How to use a combi boiler

[NomoneyNohoney]

Our family abroad have a new combi boiler fitted, and the first bill seems very high. No-one seems to know how to deal with it, so I'm trying long-distance diagnosis and suggestions.

First, the new boiler is a Schuster Combo S 24HE. I've found installation and users operation manuals online,(well, generic Schuster manuals, but nothing mentioning the specific boiler they have,) but they still leave unanswered questions.

It seems that the boiler has no time-clock fitted, which if correct, means the heating is running 24/7 - which would probably account for the high bill!

Looking at the two manuals mentioned, I can't see anywhere mention of connecting a time clock.
In the section for Electrical connections, there are three sections which (ignoring the pictures of the terminal blocks) say:-

ON/OFF room thermostat connection        ON/OFF room thermostat connection       External Probe Connection
TA On-off                              TA Mod                                               SE
(terminal block diagram...)           (terminal block diagram...)                  (terminal block diagram...)

Remove the jumper and connect        Connect the modulating thermostat          Predisposed on the terminal
the room thermostat wires           between terminals TA1/OT                     board, terminals SE
between terminals TA2                after having removed the jumper

To anyone familiar with boilers, does any of that give a clue or indication?

What I have in mind, does a simple time clock fit across the thermostat connection, so that when it switches on and off, does the thermostat connection think the boiler needs to fire up, or alternatively, think that it isn't needed? I can't see anything online explaining how a time clock interfaces with a combi boiler, and as there's no mention of connecting a time clock in the manual, that's why I'm grasping at straws. Can anyone give me any pointers?

[martint123]

Just a quickie reply.
From what I have seen combined thermostat/timer in one device is normal/common. Effectively the two are in series so that to call the boiler the time has to be in the window and the thermostat colder than requested. Out of hours the thermostat is out of circuit.

If it is an intelligent thermostat conforming to the "opentherm" protocol then the thermostat is much more controlling of the boiler and can play with the water flow rate and keep teh system running "warm" rather than on/off hot/cold.

The reference to a probe could be an outside temperature probe that can be used to modify boiler controls to maybe start earlier if it's cold outside?

[modellingman]

Agree with what martin123 has said.

If you are looking at http://www.schusterboilers.com/upload/blocchi/X75allegatoMANUALE_INSTALLAZIONE1-2X_00335159-swg-ec-installatore-ing.pdf, then in addition to the diagram on page 20, there is a further diagram on page 31 which identifies the location of the relevant connections on the circuit board - they are in block A3.

Accessing these connections will probably require removing the cover of the boiler. For safety reasons, the connections certainly won't be accessible without using some type of tool (such as a screwdriver) since exposing the circuit board will also expose the 230V connections from the mains supply.

Once the connections are exposed, it will be possible to confirm (or not) the presence of the "jumper" connection between the end pair of terminals in block A3. The presence of this jumper identifies that the boiler is not being controlled by a timer/thermostat.

[NomoneyNohoney]

Thank you both for your replies - it's comforting to know my deduction about how the clock would work is correct. I was pleased to see this further explained in https://www.flameport.com/electric/cent ... rammer.cs4

That has helped a great deal, so appreciate your taking the time to reply.