What the spacing does
The coil carries the heat between the air and the refrigerant across aluminium fins. The closer the fins are to each other, the more surface there is in the same volume; the same casing gives a higher capacity.
The price is paid on the air side. A narrow spacing also narrows the channel the air passes through, and when the moisture in the room builds up as frost on the fins, that channel first narrows and then bridges over. A blocked coil moves no air, whatever number of kW is written on it.
What each of the three spacings is for
Planer evaporators are built with 4, 6 and 8 mm fin spacing depending on the model. The rough division is this: in storage rooms running above zero, where little frost forms, a narrow spacing buys compactness; in frozen product rooms and in volumes taking a moist load, a wide spacing buys the air path staying open under frosting.
The middle spacing is a reasonable starting point for most commercial cold rooms; but a "reasonable starting point" is not a selection. The real decision depends on how many times a day product enters the room and how moist it is. A store loaded once a day and a dispatch room whose door is constantly opening do not want the same spacing, even at the same volume.
Why the blast tunnel is a case of its own
In a rapid freezing tunnel the product enters warm and moist and the air velocity is high; frost builds fast and thick. That is why the blast series runs with a wide spacing: the surface lost here is won back by a coil that does not block.
Who takes the decision
Fin spacing, defrost arrangement and capacity are not chosen one at a time; they are chosen together. A wide spacing lowers the defrost frequency and a narrow one raises it — and the defrost frequency sets how much the room temperature swings.
Send us the room volume, the operating temperature, the daily product intake and the door traffic, and we will run the calculation. The capacity tables are in the catalogues, and the tool for the calculation is the selection application.