Commercial Refrigeration

Sometimes, but check two things before assuming so. The distribution device is matched to how a refrigerant behaves at the inlet, which is why the P-series is optimized for R410A and the S-series for R134a. An evaporator tuned for one can distribute poorly on another.

The second is pressure. A refrigerant that runs at higher pressure may be beyond the class of the unit that is installed. Read the class letter and the stamped limits off the nameplate and send them with the new refrigerant and operating conditions. Refrigerant Compatibility covers the pairings.

The cause. A frozen evaporator is a symptom of water flow that stopped or fell while refrigerant was still evaporating, and a new unit dropped into the same circuit meets the same end.

Before fitting the replacement, prove the flow switch actually trips the compressor, confirm the freeze thermostat setting, and look at what happens at shutdown: a pump that stops before the compressor has finished pumping down leaves cold refrigerant against still water. Check the strainer too. Debris that blocks a few channels starves them of water, and those are the channels that freeze first.

It depends on the refrigerant's operating and standstill pressures. As categories: S is 31 bar at 155 C and serves a wide variety of duties; M is up to 45 bar at 135 C and is fatigue tested, aimed at refrigerants such as R410A; H is 45 bar at 155 C, the class of the B250AS.

The fatigue testing matters on refrigeration more than the headline pressure. Compressors cycle, and every start and stop loads the braze joints again. These are class descriptions, not the stamped rating of a particular unit, so read the nameplate on a replacement. See Pressure Classes.

When two independent refrigerant circuits share one water stream - typically two compressors that stage. Each refrigerant circuit is interleaved through the whole pack, so with one compressor off, the running circuit still sees the full water flow across its plates and part-load performance holds up.

Two separate exchangers piped in parallel do not behave that way: half the water bypasses through an idle unit. The trade-off is at failure. A leak in either circuit condemns the whole dual unit, and both circuits are down for the change.

Because of what is on the other side. A desuperheater usually recovers heat into water that people will use, and a single-wall leak would put refrigerant and compressor oil into it without any sign. A double-wall plate vents a leak to atmosphere where it can be seen.

Two further points apply to this role. Discharge gas is the hottest stream in the system, so hard water scales the plates quickly and the copper braze ceiling of roughly 185 C has to be respected. And the unit should be sized to take the superheat only; allowing condensation in it upsets the condenser downstream.