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ASSA ABLOY Hospitality
66 8003 016-3
3.1.4.7 Connection examples for outputs N, L, RV, Y and W
In HVAC (Heating Ventilation and Air Conditioning) systems, a difference is often
made between 2-pipe systems and 4-pipe systems.
In a 2-pipe system there is one pipe in and one pipe out; both pipes either have cold
water or hot water. If there is cold water in the pipes, the air conditioning can only
be used for cooling. If there is hot water in the pipes, the air conditioning can only
be used for heating. In most cases, cold/hot water in the pipes is changed twice a
year (Spring/Autumn) through an actuator connected to the cool output on the
thermostat.
In a 4-pipe system there are two pipes in and two pipes out; one set of pipes in/out
has cold water and the other set of pipes in/out has hot water. The thermostat can
choose whether cooling or heating is applicable by activating either the cool output
or the heat output on the thermostat.
For a thermostat to know whether the water in a pipe is cold or hot, a pipe
temperature sensor is used. There are two types of pipe temperature sensors;
see details here
.
Figure 19
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