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underfloor heating problems

Like any heating system, there may be times when your underfloor heating (UFH) does not seem to be working as it should.

Nu-Heat can help you find the root cause of your underfloor heating problems – whether the cause is electrical or down to a failed thermostat or manifold part – we’ll help you get the system up and running again.

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First, let’s look at a few of the potential underfloor heating problems that you may come across with water UFH, and how to go about solving them.

Warm Water Underfloor Heating Problems

Single Zone is Not Heating Up

If a single zone is not heating up as expected, or won’t turn off at all, it could be caused by a number of underfloor heating problems. Most are fairly simple to resolve by yourself:

Underfloor Heating Actuator Problems

  • Sticky pin valve underneath an actuator

    There is a small pin underneath each actuator. You need to remove the actuator from the affected zone to check that the pin valve is free. If the actuator is stuck down, it can be freed using a silicone spray. You can also use a pair of long nose pliers to try and free the pin.

  • Actuator has failed completely

    If an actuator has failed, this is most likely due to an electrical issue that could relate to the thermostat or wiring board. It’s best to consult a qualified electrician to check the circuits. A faulty actuator can also cause underfloor heating that won’t turn off and stays on constantly.

Underfloor Heating Thermostat Problems

  • Faulty thermostat or low battery

    You can easily reset a thermostat by following the user guide provided. If your system uses wireless, battery-powered thermostats then it’s also a good idea to check the batteries. If neither of these works, it could potentially be an electrical fault, so a qualified electrician should be called. A faulty thermostat can also cause underfloor heating to be permanently switched on.

  • Thermostat not set up correctly (E1 & E2 errors)

    Most thermostat errors will be displayed on the face of the stat. Simply reset the thermostat following the user guide to clear the error. We’ve produced some setup videos to help you with this process for the neoStat and PbS.

How to remove E1 & E2 error codes from the Nu-Heat neoStat

How to remove error codes from Nu-Heat’s PbS thermostat

Problems with Other Underfloor Heating Parts

  • Air bubble or airlock in UFH loop

    There could be some air trapped in the UFH pipework. In order to remove the air you will need to:

  1. Isolate all of the UFH zones except for the zone that is not heating up
  2. Remove the actuator
  3. Connect a hosepipe to the flow valve on the manifold and connect to a cold mains tap
  4. Connect a hose to the drain off point on the manifold and take out to waste
  5. Turn the cold tap on, open both the taps, drain off point and the flow point and flush the water through that zone

Once the air bubbles have been removed, you can then turn off the valves and the cold tap and disconnect the hose. A qualified plumber is best to carry out this task.

Multiple Zones or Entire System is Not Heating Up

Another underfloor heating problem you may encounter is the system not heating up as it should. This could affect multiple zones or the entire system. There are a few reasons why this may be happening:

  • Circulation pump failure

    The circulation pump may have failed. This is an electrical issue, so it is best to consult a qualified electrician.

  • Pump relay on wiring boards

    This is another electrical issue that ought to be checked by a qualified electrician.

  • Isolation valves closed on the manifold

    The isolation valve lever should be in line with the pipework on the manifold, in the open position. If an isolation valve is closed, it will be at 90 degrees on the pipework.

  • Blending valve pin stuck

    To resolve this issue you should remove the white thermostatic valve head and check that the pin valve is not stuck. If it’s stuck down it can be freed using a silicone spray. You can also use a pair of long nose pliers to try and free the pin before replacing the thermostatic head.

  • Boiler not firing (no signal)

    In this situation you will need to consult a qualified electrician who will check the wiring board connections and relays.

  • No power to the wiring boards

    Check that the main isolating switch supply is switched on. If it is off, call a qualified electrician.

Pump is Running All the Time or Won’t Turn Off

If you come across this underfloor heating problem, it could be because:

  • The pump relay is stuck on the wiring board

    Again, this is an electrical issue and so a qualified electrician should be called.

  • Faulty thermostat or low battery

    As mentioned earlier, you can easily reset a thermostat by following the user guide. It’s also a good idea to check batteries if the system uses a wireless, battery-powered thermostat.

