Every Nu-Heat system is a custom design. Please record your unique System Reference number for future reference: System Ref: Nu-Heat U N D E R F L O O R & R E N E W A B L E S user guide hitachi yutaki air source heat pump design innovation expertise service 04.12.14
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user guide for the hitachi yutaki air source heat pump This guide is aimed at providing a basic understanding of the heat pump system installed within your property. You will find references here to other leaflets, such as the manufacturer s user guide for the Hitachi wireless room unit and also the Nu-Heat Underfloor Heating User Guide. Contents Page 4 The Installation 4 System component identification 5 The Heat Pump and System 5 How do heat pumps work? 5 Running patterns and flow temperatures 6 Buffer tank 6 Average house temperature 6 Weather compensation 6 Domestic hot water 6 Coefficient of Performance or CoP 6 Bivalent point 7 The Controls 7 Room thermostats 7 Wireless room unit 7 Increasing the room temperature in a particular room 7 Increasing the room temperatures generally 8 Hot water programmers 8 Domestic hot water programmer 8 Legionella purge programmer 8 Secondary hot water loop programmer (if installed) 8 Separate towel rail circuit programmer (if installed) 9 Running the System Economically 9 Heat pump set-up 9 First year of use 9 Choice of heating mode 9 Hot water temperature 9 Hot water reheat 9 Electrical tariff 9 Extreme weather 10 Maintenance 10 Heat pump 10 Controller 11 Heating system 11 Radiator system 11 Domestic hot water cylinder 12 Maintenance log 14 Glossary of terms 3
1 2 3 4 5 6 7 HITACHI i SEL HITACHI + - SET 0 2 1 3 4 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 10 10 11 11 12 12 The Installation Comprehensive information about the heat pump installation is in the MCS Handover Pack you should already have received from your system installer. System component indentification Example layout (actual layout may differ) Legionella purge programmer 2 6 13 4 3 5 12 1 7 Towel rail programmer Towel rail circulation pump 8 Towel rail zone valve Towel rail circuit Pipe stat 11 UFH circuit Radiator circulation pump 10 9 14 Radiator circuit Nu-Heat 2010 1. Air source heat pump, Yutaki 2. Domestic hot water cylinder 3. Heat pump controller 4. Room unit (heating programmer) 5. Domestic hot water timer 6. Domestic hot water loop (if installed) 7. Towel rail circuit (if installed) 8. Heating system expansion vessel, pressure gauge and filling loop 9. Heating system filter and isolation valves 10. Heating system air separator (self venting) 11. Backup immersion heater and thermostat 12. Domestic hot water immersion heater and thermostat 13. Domestic hot water cylinder overheat cut-out 14. Buffer tank 4
The Heat Pump and System The air source heat pump installed in your property has been carefully chosen by Nu-heat to provide the highest level of efficiency. If the system is operated as recommended in this user guide, and in the user guide supplied with the heat pump controller, then it should operate efficiently and reliably for many years to come. Keep the heat pump clear of vegetation and debris such as sticks or fallen leaves. Make sure air circulation is not obstructed by garden furniture or bicycles etc being leant against it. The unit contains powerful fans which must not be obstructed. During the winter ice will build up on the heat exchanger at the rear of the unit (the evaporator ). The heat pump has a built in feature to allow it to feed heat through to periodically melt the ice. This will result in water and steam issuing from the unit and is part of the normal operation of the heat pump. Keep drain ways clear around the unit so that this water can run away. Read the rest of this guide to find out how to get the best from your heat pump. How do heat pumps work? Air source heat pumps work by compressing low grade energy from the air outside into high grade energy for heating and hot water production. Hitachi heat pumps use the vapour-compression refrigeration cycle to transfer energy from the outdoor air to the water in the heating system. Even at temperatures as low as -20 C it can supply significantly more energy than it uses. HITACHI warm air cold air warm water Heat pump systems and boiler systems are designed to operate in very different ways. It is important to understand these differences in order to ensure that the heat pump system is set up and operated correctly. Running patterns and flow temperatures A traditional boiler system is usually oversized for the property and is designed to work at a high flow temperature. The boiler will generally run for limited periods of time even in cold weather. In contrast the heat pump will have been sized to match much more closely the steady state heat load for the property, and is therefore able to run all day economically in cold weather. This is done to utilise the lower water flow temperature that the heat pump produces. If it were required to produce higher temperatures then the efficiency would be compromised efficiency goes down as the water flow temperature goes up. Radiators supplied from a heat pump will be warm rather than hot to the touch but, being larger than usual and warm for a longer period, will still maintain the house at a comfortable temperature. Underfloor heating, which by its nature requires lower water temperatures than radiators, is often the preferred choice. 5
