Danfoss 28 VX-FI Heating Controller

Functional description

District heating substation for indirect heating.

• Space heating
  The Termix Compact 28 VX-FI is a heat exchanger unit for the production of heating in large buildings such as sports centres, schools, blocks of flats etc. It can be used for connection to indirect district heating in places where the district heating plant requires a hydraulic break on the plant side. It is also suitable for conversion to district heating when the secondary heating system is suitable to being connected to direct district heating or when a particularly effective security against leakage in the heating system is required. It is possible to connect a hot-water tank.
• Efficient heat exchanger
  The substation is fitted with an efficient plate heat exchanger, which ensures the most favourable heat extraction and achieves optimum comfort and operating economy.
• Several variants
  Termix Compact 28 VX-FI is built with a heat exchanger for space heating, flow controller, pump, electronic regulation of the heating circuit as well as a direct outlet for a hot water tank. The electronic controller is factory pre-set. Electrical components are pre-wired, and the unit is equipped with a plug for 230 V a.c. It is recommended that dynamic balancing valves are installed in the building’s risers in the heat supply and on the heating system’s return line immediately before the unit.

Termix Compact 28 VX-FI is produced in standard constructions:

• VX with heat exchanger for indirect heating.
• VX with heat exchanger for indirect heating and integrated tank regulation.

Flexible solution
Pipe connection can be made from either the top or bottom, which makes this solution highly flexible. At the same time, both space and time are saved when installing.

• Minimal heat loss
  Complete insulation of the unit ensures minimal heat loss.
• Reliable and easy to install
  Termix Compact 28 VX-FI is operationally reliable. A quality product manufactured in Denmark, which is easy to install and quickly commissioned.

Safety notes

•  Safety Notes – general
  The following instructions refer to the standard design of substation. Special versions of substations are available on request.
  This operating manual should be read carefully before installation and start-up of the substation. The manufacturer accepts no liability for damage or faults that result from non-compliance with the operating manual. Please read and follow all the instructions carefully to prevent accidents, injury and damage to property. Assembly, start-up and maintenance work must be performed by qualified and authorized personnel only.
  Please comply with the instructions issued by the system manufacturer or system operator.
• Corrosion protection
  All pipes and components are made of stainless steel and brass. The maximum chloride compounds of the flow medium should not be higher than 150 mg/l.
  The risk of equipment corrosion increases considerably if the recommended level of permissible chloride compounds is exceeded.
• Energy source
  The substation is designed for district heating as the primary source of energy. However, also other energy sources can be used where the operating conditions allow it and always are comparable to district heating.
• Application
  The substation is designed to be connected to the house installation in a frost-free room, where the temperature does not exceed 50 °C and the humidity does not exceed 60%. Do not cover or wall up the substation or in any other way block the entrance to the station.
• Choice of material
  Choice of materials always in compliance with local legislation.
• Safety valve(s)
  We recommend mounting of safety valve(s), however, always in compliance with local regulations.
• Connection
  The substation must be equipped with features that ensure that the substation can be separated from all energy sources (also power supply).
• Emergency
  In case of danger or accidents – fire, leaks or other dangerous circumstances – interrupt all energy sources to the station if possible, and seek expert help.
  In case of discoloured or bad-smelling domestic hot water, close all shut-off valves on the substation, inform the operating personnel and call for expert help immediately.
• REACH
  All Danfoss A/S products fulfill the requirements in REACH. One of the obligations in REACH is to inform customers about presence of Candidate list substances if any, we hereby inform you about one substance on the candidate list: The product contains brass parts which contains lead (CAS no: 7439-92-1) in a concentration above 0.1% w/w.
• Storage
  Any storage of the substation which may be necessary prior to installation should be in conditions which are dry and heated.
• Authorized personnel only
  Assembly, start-up and maintenance work must be performed by qualified and authorized personnel only.
• Please observe instructions carefully
  To avoid injury to persons and damage to the device, it is absolutely necessary to read and observe these instructions carefully.
• Warning of high pressure and temperature
  Be aware of the installation’s permissible system pressure and temperature.
  The maximum temperature of the flow medium in the substation is 110 °C.
  The maximum operating pressure of the substation is 16 bar.
  The risk of persons being injured and equipment damaged increases considerably if the recommended permissible operating parameters are exceeded.
  The substation installation must be equipped with safety valves, however, always in accordance with local regulations.
• Warning of hot surface
  The substation has got hot surfaces, which can cause skin burns. Please be extremely cautious in close proximity to the substation.
  Power failure can result in the motor valves being stuck in open position. The surfaces of the substation can get hot, which can cause skin burns. The ball valves on district heating supply and return should be closed.\
• Warning of transport damage
  Before substation installation, please make sure that the substation has not been damaged during transport.
• IMPORTANT – Tightening of connections
  Due to vibrations during transport all flange connections, screw joints and electrical clamp and screw connections must be checked and tightened before water is added to the system. After water has been added to the system and the system has been put into operation, re-tighten ALL connections.

