SWEP B8DW

Very little. SWEP publishes a per-channel volume for each side, and on the B8DW the two sides differ slightly (0.0166 and 0.0169 in the datasheet's units) because of the double-wall plate geometry. Total hold-up per side is that figure multiplied by the number of channels on that side, roughly half the plate count.

On tap water duty the small volume is an advantage: the outlet temperature follows the control valve almost immediately, with no stored slug of hot water. The trade-off is that there is no thermal buffer, so a slow or oversized valve shows up as temperature hunting at the tap.

Measure the port centres first, then the outline, then the depth. The B8DW is 318 x 76.5 mm overall with ports on 278 x 40 mm centres (10.94 x 1.57 in). The port centres are what the pipework is built around. Sibling models on this frame have near-identical outlines, which is why dimensions alone do not identify the model.

Depth depends on the plate count, so count the plates or read the count from the nameplate. Then confirm the connection type and size on each port. A unit that matches on A x B and port centres but arrives with solder stubs where the old one had threads still does not fit.

Usually enough. A designation reads model, plate type, plate count, pass arrangement, material code and pressure class - SWEP's example for this model is B8DWH/1P-SC-M. If the model and plate count survive, the rest can often be confirmed from the unit itself.

If the count is missing, count the plate edges down the side of the pack; on a double-wall unit each wall is two plates, so count carefully and tell us how you counted. Note the connection type and size on all four ports and take the outline dimensions. A SWEP article number, if legible, is the fastest route of all. A photo of the plate edge and the ports helps.

Ordinary potable water, heating water, glycol mixtures and most oils are fine with this combination, which is why it is the general-duty construction.

It is the wrong choice for ammonia, which attacks copper braze, and for deionized or ultrapure water, which leaches copper out of the joints. Chloride-bearing water - pool water, brackish or heavily chlorinated supplies - pits 316, and the B8DW is published in 316/316L only. The double wall protects against cross-contamination; it does not make the unit more corrosion resistant. If the water chemistry is doubtful, send us the analysis before ordering. Plate and Brazing Materials covers the options.

Not as a design point. The 4 m3/h (17.61 GPM) figure is a ceiling set by the ports - the flow at which port velocity becomes the limit - and has nothing to do with what the plate pack can transfer at an acceptable pressure drop.

A B8DW selected for a real duty normally runs well below that. If the required flow is close to the ceiling, or the pressure drop comes out higher than the pump can give even at 70 plates, the duty has outgrown the frame and the answer is a larger double-wall model rather than a B8DW pushed to its limit.

It is meant for small to medium duties where a leak between circuits is unacceptable or where the plumbing code calls for double-wall separation: heating tap water from a boiler or solar loop, or recovering heat into potable water. SWEP also describes it as having a high thermal length, which gives a tight approach and a low return temperature.

It is the wrong choice where separation is not required. Two plates in every wall add resistance to heat flow, so a double-wall unit needs more plates than a single-wall one for the same duty and costs more. On a closed heating loop a single-wall model on the same frame does the job with less.

Up to 70. More plates mean more parallel channels: lower pressure drop, a closer approach and more capacity at the same flow, until the port ceiling becomes the limit.

Weight rises with the count by the published formula, 0.84 + 0.118 kg per plate, so a full 70-plate unit is about 9.1 kg (20 lb). That is light enough to hang on a bracket, but too heavy to leave hanging on soldered stubs - support the body, not the connections.

These models are catalogued alongside the B8DW. Each has its own page with its dimensions, materials and part numbers.

SWEP B8T - Nickel-brazed - the copper-free option at small size, for ammonia and aggressive media.

SWEP B8LAS - Compact AsyMatrix brazed plate heat exchanger pairing high thermal performance with low pressure drop.

SWEP BX8T - Compact All-Active brazed plate unit for heat pumps and container refrigeration, to 17.61 GPM.

SWEP E8AS - AsyMatrix brazed plate heat exchanger on the B8T frame, used mainly for heating tap water.

SWEP E8LAS - AsyMatrix brazed plate heat exchanger on the B8T frame for the highest thermal demands in tap water.

SWEP E8T - A compact copper-brazed plate heat exchanger for wall-hung, non-condensing boilers.