BPT TH 124 Thermostat: Installation and Use Manual

If you are looking for the BPT TH 124 thermostat manual, this page gives you the practical instructions most users need: how to read the display, set the clock, switch between manual and automatic mode, understand common problems and download the PDF manual.

The BPT TH 124 is a classic daily thermostat still found in many homes. It is simple, reliable and effective, but because of its age it often raises the same questions: batteries, wrong mode selection, dirty time pins and error codes.

What the BPT TH 124 does

The BPT TH 124 is a traditional on/off thermostat. It does not work through OpenTherm communication: when room temperature drops below the required value, it closes the relay contact and asks the boiler to start heating.

Programming is managed through the daily time pins and a manual selector, so it is especially important to understand the display symbols and the current operating mode.

BPT TH 124 display symbols

Newer display version

On the newer display you can usually see:

• AUT for automatic mode
• MAN for manual mode
• OFF
• battery status
• current time
• detected room temperature
• ON when the thermostat is actively calling the boiler
• heating or cooling symbol

A very common mistake is to leave the thermostat in the wrong season mode. If cooling mode is active, the thermostat behaves in reverse and heating will not start when expected.

Older display version

On the older display version, lines and symbols indicate:

• ON when the contact is closed
• automatic program selected
• manual program selected
• battery warning
• heating or cooling mode
• error indication for faulty time pins

Buttons and controls

The main controls are:

• Hand button to switch between automatic and manual operation
• Sun / Snowflake button to change season mode
• Clock button to set time

Because the thermostat is quite old, even a small wrong setting can make it seem faulty when it is actually just in the wrong mode.

How to set the clock

For the automatic program to work, the time must be correct.

1. Press the clock button until minutes start flashing.
2. Use the double-arrow button to set the minutes.
3. Press the clock button again to move to the hours.
4. Adjust the hours.
5. Press the clock button again to confirm.

If the time is wrong, the thermostat follows the wrong time pin and heating may appear random.

Manual mode vs automatic mode

The BPT TH 124 can work in two main ways:

Manual mode

In manual mode, the thermostat follows the yellow manual pin. Heating starts only if that pin is set to a temperature higher than the room temperature.

Automatic mode

In automatic mode, the thermostat follows the pin corresponding to the current hour. If that pin is not set correctly, the boiler will not receive a heating request.

Common problems with the BPT TH 124

The thermostat does not start heating

Before assuming the thermostat is broken, check these points first:

• the boiler is in winter mode
• system pressure is correct
• batteries are new and not rechargeable
• the thermostat is in heating mode, not cooling mode
• the ON indicator appears when you raise the required temperature

If heating still does not start:

• in manual mode, make sure the yellow pin is set higher than room temperature
• in automatic mode, make sure the current time is correct and the current hourly pin is asking for enough heat

Rechargeable batteries cause problems

This model often works badly with rechargeable batteries because they may not provide enough current for the relay. The display may light up, but the boiler may not receive the call.

Poor installation position

If the thermostat is close to a window, sunlit wall, radiator or kitchen heat source, temperature reading can be inaccurate and heating behaviour may seem wrong even when the thermostat is technically working.

BPT TH 124 error codes

This thermostat shows errors in the format E xx.

In most cases, the number points to the faulty time pin.

Examples:

• E00: issue on the first time pin of the day
• E12: issue around 12:00
• E23: issue on the last hourly pin
• E24: issue with the yellow manual pin

Typical causes are:

• oxidised copper contacts
• dirty or worn time pins
• mechanical wear from age

You can try moving the faulty pin up and down a couple of times and cleaning the contact once. If the error comes back often, the problem is usually mechanical wear rather than settings.

Useful setup tips

• Replace batteries roughly every 2 years.
• Do not use rechargeable batteries.
• Economy temperature often starts around 16°C.
• Comfort temperature often starts around 18-20°C.
• Cast iron radiators usually need earlier start times than aluminium radiators.

If you want to understand comfort tuning better, you can also read our guide about thermal hysteresis and differential.

Installation advice

Install the thermostat on an internal wall, in a position that reflects the real average room temperature, and avoid:

• direct sunlight
• windows and draughts
• curtains
• nearby radiators or heat sources

Technical specifications

BPT TH 124 PDF manuals

• BPT TH 124 Manual PDF
• BPT TH/124 old series PDF

When it is worth replacing it

If the thermostat repeatedly shows pin errors, loses contact reliability or needs frequent cleaning, replacement is often more practical than repeated troubleshooting. If you need help understanding whether the fault is in the thermostat, the boiler or the wiring, you can also start from our boiler assistance in Modena page.

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