It’s all my fault……..

The fun thing about being the chief engineer at work is that bad designs by professional engineers for projects that were put in well before my time in the Captain’s chair are somehow my fault.

Friday was a 17 hour day and Saturday was a 6 hour day dealing with the A/C for a freezer room that hadn’t been designed correctly from the start, had absolutely no redundancy, and had been packed with more biological -80 freezers than it was designed to accommodate.

Had to bring in 70 kW of emergency cooling to deal with the room. This emergency cooling was comprised of four 17.5 kW water cooled A/C units.

Water hoses all over the place distributing city water to the A/C units to cool the compressors in the A/C units with the warm water going down the drain.

Had to get electrical in to install four 208 volt 3 phase plugs for the A/C units.

These units got the room under control and are cycling on and off which means that they have ample cooling capacity. More than the four 12.5 kW split A/C units that are in the room.

When sizing mechanical refrigeration for an area, if the unit is running 100% of the time and it can barely maintain its set point, the unit is grossly undersized. If the unit only comes on for 5 minutes and shuts off again, the unit is grossly oversized. For a simple reciprocating compressor with no capacity control a 20 minute run cycle with 10 to 15 minutes off between runs is about right.

So, tomorrow I gotta propose a solution for this.

Most of the system I’ll design.

I’ll propose using either four water cooled 17.5 kW units or four water cooled 35 kW units. Four 35 kW units would give the best option for redundancy. If I can get them to spring for four 35kW units, then I can have N+1 redundancy with the ability to do Lead / Lag alternating with extra capacity for out-of-the-ordinary extreme days.

I’d have to get the appropriate fluid coolers for this setup. Again, nothing too fancy, just some adiabatic coolers. I could also get some air coils put into the air handler for the Emergency Department or the 2 East unit so that the heat from the freezer room could be used to pre-heat the fresh air in the cool weather thus reducing our steam bills for these two air handlers. When pre-heat isn’t required for the Emergency Department or the 2 East unit the adiabatic cooler would just reject the heat to the atmosphere.

Pipes would have to be installed up the side of the building, but they’re tearing the place down in about 6 years, so………. And I’ve always been a function over form type of guy. And it’s not like they’d look horrible. Probably be a pair of 76mm pipes.

So, we’ll see what I’m up for tomorrow when I get in to work.