 Mounting

Mounting the Compactstation

Installation must be in compliance with local standards and regulations. District heating (DH) – In the following sections, DH refers to the heat source which supplies the substations. A variety of energy sources, such as oil, gas or solar power, could be used as the primary supply to Danfoss substations. For the sake of simplicity, DH can be taken to mean the primary supply.

Connections:

1. District heating (DH) supply
2. District heating (DH) return
3. Heating (HE) supply
4. Heating (HE) return
5. Tank flow line (TFL)
6. Tank return line (TRL)

Connection sizes: Termix Compact 28 VX-FI / HWP |
DH + HE + TFL + TRL: G 1” (int. thread)

Connection sizes: Termix Compact 28 VX-HWS

• DH + HE : G 1” (int. thread)
• TFL + TRL: G ¾” (int. thread)

Dimensions (mm):

• With insulation: H 890 x W 905 x D 400
• Weight (approx.): 60 kg

Authorized personnel only
Assembly, start-up and maintenance work must be performed by qualified and authorized personnel only.

Termix Compact 28 VX-FI / HWP:

Termix Compact 28 VX-HWS:

The pipe placement can deviate from the shown drawing. Please note the markings on the station.

• Remove the front.
• Remove other blocks.
• Attach the mounting rail to the wall.
• Lift the station.
• Mount the station on the mounting rail.
• Attach the station to the wall in the holes on the mounting plate.
• Install the safety valve.
• Install ball valves.
• Mount block A (C if it is the Magna pump) on the left-hand side of the pump. Attach block E to block A/C, and attach it to the pipe above the pump by clicking it in place.
• Mount block B (D if it is the Magna pump) on the right-hand side of the pump.
• Mount block F (G for VM2 valve). The block is hinged and can be drawn around the valve. Attach the block to block B/D and E.
• Mount block J and H around the valve for the tank control.
• Mount the front cover.

Installing the Compactstation

• Mounting:
  Adequate space
  Please allow adequate space around the substation for mounting and maintenance purposes.
• Orientation
  The station must be mounted so that components, keyholes and labels are placed correctly. If you wish to mount the station differently please contact your supplier.
• Drillings
  Where substations are to be wall-mounted, drillings are provided in the back mounting plate. Floor mounted units have support.
• Labelling
  Each connection on the substation is labelled.

Before installation:

• Clean and rinse
  Prior to installation, all substation pipes and connections should be cleaned and rinsed.
• Tightening
  Due to vibration during transport, all substation connections must be checked and tightened before installation.
• Unused connections
  Unused connections and shut-off valves must be sealed with a plug. Should the plugs require removal, this must only be done by an authorized service technician.

