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Like any heating system, there may be times when the underfloor heating (UFH) doesn’t seem to be working as it should. Nu-Heat’s Technical Team helps you to find the root of the problem, whether electrical or down to a failed part, to get the system up and running again.

Let’s take a look at a few of the potential problems you may come across with UFH and how to go about solving them.

Underfloor heating single zone not heating up

If a single zone is not heating up as expected, it could be caused by a number of small problems that are all fairly simple to resolve:

  • A 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 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.
  • Actuator failed
    If an actuator has failed, this is most likely due to an electrical issue that could relate to a thermostat or wiring board. It’s best to consult a qualified electrician to check the circuits.
    A faulty actuator can also cause the UFH to be permanently switched on.
  • Faulty thermostat
    You can easily reset a thermostat by following the user guide. If the system uses wireless, battery-powered thermostats then it’s also a good idea to check the batteries. If neither of these options works, it could potentially be an electrical fault so a qualified electrician should be called.
    A faulty thermostat can also cause the UFH to be permanently switched on.

  • Air 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.

  • Wiring issue: faulty connection – dry joint
    This could be to do with an actuator, thermostat or wiring board. As an electrical issue it is best to contact a qualified electrician to resolve the problem.
  • Thermostat not set up correctly (E1 and 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 videos to help you with this process for the neoStat and PbS – click here to view.
  • Flow gauges not opened up correctly on manifold
    You will need to adjust the flow rates on the manifold. To do this, refer to the UFH manual for the system as manifolds can vary.

Underfloor heating multiple zones/entire system is not heating up

You may also find that multiple zones or an entire UFH system is not heating up as it should. 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.

The underfloor heating pump is running all the time

If you come across this issue, 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
    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 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.

Rise in pressure on the system

There are a few potential issues 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 pipework
    If the pressure remains high 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 to be replaced. Alternatively, the diaphragm may just 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 and then connect a foot pump to the vessel’s Schrader valve, pumping it up to 2 bar. Re-fill the water side up to normal working pressure.

Pressure loss 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) 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.

If you are trouble-shooting a Nu-Heat UFH system, you can always call our Technical Team on 01404 540650.

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