How to find if boiler is modulating

[Dylan T]

Hi all - Like many at the moment I'm doing what I can to make my central heating more efficient and am looking to replace my controller (which is in need of replacing anyway). Every day's a school day and I've learned about boiler modulation and the compatible controls for this as shown in this helpful video. However I cannot for the life of me find out if my boiler offers modulation and was hoping someone could help me find it out (perhaps there's something I need to look for on the boiler itself). It's a Worcester Greenstar 37CDi and was here when I moved in 7 years ago; the model itself seems discontinued and there's little about it online.

Thanks so much

 

[Alec_t]

You should be able to tell just by listening to it when it starts up. My Greenstar 26i starts up at 'full throttle', then audibly drops back to something less.

 

[Dylan T]

You should be able to tell just by listening to it when it starts up. My Greenstar 26i starts up at 'full throttle', then audibly drops back to something less.

Thanks I'll have to check that but I think it might be the same which is good. How is your boiler reading the temperature - at the thermostat, at the boiler itself or does it have an external sensor outside somewhere?

 

[Harry Bloomfield]

If it modulates, it is fairly obvious from the amount of noise the boiler makes. It will begin noisy, then near the end of the burn it will become much quieter.

 

[Harry Bloomfield]

Thanks I'll have to check that but I think it might be the same which is good. How is your boiler reading the temperature - at the thermostat, at the boiler itself or does it have an external sensor outside somewhere?

How is the boiler reading which temperature? The boiler measures it flow temperature, the room temperature and or hot water temperatures determine whether there is a demand for heat, probably also dependant on time.

 

[Dylan T]

How is the boiler reading which temperature? The boiler measures it flow temperature, the room temperature and or hot water temperatures determine whether there is a demand for heat, probably also dependant on time.

From what I understood the whole point of modulation was taking a third reading - the outdoor temperature preferably - in order to know how hard to run the boiler. The room temperature & flow temp would just work fine for boolean on/off operation.

 

[muggles]

It'll be modulating but not much. Minimum burn on this boiler is 9.8kW

 

[Dylan T]

It'll be modulating but not much. Minimum burn on this boiler is 9.8kW

Thanks - out of curiosity what are normal minimums. Would you say then it's not worth investing in a third party modulating thermostat?

 

[denso13]

Would you say then it's not worth investing in a third party modulating thermostat?

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.

 

[Dylan T]

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.

The video linked in my post explains it better than I can but it seems some controls offer settings that use modulation - for example when and what thresholds (all depending on bus compatibility).

 

[danlightbulb]

Trying to solve the same problem in my recent thread also. Seems hard to find out reliable info or solutions.

But I've now learned that the external modulating feature is on top of the boilers own modulation, and simply refers to the ability of the controller to alter the flow temp target of the boiler.

 

[danlightbulb]

I'm reading the comments on the video you linked, and it's suggesting that the tado smart stat can speak the EMS language needed for WB boilers. Off to investigate further

 

[muggles]

The video linked in my post explains it better than I can but it seems some controls offer settings that use modulation - for example when and what thresholds (all depending on bus compatibility).

Worcester have pretty much locked down their bus system to only work with their own controls. If you want proper controls-guided modulation then you need to use WB controls, although I don't think the current range will work with your older boiler either. Everything else will be on/off only.

Decent modern boilers modulate down to around 3-4kW, or 1.9kW in the case of Viessmann. Ideally to prevent cycling, and refuse fuel consumption and wear & tear, you want a boiler which can modulate to 50% of the heat loss of your property and has modulating controls too. Unfortunately at 9.8kW your boiler's minimum output is likely to be very close to or may even exceed your heat loss

 

[Dylan T]

Worcester have pretty much locked down their bus system to only work with their own controls. If you want proper controls-guided modulation then you need to use WB controls, although I don't think the current range will work with your older boiler either. Everything else will be on/off only.

Decent modern boilers modulate down to around 3-4kW, or 1.9kW in the case of Viessmann. Ideally to prevent cycling, and refuse fuel consumption and wear & tear, you want a boiler which can modulate to 50% of the heat loss of your property and has modulating controls too. Unfortunately at 9.8kW your boiler's minimum output is likely to be very close to or may even exceed your heat loss

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?

 

[Dylan T]

I'm reading the comments on the video you linked, and it's suggesting that the tado smart stat can speak the EMS language needed for WB boilers. Off to investigate further

Oo interesting. What boiler do you have?