Installation:

• Strainer
  If a strainer is supplied with the station it must be fitted according to schematic diagram. Please note that the strainer may be supplied loose.
• Connections
  Internal installation and district heating pipes connections must be made using threaded, flanged or welded connections.

Pipe connections up

• Remove the top block.
• Remove the pipe plugs at the top of the station.
• Remove U-clamps.
• Remove pipes. Angles and tees are turned so that pipes can be installed from above.
• Install the pipes. District heating supply pipes to be interchanged.
• Fit U-clamps.
• Fit the pipe plugs at the bottom of the station.
• Fit the top block.

 Start-up
Start-up, Indirect heating

Filling:

1. First fill
   When carrying out first fill, the heat exchanger must be slowly filled with water until it reaches working pressure.
2. Pressure gauge
   The HE pressure gauge indicates the pressure of the HE system. This instruction must be followed strictly, to avoid dangerous situations.
3. Supply hose
   A ball valve with plug is installed in the HE return line. To fill the system, the ball valve must first be closed, the plug removed and a supply hose connected. On re-opening the ball valve, system fill can commence.
4. Pre-pressure
   When filling the system with water, the pressure gauge should be observed closely. The expansion vessel is supplied pre-pressurised to 0.5 bar. The pre-pressure required at each substation will depend on system head (the distance between the lowest and highest point in the system), for example:
5. Filling stop
   Filling must stop when the pressure gauge shows a pressure approximately 1-2 bar higher than the pre-pressure setting. The ball valve is then closed, the hose removed and the plug put back in.

Start-up:

1. Pump speed
   Set the pump to highest speed before start-up.
2. Start pump
   Start the pump and heat through the system.
3. Open shut-off valves
   The shut-off valves should then be opened and the unit observed as it enters service. Visual checking should confirm temperatures, pressures, acceptable thermal expansion and absence of leakage. If the heat exchanger operates in accordance with design, it can be put to regular use.
4. Vent system
   Switch off the pump and vent the installation after the radiators have been warmed up.
5. Adjust pump speed
   Set the pump to the lowest speed consistent with comfort and electricity consumption.
   Normally the change-over switch is set in the mid position (default). However for systems with under floor heating or single pipe loop systems, it may be necessary to turn the change-over switch upwards.
   Higher pump speeds are only used if the heating requirement increases.

Re-tighten connections
After water has been added to the system and the system has been put into operation, re-tighten ALL connections.

Pump
The pump must be switched off during system fill.

Height (m)	Pressure (bar)
0 – 5	0,5
5 – 10	1,0
10 – 15	1,5
15 – 20	2,0

Under floor heating:
Pump stop function
If the substation is used in connection with under floor heating, the circulation pump must be connected to the pump stop function in the under floor heating controller. The pump must be stopped if all under floor heating circuits are closed.

Warranty

If this is not possible, then flow must be continued through the by-pass. Failing this, the pump will be at risk of seizure and any remaining warranty will be withdrawn.

Summer operation:

• Switch off pump
  In summer the circulation pump must be switched off and the shut-off valve to HE supply closed.
• Running pump bi-weekly
  It is recommended to start up the circulation pump (for 2 minutes) once a month during summer; the shut-off valve of the HE supply must be shut.
• Electronic controller
  Most electronic controllers will start up the pump automatically (please note manufacturer´s instructions).
•  Electrical connections
  Before making electrical connections, please note the following:
• Safety notes
  Please read the relevant parts of the safety notes.
• 230 V
  The substation must be connected to 230 V AC and earth.
• Potential bonding
  Potential bonding should be carried out according to 60364-4-41:2007 and IEC 60364-5-54:2011.
  Bonding point on the mounting plate below right corner marked with earth symbol.
• Disconnection
  The substation must be electrically connected so that it can be disconnected for repairs.
• Outdoor temperature sensor
  Outdoor sensors should be mounted so as to avoid exposure to direct sunlight. They should not be placed close to doors, windows or ventilation outlets.
  The outdoor sensor must be connected to the station on the terminal block under the electronic control.
• Authorized electrician
  Electrical connections must be made by an authorized electrician only.
• Local standards
  Electrical connections must be made in accordance with current regulations and local standards.

