How to find if boiler is modulating

[Harry Bloomfield]

I think you may be confusing different things. Boiler modulation means the boiler can turn down it's output if required. It's a boiler thing, not a controls thing.

Mainly a boiler thing, but some controls can help by 'advising' the boiler that full output is not required, to meet the heat demand.

 

[danlightbulb]

Oo interesting. What boiler do you have?

A worcester Bosch Greenstar 25Si MK4. See my other thread on this very forum area.

 

[muggles]

Thank you, that's super helpful. I live in an old stone building so you're probably right about the heat loss (I've found some good links to calculate heat loss but haven't quite got my head there yet). When it modulates is it doing so according to the temperature of where the thermostat is (perhaps it's sending that data back) or is it taking flow temp and assuming that the water coming in can give a decent indication?

It modulates according to the flow temperature, there's no communication between your boiler and thermostat other than an on/off switch switch live connection. It's not a data link, unless you have WB EMS controls

 

[Harry Bloomfield]

Thank you, that's super helpful. I live in an old stone building so you're probably right about the heat loss (I've found some good links to calculate heat loss but haven't quite got my head there yet). When it modulates is it doing so according to the temperature of where the thermostat is (perhaps it's sending that data back) or is it taking flow temp and assuming that the water coming in can give a decent indication?

Your room thermostat only turns on or off, it doesn't advise the boiler how big or small the demand for heat might be, it just tells the boiler heat or no heat required. The only modulation it can make is based upon it's flow temperature - as the flow temperature nears the set flow temperature, it can turn its heat output down rather than off.

A better control system can do much better than simple on/off, it can let the boiler know it is nearing your desired room temperature so it can modulate itself down. When there is a demand for heat, the boiler will have some idea of how much heat it needs to produce and again modulate its output to suit the demand. Rather than a constant cycle of running flat out, then off, you get a much steadier input of heat, less creaking of pipes and a much more stable room temperature.

So some modulation, but quite a limited use of its ability to modulate because of a dumb control system.

 

[denso13]

Mainly a boiler thing, but some controls can help by 'advising' the boiler that full output is not required, to meet the heat demand.

Yea, the OP was thinking that boiler modulation only meant Opentherm, which it doesn't.

 

[karlbbb]

Thank you, that's super helpful. I live in an old stone building so you're probably right about the heat loss (I've found some good links to calculate heat loss but haven't quite got my head there yet). When it modulates is it doing so according to the temperature of where the thermostat is (perhaps it's sending that data back) or is it taking flow temp and assuming that the water coming in can give a decent indication?

Most boilers modulate the size of their flame to maintain a flow temperature. If the boiler is set to 65C flow temperature, it'll vary the flame size inside to maintain a steady 65C. This is an innate function to most modern boilers, and you can generally hear it happening based on noise levels.

The modulation you're thinking of is an external control telling the boiler to change its flow temperature, and this typically uses the OpenTherm language between the controller and the boiler to communicate these changing needs. In some cases (Worcester boilers, as you've discovered) use their own proprietary language between controller and boiler.

Regardless of this, just remember the boiler will still modulate its flame size to maintain whatever flow temp is set, whether that temperature is a fixed setting from the front panel, or changed by an external control.

 

[Mister Banks]

Its a shame i didn't know about Opentherm before I bought my WB Greenstar boiler as I might have purchased a boiler that supports it. Do the Honeywell, Hive, and other programmable thermostats that use TPI give any benefits to heating efficiency? Reading on line the manufacturers extol the virtues of TPI but independent reviews appear mixed.

I have tried a couple of Honeywell TPI thermostats but the constant clicking of the thermostats was very irritating when they seemed to happen every few minutes as the stat turned the boiler on and off to maintain room temperature.

 

[mpgw]

Its a shame i didn't know about Opentherm before I bought my WB Greenstar boiler as I might have purchased a boiler that supports it. Do the Honeywell, Hive, and other programmable thermostats that use TPI give any benefits to heating efficiency? Reading on line the manufacturers extol the virtues of TPI but independent reviews appear mixed.

I have tried a couple of Honeywell TPI thermostats but the constant clicking of the thermostats was very irritating when they seemed to happen every few minutes as the stat turned the boiler on and off to maintain room temperature.

This may help https://www.worcester-bosch.co.uk/products/accessories/directory/easycontrol-adapter