SWEP E6T

More likely than a large unit, and faster. Each channel holds only 0.026 dm3, so there is almost no thermal mass to ride through a cold night once the boiler is off. Water freezing in the channels can split the plates, and the first sign is usually system water appearing on the domestic side, or the reverse, after the thaw.

The domestic side cannot take glycol, so protection there means keeping the appliance's frost function powered, or draining and blowing down the unit if the property is left empty. On the heating side, an inhibited glycol mix suited to the boiler is the normal answer.

Measure and count. The E6T plate is 210 x 73 mm with port centres of 172 x 40 mm (6.77 x 1.57 in), which separates it from other small frames that look alike. Count the plates on the edge of the pack - builds on file run from 12 to 40. Then look at the ports: the catalogued versions include 3/4 in connections and versions listed with plain port holes, and that difference decides wether it fits an appliance manifold.

The boiler make, model and the appliance part number for the plate exchanger are also useful. Send those with a photo and we will match the E6T build.

Fewer plates gives less hot water. The outlet temperature drops at high draw-off, the boiler side sees a higher pressure drop, and users notice it as a shower that cools when a second tap opens.

More plates is not automatically better. Channel velocity falls, and on domestic hot water low velocity combined with a hot surface is what lets limescale settle. An oversized pack can scale up faster than the correct one in hard water. It may also not fit, because the pack is thicker.

Keep to the original count unless the duty has changed. The frame stops at 40 plates, so a need beyond that points to a larger frame such as the B8T.

For water-to-water duty it tolerates most positions, but upright with the ports on a vertical line is the arrangement that vents air and drains best. Trapped air on a pack this small blocks a meaningful share of the channels.

Direction does matter. Pipe the boiler water and the domestic water counter-current, entering at opposite ends. Reversed, the unit still heats water but cannot reach the same outlet temperature, and the fault is easily blamed on scale. Do not let the pipework lever on the connections either: with 3/4 in fittings on a body this light, a misaligned pipe pulled into place puts its whole strain on the braze joint.

On weight alone the pipework can hold it: 0.29 kg plus 0.047 kg per plate (0.64 lb plus 0.104 lb per plate) makes a full 40-plate pack about 2.2 kg (4.8 lb).

The real loads are torque during assembly and vibration afterward. Hold the connection with a second wrench when tightening a threaded joint, and clip the pipes close to the unit where it sits near a pump.

Those three are the pressure and safety approvals SWEP publishes for the frame: the European pressure equipment approval, the North American UL listing and the Japanese high-pressure gas approval. They address the unit as a pressure-containing component.

They are not a drinking-water approval. Where the local code or the job specification requires NSF/ANSI 61 for a component in contact with potable water, raise it at the outset, and note that NSF/ANSI 61 is limited to 90 C. Likewise say so if an ASME stamp or a CRN is required. Approvals and Certifications explains what each one covers.

E6T is the frame, with the T marking the plate generation. H is the plate type: obtuse chevron, high heat transfer and high pressure drop. x20 is twenty plates. /1P is a single pass on each side.

SC is 316/316L stainless plates with copper braze, and S is the pressure class - the 31 bar at 155 C category, with the stamp on the unit giving the actual rating.

4x3/4" means four 3/4 in connections, and the bracketed number identifies the connection variant. Other E6T strings on file end in 4xHOLE instead, so the last field needs matching as closely as the plate count.