 Design

Your substation might look different than the substation shown.

Design description

• A Heat exchanger, HE
• F Electronic controller
• 4 Safety valve, HE
• 9 Strainer
• 10 Circulator pump
• 14 Sensor pocket, energy meter 20 Filling/drain valve
• 25 Pressure gauge with ball valve

Schematic diagram

Schematic diagram Termix Compact 28 VX-FI

Your substation might look different than the schematic diagram shown.

Schematic description

• A Heat exchanger, HE
• F Electronic controller
• 1 Ball valve
• 4 Safety valve
• 9 Strainer
• 10 Circulator pump
• 14 Sensor pocket, energy meter 16 Outdoor sensor
• 18 Thermometer
• 19 Surface sensor
• 20 Filling/drain valve
• 24 Delivered loose with unit

 Schematic diagram Termix Compact 28 VX-FI HWP

Your substation might look different than the schematic diagram shown. 5.2.3 Schematic diagram Termix

Compact 28 VX-FI HWS

Your substation might look different than the schematic diagram shown.

Schematic description

• A Heat exchanger, HE
• E Hot water tank with coil
• F Electronic controller Border of delivery
• 1 Ball valve
• 2 Single check valve
• 4 Safety valve
• 9 Strainer
• 10 Circulator pump
• 11 Domestic hot water pump
• 13 Charging pump
• 14 Sensor pocket, energy meter
• 16 Outdoor sensor
• 18 Thermometer
• 19 Surface sensor
• 20 Filling/drain valve
• 24 Delivered loose with unit
• 25 Pressure gauge with ball valve
• 26 Pressure gauge
• 27 Actuator
• 29 2-way motorized valve
• 30 Flow controller with integrated control valve
• 44 Immersion sensor
• 48 Air vent, manual
• 69 On/off valve
• DH Supply: District Heating Supply
• DH Return: District Heating Return
• HE Supply: Heating Supply
• HE Return: Heating Return
• TFL: Tank flow line
• TRL: Tank return line
• DHW: Domestic hot water
• HWC: Hot water circulation
• DCW: Domestic cold water

Technical parameters

• Nominal pressure: PN 16
• Max. DH supply temperature: 110 °C
• Brazing material (HEX): Copper
• Heat exchangers test pressure: 30 bar
• Sound level: R 55 dB

Controls

Heating circuit

1.  Differential pressure controller
   The differential pressure controller smooths out the fluctuations in pressure arriving from the district heating network. The operating pressure in the substation is thus held steady.
2.  Flow controller with integrated control valve
   The controller is a self-acting flow controller with integrated control valve. The controller closes when set max. flow is exceeded and can be used in combination with Danfoss electrical actuators with or with out safety function. Spring return motor can be used as safety function by power failure.
3. Electric 2–way motorized valve
   Actuators with or without safety function are available for 3-point controls. Spring-return actuators can be used to provide safety shut-off in the event of power failure.
4. Electronic control
   Substations with electronic control must be set in accordance with manufacturer´s instructions.
   Where the room temperature is controlled by radiator thermostats, it is recommended that thermostats be set for minimum temperature in each room.
5. Outside temperature sensor
   Outdoor sensors should be mounted so as to avoid exposure to direct sunlight. They should not be placed close to doors, windows or ventilation outlets.
6. Circulator pump
   The UPML, UPMXL circulator pumps are designed for circulating liquids in heating systems with variable flows, internally controlled with three proportional pressure curves and three constant pressure/power curves to be selected via user interface.
   EuP 2015 Ready.
   The MAGNA3 circulator pumps are designed for circulating liquids in heating systems with variable flows where you want to optimise the setting of the pump duty point, thus reducing energy costs.
   EuP 2015 Ready.
7. Grundfos UPML / UPMXL instructions
   • PP = Proportional pressure (fast flash)
   • CP = Constant pressure (slow flash)

HE pressure gauge
The HE pressure gauge indicates the pressure of the HE system.

