Guidance on installing domestic heat pumps.

Full details are available in the Installation Manuals supplied with the product. It is important that the manual is read before any installation begins.

Kensa heat pumps are specifically designed to be installed by competent plumbers without the need for specialist training. The key to a good heat pump application is the application engineering and is carried out by Kensa in the initial stages of the project. This allows end users to select contractors who they have a good working relationship with and reduces the cost of installation. Full technical back up is also available at anytime from Kensa.

Heat pumps should ideally be installed within a separate room such as a utility room and located away from noise sensitive areas such as bedrooms. They should be placed on a firm, level and substantial concrete base which will absorb vibration. Take into account the “Recommended Clearances” when finalising the location.

When connecting the heat pump to the underfloor and ground arrays use only plastic flexible pipe such as “Speedfit”. The reason for using flexible pipe is that the heat pump is suspended on anti-vibration mounts, so the connections must also be flexible.

The heat pump itself is operated by a live return from the underfloor control system. Also linked to the underfloor control system should be the time clock and room thermostats. If the thermostats are calling for heat and the time falls within the specified heating period, then the underfloor control system calls on the heat pump to operate. The heat pump is also controlled on the return temperature from the heating distribution system and if this is above the heat pump’s set point the unit will turn off. For wiring diagrams please see the Installation manuals.

When a heat pump is connected to radiators, as the radiators are a “demand” based system, the heat pump will “cycle” on and off several times per hour. Each time a heat pump starts, like many other appliances such as computers and washing machines, some disruption is caused on the electricity network, which usually consists of “flicker” on tungsten filament bulbs. If a heat pump is to be connected to radiators it is therefore essential to consider the robustness of the power supply to the building. Where a heat pump is connected to a power supply from a single-phase transformer shared with another property, then great care must be taken. This can be mitigated by fitting a device to the compressors that reduces the current drawn at start up. Commonly called a “soft start”, this type of device does not work with scroll compressors, and should not be fitted. A new type of device has been developed specifically for scroll compressors, and this is fitted as standard inside all single-phase Kensa Compact Heat Pumps For Radiators

Due to the high starting currents of the compressors used within heat pumps, Kensa would always recommend using a Type D Mains Circuit Breaker. This allows a high peak current for a very short period. Without a type D MCB, the heat pump could continually trip the circuit board whenever it started.

Any electrical work required to install or maintain this appliance should be carried out by a suitably qualified electrician in accordance with current IEE regulations

The Kensa Domestic Compact ranges of heat pumps come with in-built integral water pumps. One connected to the ground array loop and a second for the load side i.e. underfloor. The ground array water pump is sized for the correct number of ground arrays for the heat pump. The load side water pump is sufficient to pump water around underfloor systems with one heating manifold. If the underfloor has more than one manifold the integral pump should be used to pump water around a shunt loop to which the underfloor manifolds are connected. Each underfloor manifold is required to have its own pump to draw water as required from the shunt loop.

On any underfloor manifold the thermal mixing valves should be removed, as they are not required and to avoid the heat pump short cycling 25% of the underfloor zones should have any electric actuators removed.

The easiest way to do this is simply to have some zones left “open” – that is, without electric actuators.
In houses, the best zones to choose are ensuite bathrooms, and hallways, neither of which are likely to be overheated. (Click here for a Factsheet on underfloor zoning.)

All Kensa Compact Heat Pumps are supplied with Weather Compensation as standard. This facility will reduce the return water set-point against a schedule of external ambient temperatures. In more simple terms, the temperature of water flowing into the building’s radiators or underfloor heating is reduced in mild weather, which allows the heat pump to run more efficiently. The weather compensation developed by Kensa for use in their heat pumps is very sophisticated as it uses actual temperatures. In the UK, the use of banded tariffs such as Economy 7, or more especially Economy 10, makes the use of weather compensation on heat pumps unlikely to give any significant cost savings and can actually increase the cost of running a heat pump. This is because during a banded and cheaper rate of electricity it is desirable to run the heat pump at its maximum heat output, so that as much heat is forced into the building as possible, whilst being careful not to overheat it in milder weather.

For this reason, Kensa Heat Pumps are supplied with this function disabled in the software.

However, tariffs might possibly change in the future and so to enable weather compensation on your heat pump you can contact our Technical department, who can run through the reprogramming procedure.

Kensa heat pumps are designed with a number of in-built sensors and probes, which enable Kensa to commission over the phone with the installer present. This means Kensa takes responsibility for the commissioning and allows the end client to gain access to grants available without the installer having to pay expensive registration fees.

When initially commissioning the system it is important that the compressor MCB on the heat pump is not turned on without talking to Kensa. If the compressor is activated and the slinkies have not been purged correctly of air, or the correct amount of antifreeze added, the evaporator heat exchanger within the heat pump could freeze. While this will not damage the heat pump, it will not operate until the unit has defrosted, which could take 24 hours.

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