Air Source Heat Pump Installation and Maintenance Manual

Air Source Heat Pump Installation and Maintenance Manual Model Numbers: AroTHERM VWZAI wiring centre VRC700 remote controller Scan this code to go directly to our YouTube channel 2016 b 1

The Outdoor Unit (boiler) Position the outdoor unit so that the air flows into an open area, where there are no plants and animals Install the outdoor unit on a flat, stable surface, the unit needs to be securely mounted at least 100mm off the ground on rubber feet. The unit must be bolted down for security using 10mm bolts and Zebedee bolts. The unit must have adequate drainage away from the unit; it can produce up to 6 L / hour. The unit comes with a drain kit and a drain heater so you can pipe the water away. If you are installing the unit at height you can install a drain pan under the unit but its best to let the unit drain into the ground. 2016 b 2

The space around the unit is very important, do not install with smaller clearances than above. The wiring centre or heat pump interface VWZA1 Every Vaillant heat pump needs the control box and a VRC 700 controller to operate. The control box is a wiring center and service tool, the controller VRC is used by the end user to drive the unit. Install it indoors and out of sight so it s not played with, it s not waterproof. The box is 323mm wide, 339mm high, 131mm deep. The VRC is designed to be in the house like a room stat 2016 b 3

What comes with the unit and what you will need: Below is a list of the components you will need to buy for each of the systems, Flexible hoses the water connections to the back of the unit are 11/4 inch BSP male. We supply a reducer to make it 1 and recommend connecting the water pipework with flexible hoses for ease of maintenance and to avoid any vibration from the unit going into the house. All external pipework has to be insulated to meet MCS standards. Mounting feet, the outdoor units need to be mounted 100mm above the ground, we recommend using rubber feet with unistrut channel. These come with mounting bolts included. An expansion vessel, pressure gauge, pressure relief valve and filling loop In pressurised heating systems most heating engineers use a Robokit which combines all these components into one box. The expansion vessel is sized exactly the same way as when using a boiler. If you want to run the system open vented you don t need these components, the Samsung units are happy to run at anywhere from 0 3Bar pressure Pump the unit has a pump in it The flow rate must be more than, 7l/min for the model 5 and 20l/min for model 15. Flow meter The heat pumps have to have continuous un-interrupted flow at all times despite the loading on the system. To measure that the flow is correct there is a paddle type flow switch in the unit. If the flow rate falls the water doesn t push the paddle switch and an error will occur. To avoid this, it is common to use a hydraulic break in the system like a buffer or a low loss header. We recommend a flow meter is installed into the flow side of the flow switch as per the photo. Adaptors may be required to enable this join. The flow switch is not IP65 rated (weatherproof) and so must not be installed externally. Diverter valves If you require domestic hot water and heating, 2 x 2 port diverter valves are required, you need to supply these and they need to be 28mm diameter. Water Filter In all cases a magnetic filter and strainer needs to be installed in the return to the heat pump. The filters ensure that debris/foreign materials do not cause damage to the heat exchanger in the unit, voiding warranties. 2016 b 4

