Retrofit Heat Pumps

The range of Pure Thermal Heat Pumps enables a range of retrofit heating and hot water applications to be considered which would not normally be considered as being compatible with traditional standard Heat Pumps.

A retrofit heating project is challenging by nature and produces several key design questions:

How can a heat pump be integrated with the installed higher temperature boiler driven system?

A High Temperature heat pump system is able to operate at temperatures up to 80C which mean that a Pure Thermal Heat Pump is able to be configured to work with an existing boiler system or alternatively operate as a stand-alone system.

How should the heat pump be sized, at 100% heating and hot water capacity or to operate down to a certain ambient temperature to maximise performance versus capital cost?

Here there are options, to reduce a projects capital cost a retrofit 70C High Temperature Heat Pump system could be designed/sized to operate to 0C, rather than -10C for example, in order to maximise the return on investment and capital cost. In this case below 0C the heat pump will still operate and will be supported by the installed boiler with both operating at the same temperature.

Should the new heat pump system design maintain 100% capacity available from the installed boiler system to support the heat pump?

It is not necessary to maintain 100% available capacity from the boiler, it will only be necessary to maintain the boiler capacity required to support the High Temperature Heat Pump i.e. if the total heat load at -10C ambient is say 150kW and the heat pump will provide 135kW at a -10C ambient condition then only 65kW support capacity will be needed to be provided by the boiler. This is due to the heat pump being able to operate with the boiler in a parallel bivalent configuration with both heat sources operating together at the same output temperature of 70C.
Alternatively in this example if a stand alone heat pump only system is the driver, and capital cost is less of a priority, then the heat pump could operate at 100% of the capacity required at the -10C ambient to produce both heating and hot water.

Does the installed heating distribution system need to be modified and changed to have new radiators or heating coils fitted?

Best practice will always dictate that the heat pump should operate at the optimum flow temperature to deliver maximum efficiency. However, retrofit commercial or industrial projects can make any change to the heating circuit, to enable operation at 45C, difficult or impossible.
This is where a High temperature Heat pump system delivers real benefits.
By installing a heat pump system that is capable of delivering temperatures of up to 80C, when required, a challenging retrofit project can now be designed with a low carbon heat pump system where it would have been practically impossible to do this with lower output temperature heat pumps that are more suited to new installations rather than retrofit projects.

Can the Heat Pump operate with the boiler or does the system need to have an on/off controls where the boiler and heat pump do not operate together?

Traditionally bi-valent, or dual heat source, applications utilising heat pumps and boilers have in the main been configured with an on/off control strategy.
This would mean that a standard heat pump, with a maximum 55C output, would stop working at for example 0C and the boiler would then start operating and deliver the full heating duty without the heat pump.
However, a Pure High Temperature system is able to operate with the boiler in a parallel configuration with both heat pump and boiler operating at the same temperature, this enables maximum value to be gained from the heat pump system and provides complete design flexibility.

Can a Heat Pump deliver the hot water temperatures that the application or building requires?

All of the Pure High Temperature heat pump ranges are able to deliver temperatures that can produce hot water either on an accumulated stored basis or with minimal storage and an on-demand basis.
A complete range of Pure Thermal optimised accumulation tanks is available that enable hot water to be produced and stored during low cost electricity tariff periods which enables cost and carbon savings to be achieved from low cost and/or low carbon electricity. For example high temperature stored hot water could be produced whilst on site Solar PV electricity is being generated or alternatively when grid power is available at a low kWH cost.