Buffer tank The use of a buffer tank increases the effective volume of the heating system and allows the heat pump to build up a reserve of heat energy in the water stored in the buffer tank. This prevents the heat pump from short-cycling and also stores heat for the defrost function. Average house temperature A Nu-Heat heating system is designed to maintain the property at 21 C for living areas, and 18 C for bedrooms. With underfloor heating the temperature can afford to actually be a degree or so lower without sacrificing comfort. Whether the system comprises underfloor heating or radiators it must be borne in mind that increasing the house temperature will increase the building heat loss, and hence the running cost. It is recommended that the target room temperature is set at no more than 21 C in living rooms and 18 C in bedrooms. Weather compensation During the milder parts of the heating season less heat is required to maintain comfort levels. The heat pump measures the outdoor temperature and adjusts the temperature of water being fed to the heating system - the warmer it is outside the lower the flow temperature and so the higher the efficiency of the heat pump. This method of operation is called Weather compensation and is critical to enabling the heat pump to operate efficiently by allowing it to always work at the lowest possible flow temperature. In contrast, a boiler system usually operates at a fixed flow temperature of anything up to 86 C, irrespective of how much heat is required. Domestic hot water The efficiency of the heat pump is less when it is used for generating domestic hot water, because the heat pump is normally required to supply the cylinder with water at a higher temperature than is used for space heating. To maximise the efficiency, domestic hot water is stored at a lower temperature than in a conventional boiler system. For this reason the cylinder must be larger in order to provide sufficient capacity for normal baths and showers. Coefficient of Performance or CoP The efficiency of the heat pump is also referred to as its CoP, and is the result of the power output divided by the power input. For an air source heat pump CoP is generally in the range 2.5 to 4 but it varies all the time, as the outside air temperature varies. Bivalent point As the outside air temperature drops, there eventually comes a point where the heat pump on its own cannot maintain your comfort levels within the property. This critical outside temperature is called the Bivalent point. A typical bivalent point might be between -3 C and 0 C but the actual bivalent point for your system will depend on the characteristics of your house and of the heat pump. Below the bivalent point there is likely to be a need for backup heating. The backup heating element will then be required to supplement the heat pump s output, but it will be less efficient and noticeably more expensive to run than the heat pump itself. It is important to note that during colder than average winters this backup heating will be called into action more frequently. Conversely in milder winters the backup heat source may not be required at all 6
The Controls Room thermostats Guidance on how to use our standard range of room thermostats is contained in the Nu-Heat Underfloor Heating User Guide. For a heat pump system, room thermostats do not control the heat pump itself, just the flow of water from the buffer tank to an individual room zone. The heat pump will instead be controlled by the dedicated wireless room unit. Wireless room unit The main user control is the wireless room unit. This unit allows you to adjust for your preferred comfort level for the heating system. It works as the main heating programmer, measuring the room temperature to determine whether the heat pump shall run. The wireless room unit should be located in a room without any other form of control (i.e. there must be no other room thermostat), usually a living area or hallway. Avoid placing the unit in sunlight, in a draught or above a local heat source such as a towel rail, radiator or cooker. (The A3 Manifold & Zone Information drawings, to be found in the MCS Handover Pack, show where the wireless room unit can best be located.) Operating modes There are three different operating modes: auto mode: In auto mode the heating programme runs as set. The system will be more efficient and provide greater comfort in manual mode. manual man mode: In man mode a constant temperature is maintained. This should be 21 C. off mode: In off mode the system will only maintain a frost protection temperature of 5 C. off mode can be used during the summer when no heating is required. Increasing or decreasing the room temperature in a particular room Rooms with a thermostat: Adjust the room thermostat to your preferred temperature but you should normally avoid