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Item
Name
t
Inflow temperature sensor (boiler circuit)
V1
t
Internal mixer sensor = inflow temperature sensor
V2
(heating circuit)
A
Gas boiler
B
Storage tank (polypropylene, double-walled jacket
with PUR hard foam heat insulation)
C
Pressure-free storage water
D
Hot water zone
DS
Pressure sensor
E
Solar zone
FLS (V1)
Flow sensor (boiler circuit)
MAG
Diaphragm expansion vessel (on the building side)
STBK
Safety temperature limiter
AG
Outer thread
IG
Inner thread
ÜM
Union nut
Safety devices
Observe tightening torque!
Tab. 3-1
Legend for
Fig. 3-1
to
3.2
Brief description
The Gas Combi Unit 2 (GCU compact) is a fully preassembled gas
condenser unit integrated in a hot water storage tank. The very good
thermal insulation properties of the plastic storage tank ensure that
heat losses are kept to a minimum. The aluminium boiler body is in a
metal housing installed on the cover of the storage tank. The com-
plete flue gas unit is surrounded by fresh air.
Operating mode
The GCU compact is designed so that it can be operated independ-
ently of the ambient air (concentric flue gas/supply air pipes). The
burner suctions the combustion air directly in through an installation
shaft or a double-walled flue gas pipe. We recommend this operating
mode which has many advantages:
▪ The heating room does not need any ventilation opening into the
open air and therefore does not cool down.
▪ Lower energy consumption.
▪ Additional energy recovery in the flue gas pipe through preheating
the combustion air.
▪ Contamination from the environment of the burner is not suctioned
in. This means that the heating room can be used as a work-
space, laundry room, etc. at the same time.
▪ Can be installed in loft areas or attic.
The condensate is collected in the flue gas collector, led to the rear
via a condensate pipe integrated in the storage cover and then dis-
charged into the drainage system.
The unpressurised storage tank water acts as the heat storage me-
dium. Useful heat is supplied and removed via the spiral heat ex-
changer, which is made from a stainless steel corrugated pipe
(1.4404), and is completely immersed in the storage tank water.
The hot water zone in the storage tank works as a combination of
heat storage and geyser (see
Fig. 3-2
The cold water that flows out when the hot water is removed is first
routed to the storage tank at the very bottom of the heat exchanger,
where it cools the lower area of the storage tank down as much as
Gas Combi Unit
Floor-standing gas condensing boiler with integrated heat storage
008.1543899_02 – 04/2019 – EN
Fig. 3-5
and
Fig.
3-4).
3
possible. The readiness zone is flowed through and heated from top
to bottom by the heat exchanger for the storage tank charging
(SL-WT), which is heated by the gas burner.
On its way to the top, the domestic water continuously absorbs the
heat of the storage tank water. As the flow direction makes use of
the counter flow principle and the heat exchanger has a spiral
shape, there is definite temperature stratification within the hot water
storage tank. As high temperatures can be maintained for a very
long time in the upper section of the storage tank, a high hot water
output is achieved even if water is drawn off over a long period of
time.
▪ In the GCU compact 5xx (Biv) models, the SL-WT ends approx.
25 cm above the floor of the container. Only the hot water zone
above that point is heated by the boiler. The water below that
point in the tank is heated by solar power alone.
▪ In the GCU compact 3xx (Biv) models, the SL-WT descends to the
floor of the container. The entire storage volume is heated by the
boiler (greater hot water output readiness).
Optimum water hygiene
There are no low-flow or unheated zones on the domestic water side
with the GCU compact. It is not possible for sludge, rust or other
sediments to be deposited, as can be the case with other large
volume tanks. The water that is fed into the system first is also dis-
charged first (first in, first out principle).
Low scaling
On the storage tank side, scale can only be deposited once. All the
stainless steel heat exchanger pipes in the storage tank water
largely remain virtually free of solid deposits. This means that the
scale cannot build up, which would continuously reduce the effi-
ciency of heat transfer (as is the case for other storage designs) dur-
ing the operation time.
The thermal and pressure expansion and high flow rates in the do-
mestic water heat exchanger cause any scale deposits to be re-
leased, which are then flushed away.
Using solar power
The hot water storage tank of GCU compact can also be heated by
solar energy. The entire hot water storage tank can be heated up de-
pending on the heat available from the sun. The stored heat is used
for the hot water preparation and for heating system support. The
ISM ("Intelligent Storage Manager") controls the integrated 3-way
valves in such a way that the solar heat yield is optimally divided and
used for domestic hot water preparation and heating support. The
high total storage capacity enables the bridging of periods without
solar yield.
When a pressurised solar system or an external heating boiler is
used as an external heat generator, only one of the GCU compact
with Biv configuration – listed in
the primary hot water storage unit.
In the GCU compact Biv models, the complete storage tank is de-
signed as a hot water zone. It is possible to make thermal use of
solar energy for domestic hot water preparation. The solar compon-
ent is optimised in combination with an upstream Solaris system
(pre-heating stage).
Safety management
The entire safety management of the GCU compact is managed by
electronic control. It performs a safety switch-off in the event of water
shortage, gas shortage or undefined operating states. A correspond-
ing fault signal provides an engineer with all the information neces-
sary for troubleshooting.
Electronic controller
An electronic digital controller combined with the burner "intelligent"
combustion control automatically controls all heating and hot water
functions for the direct heating circuit and a storage tank charging
circuit.
Product description
chap. Chap. 3.1
– is permitted as
Installation and operating instructions
13
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