120
Thermo Fisher Scientific
Operation Manual HM550
Theory of operation
Specimen and chamber cooling, defrosting
Inevitably, when working on the microtome the dry cold air of the mi-
crotome chamber mixes with the warm humid air outside the chamber.
Frost forms on the finned evaporator. e increasing thickness of the
frost reduces the efficiency of the evaporator. For this reason, the daily
defrosting of the evaporator becomes necessary. To carry out the defrost-
ing cycle, a heating warms the evaporator from below.
Set the time of the daily defrosting on the control panel. e period of
the defrosting takes approx. 40 min. and varies according to the thick-
ness of the frost.
Possible frost built-up on the microtome or on the knife carrier are not
removed by defrosting the instrument. However, the frost recedes after
defrosting as now the evaporator is fully efficient again.
In addition, the instrument is equipped with an immediate defrosting
function.
To avoid condensation the sliding window is heated when closed.