settings above 21 C. If the room is not warming then an increase of flow rate may be required. Rooms without a thermostat: If individual rooms are not warm enough then firstly the flow rate should be adjusted (see Underfloor Heating User Guide Heat Pump Systems, or the radiator manufacturer s instructions). If adjusting the flow rate is not enough, or if there are multiple rooms (or zones) which aren t up to temperature, then the wireless room unit can be adjusted to increase the flow water temperature generally. Decreasing temperature is achieved by the reverse of the above. Increasing or decreasing room temperatures generally The general room temperature can be increased or decreased using the temperature adjustment buttons which can be seen when the flap on the wireless room unit is closed. The temperature can be adjusted at any time using these buttons, however if the room unit is in the Auto operating mode then the temperature will revert back to the preset temperature at the next time period. If this causes an issue then the preset time and temperature programs will need to be altered as detailed in the Hitachi Room Unit User Guide. 7
Hot Water Programmers Domestic hot water programmer A Danfoss TS715 programmer is supplied to control when the heat pump heats the Domestic Hot Water (DHW) cylinder. Full details on how to operate the programmer are provided in the Nu-Heat Underfloor Heating User Guide supplied with the system. When setting the programmer ensure that the time settings chosen allow for the heat pump s longer cylinder re-heat time compared to a boiler system. This could be anywhere between 2 and 4 hours to reheat from cold, depending on heat pump size and outside air temperature. TS715 Hot water programmer The Aquastar2 hot water circulating loop Legionella purge programmer A 13amp programmer is provided to operate the DHW cylinder immersion heater. The main function of this is to raise the cylinder temperature to 60 C for an hour once a week, to purge the cylinder of Legionella and other bacterial growth. This programmer normally runs in automatic timed mode and the commissioning engineer will have been advised to set it to run once a week on Monday morning between 1am and 4am. This should not normally require to be altered. The button can be used to override the programming if the immersion is on then it would be switched off and vice versa. The timer will revert to the programme at the next timing stage. Please see the manufacturer s instructions for more detail. C Secondary hot water loop programmer (if installed) The hot water secondary return should be set to operate for the minimum amount of time required. Ideally it should operate for a maximum of 2 hours in the morning and 3 hours in the evening. Separate towel rail circuit programmer (if installed) The towel rail programmer should be set to operate for the minimum amount of time required. Ideally it should operate for a maximum of 2 hours in the morning and 3 hours in the evening, in periods when the hot water cylinder is up to working temperature. Towel rail 8
Running the system economically The heat pump system has been carefully designed to operate efficiently down to below-average weather conditions, however a few things should be taken into account to get the best from it. Heat pump set-up The heat pump has been set up by the commissioning engineer. Its settings should not be changed without full working knowledge of the system and of the parameters calculated during the design process. If there are any doubts about the way a heat pump is set up, Nu-Heat technical support are able to assist customers in checking system parameters. First year of use During the first year after a house has been built the energy required to heat the house can be up to 30% higher than normal due to the need to dry out the fabric of the building and because the damp walls and floors are more thermally conductive. If the initial switch-on of the system occurs in the winter then this can cause issues with poor heating performance as the heat pump is trying not only to heat the house and counter normal heat loss, but also to dry the building out. This can result in a higher than expected amount of supplementary energy being consumed (e.g. direct electric immersion heater). Choice of heating mode In summer the wireless room unit should be set to off mode to reduce standby energy consumption. At other times use auto mode or manual mode and avoid calling on the supplementary heating element unless this is essential. Hot water temperature The hot water temperature must be set so that it is within reach of the compressor without the need for additional heat. A setting of 48 C is normally adequate and is within the capability of all Hitachi heat pump compressors, (the single fan unit is capable of higher temperatures, up to 53 C is sensible). The cylinder immersion heater is normally only required during the periodic Legionella purge cycle. Ensure that the hot water and Legionella purge timeclocks have been correctly identified and set. Hot water reheat Air source heat pumps are most efficient during the warmer daylight hours. With