,” at least think about what is your worst-case footprint and realize they might change their opinion later. I like bypass isolation for the reliability of maintenance and not losing the load. Same thing for closed transition. I like it for basically transferring from emergency back to normal and not having a blip that drops every computer.
Is that a problem for a hospital? What about when motor overloads trip out, because with that few cycles of difference that an open switch has, comes in at a different phase. Maybe it doesn’t do it all the time, but doing it a couple of times might be enough of a reason to move to closed transition. A three-pole versus four-pole conversation could happen over an hour. The takeaway is, if you’re going to go into a remodel scenario, pay very close attention to what’s already there and make sure that you vet that system to ensure what’s separately derived and what’s not. And do I have any accidental or intentional ties between neutrals in the same system? This relates also to N plus one, if I’m going to have one big critical transfer switch and that one switch fails or hangs up, I’ve lost the whole facility.
We’ll talk about category one and two and alternate sources and a little bit here, but the more switches I have, the more load shedding capability I have on the equipment side and that’s going to be cabling as well. Now, EPSS or transfer switches have a variety of cabling requirements to them. Now keep in mind 2017 NEC says that we now have to monitor the integrity of a start conductors and doing that might actually add a third conductor. So, if you’re complying with 2017 NEC because maybe you have multiple things to comply with not just CMS, but maybe also a local jurisdiction and they want to see that third conductor, you have to plan for it as well as any fire rating or two-hour rated protection that those conductors might have.
There’s a variety of communication protocols. We might want switch position and source availability both at a piece of paralleling gear. If you’re going to do load shed through transfer inhibit, that’s also additional conductors. An elevated pre-signal requires that you actually have cables that connect the ATS to the elevator, sometimes that gets missed. Now, David, how do you feel about the future of using the internet to connect transfer switches to a facility for annunciation?
David Stymiest: With respect to annunciation locally and annunciation outside the facility, unfortunately, for those who basically fall under the CMS requirements at this point that would be 2012 codes, which have invoked the 2010 edition of 110. The 2010 edition does not presently allow this sort of transmission, this sort of connectivity or the emergency power supply section. The good news is moving forward is the 2013 edition does. So as soon as CMS adopts a future edition, future being anything newer than the 2012 life safety code, then we’ll be able to use the edition of 110 that also has this this type communication back and forth.
Richard Vedvik: I am going to bring up something that I’m personally concerned about. And that is how arc energy reduction systems can have a negative impact on selective coordination. If we look at this graph on the right here, if that far breaker to the right has arc energy reduction and you see that bottom instantaneous tail, when I crank it down, when I flip that maintenance switch and that tail goes all the way to the left and starts to class with the downstream breakers. I’ve essentially lost coordination in instantaneous range. Now that matters to me in certain health care applications. Does it matter that I lose selective coordination? I like coordination in general.
So, a maintenance mode switch that gets turned on, what if it gets left on? Does anybody know that that got left on? If I have zone selective interlocking or ZSI and is that sufficient? Because that’s actually capable. It’s one of the required ways that you can meet the arc energy reduction because you’re coordinating your breakers not through the trip settings, but through a timing signal. And that applies for only the breakers and ZSI, not the big molded case breakers that might be downstream.
So, I want the take away here, for engineers, when you’re applying codes, you’re still looking holistically and trying to build the most redundant and reliable system that you possibly can. Now, speaking of redundancy and reliably, David, I think you’ve got something to say about common mode failures.
David Stymiest: I surely do. I’ve been in this business more than 45 years. And part of my experience is that I have been the hospital engineer, working within health care facility. And I’ve seen both in my own hospitals and as a consultant that there are common mode failure vulnerabilities. What do I mean by common mode failure? Basically, think of the thing of it this way, any part of … let’s talk about the emergency electrical system, any part of the essential electrical system, as an example, using the code phrase that where you’ve got redundant equipment in the same space, say for example, two critical branch transfer switches that feed different critical branch loads, that are in the loads themselves are considered to be redundant to one another. The switches are redundant to one another.
And let’s say for argument’s sake that they’re in this same room, something happens in that room. In that case, the two redundant switches are gone. It doesn’t really matter that you have two redundant switches. Let’s talk about multiple generators being fueled by the same fuel source or the same fuel pump control. In those cases, and this is not an uncommon situation, this is actually probably one of the more common design practices in America. And in cases like this, you may well have two different fuel pumps, but if the two fuel pumps are on the same skin and get their power from the same control panel, which you may well get its power from the same branch circuit, then you have the potential for common mode failure.
Talk about different subsystem. Let’s say your subsystem is for example, a critical branch or to be a little bit more precise, you have a riser or a couple of risers coming out of a distribution panel or they’re downstairs. If you lose the distribution panel, you’ve lost both risers, even though the two risers may well have been intended to be redundant to one another, same thing with parallel and switch gear. You have four generators all tied into the same parallel and you switch gear, in cases like this … and again, this is the most common design thing in America, are having this sort of situation. In a case like that, the … let’s say the paralleling switchgear fail, it’s rare, but it can happen and sometimes it does happen. In those particular situations is the potential for common mode failure. So, what do we do? How do we deal with those issues?