Glycol / anti-freeze In Monobloc heat pumps the water goes outside the building. The unit can protect itself from freezing up, but if the power goes off there is a risk that the unit will freeze causing damage. To prevent this, we recommend putting propylene glycol mixture in the system. It is important that the glycol concentration is adequate to protect the unit, if the unit freezes up there will be no warranty. Manufacturer dependant, a mix of 25% is normal for UK conditions. Adding too much glycol is not a good idea as it increases the water pump power and slightly reduces the capacity of your system. Buffer vessels, heat exchangers and low loss headers Historically every heat pump had a buffer vessel, the reason for this is that heat pumps were once single speed machines. In low load conditions this meant the heat pump had to cycle on / off to match the demand. A buffer vessel allowed the heat pump to operate for longer periods and to rest for longer periods. Modulation and Inverters. With the introduction of variable speed units using Inverter technology the buffer vessel is no longer essential. In a boiler you can alter the output by turning the gas up and down, you can see the flame size change in the little window on the front of the boiler, this is called modulation. In a heat pump the inverter changes the speed of the compressor to give the same effect. Inverters are modulation for heat pumps. Samsung Inverter driven units can vary their output right down to be 10% meaning cycling is a thing of the past. Defrost In cold wet conditions the outdoor unit freezes up, a coating of ice can be seen forming on the unit. In very cold weather, below -2C the coils don t freeze as there is less water in the air. If the coil gets blocked up with ice the unit needs to clear it, to do this it enters defrost mode, in worst case this happens for 6 minutes every hour. Defrost just reverses the operation of the unit, it uses the heat from the water in the house to warm the coil outside. The effect of course is that the radiator temperature falls. All the ice will melt off the back of the unit and pour out of the unit. It looks like the unit has sprung a leak but it s just condensation and it s safe to drain it into the ground. Every time the water goes through the unit it loses 5 degrees C, the flow rate will be 20l/ min so if the system volume is very small the temperature can drop dramatically. For example, if the system holds 20l, all the water will go through the unit 6 times in 6 mins dropping 30C in temperature. If the system holds only a tiny Volume a buffer can be used to increase this. Flow In most heating systems the flow rate through the unit changes with load, when all the heat emitters are open the flow is high and when most of them are closed the flow rate reduces. In a heat pump we cannot let this happen, we need to keep the water through the heat pump at a constant speed. To balance the flow through the emitters and the flow through the heat pump we need to allow for some bypass. This can be achieved in 4 different ways: 2016 b 5

Low loss headers A low loss header is a large pipe with 4 connections, a flow and return to the heat pump and a flow and return to the heating circuit. If the flow rates either side of the header don t match the water flows through the header making up the difference. Buffers A buffer vessel looks like a hot water cylinder but the pipes connect directly into the cylinder, there are no coils. They are just high pressure, insulated, buckets. A buffer is just a bigger version of a low loss header. Heat exchanger A plate heat exchanger also has 4 connections a flow and return to the heat pump and a flow and return to the heating circuit. But in this case the two flows are separated. The advantage with a plate heat exchanger is you can separate the antifreeze from the water circulating around the house. Plates are the best solution but they can be expensive. Bypass valves. It is possible to put automatic bypass valves in the heating circuit to keep the flow rate constant. This is the cheapest option BUT setting up the bypass valves is very important and often forgotten, causing return visits. Install the bypass valve in the heating circuit as far away from the heat pump as possible. The bypass valve enables flow to be maintained as the trv s shut down at all times to prevent unit flow fault. Micro Bore If you connect a heat pump directly to micro bore it can be very noisy, it sounds like a running tap. To avoid this, we always recommend a low loss header. With this set up its possible to have two different flow rates one for the micro-bore and another for the heat pump. Radiators will need to be sized for a 45C average temperature 50C in 40C out. The Cylinder: If you want to heat water with a heat pump you need a dedicated heat pump cylinder. these are 600mm diameter and are pre-insulated and can store water at up to 3 bar pressure. The cylinder needs to be installed less than 15m from the control box to allow for the temperature sensor cable. Note the size and weight of the cylinder. Full installation instructions will be included with the cylinder. Cylinders can only be used IF the coil area is more than 2.5m^2. Smaller coils are not acceptable and cannot be used. Please do not attempt to utilize a standard central heating, non-heat pump optimized cylinder. Cylinders can be pressurised or open vented. 2016 b 6

Gaining access to the units: to get to the wiring terminals remove the two Torx T20 screws and slide down the cover. 2016 b 7

Heating and Hot Water Systems. Page 1 of 3 Reduced Glycol System. If you want to reduce the amount of Glycol to be used in the system, you can install a plate heat exchanger. The heat exchanger needs to be suitably sized and a pump installed on either side. 2016 b 8