Other

Safety valve
The purpose of the safety valve is to protect the substation from excessive pressure. The blow-off pipe from the safety valve must not be closed. The blow-off pipe outlet should be placed so that it discharges freely and it is possible to observe any dripping from the safety valve. It is recommended to check the operation of safety valves at intervals of 6 months. This is done by turning the valve head in direction indicated.

Strainer
Strainers should be cleaned regularly by authorized personnel. The frequency of cleaning would depend on operating conditions and the manufacturer’s instructions.

Fitting piece
The substation is equipped with a fitting piece for energy meter.
Assembly of energy meters:

1. Close ball valves
   Close the ball valves on DH Supply and DH Return, if there is water on the system.
2. Loosen nuts
   Loosen the nuts on the fitting piece.
3. Remove fitting piece
   Remove the fitting piece and replace it with the energy meter. Do not forget the gaskets.
4. Tighten connections
   After mounting of the energy meter remember to check and tighten all threaded connections.
   Sensor pocket, energy meter
   The sensors of the energy meter is mounted in the sensor pockets.

Maintenance
The substation requires little monitoring, apart from routine checks. It is recommended to read the energy meter at regular intervals, and to write down the meter readings.
Regular inspections of the substation according to this Instruction are recommended, which should include:

• Strainers
  Cleaning of strainers.
• Meters
  Checking of all operating parameters such as meter readings.
• Temperatures
  Checking of all temperatures, such as DH supply temperature and DHW temperature.
• Connections
  Checking all connections for leakages.
• Safety valves
  The operation of the safety valves should be checked by turning the valve head in the indicated direction.
• Venting
  Checking that the system is thoroughly vented.
  Inspections should be carried out minimum every two years.
  Spare parts can be ordered from Danfoss. Please ensure that any enquiry includes the substation serial number.

Authorized personnel only
Assembly, start-up and maintenance work must be performed by qualified and authorized personnel only.

Troubleshooting

 Troubleshooting in general
In the event of operating disturbances, the following basic features should be checked before carrying out actual troubleshooting:

• the substation is connected to electricity,
• the strainer on the DH supply pipe is clean,
• the supply temperature of the DH is at the normal level (summer, at least 60 °C – winter, at least 70 °C),
• the differential pressure is equal to or higher than the normal (local) differential pressure in the DH network – if in doubt, ask the DH plant supervisor,
• pressure on the system – check the HE pressure gauge.

Authorized personnel only
Assembly, start-up and maintenance work must be performed by qualified and authorized personnel only.

