Gyr Rwb2 Timer User Manual

Getting Started With the Gyr Rwb2 Timer User Manual

The Gyr RWB2 is a programmable time switch commonly found in commercial HVAC and building management installations across the UK and Europe. It handles weekly scheduling, event-based switching, and basic interlocking for ventilation, heating, and lighting circuits. If you are staring at one of these units mounted in a cupboard somewhere, the manual will at least tell you which buttons do what. You can usually find it by searching for "Gyr Rwb2 Timer User Manual" on the Belimo website or through older distributor archives, since Belimo acquired Gyr's building controls division a few years back. The PDF is roughly 40 pages and covers commissioning, fault codes, and maintenance procedures. I have dealt with these things in server rooms, plant rooms, and attic cupboards for about fifteen years. They are reliable until they are not. The thing most people miss is that the RWB2 has two separate timing systems running in parallel: the weekly scheduler and the daylight saving / astronomical clock. They interact in ways the manual barely explains. I once spent three hours trying to figure out why a fan coil unit was kicking off at 2:15 PM instead of 2:00 PM in late summer. Turned out the daylight saving offset was being applied twice because someone had manually enabled both automatic and manual offset settings at the same time. The timer just does what you tell it. It doesn't care that you told it contradictory things.

Gyr Rwb2 Timer User Manual What You Need to Know

The unit has four main functions you will actually use. The weekly program lets you set on and off times for each day of the week, with up to four events per day. The astronomical clock calculates sunrise and sunset based on your latitude and longitude input, and can trigger events around those times. The holiday function overrides the weekly program for selected date ranges. And the manual override lets you force the output on or off regardless of the program. To enter the programming mode, press and hold the program button for about three seconds until the display flashes. Use the arrow keys to navigate between days and event slots. Each slot takes a time in 24-hour format and a day assignment. The interface is deliberately minimal. There is no graphical timeline. You are entering data row by row, which is fine for simple schedules and slightly painful for complex ones with many devices. One thing the manual doesn't highlight enough is the battery backup. The RWB2 has a built-in coin cell that maintains the program and current time when power is lost. In my experience, that battery lasts roughly five to seven years depending on ambient temperature. If the unit loses power and you come back to find it has reverted to a default state, check the battery first before blaming the programming. I've replaced batteries in units that had been in service for eight years without anyone noticing. The display would go blank occasionally and then come back with yesterday's schedule still intact. Annoying but fixable.

The relay output ratings are worth paying attention to. The RWB2 typically provides one changeover relay rated at 16 amps resistive load. That means you can switch equipment directly if it is small enough, but most people wire it through a contactor or relay module for anything above a few kilowatts. If you try to switch a large motor load directly, you will arc the contacts and shorten the relay life significantly. I've seen this more times than I care to admit on site. Fault indication is straightforward. The display will show error codes like "Err" followed by a number. The most common one is Err 1, which indicates a battery fault or depleted backup cell. Err 2 relates to an internal clock malfunction, which is rare but happens if the unit is subjected to voltage spikes or improper wiring during installation. Keep a multimeter handy and verify the supply voltage is within the specified range before assuming the unit is broken. When it comes to commissioning, the manual walks you through setting the date, time, latitude, and longitude. Get the latitude and longitude wrong and the astronomical clock will be off by minutes or even hours depending on how far you are from the correct coordinates. I once commissioned a unit with coordinates that were rounded to the nearest degree instead of using the precise values. The sunrise-based event was triggering about twelve minutes early. Not catastrophic but noticeable if you are monitoring it closely.

There is also a test mode that lets you step through the program events manually. This is useful when you are commissioning a new installation and need to verify that each event triggers the correct output at the right time without waiting for the actual scheduled moment. Hold the test button to enter this mode, then use the arrow keys to advance through each programmed event. The relay will activate for each event so you can confirm the wiring is correct. One limitation worth mentioning is that the RWB2 does not support remote programming or monitoring. If you need to adjust schedules from a central system, you are looking at a different product line. This is a standalone timer. It does exactly what it says and nothing more. Some people buy these hoping they will integrate with BMS systems and then spend a lot of time figuring out why they don't. There are models in the Gyr Belimo range that support BACnet or Modbus, but the RWB2 is not one of them. The manual also covers periodic maintenance, which basically amounts to checking the display for any persistent fault codes and verifying the battery condition every few years. The relay contacts can accumulate wear over time, especially if you are switching inductive loads without proper suppression. If the unit starts behaving erratically or the relay fails to actuate, a contact cleaning or replacement might be needed. I usually recommend testing the output with a known good load during any scheduled maintenance visit rather than waiting for a failure.

If you are working with an older RWB2 unit that has been in service for a long time, the plastic housing can become brittle and the display contrast may fade. These are cosmetic issues but they can make programming more difficult. I've replaced displays on a few of these units by sourcing second-hand parts from decommissioned installations. It works but it is not a solution anyone should rely on for a new project. The download link for the manual is typically available on the Belimo documentation portal. Search for the document number which is usually something like 552-000-xx depending on the variant. Make sure you grab the correct version for your specific model number, which is printed on the front of the unit. There have been a few hardware revisions over the years and the programming steps can differ slightly between them. I also want to mention the interlock function, which is one of the more useful features that people overlook. You can set the RWB2 to only activate an output if a separate input signal is present. This is commonly used for freeze protection interlocks where the heater only runs if the water temperature is above a certain threshold. Set this up in the input configuration section of the manual. It adds a layer of safety that is worth the few extra minutes of setup time.

Finally, if you are replacing an old Gyr timer with an RWB2, double-check the wiring diagram. The terminal layout is similar but not identical to older models. I've seen people wire things up assuming the terminals matched their old unit and then spend an hour troubleshooting why nothing was working. The manual has a wiring diagram on one of the later pages. Use it.