Heat Pumps for RAS: A look at Common Knowledge

Eggs are good for you now! Saturated fats and salt? Make sure you get some in moderation. “Common knowledge” can change without basis in facts. Most of us rely on the media to interpret scientific studies and bring us the practical applications. Problem is, the media gets paid to bend your ear, not to be your health coach.

“Common knowledge” about heat pumps is equally wanting.

Let’s consider the following

• Heat pumps are complicated to build and/or operate and/or maintain and repair

• Heat pumps are expensive

• Heat pumps have low operating costs

• Heat pumps are the greener alternative

1. Is your fridge complicated? How about a cooler? These are both heat pumps. None of us have to go far to find refrigeration these days. Heat pumps should be simple enough to be installed and serviced by any local refrigeration technician.

2. Expensive means “very looong projected ROI.” There are many times where heat pumps do not have the best ROI. Some RAS, for example, will have a far greater cooling load than heating load. Yet a heat pump produces about 5 units of heating for every 4 units of cooling. Where a heat pump can deliver a “no-brainer” ROI is in a RAS that would normally require a heating system and a cooling system of similar magnitudes. To get the best ROI for your application talk to a heat pump designer familiar with RAS applications.

3. To correctly project heat pump operating costs, make sure to look at the entire heating system. Glycol pumps? plate exchanger bio fouling? These are costs too (often avoidable with proper heating/cooling design). Operating costs can be higher than projected because of issues with poor heat recovery, or poor insulation. An emphasis on getting the whole heating system designed and optimized correctly is the only way to get the benefits of low operating cost. Sure a heat pump will cost 50-70% less than other options to operate, but what if you could have had a much smaller heating load by proper heat recovery design? You think that the heat pump delivers the best ROI, but this may only be true because your heat recovery system is grossly inefficient. Find an engineer with expertise in both RAS and heating/cooling to get more holistic approach to heating/cooling system design. Remember to think about costs of bio-fouling. Much money has been burned due to lack of consideration for the effect of bio-fouling on heating/cooling systems.

4. If “going green” is an important criteria, backup. Choosing a heat pump may appear green but it is the last step and NOT the first. Go green is in this order:

A. Process - (RAS efficiency, insulation, heat recovery)

B. Controls - (Keeping #1 operating as designed)

C. Equipment - (If 1 & 2 optimized, heat/cool system is often much smaller to begin with)

Many have fallen into the trap of going one shade of green (environmental) without the other necessary shade (ROI).