LPHW Unit Heaters

LPHW Unit Heaters

LPHW Unit Heaters- an air heater for a heating hot water system which can be powered by renewable sources of energy such as an air source heat pump, ground source heat pumps or a traditional hot water boiler from Flexiheat UK

A LPHW (which donates Low Pressure Hot Water) heater is fed by a hot water system. A boiler, which can be a gas or oil boiler, biomass boilers or a heat pump, is the external warm water heat source used by these water heaters. The warm water is transported to the LPWH unit heaters by the heat source. Then a fan disperses the warm air throughout the area being heated, such as exhibition halls, production lines, sports halls , warehouses, garages and many other commercial or industrial buildings that require heating.

LPHW heater

In gravity feed systems, the flow and return pipework pressures for LPHW are frequently less than one bar in operation and 2 to 4 Bar in pressurised heating systems.

Our lphw unit heaters can operate up to a maximum pressure of 16 Bar with various discharge options – either downward discharge (vertical installation) or horizontal discharge units.

We also do an air heater version especially for a heat pump system, that has a larger delta T flow and return system, that these heat source systems can operate on.

Warm air flow

This cost effective water fed unit heater range are fitted with a three speed energy efficient fan installed on every model. The fan motor speed is controlled by optional control accessories, which range from a basic control option to a full BMS (Building Management System) compatible control model, which is frequently required and suited to commercial and industrial warehouses.


All of our manufactured controllers have temperature control, to turn off the air heater or heaters when they reach a certain temperature, or to modulate the fan motor on the units as required.

Product Construction

Because it is specially developed and made of expanded polypropylene, it weighs up to five times less than a conventional steel cased unit heater at the larger heat output sizes. This makes installation of the fan coil unit space heater easy even in tight space configurations.

Both these accessories make installing these heaters an easy task in warehouses or factories, especially when a unit heater mounting position may be required directly over production lines or to avoid pallet racking, etc.

Pallet racking in industrial warehouses

Heat exchanger

The heat exchanger in this extensive range of warm water heaters , made of copper with aluminium fins, ,which guarantees optimum heat output with high efficiency from the equipped heating coils. The air flow generated by the fan and motor is directed through the adjustable louvers fitted to the heaters into the rooms being heated.

hot water heat exchangers with aluminium fins for our warm air heater

The heat output of this extensive range of unit heaters for low pressure hot water systems is directly related to the heating hot water temperature, which is used to supply the unit heater or heaters.

Our units can work with a warm water medium temperature of 120 C and a maximum pressure of 16 Bar, so LPHW heating is not a problem for these units.

The fan speed of the unit heater, as well as the air throw of the model, influence the leaving air temperature and heat output of the unit heater.

We do steam heating models, which are listed on their own dedicated webpage here: steam unit heaters


Address all conceivable likely space configurations that require heating with two discharge options—horizontal or downward (installed hung from the ceiling).When air flow from a horizontal warm water unit heater might be impeded by obstacles in complex areas such as exhibition halls, downward discharge is especially well suited.

LPHW heater for directional heating with a downward discharge installation – we can accommodate all likely space configurations or complex areas

LPHW heater for directional heating with a downward discharge installation – we can accommodate all likely space configurations or complex areas

However, where directional heating is needed, horizontal discharge units with adjustable louvres are ideal and are the most popular installation configuration for this range of heaters.

Horizontal discharge units

The standard bracket supplied for the horizontal unit is an adjustable rotating console that allows for 170° rotation of the unit heaters and allows for directional heating as well as the adjustable louvers.

The bracket can also be used in a downward discharge from a ceiling installation, or we can provide other accessories like corner brackets that let the air unit heater be connected to the ceiling with threaded bar drop rods.

horizontal discharge units our LEO unit heaters water fed plastic EPP case;

Horizontal discharge units – our “Leo” unit heaters EPP Plastic cased from Flexiheat UK