Performance Assessment of a high velocity zoned combination system at the Canadian Centre for Housing Technology

Authors:

J. Sager (NRCan)
M. Armstrong (NRC)
F. Szadkowski (NRCan)

Publication date: May 2013

Zoned high velocity combination systems combine the provision of space heating and domestic hot water heating in one system.  Due to their small equipment footprint, small ductwork and zoned distribution, the systems are a good fit for newer row units, townhomes and multi-unit residential buildings where mechanical system space is limited and maintaining consistent comfort conditions between upper and lower floors is a challenge. 

The high velocity combination system with two zone ductwork tested in this study was a packaged system designed for condensing level performance in space heating.  The top performing configuration B operated in conjunction with a buffer storage tank for domestic hot water production.  It consumed less energy for space and water heating and provided equivalent comfort when compared to the non-zone ducted furnace with condensing level performance and standard non-condensing water heater. 

The zoned high velocity combination system operating in configuration A included an indirect storage tank heated by the tankless water heater either directly or via the space heat return loop.  This system configuration performed with no significant difference from the standard system.

The zoned high velocity combination system was also tested in a non-zoned configuration C, with both zone supply trunk dampers fully open and the main floor thermostat operating only.  While outperforming the standard system with respect to energy consumption, this system performed least effectively with respect to comfort compared to the zoned systems operating in a zoned configuration as it tended to overheat the second floor and underheat the basement when providing space heat to the main floor.

A daytime setback was employed in the zoned house in an effort to explore the potential energy savings and comfort benefits of eliminating heating to unoccupied spaces and focusing delivery to occupied spaces during the day.  This served to eliminate over-heating on the second floor, particularly during days with high solar gains, when compared to the same system operating in the non-zoned configuration, however there was little to no change due to zoning alone when compared to the standard system.  This was likely due to a number of factors including: solar gains during the day contributing to heating on the second floor, continuous air circulation and the fairly large open stairwell between floors allowing heated air to rise to the second floor and mix/transfer heat between zones.

It is likely that several of these same factors that inhibited the energy saving potential of the second floor daytime setback made possible by the zoned systems in space heating mode would serve to highlight the energy saving potential of the zoned systems in space cooling mode (with a second floor daytime setforward).  Additional testing would be needed to confirm this hypothesis. 

For access to the full publication, please contact the CanmetENERGY-Ottawa Business Office.