Heating and Hot Water Systems. Page 2 of 3 Operation: Hot water is controlled using the cylinder sensor and controller supplied. This controller has inbuilt time clock control and includes both a daily and weekly legionella sterilisation function. The system can be either open vented or pressurised. The cylinder must have a coil at least 2.5m^2 Cylinder size normally allows 55l of water per person per day. We would recommend sizing the heat pump to recover the cylinder in 1 hour. It is possible to connect this system to solar PV powered immersion heaters (I boost, Immersun etc.) Heating is controlled using a wall mounted thermostat / time clock (field supplied). There are no limits to the number of heating zones which can be connected to this system. This system shows 2 heating zones. (Z1 and Z2) Each zone has its own thermostat / timer which drives a dedicated zone valve. The zone valve will control the pump and send a run signal to the heat pump. The system will run in a fully adjustable weather compensated mode adjusting the water temperature to suit the ambient conditions. We recommend a buffer; low loss header or heat exchanger is used to simplify the installation. 2016 b 9

Heating and Hot Water Systems. Page 3 of 3 3 port valve wire brown to UV1 AUF and blue to UV1 N Don t use the orange and grey wires. The heating run signal goes into EVu 1 and 2, its run when broken. 2016 b 10

Heating and Hot Water Systems. Page 3 of 3 2 port valve for heating wire brown to UV1 Zu and blue to UV1 N 2 port valve for hot water wire brown to UV1 Auf and blue to UV1 N Don t use the orange and grey wires. The heating run signal goes into EVu 1 and 2, its run when broken. 2016 b 13

Wiring and Power Supply Information, All systems: Power The AroTHERM system needs 2 power supplies: Outdoor unit, 16 Amp for the 5 and 32 Amp for the 15. The wiring centre needs a 16 Amp supply; this wires into the left hand power terminal in the box. The Immersion heater is connected into the right hand green power terminals; the wiring centre controls the operation of the immersion heater. If a fused spur is used it must be labelled do not turn off as switching it off will cause an error. Communication cable must be run from the outdoor unit terminals BUS and + to the wiring centre, terminals BUS and +. And then on to the VRC room controller BUS and +. In the controller the top terminal is +. Polarity is important, if its wrong the unit won t work properly. Use 2 core flex 0.5-1mm (its 24V ac). It must not have any breaks in it or switches. The cylinder sensor plugs on the wiring centre blue plug SP1 and into the cylinder in the top ½ of the cylinder. It must install above the immersion. You must fix it so it can t be pulled out of the cylinder. Keep it well away from any mains cables. The outdoor air sensor plugs on the wiring centre yellow plug DCFAF using terminals AF and OI. The sensor itself needs to go in a shaded space on the North side of the house. Keep it well away from any mains cables. Using two port valves 2 port valve for heating wire brown to UV1 Zu and blue to UV1 N 2 port valve for hot water wire brown to UV1 Auf and blue to UV1 N Don t use the orange and grey wires. Using 3 port valve 3 port valve wire brown to UV1 AUF and blue to UV1 N Don t use the orange and grey wires. Pump Z1 used for heating Pump Z1 is wired into MA1 live and Neutral. This pump will only run when the heating is operating but the hot water is not running. 2016 b 14

Controlling your heating: There are two options available here: If you have radiators ONLY and want to run them as one zone. You can use the Vaillant room controller as a thermostat, mount it somewhere sensible and off it will go. When the heating is running the wiring centre will start the pump Z1 and push water round the rads. If you have any underfloor heating OR more than one heating zone In this case we will use a run signal from the UFH and/or external timers and thermostats to tell the unit to run. When we exit the buffer, header or heat exchanger each zone will have a valve. Wire your stat or UFH to open the valve for that zone. In each valve use the orange and grey cables as a run signal as per diagram below. The heating run signal goes into EVu 1 and 2, its run when broken. This means you have to reverse all the signals you receive from valves and thermostats using a relay. 2016 b 15

