Temperance? I Thought I Was Being Careful

When you start a geothermal design you have to think about what could happen because if you don’t you’ll end up undersized and then you’ll have a facility manager on the phone saying their loop temperature dropped below freezing and the compressors are locking out and honestly who could blame them because nobody wants to sit in a cold building, so you just have to start with what the calculations say, sure, but then you add some boreholes, because soils vary and thermal conductivity reports aren’t perfect, and even if they’re close, what if there’s groundwater flow that nobody detected because sometimes the test borings miss things, and then you add a few more because what if the building load grows, it happens all the time, they say it won’t but they always add another wing or server room or a commercial kitchen because people change their minds, and you can’t just drill new boreholes once the landscaping’s in, it’s too late then, so it’s better to add the extras now and maybe add a little more after that just to be sure, and once you’re thinking like that it’s really hard to stop because every what-if is just another borehole waiting to be drilled.

And pumps, you can’t just put in one pump even if that’s what the schedule says because pumps fail, everybody knows that, seals leak, motors burn out, and if you only have one you’re basically asking for it to fail the second the building hits peak load, so you need a backup, that’s obvious, but what if the backup pump also fails because what if they both got installed at the same time and they both wear out at the same rate, it happens, equipment doesn’t know how to stagger its failures just because you designed it that way, so it’s probably safest to have three pumps, maybe four if you can fit them, because you don’t want to be the reason people are freezing, and it’s not like pumps take up that much room compared to the cost of a lawsuit, and once you think about it that way it just makes sense.

And heat pumps too, you can’t size to actual peak demand because what if the peak is wrong, what if the utility power drops and the voltage sag makes the compressors trip and now you have to run partial loads for hours or days and then the heat pump staging gets all messed up and you’re trying to re-balance a system that was already stretched too thin, so if one 10-ton unit covers the load on paper you probably need at least a 15-ton, maybe two 10s running side-by-side because redundancy is better even if it’s not strictly needed, because it will be needed when things go wrong, and things always go wrong, and the bigger question is just how prepared you want to be when they do.

And I know controls are supposed to manage all this but controls fail too, you can have the best BAS in the world and it only takes one failed sensor to throw the whole loop staging into chaos, especially if nobody’s watching it, and people don’t monitor systems like they say they will, they lose passwords or reboot panels without thinking or shut off alarms because they’re annoying, so you have to assume the controls will fail, and then you have to ask yourself what happens if they fail, and if the answer is “the building freezes” then you didn’t design enough backup and you probably need local manual overrides and local alarms and maybe even handwritten cheat sheets laminated and hung in the mechanical room just in case nobody remembers how anything works when things go sideways because that’s usually when they call you, and I don’t like getting those calls.

So I always make sure every project has the essentials covered, at a minimum, because you just have to be smart about it:

• Primary circulation pump
• Backup pump for the primary pump
• Backup pump for the backup pump (because two pumps can fail, it’s happened)
• Manual bypass for the automatic manual bypass (just in case the automatic fails automatically)
• Backup glycol monitoring station (because if the first backup misses something then what)

I mean that’s just common sense, right? It’s not overkill, it’s just careful planning, because you can’t predict everything and when you really think about it it’s almost irresponsible not to add the extra safety measures, and anyway once you’re thinking about it, it’s too late to pretend you didn’t think about it, so you might as well plan for it because otherwise what happens when someone needs heat and you didn’t give them enough, I mean honestly, what would you do?

Because it’s not really about temperance when you think about it, it’s about making sure the building doesn’t freeze and the lawyers don’t call and the facilities director doesn’t put your drawings up on a projector screen and point at them in a meeting while everyone stares at you, and maybe people say it’s too much, maybe they say it’s excessive, maybe they say, “Cassidy, this is not what we asked for,” but at least they’ll never say, “Cassidy didn’t think ahead,” because I do think ahead, I think ahead a lot, I think ahead all the time.
 

I mean that’s right, isn’t it?
 

Isn’t it?
 

Please tell me that’s right.

About the Author

Cassidy Redundra, C.E.P (Certified Emergency Planner)

Junior Engineer, SafeSide Engineering 

Motto: “If it never fails, I still planned for it.”

Fun Fact: Once included so many backups in a pump schedule, the contractor thought it was a prank and called to ask, “No, seriously—which ones do we actually install?”