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6.4. Medium connections / Heating Coil
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Before connecting heating coil, the duct system must be thoroughly cleaned.
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Use only permitted sealants (DIN EN 751-2, DVGW tested).
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Water connections to be carried out as marked on the heat exchanger.
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When making pipe connections to the unit with screw connections, a wrench, for example, must
be used to hold against the tightening torque.
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The connection must be executed without tension.
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Air bleeding must be done on site.
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All pipes and fittings of the medium connections must be insulated.
Hydraulic circuits
For air conditioning applications, there are three basic circuits:
Bypass circuit
With the bypass circuit, only the hot water is fed to the heating coil. The rest of the water supplied
by the pump, bypasses the heating coil. This can lead to a temperature difference between top and
bottom of the heating coil if the flow of water through it is very small. The resulting temperature gra
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dients can lead to false temperature measurements in the duct or to draught effects in the room. The
bypass circuit is usually used in air coolers. In air coolers, the air is partly cooled below the dew point
and thereby dehumidified.
Admixture circuit
In the admixture circuit, the circulating pump always supplies the full amount of water required by the
heating coil with an amount of hot water determined by the valve setting. The temperature is thus
constant over the whole heating surface. The temperature control is thus much better. Furthermore,
the risk of frost damage when the pump is running is reduced as the continuous circulation and incre
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ased pressure reduce the freezing point of the water.
The only advantage of the bypass circuit over the admixture circuit arises when the pipe lengths bet
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ween three-way ball valve and water heater are very long. Because the pump is ahead of the valve,
there is always hot water available at the valve that can be immediately fed to the heat exchanger
if required. It is possible that the water in the pipe to the valve cools during admixture circuit. When
heating is required there is a short delay before hot water gets into the heating coil.
Injection circuit
The combination of these circuits is the injection circuit which is generally recommended.
Fig. 6:
Bypass circuit
Fig. 7:
Admixture circuit
Fig. 8:
Injection circuit
6.2. Duct connections
Duct connections should be made such way that no condensate can get into the unit via the ducts.
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Insulate cold ducts in warm rooms
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Insulate warm ducts in cold rooms
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Ground heat exchangers should be equipped with a controlled condensate drain positioned
before the unit
Duct connections should match nominal width NW. (see 15. Technical Data)
Fig. 5:
Connection air duct
6.1. Permitted installation positions
6.3. Einsatzgrenzen
Exclusive mounting in upright position, connection nozzles upwards. (Fig. 4)
Fig. 4:
Operating limits indoor installation
Fresh air temperature
-20 °C to +40 °C
Installation place:
min. +5°C
Operating limits outdoor installation
Fresh air temperature
-20 °C to +40 °C
Installation place:
min. -20°C
Outdoor installation only allowed with adequate weather protection.
Extract air class EN 13779
ETA 1 / ETA 2
For the ventilation of rooms where the emission sources are human metabolism or building materi
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als and structures, e.g. offices, spaces for public service, meeting rooms as well as in rooms where
smoking is allowed.
The suitability for enclosure condensation has to be checked by the customer, it is possible that
suitable measures like ventilation of the installation area, or an additional insulation of the outdoor
air intake area, are going to be necessary.
Summary of Contents for ETA K 1200 V W
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