Start-up Procedure: Filling and flushing, when installing any Heat pump we insist on a thorough system flush prior to connection in line with the Building Regulations for England and Wales, Part L, 2006. Using the power flusher fill the system with water and 25% Propylene Glycol, there is no pressure sensor in the unit so we can operate from open vented to 3 bar maximum. Setting up the cylinder immersion heater The immersion heater has its own stat; this MUST be set to 70C. This is to avoid the immersion heater cutting out before the legionella function is complete Powering Up Makes sure all your room thermostats are off and all underfloor run signals are off. Apply power to indoor wiring centre first then the outdoor unit. The wiring centre will be dead for about a minute, after that it will come to life. And say loading it will then enter the installer assistance, press Ok It will ask if you want English, press next and then it will do an air purge of the heating and HW circuits automatically, it s a good time to check your flow rates and check your zone valve or valves are operating correctly. Be quick it only does this test for about a minute. 2016 b 16

Configuring the system: You need to make a few setting to the system first or it won t work properly or efficiently: On the remote controller Press menu 2 x turn the knob to installer level press select. It wants a password, its factory set to 000 press ok. If you are using a system with a heat exchanger, buffer or low loss header in the heating circuit, scroll to system configuration press ok, scroll to system diagram press select, using the scroll set this to 10 press ok. This activates the heating pump on the output side of the header. If you don t want to use a hydraulic break, (pools etc.) set this to drawing 8. This does not activate the heating pump on the outlet of the header. Scroll to heating curve, press select, change this to 0.8 for underfloor heating and 1.2 for radiators. Scroll to heating 1, press select, type of circuit, you can choose from inactive if you don t want heating, Heating if you want to use weather comp or Fixed value if you want a constant flow temperature. If you want to use a fixed flow temperature also go to heating 1, target flow temperature day and set the temperature here, also set target flow temperature set back. If you want to use external controls or UFH manifolds to drive the unit scroll down to energy supplier select, heat off the unit will run when the link from evu1-2 is removed. If you are using the unit to heat a cylinder: Scroll to DHW cylinder, change this to active Scroll to domestic hot water temperature set this to 50C Change maximum charge time to 60 mins for a 210L and 90 mins for a 300L cylinder Change DHW req anti cyl time to 90 mins. Change anti legionella day to a Wednesday Set the anti-legionella time to 3 AM And finally scroll to change code if you want to change the installer code. When you are finished, keep pressing back until you get to the main screen again. Cylinder Timer, if you are heating a hot water cylinder To avoid the cylinder heating being switched off we always add 2 on timers a day, one at 3-00 am and one at 15-00 pm. This stops nuisance tripping, resets the unit after power cuts and insures the cylinder is hot 24 hours a day. We don t normally set any off times. On the remote controller press menu, scroll to time programmes, press select, you can time the heating zone 1 or the DHW, select DHW, press select and enter timers in here. Systems with Solar or Immersun With solar systems its best to switch off the cylinder heating during the day to give the solar the best chance of heating the cylinder for free. 2016 b 17

Electrically testing the unit: It is possible to test each component one after another using the service function. You can use this to make sure you have wired everything correctly. To access service mode on the wiring centre, press the two top buttons together, release and do it again, press + 5 times till you get to installer menu, press select. It will ask for the password, press + and hold it till you get to 17, press ok. Press + till you get to test menu, press select then press + till you get to sensor actuator test. Press + and you will see it says building circuit pump power, press select and press + to increase the speed of the pump up to 100%. Leave the pump at this speed. Flow Test: if you have a header, heat exchanger or buffer. because you have hydraulic seperation it makes no difference to the flow rate whetehr the radiators underfloor heating etc is running, we can pump into the header, buffer or excahnger. Now check your flow rate, it should be at least 12l/min on a 5 and 20l/min on a 15. If you look into the flow meter you can see the flow in litres per minute in this picture you can see a flow rate indicated, this shows 25l/min NOT 35l/min If the flow rate is too low, you need to fix this before moving on. remove any air and if it s still not enough you need bigger pumps. The unit won t work if the flow rate is too low. Flow Test: if you don t have a header, heat exchanger or buffer. Setting up the bypass valve Carry out the test above but now close every TRV on every radiator and shut off all underfloor heating loops. This is the worst case scenario for flow, the bypass valve needs to be adjusted to make sure the flow rate is still above 12l/min on a 5 and 20l/min on a 15. Adjust the bypass valve to achieve this. If you open the bypass fully and you still can t get to these levels I can assure you, you will be back again and again with flow problems, you need to fix this before moving on. Once you are happy open the TRVs again. Testing the flow in Hot water mode, with the pump running press back once to go to the menu again, press + 27 times until you see diverter valve 1, press select and open this valve. The flow will now be into the cylinder, again check the flow rate, the same as above. Once you are happy with the flow rate keep pressing back until you get to the normal screen and the pumps will stop. 2016 b 18

