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Operation & maintenance underfloor heating

A Thermotech underfloor heating system which has been installed according to the drawings and installation guide included in the delivery is basically maintenance-free. 

However, the following control measures should be performed frequently.

General maintenance
The pressure in the heating system should be checked and filled if needed (usually in the beginning of spring/summer). Check that there is no air in the system. Air in the system will jeopardise the circulation.

Possible reasons for air being in the system and the fluid levels being lowered could be:

  • The boiler has reached a too high temperature, i.e. boiled.
  • Leakage in connections or other joints where water could possibly seep out.
  • Natural evaporation of oxygen in the water occurs and for this reason the system may have to be refilled.

Flow and flow temperature during operation should be checked occasionally.

Commissioning
The following precautions must be taken prior to putting the underfloor heating system in to operation:

  • The whole underfloor heating system has to be free from air and the pressure must be tested.
  • The thermostats should be set to on a low indoor temperature, for example 16°C, if the rooms are not heated by other sources, such as fans etc. This is to prevent all thermostats to turn on simultaneously which would put a heavy load on the electrical installation.
  • The temperature of the warm water that circulates in the loops should be low at start-up, approximately 28-30°C. When the concrete slab or wooden flooring and joists are dried (usually takes 17-20 days) the temperature can be set to the operational temperature found in the design plan.
  • Function test of thermostats and actuators should be made to ensure that the right thermostats are connected to the right loop/actuator. The easiest way to test this is by increasing the temperature on a thermostat and see if the corresponding actuator moves, and to do the same thing for all the other thermostats and actuators.

Room regulation
The motors are closed when they are powered off. Therefore, in a cold system, the pin on the valve has to be pressed in to be able to mount the actuator.

On some actuators an adapter has to be mounted between the thermostatic valve and the thermal actuator. Check that the adapter and pin are mounted properly when installing the system, according to the instructions.

The diode on the transformer list will light up when the thermostat calls for heat, i.e. opens the loop. If the diode does not light up, check that the electrical connections have been installed properly.

If the room temperature is generally low, the settings of the heat source should be checked and possibly adjusted. This may happen if some factors have changed since the design phase (other types of flooring etc) or if the heat requirement is higher or lower than anticipated.

If adjusting the settings of the heat source is not enough, a new adjustment has to be made (throttling). Please contact a service technician or the person responsible for the installation to fix this issue.

Suggestions
Establish a protocol (operation journal) and take notes on dates, events and any actions taken to “get to know” the heating system. Archive all the original documents, guidelines and adjustment protocols.

Troubleshooting
Follow these procedures prior to calling for an installer, or together with the installer:

The house is cold (not hot enough)
Check that the heat source and the circulation pump are in operation. Adjust the heat source or circulation pump’s flow and pressure settings so that the performance indicated in the project design plan is achieved.

Waterborne underfloor heating is a low temperature system, and if the control unit works with curve settings, the settings should generally be flat. Incorrect settings may give undesired results.

A steep curve setting can for example cause an uneven or inadequate heating when the outdoor temperature changes quickly.

The thermostat’s uptime is shortened as a high temperature runs through the pipe and a set room temperature is reached too quickly, causing variations.

Individual rooms are too cold (not hot enough)
Check that the electrical connections have been made according to the circuit diagram shown in the product guide.

Also check that the actuator is mounted properly so that the fittings go all the way down. There is a fuse is the thermostat which protects the equipment.

If the thermostat stops working, this fuse should be checked and possibly changed. It is easy to check if the actuator receives power by demounting it from the valve and then change the thermostat’s settings so that the actuator closes or opens (uptime approximately 3 minutes).

There could also be a problem with the loop “jamming” which can be checked by pressing the spring-loaded pin repeatedly. The spring-loaded pin should expand again.

There is no electric current
Check that the fuse in the transformer list is intact (230V). Also check that the connections have been made according to the circuit diagram.

 

Installation with heat pump
Here are some suggestions and advice for systems using a heat pump:

Mount a bypass valve between the flow and return to ensure a constant circulation through the system even when all the loops in the underfloor system are closed. Alternatively, leave one loop in the system without thermostatic control, i.e. manual. It will then be opened all the time. There are also pressure controlled bypass valves available that opens when a set pressure is reached.

Check the recommendations from the heat pump supplier.

Many heat pumps have centrally placed indoor reference sensors, which attempt to use the lowest possible flow temperature. This may cause rooms that require a high temperature, or heating for a longer period of time (bathrooms for example) to get an inadequate temperature.

This collision is generally avoided by using the underfloor heating room thermostats only, i.e. switching any indoor reference sensors off. Alternatively bathrooms and rooms of similar conditions can be over-dimensioned. This should be discussed with the person responsible for the installation prior to commissioning the system.

The temperature adjustments may not work accurately if there is in indoor reference sensor installed in an area with another heat source, for example a fire place. As a fire place generates a lot of momentary heat this will have an effect on the sensor, which will lower the heating curve for the entire building.

The heat pump’s overheating protection may be trig gered if the circulation stops. This is fixed by checking that there is a bypass flow when all the loops are closed. To make sure that there is a constant bypass flow, do not install an actuator or room thermostat on one of the loops, or install a bypass.

If a pressurised bypass is installed, check that its settings are correct.