SWEP F250AS

Treat the changeover and defrost periods as the risk, not just steady cooling. In a reversible machine the exchanger's role flips, refrigerant temperatures swing quickly, and the water side can be exposed to sub-freezing refrigerant for a short time with the flow still settling. Water that freezes in the channels can split the unit.

The protections are a proven water flow before the compressor runs, a low-pressure or low-temperature cutout that is set correctly and not bypassed, and glycol where the leaving temperture runs near freezing or the unit sits outdoors. Glycol changes viscosity and heat transfer, so it has to be in the selection from the start. Freeze Protection goes through each.

No - 62 m3/h (272.98 GPM) is the port ceiling. A unit operated near it pays in pressure drop and pump energy.

Size to the duty and the allowable pressure drop, then check that the design flow sits comfortably below the ceiling. Plates can be added up to 250 to bring the channel pressure drop down. If the design flow is still pressing on the port limit at that point, the frame is too small.

It is a single-circuit evaporator for reversible chillers, air-cooled or water-cooled. The asymmetric channels are matched to a refrigerant on one side and water or brine on the other, which is that duty exactly.

It is the wrong choice in three cases. A machine with two independant refrigerant circuits sharing one exchanger needs a dual-circuit model, not this one. A liquid-to-liquid duty with similar flows on both sides gains nothing from asymmetric channels and is better served by a symmetric plate. And any copper-hostile fluid - ammonia, deionized water - rules out a copper-brazed unit regardless of the plate pattern.

The class is the last letter of the designation, after the material code. SWEP's example for this model, F250ASH/1P-NSC-H, ends in H: the class described as 45 bar at 155 C and associated with process industry duty. NSC ahead of it is the material code - 316 channel plates, 304 cover plates, copper braze.

A class letter is a category. The design pressure and temperature stamped on the unit are what an inspector reads, and they are what the replacement has to meet or exceed. Other class letters exist; where your nameplate shows one, send it and we will confirm the rating. Pressure Classes explains the scheme.

Ideally all of it, but the plate count and the connections are the parts most worth recovering. The model code can be confirmed from the 620 x 202 mm outline and the 538 x 112 mm port centres. The plate count can be counted on the edge of the pack. The connections can be measured.

What cannot be read off the unit is the material code and the pressure class. On this frame that matters: the F250AS has 316 channel plates where the B250AS and P250AS are 304, and nothing on the outside shows the difference. The chiller's model and serial number usually let us trace the original designation.

These models are catalogued alongside the F250AS. Each has its own page with its dimensions, materials and part numbers.

SWEP B250AS - AsyMatrix in the H pressure class - 45 bar at 155 C.

SWEP P250AS - A copper-brazed 304 stainless single-circuit AsyMatrix evaporator for reversible chillers.