Starting the unit in heating mode: If you are using the Vaillant remote controller Press op mode, scroll to heating, press change, scroll to auto, press ok. Press back till you get to the main screen. Adjusting heating temperatures: Press menu, scroll to desired temperatures, press select, scroll to zone 1, press select, scroll to change the temperature, press ok, press back a few times to return to normal screen. If you are using field supplied controls or UFH. Turn up your thermostats or underfloor heating to send a run signal to the unit, the pump will start immediately, The pipework will begin to heat up, to see how the units doing go to the wiring centre, press top 2 buttons together. Press + to go to live monitor. Press select, press + to scroll through the screens, you are looking for desired temperature, this is the set point and current flow temp. Starting the System in hot water mode: On the Vaillant remote controller, Press op mode, scroll to domestic hot water, press change, scroll to auto, press ok. Press back till you get to the main screen. Adjusting Hot water temperatures: Press menu, scroll to desired temperatures, press select, scroll to DHW, press select, scroll to change the temperature, don t set higher than 50C, press ok, press back a few times to return to normal screen. The pipework will begin to heat up, to see how the units doing go to the wiring centre, press top 2 buttons together. Press + to go to live monitor. Press select, press + to scroll through the screens, you are looking for desired temperature, this is the set point and current flow temp. Performance testing With the unit running flat out measure the air temperature as it enters the back of the unit and the ambient temperature well away from the unit? They need to be the same for the unit to operate properly. Note these on the commissioning report Not enough hot water. The Water storage temperature is lower (48C) than a normal fossil fuel cylinder. It s important to check that any shower or bath mixers do not further reduce the water temperature. Using your thermometer check that the hot water comes out the tap at the same temperature it leaves the cylinder. If it doesn t you might need to make adjustments to taps mixers etc. DON T raise the cylinder temperature to compensate. You now need to fill in the Vaillant warranty card and commissioning sheet. 2016 b 19

Handover of the system. Leave this page with the Homeowner Thank you for buying a Vaillant heat pump system, your Vaillant heat pump heats the house and hot water cylinder much like a normal fossil fuel boiler however there are a couple of differences which you should take notice of. Your installer should have provided you with a room thermostat if you have radiators or a thermostat in every room if you have under floor heating. To turn on the heating all you need to do is turn up the thermostat, to turn it off you need to turn all the stats down. The thermostat sends a run signal to the heat pump. Once the unit starts up it will take time to get to temperature, it is not instant. Within 10 minutes you should feel the radiators beginning to warm up. Weather compensation and water law: The radiator temperatures will be lower than you are used to with a gas or oil boiler. To add to this, we run them in a weather compensation mode, this means that the unit measures the outside temperature and adjusts the radiator temperature to suit. The colder it is outside the warmer the rads will be and vice versa. This function is automatic and is designed to save you money. In very cold weather the radiator will be at their hottest, they will reach 50C. water temp in weather comp mode flow temperature C 55 50 45 40 35-5 0 5 10 15 Ambient temperature C Running your machine efficiently It is very expensive to heat the house up from cold, with a heat pump the best advice is to maintain the house at as close to constant temperature as possible all the time. Please DON T set the room temperature too low when you leave the house, ideally drop it 2 degrees below your normal set temperature when you go out or it will take a long time and a lot of money to recover. To switch off the heating in summer set the thermostats down to 16C to avoid the heating starting up. Your radiators will have thermostatic valves on them, you can adjust each room s temperature with these. 2016 b 20

