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Operation and Maintenance
Envistar Top 04-21
DSET.190501.01.EN
Continuous product development may give rise to specification changes without notice.
Cleaning
The counter-flow exchangers are designed to prevent dirt and deposits from coming
into contact with the heat transfer surfaces. Most of the particles in the air will pass
through the counter-flow exchanger. The main risk for fouling of the counter-flow ex-
changer comes from slow-moving substances that condense on the surfaces, and also
from fibres from tumble dryers, for instance.
The recommended way to clean the counter-flow exchanger is by flushing with hot
water, if necessary adding some mild detergent. The counter-flow exchanger is
equipped with a drip tray that is used for collecting the water used for flushing. Inspect
the waste outlet and water trap before flushing.
NB:
High pressure flushing must not be directed at the fins.
Be careful in order to ensure that the fins do not become deformed or
break.
At operating temperatures below 0°C, the counter-flow exchanger must be dry before
commissioning.
Functional description, defrost and bypass function (ODS)
(code TXMM-XP/NP)
Under certain operating conditions, frost and ice may form on the extract air side of the
counter-flow exchanger. In order to optimise heat recovery, there is a built-in defrost
function. This is based on the principle that the defrost function is engaged when the
pressure drop over the extract air side of the counter-flow exchange exceeds a certain
value.
Defrosting takes place through the regulation of dampers on the outdoor air side of
the counter-flow exchanger. The dampers have separate damper motors that are con-
trolled by a defrost program. Damper control means that there are a number of different
combinations of damper positions, for instance that one of the dampers can be partly
open while another is closed and the third damper is fully open.
During full heat recovery and when the unit is switched off, the dampers should be fully
open (bypass damper closed). When there is a risk of frost, the dampers can be in dif-
ferent positions.
The defrost and bypass function is preset at the factory and any adjustments must be
performed by IV Produkt.
Functional description, frosting function (BYP) (code TXMM-NP)
Under certain operating conditions, frost and ice may build-up on the extract air side
of the heat exchanger. In order to optimise heat recovery, and avoid freezing, there is a
built-in frosting function. The principle is based on the frosting function starting when
the temperature of the exhaust air side’s coldest surface falls below a certain value.
The freezing process is prevented by reducing heat recovery gradually through
regulating dampers on the heat exchanger’s exhaust air side. The heat recovery
damper closes and the bypass damper opens. In this way, the exhaust air temperature
is increased and freezing is avoided.
During full heat recovery and when the unit is switched off, the dampers should be fully
open (bypass damper closed).
The frosting and bypass functions are preset at the factory and any adjustments may
only be performed by IV Produkt.
