SWEP E8LAS

Watch the tap water outlet temperture at peak draw and the pressure drop across each side. An undersized unit falls short of setpoint at high flow and throttles both circuits; the complaint is hot water that fades when a second tap opens.

An oversized unit meets temperature easily but runs slow channels, and slow channels in hard water scale. With catalogued builds from 20 to 70 plates, there is a lot of room to get this wrong in either direction. On a like-for-like replacement keep the plate count; if the load has changed, give us the new flows and temperatures and we will rate it.

It can freeze, and a frozen brazed pack splits. Each channel holds only a thin film of water, so a unit sitting in an unheated plant room or a draft from an outside-air intake freezes long before the pipework around it does.

Glycol is fine with the 316/316L plates and copper braze on the heating side, though not on the potable side of a tap water duty. It costs performance: the mix is more viscous and carries less heat than water, so pressure drop rises and the approach widens. On a model chosen for a tight approach that matters - state the glycol type and percentage when asking for a rating.

All of them share the 17.61 GPM port limit and nearly the same face, so the differences are in the plate and its purpose. The E8AS (315 x 74 mm) is the tap water heater; the E8LAS (316 x 74 mm) is for the highest thermal demands in tap water. The E8T and BX8T are 315 x 73 mm, the E8T being aimed at wall-hung, non-condensing boilers.

The B8LAS is a little larger on the face at 317.7 x 76.2 mm and is described as combining highest thermal performance with low pressure drop. The B8DW (318 x 76.5 mm) is a double-wall unit. None is a blind substitute for another - compare SWEP E8AS and SWEP B8LAS.

It matters twice over. First, the two fluids must run counter-current, entering at opposite ends of the plate; that is what produces the close approach this model is chosen for. Piped co-current, the tap water outlet can never get near the heating supply temperature.

Second, the channels are asymmetric, so the heating circuit and the tap water circuit each belong on a particular side. Reversing them changes the pressure drop on both.

Mount the unit vertically, and support the pipes independently. With up to 70 plates the pack is long from front to back, so do not let it hang from its four threaded connections.

No. The published 4 m3/h (17.61 GPM) is a ceiling set by the ports, not a design flow. It is the most the connections should pass regardless of how many plates sit behind them.

The practical limit is usually pressure drop. Adding plates, up to the 70-plate maximum, spreads the flow over more channels and brings channel pressure drop down, but the port loss stays. If the rated pressure drop is still too high near the top of the plate range, or the flow is close to the port ceiling, the duty belongs on a frame with larger ports.

It is the right choice for tap water production where the outlet has to come close to the heating water temperature, at flows inside 4 m3/h (17.61 GPM).

It is the wrong choice in three situations. Where codes call for double-wall separation between heating fluid and potable water, a double-wall model such as the B8DW is needed. Where the fluid is ammonia or deionized water, the copper braze rules it out. And where the temperature program is easy, a tap water unit with a less demanding plate will do the job with fewer plates. Choosing it only because the old unit was the same size is how the mismatch starts.

By circulation, since the pack is brazed shut. Isolate the unit, connect a pump and tank to the tap water side, and circulate a descaling solution in the reverse of the normal flow direction so loosened deposits leave by the way they came in. Flush with clean water untill the rinse runs neutral.

Use a cleaner that is compatible with stainless steel and copper; an aggressive acid shortens the life of the braze. A unit sized for a tight approach shows fouling early, because it has little margin, so a slow fall in outlet temperature is the cue to clean rather than to replace.

These models are catalogued alongside the E8LAS. 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 B8DW - The most compact double-wall brazed plate heat exchanger in the SWEP range.

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