Q. You have mentioned that traditional pumped glycol energy recovery systems were your least favorite choice for air-to-air energy recovery. What are the reasons for that?
A. It starts with efficiencies. Pumped Glycol systems in this country, until the recent introduction of Konvekta, have provided the lowest efficiencies for all choices. The best we could expect from a system would be 45%. After subtracting pumping cost, the efficiencies would drop below 40%. And that’s the best we could get. That’s not good compared to 60 to 75% for other types of air-to-air energy recovery (wheels, plates & heat pipes).
Traditional pumped glycol energy recovery systems have also been the most maintenance intensive choice.
Other common causes for poor performance:
- Design Issues
- System is designed for a degree day that never happens
- Supply and exhaust coil design doesn’t match
- Single speed pumping system doesn’t match VAV airflow
- No glycol expansion tank in the system
- No Deaerator or malfunctioning deaerator
- Operating Issues
- Air volumes don’t match design
- Running the pump in the ‘dead window’ of temperatures
- Picking wrong design point to shut system down – can result in overheating the supply air
- No system performance verification
- Maintenance Issues
- Dirty Coils
- Air in glycol loop
So why do we use pumped glycol loops? They my be the most inefficient but are also the most flexible. When supply and exhaust air streams can’t be run side by side pumped glycol systems are the only choice. That’s the big reason why they are used. Most of the pumped glycol run around loops that we have designed over the past 20 years have supplied marginal performance, but it was the best we could get. Today we use Konvekta systems which provide efficiencies comparable to other devices but also provide system flexibility.
For more information on pumped glycol systems, askRick?
Looking for better solutions for pumped glycol; read these Blog Posts:
Pumped Glycol Energy Recovery | What’s so special about Konvekta?
Pumped Glycol Energy Recovery | Konvekta High Performance Heat Exchanger Coil