Richard Vedvik: Well, that’s a good point. When we look at how do we break apart these systems that are so commonly located in a single room? One idea might be to take that double energy unit substation that we’ve always considered to be the best option and break that into a main tie, tie main arrangement and put them in two physically different rooms. Are we giving up some space in the facility? Yes, but are we gaining resiliency? Also, yes. If you have a really small facility and you have a single 150 kW genset, code says, “You know what? You can use just one switch.” Now, does that make sense? It depends on the application. It depends, that’s the answer, right? We have to know whether or not we’re going to sacrifice that kind of redundancy, right David?
David Stymiest: Yes, sir. It really does.
Let’s talk about contingency planning and this before. So, any piece of equipment can fail and the piece of equipment that fails might be one with common mode failure potential, whether the failure is a generator or a lineup of paralleling switch gear, which may well cause the inability that takes the power that’s coming out of multiple generators until that particular issue is solved. Over the years, I’ve heard a number of people say, “I don’t care about the normal power because I’ve got a generator.” Well, the fact is that whether you have a generator or not, whether you have emergency power to a transfer switch or not, the transfer switch has to operate properly when it’s required to or as long as it’s required to.
It’s like any part of emergency power, whether the transfer system feeds the critical branch or the life safety branch or the equipment branch or in the smaller facility a branch which might be more than one of those three types of loads. In those cases, any switch can fail, any transfer switch can fail. Any transfer switch, any one of those three branches, you’ve got no power coming into it and you’ve got some form of emergency power coming into it. And as long as the transfer switch works, then it will deliver power to the wiring that’s on the load side. What if the wiring on the load side fails? It can happen. It’s rare, but it can happen. Very frequently, we have multiple generators and the multiple generators are generally all in a similar room, they’re all indoors.
I’ve seen these rooms are gorgeous. I mean, I’m an engineer, I could say that. But what happens if the generator room becomes untenable or if you have, say, 12 or 15 or 30 transfer switches in a transfer switch room and the room becomes untenable or the distribution pathway itself, whether the distribution pathway is from a generator to a paralleling gear, from a paralleling gear upstairs in a high-rise building, from a transfer switch up to the distribution panel? Any one of those distribution pathways can fail. And with that all in mind, there’s a lot. But basically, those are the things that need to be taken into account.
Richard Vedvik: That’s right, David. I mean, when I look at these images here, I have to ask myself and ask my client, “Where do you want resiliency?” Sure, NEC and NFPA 99 are going to talk about critical care, general care, but that doesn’t apply to all facilities. And as David mentioned, we can have all kinds of failures. We can have islanding problems in which we actually lose connection to the entire facility and that could be an entire discussion in itself. When we do branch circuit redundancy, I’ll ask my clients, “Here’s the list of all the departments in your facility, maybe there’s more or less, what outage can you tolerate? A second, 10 seconds, an hour or even a day? Do we want critical switch one and critical switch two to serve that same space? What kind of outages can we tolerate?” And that’s going to directly tell me, here’s the amount of resiliency and redundancy I need to build in.
For example, a lab doesn’t have to meet the patient space requirements of normal and critical. But if you ask the lab, “Hey, can I shut down power for an hour?” They’re going to say no. In which case, the outage they can tolerate is moving a plug from outlet A to outlet B on a separate branch. And all of that comes back to how do we mitigate this? I mean, the image on the right is what it looks like to pull wire inside of a conduit at 400 amps per phase. So, if an engineer says, “I would like an internet breaker in that existing critical distribution panel,” what does that physically mean to the facility? What are the outages?
I want us to get away from just showing dash lines and actually having outage mitigation plans. How long is this going last? And what impact does that have on the facility? What does that have on the department? Is that serving an ICU wing? Can that ICU wing go down for two, three hours? The answer is probably no. So, if you need to plan a relocation of patients or if you’re going to shut down the elevators for a couple of hours and those elevators need to take patients to the [inaudible 00:47:05], what are the contingency plans? You have to have those talks with your own ahead of time.
And lastly, we can’t have a slide in 2020 alone without talking about the impacts of COVID-19. And what I’d like to say briefly is that what we’re seeing as owners ask for resiliency and flexibility in the acuity of their patients to say, “I would like more negative pressure room.” Well, if we’re going to do that, should we also electrically be saying, “I want any room to be defined as critical care.” Even if most of the wing is general care, should I design any room to be an ICU? That’s going to affect our transformer loading and therefore it’s going to affect our electrical room sizing, right David? What do you have to say about any of the future impacts that you see?
David Stymiest: One of the biggest things that I’m going to say moving forward is that I think we’re going to see more technology connected to emergency power, not because the codes say to do it. I think we’re going to see more islanding moving forward, simply because health care systems may well be looking at this as a business decision.