SWEP V120T

Upright, with the water flowing counter-current to the refrigerant. Vertical mounting is what lets the two-phase refrigerant spread across the plate pack; counter-current flow gives the closest approach between leaving water and evaporating temperature.

The connections on this model are solder, and on the catalogued units the refrigerant outlet is a 42U - a large copper line that carries compressor vibration and its own weight. Clamp that line close to the unit so the joint is not the support, and keep the torch heat on the fitting and off the plate pack when brazing. Mounting and Piping shows the supports.

An undersized unit shows low suction pressure at design load: the evaporating temperature has dropped to force the capacity through too little surface. Water pressure drop is high and the low-temperature cutout trips on warm days, when the load is greatest.

An oversized unit looks healthy at full load and misbehaves at part load. Refrigerant velocity in each channel is too low to keep distribution even or to carry oil back, superheat wanders and the expansion valve hunts. In an economizer, oversizing also shifts the intermediate pressure away from the point the compressor was selected for. Size from the duty at both ends of the operating range.

SWEP publishes the channel volume as 0.241/0.241, per channel and equal on both sides. Total hold-up on a side is that figure times the number of channels on that side, which is about half the plate count.

On the refrigerant side this is part of the system charge, so a change in plate count on a replacement changes the charge and may need the receiver and charge label revisited. On the water side, a small hold-up means little thermal buffer: leaving water temperature follows compressor staging closely, and a short-cycling problem in the loop will not be hidden by the exchanger.

The published formula is 8.33 kg plus 0.424 kg per plate (18.36 lb plus 0.935 lb per plate). At 100 plates, the largest configuration on file, that is about 51 kg (112 lb); at the 250-plate maximum, about 114 kg (252 lb), all dry.

A bracket or base under the plate pack carries it. The soldered copper lines must not: they are the weakest part of the assembly and they already see vibration.

Both appear, so read the last letter of the designation. The published example, V120TH/1P-MC-S, is class S: 31 bar at 155 C, the general-purpose class. The part numbers on file are class M: up to 45 bar at 135 C and fatigue tested, the class used with refrigerants such as R410A.

These are categories, not the stamped rating of a particular unit, but the direction matters. Replacing an M unit with an S unit puts a lower-pressure exchanger on a high-pressure refrigerant circuit. Match the letter, and check the design pressure on the equipment data plate. See Pressure Classes.

These models are catalogued alongside the V120T. 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 P120T - A copper-brazed 316/316L evaporator on the 120T frame with six catalogued connection types.