IN-91-10-3 -- An Experimental Study of the Control of Radiant Floor Heating Systems - Proportional Flux Modulation vs. Outdoor Reset Control with Indoor Temperature Offset PDF

Notes that general understanding that floor heating supply water temperature should be varied in accordance with outdoor temperature due to the time lag between thermostat demand and heat delivery to the space. However notes the recent concept of proportional flux modulation, with flux, not the temperature being controlled, because the rate at which energy enters the slab is correlated with the supply/return water temperature difference, not with the supply water temperature. States that to evaluate these issues, two identical thermal test chambers were constructed and separate control systems installed in each chamber. Comparative analysis was then conducted through physical experiments in a laboratory setting. States the results show that both control systems are competitive in maintaining stable indoor temperatures. Proportional flux modulation shows faster response to certain thermal transients than does outdoor reset control with indoor temperature offset.

KEYWORDS: Floor heating, radiant heating, experiment, laboratory testing, controls, water temperature, water flow, supply temperature, outdoor temperature, temperature difference