SWEP F85

Whatever fragment survives, plus a few things read off the unit itself. A designation follows a fixed order - model, plate type, plate count, pass arrangement, material code, pressure class, then connections - so even a partial string such as F85H or NSC narrows it down. The SWEP article number, if it is legible, identifies the unit on its own.

Do not try to separate an F85 from a B85 with a tape measure: the published outlines differ by only 2 mm each way, which is inside the error of measuring an installed, insulated unit. Count the plates along the edge, note the connection type and size on each port, and photograph the unit and what is left of the plate. That is enough for us to confirm the match.

Not in capacity ceiling - all four are published at 74.85 GPM. The differences are construction and plate pattern. The F85 uses 316 channel plates with 304 cover plates and copper braze. The B85 is 316/316L with copper braze. The B85S has 316 plates with stainless steel brazing, the All-Stainless build for systems that cannot tolerate copper or that run hot.

The F85AS matches the F85 in outline and materials but uses AsyMatrix asymmetric channels, which SWEP describes as raising thermal performance and lowering pressure drop. A replacement should carry the same prefix as the unit that came out; a neighbouring model may bolt up to the same space and still be a different exchanger.

Less often than an evaporator, but it is not exempt. A condenser's water side freezes in three situations: a machine parked for winter with water left in the channels in an unheated space, a reversible unit where the exchanger takes the evaporator role in the other mode, and a system pumped down with the water side stagnant. Water freezing in the channels can split the unit.

Drain and blow out the water side for cold storage, or keep the loop on glycol. If glycol is used, size at the real concentration - it raises viscosity and pressure drop and costs some heat transfer. Glycol and Fluid Properties covers the correction.

The F85 builds up to 100 plates. More plates split the same flow across more channels, so pressure drop falls and the approach temperature tightens. The cost is depth, weight and price: SWEP's weight formula adds about 0.15 kg (0.33 lb) per plate, putting a 100-plate unit at roughly 16.5 kg (36.4 lb).

More is not always better. Too many plates for the flow leaves channel velocity low, which invites fouling and uneven distribution. And plate count cannot raise the 74.85 GPM port ceiling. On a replacement, keep the plate count the nameplate shows unless the duty has changed.

Four things. The outline is 524 x 117 mm (20.63 x 4.61 in). The port centres are 470 x 63 mm (18.5 x 2.48 in); these are what the existing piping is built to, so they matter more than the outline. Third is depth, which is set by the plate count and grows with it. Fourth is the connection on each port - threaded, solder or combo - and its size.

Check also which side of the unit each connection is on. A unit with ports on the back cover is a different configuration from one with all four on the front, even at the same plate count.

These models are catalogued alongside the F85. Each has its own page with its dimensions, materials and part numbers.

SWEP B85 - 160 plates on the 526 mm frame, with tighter channels than the B80.

SWEP B85S - An All-Stainless, high-efficiency brazed plate heat exchanger with large ports.

SWEP F85AS - AsyMatrix evaporator on the 85 platform with integrated distribution for high-pressure refrigerants.