A common approach to the control of radiant slab heating systems is outdoor reset with zoning. In this approach, the building loop is supplied with water at a temperature proportional to outdoor temperature, while control is refined within each zone by one of three algorithms - by inhibiting circulation to the zone when demand is met or by modifying the local reset slope or its offset in proportion to temperature within each zone. These three refinements to outdoor reset control are analysed and simulated. Only a slight improvement in step or sinusoidal response is projected by inhibiting circulation upon overheating. Modulating the reset slope or offset in proportion to zone temperature improves tracking but can induce instability.

KEYWORDS: radiant heating, controls, slabs, outdoor temperature, zones, algorithms, circulating, inhibitors, automatic, weather compensated controls