Troubleshooting HE

Problem	Possible cause	Solution
Too little or no heat.	Strainer clogged in DH or HE circuit (radiator circuit).	Clean gate/strainer(s).
	The filter in the energy meter on DH circuit clogged.	Clean the filter (after consulting the DH plant operator).
	Defective or wrongly adjusted differential pressure controller.	Check the operation of the differential pressure controller – clean the valve seat if required.
	Sensor defective – or possibly dirt in the valve housing.	Check the operation of the thermostat – clean the valve seat if required.
	Automatic controls, if any, wrongly set or defective – possibly power failure.	Check if the setting of the controller is correct – see separate instructions.Check the power supply. Temporary setting of motor to “manual” control – see instructions on automatic controls.
	Pump out of operation.	Check if the pump is receiving power and that it turns. Check if there is air trapped in the pump housing – see pump manual.
	The pump is set at too low speed of rotation.	Set the pump at higher speed of rotation.
	Pressure drop – the pressure drop on the radiator circuit shows lower than recommended operating pressure.	Fill water on the system and check the functioning of the pressure expansion vessel if required.
	Air pockets in the system.	Vent the installation thoroughly.
	Limiting of the return temperature adjusted too low.	Adjust according to instructions.
	Defective radiator valves.	Check – replace.
	Uneven heat distribution in building because of incorrectly set balancing valves, or because there are no balancing valves.	Adjust/install balancing valves.
	Diameter of pipe to substation too small or branch pipe too long.	Check pipe dimensions.
Uneven heat distribution.	Air pockets in the system.	Vent the installation thoroughly.
DH supply temperature too high.	Wrong setting of thermostat or of automatic controls, if any.	Adjust automatic controls, – see instructions for automatic controls.
	Defective controller. The controller does not react as it should according to the instructions.	Call automatic controls manufacturer or replace the regulator.
	Defective sensor on self-acting thermostat.	Replace thermostat – or sensor only.
DH supply temperature too low.	Wrong setting of automatic controls, if any.	Adjust automatic controls – see instructions for automatic controls.
	Defective controller. The controller does not react as it should according to the instructions.	Call in automatic controls manufacturer or replace controller.
	Defective sensor on self-acting thermostat.	Replace thermostat – or sensor only.
	Wrong placement/fitting of outdoor temperature sensor.	Adjust location of outdoor temperature sensor.
	Strainer clogged.	Clean gate/strainer.

Too high DH return temperature.	Too small heating surface/too small radiators compared to the total heating requirement of the building.	Increase total heating surface.
	Poor utilization of existing heating surface. Defective sensor on self-acting thermostat.	Make sure the heat is distributed evenly across the full heating surface – open all radiators and keep the radiators in the system from heating up at the bottom. It is extremely important to keep the supply temperature to the radiators as low as possible, while maintaining a reasonable level of comfort.
	The system is single pipe loop.	The system should feature electronic controls as well as return sensors.
	Pump pressure too high.	Adjust pump to a lower level.
	Air in system.	Vent the system.
	Defective or incorrectly set radiator valve(s). Single pipe loop systems require special one-pipe radiator valves.	Check – set/replace.
	Dirt in the motorized valve or in the differential pressure controller.	Check – clean out.
	Defective motorized valve, sensor or automatic controller.	Check – replace.
	Electronic controller not adjusted correctly.	Adjust according to instructions.
Noise in system.	Pump pressure too high.	Adjust pump to a lower level.
Heat load too high.	Defective motorized valve, sensor or electronic controller.	Check – replace.

 Disposal

Disposal note
This symbol on the product indicates that it may not be disposed of as household waste..
It must be handed over to the applicable take-back scheme for the recycling of electrical and electronic equipment.

• Dispose of the product through channels provided for this purpose.
• Comply with all local and currently applicable laws and regulations.

 

Gemina Termix A/S Member of the Danfoss Group
danfoss.com

• +45 9714 1444
• mail@termix.dk

Any information, including, but not limited to information on selection of product, its application or use, product design, weight, dimensions, capacity or any other technical data in product manuals, catalogues descriptions, advertisements, etc. and whether made available in writing, orally, electronically, online or via download, shall be considered informative, and is only binding if and to the extent, explicit reference is made in a quotation or order confirmation. Danfoss cannot accept any responsibility for possible errors in catalogues, brochures, videos and other material. Danfoss reserves the right to alter its products without notice. This also applies to products ordered but not delivered provided that such alterations can be made without changes to form, fit or function of the product. All trademarks in this material are property of Danfoss A/S or Danfoss group companies. Danfoss and the Danfoss logo are trademarks of Danfoss A/S. All rights reserved.

FAQ

Q: Are special versions of substations available?
A: Yes, special versions of substations are available upon request. Contact customer support for more information.

Documents / Resources

Danfoss 28 VX-FI Heating Controller [pdf] User Guide HWP, HWS, 28 VX-FI Heating Controller, 28 VX-FI, Heating Controller, Controller

References

• User Manual