General Advice: The heat pump comes with a wiring centre which looks like this, you should not use this or press the buttons, it is used for commissioning and fault diagnosing the system only. Starting the unit in heating mode: If the control of the heating is carried out using the remote controller, Press op mode, scroll to heating, press change, scroll to auto, press ok. Press back till you get to the main screen. If you are using field supplied controls or UFH. Turn up your thermostats or underfloor heating to send a run signal to the unit. Adjusting Heating temperatures: Press menu, scroll to desired temperatures, press select, scroll to zone 1, press select, scroll to change the temperature, press ok, press back a few times to return to normal screen. Starting the System in hot water mode: On the Vaillant remote controller, Press op mode, scroll to domestic hot water, press change, scroll to auto, press ok. Press back till you get to the main screen. Adjusting Hot water temperatures: Press menu, scroll to desired temperatures, press select, scroll to DHW, press select, scroll to change the temperature, don t set higher than 50C, press ok, press back a few times to return to normal screen. Hot Water: The hot water in your cylinder is set up to maintain the water between 43 and 50C all the time. As you use the water the heat pump will constantly top up the cylinder. The hot water cylinder has priority over the heating, if the cylinder temperature falls 5 degrees below its set point the unit will automatically switch to heating the cylinder. Once set temperature is achieved the unit will go back to heating the house. An anti-legionella / disinfection safety operation will be completed at a 3am every Wednesday morning. The hot water will be hotter on a Wednesday morning than the rest of the week. If you don t require 24/7 hot water It is possible to time clock the hot water to reduce costs, your engineer will show you how to do this. Faults: If the system goes into fault, the screen will show a number at the bottom starting with F, for example F.536. The engineer will want to know this number when you call. Please avoid turning the unit off at the power supply especially in cold weather. If the unit is off and the weather is very cold, it cannot protect itself. Maintenance Monobloc Systems 2016 b 21

The Samsung heat pump should be maintained at least once a year to comply with warranty and RHI. The warranty card also doubles up as a maintenance sheet. Maintenance procedure Stop the unit, clean the strainer or magnetic filter in accordance with manufacturer s recommendations and replace it. Test the concentration of the Anti-freeze (glycol) in the system using a Glycol tester the level should be 25%. If you don t have a glycol tester a glycol tester / refractometer can be bought from your heat pump supplier or online. Refill the unit, pressure should be 0-3 bar, We need to test the operation of the unit against the hot water cylinder. So first we need to draw off 50 liters of water, run a couple of taps for 5 mins to achieve this. The unit should start up automatically in hot water mode, if it doesn t press the DHW power button on the controller, in 3-4 mins it will start heating the cylinder, a coke can symbol will show in the status section of the remote controller. The heat pump should be able to achieve 48C cylinder temperature without using the immersion heater. While running, check the outdoor unit for damage & debris, the coil needs washing, we recommend you use an approved EHS heat pump cleaning chemical, your distributor will stock this. Instructions are given on the bottle. You also need to clean and polish the outside casing we recommend car wax to do this. Hot water Cylinder: Check electrical connections & sensor are fixed properly and the overheat thermostat is set to 70C. Overheat Thermostat Adjustment Press the mode button until a bath symbol shows on the Samsung remote controller; this will force the immersion heater on. Check immersion heater works properly, Measure the current drawn by the heater; it should be 12-13 Amps. Measure the temperature of the flow using the remote controller. Measure the flow rate from the flow meter. With the unit running flat out measure the temperature of the air as it enters the coil and the temperature of the air in the garden. They should be the same check cold air is not recirculating. 2016 b 22

