THIS IMPORTANT ASPECT of an operating Hospital – Manufacturing Plant – Municipal Building – Services Building and many others to numerous to list, the failure of the emergency system can be catastrophic to say the least. Why are we hearing so many cases of system failures?

The answer appears to be somewhat complex, starting with incomplete written operational sequence for the entire complex. Who’s to blame? No one! It’s the lack of communication between a lot of disciplines and each paying attention to their own bailey wick without much worry about an emergency power outage.

Let’s take the following scenario. The building has three – 1500 kilowatt diesel generators. Calculations show that two of these units will handle the expected load and one unit would be on stand by. In a power outage, as designed, which ever unit started first and came up to the proper voltage, would go on line, The second unit would then synchronize with the first operating unit and share the load while the third would be in a stand by mode and time out if not required.

All of this sounds pretty good and calculates out on paper. Dose it happen this way? Not quite. So-called critical loads (many air conditioning units – 12 elevators – booster pump etc.) were added to the 10second on line requirement, in all about 9 hundred horsepower. The first unit couldn’t handle the starting load and the second unit couldn’t synchronize with it due to the overload. Bang go! Two main breakers popped, shutting down the entire system.

I was glad I wrote about this possibility prior to the happening, to the architect, owner and involved engineers. I would never use the phase, I told you so. However, I’ve been tempted.

Some designers feel the overall operation of equipment is a contractors problem, and if they layout starting sequences they are taking on more responsibility than they should. Having worked as a startup and run electrician (as we used to be called), I had the privilege of working with some old time engineers and cotton gins, creameries, sawmills and the like, that had large motors and heavy machinery to start. In the days prior to sophisticated starters we used oil filled dashpots to control inrush currents and sequencing of heavy equipment motors.

What I am leading up to is, the basics are still the same and the electronic controls of today give us a great deal of flexible means to control timing of building equipment.

Let’s start with the basics for a hospital system with multiple emergency generators that normally come on line in 3 to 5 seconds.

First, loads that should be on within 10 seconds: Emergency lighting – All safety alarm systems – communication systems – uninterruptible power.

Next, 10 to 20 seconds: elevators, if in groups (50 to 75 horsepower each) allow 3 seconds between units and groups. All elevators would return to the first floor, doors lock open, and one of each group operates by key.

Next (third) 20 to 120 seconds: air condition units serving communicable disease areas, - critical care areas – operating rooms – nurseries – emergency room areas.

All AC units should have supply fans start first and the returns, 3 to 5 seconds later, (assuming these are 40 to 75 horsepower supply and 15 to 30 horsepower return fans). Multiple units should have 5 to 10 seconds between units. I’m sure there are other critical loads that can factor in as needed not mentioned here.

These are only guide lines that I feel will give a good start to the thinking of our design and regulator people to help keep out important buildings on line in cases on emergency operating conditions.

In passing, remember, you can’t start moving a loaded big rig truck with out going through a whole lot of gears, manual or automatic. Our buildings come under that same type of operation getting started after an emergency shut down.