  • Faulty or failed actuator

    If an actuator has failed, this is most likely due to an electrical issue that could relate to a thermostat or wiring board. You should consult a qualified electrician.

underfloor heating problems

Rise in Underfloor Heating System Pressure (Pressure Testing)

There are a few potential underfloor heating problems, which can be identified by pressure testing, that could be causing the system to rise in pressure:

  • The filling loop has been left on or is letting by

    Check that the valves at either end of the flexible hose are closed, and disconnect the filling loop.

  • There is a restriction in the UFH pipework

    If pressure stays high during pressure testing, even when the system is off, then pipework restriction is unlikely to be the cause. However, if the pressure varies by changing the pump speed (or switching the pump off) then there is likely to be a restriction – either a blockage or air locks. It’s important to note that if the pump is plumbed in close to the value, there will be an initial pressure rise or drop on start up.

  • Expansion vessel failed (diaphragm damaged)

    To test if this is the case, depress the needle in the Schrader valve on the underside of the expansion vessel. If water escapes, the diaphragm within the vessel will have ruptured and the whole vessel will need replacing.

    Alternatively, the diaphragm may be empty of air, meaning there is no room for the water to expand as it heats, resulting in increasing pressure. Relieve some of the water pressure via the pressure relief valve, then connect a foot pump to the vessel’s Schrader valve, pumping it up to 2 bar. Refill the water side up to normal working pressure.

Pressure Drop on System (Boiler Locks Out on Low Pressure)

Rather than a rise in pressure, you may find that the system is losing pressure. There are a few ways that you can identify what is causing this:

  1. Check over the system for any leaks on pipework, manifolds and cylinder. This includes a quick look over the pressure relief valve, automatic air vent and expansion vessel.
  2. Re-pressurise the system (refer to manual for more information on pressure testing underfloor heating) and isolate all manifolds. Check which side on the manifold drops in pressure. This will help you to identify where the leak is.
  3. Check the temperature/pressure relief vale is not letting by to waste.
  4. Check that the expansion vessel on boiler side is not letting by.
  5. Check that the boiler blow off valve is not letting by.

All of the above should be carried out by a qualified plumber.

Electric Underfloor Heating Problems

Running into electric underfloor heating problems? Many of the above solutions apply to both water and electric systems – such as a faulty thermostat or electrical wiring problems. However, here are some troubleshooting tips specific to electric UFH.

  • Electric underfloor heating won’t turn off OR Electric underfloor heating isn’t warming up

    The underfloor heating problem could could be down to a thermostat or wiring problem – check our thermostat tips or our user manual section. You should also check whether the floor probe/sensor hasn’t failed, and is connected to the thermostat correctly.

    If the thermostat and temperature probe seems fine, you may need an electrician to come and check the system.

  • Floor isn’t getting up to the desired temperature

    If your electric underfloor heating isn’t warm enough, you may need to adjust your thermostat settings or check the system’s power output. This could also be down to the insulation in your home – check this before installation.

  • I’ve damaged or cut an electrical heating cable

    You can buy an underfloor heating cable repair kit, but this work should be carried out by a qualified electrician. Call us on 01404 540650 and our experts will be able to advise what to do.

  • Electric heating is more expensive than I expected

    Electric underfloor heating is more costly than water underfloor heating systems – which is why we recommend it for smaller rooms and not whole-house installation.

    If you’re using more electricity than estimated, try different thermostat or programme settings. Insulation, lifestyle, and air flow around the area can also all have an effect.

  • I’ve installed my electric underfloor heating wrong

    Although electric underfloor heating systems are simple to install, things can go wrong during installation. If you have any questions or concerns, just give us a ring!

If you are troubleshooting a Nu-Heat UFH system, or you are still encountering underfloor heating problems after reading this guide, then you can always call our knowledgeable Technical Team on 01404 540650.

More about Jon Terry

As the Technical Service Manager at Nu-Heat, I am proud to support our customers through the life of their systems and to help customers with solutions to help them heat their homes in a better way.

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