Extra testing, optional It is possible to test each component one after another using the service function. You can use this to make sure the unit is running correctly. To access service mode on the wiring centre, press the two top buttons together, release and do it again, press + 5 times till you get to installer menu, press select. It will ask for the password, press + and hold it till you get to 17, press ok. Press + till you get to test menu, press select then press + till you get to sensor actuator test. Press + and you can scroll through all the actuators, ive hi lit in red the important ones. Display T.0.01 Heating pump power, used to run the pump in the unit T.0.05 Fan power, you can force the fan to operate T.0.07 4-way valve used to defrost the unit T.0.08 Position of the electronic expansion valve, don t adjust this T.0.09 Heating coil compressor, don t adjust this T.0.13 Flow temperature, this is the flow temperature T.0.14 Return temperature this is the flow temperature T.0.15 Heating circuit pressure T.0.16 Heating circuit flow rate in l/hour T.0.17 Lockout contact S20 T.0.66 Air inlet temperature this is the air temperature T.0.26 Compressor outlet temp it should be less than 70C. T.0.27 Compressor inlet temperature T.0.29 Heat exchanger temperature T.0.30 High pressure T.0.31 Condensation temperature T.0.33 Evaporation temperature T.0.34 Superheating target value T.0.35 Superheating actual value T.0.36 Sub cooling actual value T.1.37 Outside temperature T.1.38 DCF status T.1.59 Multi-function output 1 T.1.60 Multi-function output 2 T.1.61 Diverter valve 1 T.1.62 Flow sensor T.1.63 Cylinder sensor this is the cylinder temperature. T.1.64 Multi-function input T.1.65 Energy supply company input T.1.66 Inlet temperature T.1.67 High-pressure switch T.1.68 Compressor rotational speed this is the speed of the compressor T.1.69 Condensate pan heating T.1.15 Water pressure 2016 b 23

Fault Codes: F.022 Water pressure too low Insufficient water in the heating system F.037 Fan fault Obstruction in the product's air guiding Fan motor not connected or faulty The connection between the main PCB and the fan PCB is damaged or broken. F.042 Fault: Coding resistance The product's coding resistance is missing or is faulty Coding resistance value outside the permissible range F.073 Fault: Water pressure sensor Line to water pressure sensor is broken or has a short circuit F.086 Contact thermostat has opened. Underfloor heating temperature too high Heating circuit flow rate too low, Underfloor heating circuit is closed F.103 Fault: Spare part detection The main PCB that is fitted as a spare part or the inverter does not match the product F.514 Sensor fault: Comp. inlet temp. Sensor is faulty or incorrectly connected to the main PCB F.517 Sensor fault: Comp. outlet temp. F.519 Sensor fault: Return temperature F.520 Sensor fault: Flow temperature F.523 Sensor fault: VF1 Line to VF1 temperature sensor is broken or has a short circuit. F.526 Sensor fault: Temp. environment circuit EEV 1) Sensor is faulty or incorrectly connected to the main PCB F.532 Building circuit: Flow rate too low Pump fault, Check the specific flow rate in the heating circuit F.536 Compressor outlet temp. too high Coolant quantity too low. F.537 High-pressure switch open The safety cut-out has been triggered F.539 Coolant pressure too low Coolant quantity too low Air flow too low F.546 Sensor fault: High pressure Faulty cabling F.554 Coolant pressure not in operating range F.582 EEV fault Cable insulation faulty F.585 Sensor fault: Temp. building circuit EEV 2) Sensor is faulty or incorrectly connected to the main PCB F.685 Communication fault: ebus The product is not connected to the controller Polarity inverted F.750 Connection fault: Compressor Cable insulation faulty Connection broken F.751 Compressor: Overcurrent fault The product's voltage supply is too low The ribbed pipe heat exchanger or heat exchanger is dirty F.752 Fault: Inverter Inverter box damaged The cooler inverter box is blocked. Faulty voltage supply F.753 Connection fault: Inverter not recognised The connection between the main PCB and the inverter box is damaged or broken. The inverter box is not switched on. F.754 Fault: Fan unit The connection between the main PCB and the fan PCB is damaged or broken. The fan PCB is faulty F.755 Fault: 4-way valve position incorrect Mechanical or electrical problem. Move the 4-way valve away from the controller. When moving it, check that the coil voltage is correct. F.774 Sensor fault: Air inlet temperature The temperature sensor is faulty or incorrectly connected to the main PCB. F.1288 Fault: SP1 cylinder temperature sensor is faulty or has not been correctly connected to the VWZ AI heat pump control module. 2016 b 24