Troubleshooting the Underfloor Heating System

• Is there an electrical supply and is it ON?
• Are there any fuses that have blown and need replacing?
• Are any components overloaded?
• Is everything wired correctly?

• Is the boiler/heat source firing?
• Is there a primary pump and is it running? (Manifold pump is only for underfloor loops and not for flow too and from heat source).
• Is primary pipe work from heat source adequately sized?
• Is there a motorized valve for the underfloor circuit and is it open?

• Is the pump running?
• Is the thermostatic valve set at correct temperature: 45°C for screed / 65°C for suspended floors? Temporarily remove thermostat from valve to establish valve opens and lets hot water enter the manifold. Do not leave off as damage could occur to the floor if over heated. If flow gauges are showing circulation there could be a blockage in feed/ return to the manifold.
• Is return valve fully open (bottom right-hand side)? Turn the valve anti-clockwise to open.
• Is by-pass valve only open 2 turns (factory set)?

• Is the pump running? Check the speed.
• Are the flow gauges showing any flow? To open, turn anticlockwise.
• Are the actuators on return bar open (warm to the touch)? If not, check room thermostat is calling for heat or temporally remove actuator to establish flow thru that loop.
• Is there at least 7°C difference between Flow bar temperature and return bar temperature?
• There could be air trapped in the loops, which will require purging. Shut down all but the problem loop to concentrate the pump pressure and force out the air. This will be heard running through the pump and the flow gauge will flutter.

This is when the manifold appears to be functioning correctly and flow rates seem correct but particular rooms do not heat up.

• This invariably means that rooms are not matched with there room thermostat, actuator and loop/s. between the first and second fix the potential for room loops and their thermostats to get mixed up is quite high. The only logical way of sorting this out is from cold. Start with one room at a time, turning on the room thermostat and checking that its floor warms up. This could take an hour before moving to the next room. Clearly mark the loops and actuator/s for future reference.
• Floor covering provides too much thermal resistance to allow heat transfer and therefore output.

These tend to be installation and commissioning problems which are sorted out with good workmanship.

• All pumps will produce low level noise and therefore should not be installed in areas of sensitivity but with careful installation practices can be reduced to a barely audible hum. Try to avoid mounting on a stud wall with only plasterboard walls as this tends to amplify any noise. The use of rubber isolation mountings on brackets etc can help.
• Unless the system has been filled as instructed in the installation manuals the potential for trapped air is quite high. This air passing thru valves and pumps will not only produce noise but also promote corrosion. It is a condition of our guarantee that the system is correctly dosed with inhibitor for both the above reasons. An untreated system will quickly discolour the flow gauge sight glass, these can be easily cleaned by shutting valve (clockwise) and while holding shut undo glass anticlockwise, clean and replace.
• The pump should be set to the lowest speed to achieve the design flow rates; this will save on energy and noise.
• Pumps on the primary side of the system should also be checked to reduce noise at the manifold. It is also recommended to have a primary system by-pass fitted (now included in a lot of current system boilers).

It is very rare to get leaks in an underfloor heating system after the construction process has ended. As there are no joins in the floor most leaks are at the manifold and are generally fixed by tightening. Leaks in pipe work are normally found by a damp patch and repair couplings for 16mm MLC pipe can be purchased from Wundafloor. Do not keep topping up a leaking system for a long period as this reintroduces fresh un-inhibited water and air into the system.