an air source heat pump it is therefore sensible to time the domestic hot water reheat period(s) to occur during the day, but preferably at times when space heating is not a priority. If you have prolonged hot water demand you can alternatively set the hot water timeclock to an extended on period to ensure immediate reheat of hot water on demand. Electricity tariff Studies conducted by Nu-Heat suggest that there is little or no benefit from using an Economy 7 tariff with an air source heat pump, as the majority of consumption occurs outside the low-rate period. However, you will need to consider your other energy usage before choosing the best tariff for your requirements. Whether you choose an Economy 7 or Standard tariff, you should always look around for the best deal in your area as tariffs can vary considerably between different suppliers. Extreme weather In 2009/2010/2011 the United Kingdom experienced two unusually cold winters. Temperatures of 10 degrees below zero, or lower, were common during several months. In these conditions the output of any air source heat pump is significantly reduced, while the heat loss of the building is greatly increased. Any heating system must use fuel more heavily during such a period, and a heat pump is no exception to this rule. Below the bivalent point however, a heat pump system will start to draw on its supplementary heating element, the efficiency of which is far below that of the heat pump itself. If you have a cheaper form of supplementary heating than direct electric, such as a wood burning stove, then this is the time to use it. 9
Buffer tank floor or wall mounted dependant on installation space. Maintenance Whilst heat pumps are, in principle, maintenance free it is recommended that your heating system should be checked annually to ensure that it runs as efficiently as possible. This is also a condition of the heat pump and hot water cylinder warranties. This maintenance must be carried out by a competent person, and with reference to the manufacturer s instructions. The heating system filling loop is used to re-fill the system should the pressure on the gauge fall below 1 bar. When the system is initially setup there will probably be a small amount of air in the system, this should be released through the automatic air vents. The lost air will cause a pressure drop in the system, easily corrected by the addition of water via the filling loop. However, a frequent need to pressurise the system may indicate a leak, you should contact your installer to have this investigated. There is a filter (see p.4 item 9) installed on the return pipe back to the heat pump to ensure that any debris in the system does not block the heat exchanger inside the heat pump. This filter should be cleaned periodically to maintain the required water flow rate. The backup immersion heater thermostat in the buffer tank should be set to 60 C. The immersion heater thermostat in the cylinder should be set to 65 C. It is used weekly to purge the cylinder of any bacterial growth (Legionella, for example). This immersion heater can also be used to produce extra hot water, however such use is bound to increase running costs. The cylinder overheat cut-out is a requirement of Building Regulation G3. In the unlikely event that the cylinder temperature exceeds 80 C the switch will cut out, and shut the valve between the heat pump and cylinder. To reset, the black cap should be unscrewed and the reset button depressed. If this is recurring problem then you should contact your installer. Heat Pump Hitachi Yutaki Yutaki (outdoor unit) Check condition of casing Check electrical supply connections Check all visible pipe joints for leakage Check that the inlet and outlet grilles are free from debris (leaves, snow, etc.) Warning: beware of the rotating fan isolate unit if necessary Check that the heat pump base is free draining of condensate Verify correct refrigerant charge by indirect measurement (registered Level A MCS installers only) Controller Check the alarm log for any faults Check electrical control functions (relay test) 10
Heating system Please refer to the Underfloor Heating User Guide for details of servicing the Underfloor heating. Clean strainers on heating circuits, ensure system is re-pressurised and introduced air is flushed from system Check the system for any visible signs of leakage Radiator system Check inhibitor levels, and top up if necessary Check the heating system pressure (this should be around 1 bar for a 2-storey building, or more for a taller building) Domestic Hot Water Cylinder Please check the manufacturers cylinder manual for any service record that may be a condition of warranty. Check correct operation of inlet group safety valve Check correct operation of temperature and pressure relief valve Check that all discharge pipes are free from obstruction Check the gas pressure in the potable water expansion vessel Check cylinder sacrificial anode indicator (where applicable) Check the settings and operation of the cylinder hygiene purge The Nu-Heat EnergyMaster2 cylinder 11
Maintenance Log Date Engineer s name Company Telephone no. Comments Signature 12
