SWEP P120T

The last one before the connections. In SWEP's example, P120TH/1P-SC-M, SC is the material code - 316/316L plate, copper braze - and M is the pressure class. M covers units rated up to 45 bar at 135 C and fatigue tested, the class used with higher-pressure refrigerants such as R410A.

That is a class description, not the rating of a particular unit; the nameplate figures govern. When replacing, match the letter.

All four are 525 x 243 mm with a 120.64 GPM ceiling and copper braze, so the comparison comes down to plate steel and catalogued purpose. The B120T is 304. The P120T and F120T are 316/316L and are both described as high-performance evaporators with long thermal length. The V120T is SMO254, described as an evaporator optimized across many refrigerants.

For a replacement, the steel is the practical divider. A 304 unit in place of a 316/316L one gives up corrosion margin on the water side; an SMO254 unit is the choice where chlorides are present. Between the P120T and F120T the published figures do not separate them, so order the prefix the nameplate shows.

Evaporating refrigerant against water or brine in chillers and heat pumps, and economizer duty. The long thermal length plate is chosen for a close approach between the leaving water and the evaporating temperature, which is what raises machine efficiency.

That same plate makes it a poor fit for high-flow, low-temperature-change liquid duties, where a long thermal length just produces pressure drop. It is also the wrong unit for ammonia or deionized water, because of the copper braze, and for chloride-bearing water, where 316/316L pits. For general water-to-water work a B-series frame is the more natural starting point.

It means that particular unit is single pass: each fluid makes one trip through the plate pack. The example designation P120TH/1P-SC-M is built that way, and single pass is the normal arrangement for an evaporator.

Single pass keeps all four connections on the front cover and the pressure drop low. A multi-pass arrangement sends a fluid through the pack more than once to stretch the thermal length further, and puts connections on the rear cover. If your nameplate shows something other than 1P after the slash, quote it exactly, because the pass arrangement changes where the pipes land. The Model Number Guide shows how to read that position.

The outline, 525 x 243 mm (20.67 x 9.57 in), and the port centres, 456 x 174 mm (17.95 x 6.85 in). Measure centre to centre on the old unit's connections; that pair of figures is the one the pipework depends on.

Depth is not a fixed figure - it follows the plate count, so a 90-plate and a 170-plate P120T have the same face and very different depths. Weight follows too: SWEP's formula is 8.33 kg plus 0.424 kg per plate (18.36 lb plus 0.935 lb per plate), so a 170-plate unit is about 80 kg (177 lb). Check the bracket and the clearance behind.

By port, in the order the designation gives them. Threaded, Victaulic, solder, combo, flange and weld connections are all catalogued, and a single unit commonly mixes them: solder on the refrigerant ports, something heavier on the water ports.

On a replacement, copy the old unit exactly, including size. On a new installation, pick the water-side connection to suit how the unit will be serviced. Grooved and flanged connections let the unit be removed without cutting pipe; welded and soldered ones are compact and leak-tight but permanent. A combo connection is worth asking for where the site may use either of two joining methods.

These models are catalogued alongside the P120T. Each has its own page with its dimensions, materials and part numbers.

SWEP B120T - The widely stocked mid-large frame, to 250 plates.

SWEP F120T - A copper-brazed 316/316L evaporator with long thermal length for chillers and heat pumps.

SWEP V120T - Evaporator on the B120T frame, 525 x 243 mm, up to 250 plates, 120.64 GPM max flow.