How do I set the cut-in and cut-out pressure on an Alco pressure switch?

Alco pressure switches have a main scale for cut-out pressure and a differential scale for cut-in. To set: (1) set the main scale to the desired cut-out pressure; (2) set the differential scale so that cut-in = cut-out + differential. For low pressure control: cut-out at 0.5 bar, differential 0.5 bar = cut-in at 1.0 bar. Use Alco's refrigerant pressure charts to convert temperature setpoints to pressures.

What does the Alco FDB filter-drier 'wet' indicator mean?

The Alco FDB sight glass/moisture indicator changes from green to yellow when the refrigerant moisture content exceeds 30 ppm for R134a or 20 ppm for R404A. A yellow indicator means the filter-drier is saturated and must be replaced immediately. If left unchecked, moisture causes acid formation, ice blockage at the expansion valve, and compressor bearing damage.

How do I select the correct Alco expansion valve for R404A?

Select an Alco TX expansion valve for R404A by: (1) calculating system capacity in kW at the operating conditions (evaporating temperature, condensing temperature); (2) selecting the valve from the Alco capacity tables for R404A; (3) matching the orifice size and external equalizer requirement (external equalizer is needed when pressure drop across evaporator exceeds 0.3 bar). Use Alco's online selector or AskWhiz for guidance.

What is the bypass orifice in an Alco solenoid valve?

Some Alco solenoid valves include a bleed orifice that allows a small refrigerant flow even when the valve is closed. This is used to equalize pressure across a compressor crankcase pressure regulator (CPR) or to allow slow pressure equalization for pump-down circuits. If a pump-down circuit is not pulling down correctly, check that you have a non-bleed valve installed in the liquid line.

Refrigeration

Alco Controls error codes, decoded.

Look up any Alco Controls fault code below. Each one is grounded in Alco Controls's own service documentation — the meaning, the symptoms, the causes, and the steps to clear it.

By Octavian Ghindea

Co-founder & CTO · Reviewed August 2026

Working on a Alco Controls unit? The complete Alco Controls code pack in your inbox — free.

Alco Controls sits in our Refrigeration coverage. Every page here is transcribed from the manufacturer's manuals, not scraped from forums.

What error codes does Alco Controls display?

Tap a code for the full breakdown — meaning, symptoms, causes, and fix steps.

Yellow moisture indicator

Filter-drier saturated — replace immediately

LP trip

Low pressure cutout — check refrigerant charge and expansion valve

HP trip

High pressure cutout — check condenser and overcharge

Get the complete Alco Controls error-code pack by email

Every Alco Controls code, meaning and first checks in one document you can save, print or forward. Free.

Common questions about Alco Controls equipment

Other Refrigeration brands we cover

AskWhiz documents error codes for these manufacturers in the same vertical:

3M Accurex AHT Cooling Systems AKO Alfa Laval Arneg Aspera BAC Bitzer Bock Carel Carrier Commercial Refrigeration