Technical data

4.6.3 Weather Compensation (Optional)

All Vent-Axia 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. This is particularly important with

radiators, as much higher temperatures are required. In cold weather, many people already turn up the

temperature of water flowing from their boiler by hand and are therefore weather compensating their

heating system manually.

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, Vent-Axia Heat Pumps are supplied with the required sensors for installation, however the

function is disabled in the software and it is recommended that this function is not enabled. Tariffs might

possibly change in the future and so to enable weather compensation (if required) on your heat pump you

can contact our Technical department, who can run through the reprogramming procedure.

The weather compensation sensor is supplied in a small waterproof enclosure.

This sensor needs to be fixed to a North-facing wall, and connected with 2 core 0.5 mm cable, unshielded,

to the heat pump. The cable should be routed inside the heat pump case and left coiled up inside, with

the small green terminal block attached. The weather compensation should then be left disabled. If

weather compensation is required contact Vent-Axia Technical Department.

Do not disconnect or connect any terminal blocks until Vent-Axia Technical Department has been con-

tacted on 01293 441523.

Small green terminal

block

Weather compensation

sensor

Waterproof container

sensor

Green Terminal

block

Main terminal block

Fig 19 Weather

compensation sensor