Maintenance Log Date Engineer s name Company Telephone no. Comments Signature 13
Glossary of Terms Steady state heat loss: Nu-Heat designs heating systems to an indoor temperature of 20 C (18 C for bedrooms) and an outdoor temperature of -3 C. The steady state condition is when the amount of heat being input by the heating system exactly balances the amount of heat being lost from the building, and is assessed at the design temperatures. In order to raise the room temperature it is necessary to input more heat than is being lost. Coefficient of Performance (CoP): Coefficient of Performance is a measure of efficiency for heat pumps. A CoP of 4 means an efficiency of 400%, so for every unit of energy that you put in (electrical energy into the compressor) you get four units of heat out (i.e. three free from the air). The efficiency of a heat pump will vary with the temperature of the source (outside air) and the temperature of the heating water being generated. As the outdoor air temperature increases, so does the efficiency of the heat pump as the compressor has to work less hard to achieve a given output temperature. As the temperature of the heating water rises, the compressor has to achieve a higher gas pressure, using more energy, and the efficiency of the heat pump falls. The actual efficiency is calculated by dividing the power output by the power input. For example, a heat pump delivering 10kW may have a power input of 2.5kW. Hence the CoP is 10/2.5 = 4 (or 400% efficient). The quoted value of an air source heat pump s CoP is often calculated with a source temperature of 7 C and an output water temperature of 35 C. A more useful figure is a seasonally adjusted CoP (Seasonal Performance Factor, SPF) which takes into account average weather conditions over a year in a broad geographical location, and a model of the specific load in question. It also takes into account the amount of energy required from additional heat sources, pumps, valves and other energy consuming devices. Whilst this can only ever be a best guess as there is no such thing as an average year, it does give a better indication of reality than published benchmark figures. Heat pumps are least efficient when producing domestic hot water. In winter, CoP for hot water production can be as low as 2. This is still much better than using a direct immersion heater, whose CoP would be 1 only. Weather compensation: Weather Compensation is where the heating water temperature from the heat pump is changed in accordance with the outdoor temperature. When it is warm outside, not very much heat is being lost from the building and so the heating water can be quite cool and still maintain a comfortable temperature inside. As it gets colder outside, more heat is lost from the building and the water in the heating system needs to be warmer in order to maintain comfort levels inside. The line as shown on the graph above defines the relationship between these two temperatures is called the heating curve. This curve can be selected on the heat pump controller, normally as a number and the shape of the curve can be altered in order to optimise comfort and efficiency of the system throughout the year. 14 Heating water temperature ( C) 60 50 40 30 20 10 0-5 0 5 10 15 Outside temperature ( C)
Glossary of Terms continued Bivalent point: The bivalent point is defined by a temperature at which the output of the heat pump cannot be increased and is exactly equal to the heat loss of the building. The idea being that at temperatures below the bivalent point the secondary heat source (e.g. direct electric heating) is allowed to switch on. Correctly identifying this temperature will optimise the running of the system to minimise energy costs. Four things are important here: 1) The calculated heat loss of a building at a nominal minimum temperature (say -3 C) 2) The output power of the heat pump 3) The average amount of energy required to run the heat pump 4) The proportion of the year when the temperature falls below the nominal minimum These factors are all taken into account in order to best predict which size of heat pump is suitable for a property. The graph shown below indicates the salient factors of the final design. Building heat loss at -3 degrees outside temperature e.g. 12kW Heat pump output at 15 degrees outside temperature (assume 20 degree flow temperature) e.g. 14kW Heat pump output at -3 degrees outside temperature (assume 45 degree flow temperature) e.g. 8.2kW 0kW 0 5 10 15 Bi-valent point at which additional heat source is required to be enabled e.g. outside temperature of + 1 degree C Heat loss at 15 degrees outside temperature The outside temperature drops in winter and so does the output power of the heat pump. However the energy required to heat the building increases and at a given temperature the two values will be coincident. This temperature is called the bivalent point. Below this point, the heat pump cannot deliver enough power to heat the building to the designed temperature, at which time the secondary heat source will be called into operation. 15
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