Boiler modulating - best preformance?

JohnB47

We have a Worscester Bosch Greenstar 8000 Life boiler (fitted two years ago) and a wireless Comfort + II RF thermostat/programmer.

We have the hall stat temperature set to 21 degrees between 7:30 and 18:00 and in this relatively mild weather I see that the boiler is staying on fairly constantly and showing a flow temperature between 35 and 48 degrees. It does switch off occasionally and today, when the sun is out, I know that it will stay off for most of the time. Yesterday, really dull, windy and rainy, it was on most of the time, always with the rads feeling lukewarm. When the boiler is running like this, the stat temperature is showing 21 Degrees, the target temperature. (I can set the stat only temperature in 0.5 degree steps). The boiler flow temperature is set to 60 degrees.

I'm wondering if this is the most efficient way of running things.

For example, on our electric under floor heating programmer, I seem to remember that I can set a sort of over and under temperature range. So if I set it to 1%, and set the UFH to 28 degrees, it means that the UFH stays on until the temperature reaches 29 degrees and then goes off. It will only come on again when the temperature drops to 27 degrees. This stops the UFH cycling too often around 28 degrees. Anyway, it's something like that - I might have to look at the manual.

I can find no such range setting on the Boiler thermostat/programmer, so it seems to be purring away supplying low temperature water even though the stat is saying it's reached the required temperature.

Any thoughts?

FreeBear

JohnB47 said: We have the hall stat temperature set to 21 degrees between 7:30 and 18:00

Any thoughts?

Do you really need the temperature set at 21°C ??

I'd knock it back to 19°C or even lower and then set it to increase the temperature at different times of day - You can save an awful lot of gas (and cut your energy bills) that way.

rob7475

I'm about to have an 8000 fitted myself so will keep an eye on this.

It sounds like your boiler is modulating well to keep the set temperature. Without modulation, the temperature would overshoot to around 22 before the boiler goes off and then comes back on when it drops to say 20. Modulation helps keep the temperature steady by adjusting the flow temperature at the boiler. This also helps keep the boiler running in condensing mode for longer.

In theory, it all sounds great, whether it saves any gas or not, I'm not sure. I think in a well insulated house, it may do but in older less well insulated properties, I'm still to be convinced.

JohnB47

FreeBear said:

JohnB47 said: We have the hall stat temperature set to 21 degrees between 7:30 and 18:00

Any thoughts?

Do you really need the temperature set at 21°C ??

I'd knock it back to 19°C or even lower and then set it to increase the temperature at different times of day - You can save an awful lot of gas (and cut your energy bills) that way.

Thanks. The problem is that the missus feels the cold more than me. I could manage what you suggest but the result would be frosty!

daveyjp

A wireless stat which can be moved to the room you spend most of the time during the day may be cheaper.

BUFF

That is what he already has ("RF"= radio frequency).

The Comfort II + RF has load (but not weather) compensation. The fact that the op sees it running constantly but with flow temps varying between 35C & 48C  even though set to 60C suggests that the controls are doing their job.

Miser1964

>I'm wondering if this is the most efficient way of running things.<

I'd suggest adding an external weather compensation sensor to the boiler

>I can find no such range setting on the Boiler thermostat/programmer<

The Greenstar Comfort+ is already doing load compensation to avoid short cycling and over shooting the target temp

Ectophile

JohnB47 said:

FreeBear said:

JohnB47 said: We have the hall stat temperature set to 21 degrees between 7:30 and 18:00

Any thoughts?

Do you really need the temperature set at 21°C ??

I'd knock it back to 19°C or even lower and then set it to increase the temperature at different times of day - You can save an awful lot of gas (and cut your energy bills) that way.

Thanks. The problem is that the missus feels the cold more than me. I could manage what you suggest but the result would be frosty!

There's a solution to that.  Buy a second thermostat, and don't pair it to the receiver on the boiler.  Set the new thermostat to 21C, and hang it on the wall.

Set the old thermostat to 19C and hide it somewhere.

ThisIsWeird

Ectophile said:

JohnB47 said:

FreeBear said:

JohnB47 said: We have the hall stat temperature set to 21 degrees between 7:30 and 18:00

Any thoughts?

Do you really need the temperature set at 21°C ??

I'd knock it back to 19°C or even lower and then set it to increase the temperature at different times of day - You can save an awful lot of gas (and cut your energy bills) that way.

Thanks. The problem is that the missus feels the cold more than me. I could manage what you suggest but the result would be frosty!

There's a solution to that.  Buy a second thermostat, and don't pair it to the receiver on the boiler.  Set the new thermostat to 21C, and hang it on the wall.

Set the old thermostat to 19C and hide it somewhere.

I love it!

ThisIsWeird

I suspect it's as Rob says - a much more delicate way of controlling the boiler output to match demand, and largely in fully condensing mode. 

Sounds a bit like the 'Opentherm' protocol that other systems use. 

If your boiler doesn't have weather comp, then as Miser says that's likely to add a further element of control - the boiler's output will also be adjusted to cope with external temps.

But, lawdie, 21oC? Tsk...

JohnB47

Ectophile said:

JohnB47 said:

FreeBear said:

JohnB47 said: We have the hall stat temperature set to 21 degrees between 7:30 and 18:00

Any thoughts?

Do you really need the temperature set at 21°C ??

I'd knock it back to 19°C or even lower and then set it to increase the temperature at different times of day - You can save an awful lot of gas (and cut your energy bills) that way.

Thanks. The problem is that the missus feels the cold more than me. I could manage what you suggest but the result would be frosty!

There's a solution to that.  Buy a second thermostat, and don't pair it to the receiver on the boiler.  Set the new thermostat to 21C, and hang it on the wall.

Set the old thermostat to 19C and hide it somewhere.

Ha! Great idea. But I always get found out!