Heat Pump Information

What are the benefits of Air Source Heat Pumps over Ground Source Heat Pumps?
There are a number of benefits when using an Air Source Heat Pump (ASHP). Capital cost is lower as ASHP’s are self-contained units without additional heat transfer requirements such as ground pipes.

Can units be hidden behind fences, bushes etc...?
Units may be installed behind barriers or even inside enclosures. The important consideration is ensuring that adequate airflow is available and that the discharge air cannot be re-circulated back onto the inlet as this will result in a continual lowering of the air temperature reducing the efficiency of the unit.

How does the heat pump noise level compare with other heating appliances?
Sound levels inside the house are generally lower than those that would be expected from a gas or oil boiler with a fan assisted flue and will not cause a nuisance provided the installation guidelines have been followed correctly. Noise levels outside may be 2-3 dB higher than those expected from a condensing boiler flue and this should be considered when selecting the position of the heat pump. Low noise options are available.

Can the heat pump cool as well as heat?
Heat king BWarm and BWarm i heat pumps are available from Renewable Solutions North Norfolk and are supplied for heating only. However if cooling is required the BCool2 range of units is available to provide both heating and cooling. Cooling may be used with under floor heating or with fan coil units but it is not recommended with radiators as even though the minimum water temperature can be controlled, on certain days, depending upon conditions, the radiators could sweat and cause water damage to carpets or flooring.

Can radiator and under floor systems be combined?
Yes, but if used in this way the heat pump return water temperature should be set to suit the radiator system and a mixing valve used to reduce the under floor supply to the design temperature. A 2nd set point kit is available for use with this type of system.

What is the Design Outdoor Temperature (DOT)?
This is the lowest normally expected temperature in the area where the heat pump is to be installed. The DOT will vary from region to region, being lower in the North of Scotland and gradually increasing moving south.

How often should the water temperature be boosted to raise its operating temperature?
In most conditions the heat pump will start and raise the water temperature as expected. In periods of very cold weather, when the external ambient temperature drops below the external design temperature, a boost heater is available to top up the heating duty available. This can be programmed to switch on automatically with the addition of a digital stat kit. The boost heater will increase the flow to the radiators and will also aid the heat pump at start up.

Can the heat pump raise the water temperature to 65°C?
This would depend on the system chosen. The standard heat pump will raise the supply water temperature to 55°C as set by the controller. If applying the BWarm (or BCool2) 9000i or 13000i heat pumps, water temperatures of up to 65°C will be possible but the higher the water temperature the lower the overall unit efficiency.

What size should the radiators be?
Radiators should be sized to operate with a supply water temperature of 55°C (65°C for BWarm i units), available from Renewable Solutions - Renewable Energy North Norfolk and a return temperature of 45°C (55°C for BWarm i units) using the radiator manufacturers data to select appropriately sized radiators for the application.

How should Domestic Hot Water be heated?
The heat pump should be used to pre-heat the water before additional heating is added to raise the water to the desired temperature. If connected in parallel with a Solar Heating System the heat pump should be set to operate if the Solar cannot provide adequate heating. DHW systems should be designed to comply with current regulations. BWarm i models are able to supply domestic hot water at 65°C.

What is the best type of wet system to connect a heat pump to?
For optimum efficiency an under floor system provides the best results, as it requires a lower flow temperature and the heat pump can be programmed to provide the water at the required temperature with no need for a mixing valve. Any system will benefit from using a thermal store rather than a direct feed which will allow the heat pump to raise the water to the correct operating temperature more quickly as there is no direct heat loss from the thermal store during the start up period.

What is the lower limit operating temperature?
-20°C is defined as the lower operating limit but the heat pump will not switch off at this temperature. At -20°C the maximum supply water temperature will be 45°C (55°C for the 13000i unit).

What controls will the heat pump work with?
The heat pump is fitted with a controller that is pre-programmed with all of the operating set points and alarms and simply requires an input from an external time clock/thermostat. Any standard type of central heating controller will work with the heat pump but the best solution is to use a controller with a number of on/off options for each day to take advantage of any special off peak tariffs available.

Radiator Systems
The heat pump should be serviced once a year by a qualified technician and the following items checked; The unit structure for signs of corrosion or damage. Panels are securely fastened and vibration free. All electrical connections are secure and that there is no damage to any of the wiring. All water connections are tight and the system water pressure is correct. Pipe insulation has not deteriorated or come loose. The air path to and from the unit is clear. Condensate drain pan and pipe are clear and clean (if fitted).

Sufficient space is required for airflow into the machine and adequate clearance is needed at the front of the heat pump to prevent cold air re-circulation. Access is also needed for service and maintenance. If possible the unit should be sheltered from high winds to improve efficiency by reducing the fan power requirement. Units are best placed in a south facing aspect to gain maximum benefit from solar gains.

Each unit has a different mains power requirement as the compressor size differs from unit to unit and it is the compressor that draws most of the power. To minimise the peak starting current a soft start device is fitted to all single phase units.

This device reduces the starting peak to a level acceptable to the electricity suppliers and also prevents possible interference with other electrical equipment.

The 6000, 8000 & 9000i units require a 32A ‘D’ Type motor rated MCB.

The 12000 & 13000i units require a 40A ‘D’ Type motor rated MCB.