Underfloor Heating

Thermostats - vs - Continuous Control

Thermostats are On/Off control devices; - when they get too cold, they turn On - when they get too hot, they turn Off

As a result, the room or medium controlled by the thermostat will always be too hot, or too cold, and the temperature will cycle about this point.

on/off control

Continuous control is a process used in smartModules where the temperature is measured using a sensor, and compared against a required temperature electronically. A complex algorithm, using Fuzzy Logic, calculates the precise amount of heat needed to keep the temperature at the required value. By controlling the position or duration of opening of a valve, we can modulate the amount of heat sent to the heat emitter (e.g. radiator or the underfloor loop)

continuous control

Conventionally, wet Underfloor Heating consists of loops of plastic pipe buried in the floor, fed by distribution manifolds which are connected to the primary heating pipes.

underfloor heating manifold

At each manifold, thermo-electric actuators, switched by wall-mounted thermostats, allow water to flow in each loop. As the room temperature drops, the thermostat “makes” its electrical contact, and the valve allows flow to the floor. As the temperature rises, the thermostat “breaks”, and the valve closes, shutting off the flow to the floor. Timed operation of the system is normally achieved by isolating the whole manifold using a Zone Valve driven by a timeclock.

This approach is far from perfect.

- Thermostats result in temperature cycling around the desired temperature (see inset) which is more pronounced with underfloor heating, because of the large thermal mass of the floor

- Manifolds, zone valves, timeclocks and other boiler loads (e.g. Domestic Hot Water) need to be hardwire-linked together to make sure everything works when it should - this can get complicated and rarely works well.

thimble sensor

The smartkontrols approach allows the Thermo-electric actuators supplied by the Underfloor Heating manufacturer to be retained. Thermostats, timeclocks and wiring centres can be deleted, and replaced by discrete temperature sensors (called Thimble Sensors - see user interface section) for wall mounting, and a small “smartBox” control panel mounted next to the manifold.

Key Benefits:
- Temperature regulation is much more accurate (see inset)
- The manufacturer’s control valves can be retained, but controlled in a continuous rather than on/off manner
- Control of the manifold water temperature, and control of the manifold pump can be via another smartModule.
- The manifold zone valve is no longer needed, as the Thermo-electric actuators now act as time and temperature controls
- Each room can be controlled individually for timed operation and temperature, from the wall (using a Zone Controller or Touchscreen),or from a PC.
- The associated pumps and boilers are controlled by other smartModules, and run only when needed.
- Floors with a stone finish can be kept warm using a floor sensor (see sensor section)

For Electric Underfloor heating systems, the manifold controller is simply replaced by a smart module switching a noiseless Solid-State switching device. This modulates the power to the heating element laid in the floor.

It is essential in most cases for floor sensors (see sensor section) to be fitted to every floor zone, in addition to the air sensor. Unlike wet heating, where the temperature of the water is carefully controlled, and hence it is impossible to generate dangerous surface temperatures, electric heating elements can cause the floor to become uncomfortably warm. Using floor sensors, we can set both minimum and maximum temperatures for the floor.