Model Number Guide

No, and using it that way is a common error. The letter names a category. M reads as up to 45 bar at 135 C, and "up to" is the important part: the stamped rating of a particular unit depends on its frame, plate count, connections and the approval it was built under.

Take the working figures from the nameplate of the unit, or from the rating we confirm with the quote. Use the letter to check that a replacement is in the same class as the original. A different letter on an otherwise identical string is a different unit. The pressure classes page lists the categories.

Physical measurements recover most of the string. Height and width identify the frame. The port centres, measured center to center both vertically and horizontally, confirm it and separate frames with similar outlines. Plate edges counted along the side of the pack give the plate count. Connection type and size can be read directly from the fittings.

Material code and pressure class cannot be seen from outside. For those, send the fluids on each side, the operating pressure and temperature, and the make and model of the machine the unit came out of. Photos of the nameplate remnant help too, since a few surviving characters often settle the rest.

It says how many times each fluid travels the length of the plates. /1P is single pass: each fluid goes through once, and all four connections can sit on the front cover. That is the usual arrangement and the easiest to pipe and service.

A multi-pass unit turns the flow around inside the pack. It suits duties that need a long thermal path, at the cost of higher pressure drop, and it places some connections on the back cover. On a replacement the pass field must match. A single-pass unit will not connect to pipework laid out for a multi-pass one.

As a list of the four ports in port order, joined by plus signs. A multiplier groups identical ports, so 2x1"NPT is two ports with 1 in NPT threads. A U marks a universal solder connection, so 22U takes both 7/8 in and 22 mm pipe. The string above therefore describes a unit with mixed connections: two differently sized ports on one circuit and a threaded pair on the other.

The order matters because it fixes which fitting is at which corner. Two units with the same frame, plates and material but a different connection string are not interchangeable without repiping. Quote the whole field when ordering, including any letters after the size.