How to optimise your combi boiler

I set my CH flow temperature to 55c (was previously set to 75c). Will see how it behaves when it eventually comes on. Although I think 55c seems too low and may struggle to warm our reasonable sized four bed detached. Boiler is a valiant condenser combi.
 
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Been doing a lot of research lately into boiler controls. Have another thread for my specific installation. But as a general point I am quite confused as to why the dials on a boiler go up to 6+ high when any setting above 1 or 2 on the heating will not be in the most efficient condensing mode. They are called condensing boilers for god sake, yet so many people will set the dial to a high number not even being aware that only 1 or 2 on the dial will make the boiler condense. Its a poor show from manufacturers imo, and also the failure of the UK not to make opentherm mandatory. I also have seen some information about the hot water temperature, basically saying that 40 degrees is enough. Well that is 1 or 2 on my dial so why does it go up to 6 then?

Whilst on the subject of Opentherm and other modulation methods - again I have been researching and it seems that even a device like the Tado will start the boiler off on a high flow temperature then modulate it down. But it also seems to indicate that the device can run the boiler at a lower temperature than the minimum setting on the dial - still investigating this one but if true, why don't the manual dials go lower? My boiler manual doesn't seem to specify the lowest power that the boiler can go to via modulation.

Bit of a moan really but it seems to me that these boiler companies left a lot of efficiency scope on the table in their designs.
 
danlightbulb said:
Been doing a lot of research lately into boiler controls. Have another thread for my specific installation. But as a general point I am quite confused as to why the dials on a boiler go up to 6+ high when any setting above 1 or 2 on the heating will not be in the most efficient condensing mode. They are called condensing boilers for god sake, yet so many people will set the dial to a high number not even being aware that only 1 or 2 on the dial will make the boiler condense. Its a poor show from manufacturers imo, and also the failure of the UK not to make opentherm mandatory. I also have seen some information about the hot water temperature, basically saying that 40 degrees is enough. Well that is 1 or 2 on my dial so why does it go up to 6 then?

Whilst on the subject of Opentherm and other modulation methods - again I have been researching and it seems that even a device like the Tado will start the boiler off on a high flow temperature then modulate it down. But it also seems to indicate that the device can run the boiler at a lower temperature than the minimum setting on the dial - still investigating this one but if true, why don't the manual dials go lower? My boiler manual doesn't seem to specify the lowest power that the boiler can go to via modulation.

Bit of a moan really but it seems to me that these boiler companies left a lot of efficiency scope on the table in their designs.
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Boiler mfrs arent at fault, its the lazy or incompetent installer base, there is pretty much zero thought into a heating system design at domestic level. So the plumber comes in, whacks a boiler on the wall and aslong as it lights and gives out heat, hes off down the road.

European engineers in the industry are a different breed, if i look at the guys in Germany and France, even Italy, there is a huge gulf in attitudes and skill sets.
 
Tinders said:
Boiler mfrs arent at fault, its the lazy or incompetent installer base, there is pretty much zero thought into a heating system design at domestic level. So the plumber comes in, whacks a boiler on the wall and aslong as it lights and gives out heat, hes off down the road.

European engineers in the industry are a different breed, if i look at the guys in Germany and France, even Italy, there is a huge gulf in attitudes and skill sets.
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But is it the boiler manufacturers who should be stronger / stricter in their specifications? For example, why don't they mandate an outside weather compensation sensor on a boiler that supports it? That simple act alone would improve efficiency and give every install immediate flow temperature modulation. Doesnt even need a smart thermostat or opentherm.
 
Like the other combi thread you need the Tado eu digital interface to get it to modulate the boiler.

After reading the procedure to set up pump flow rate https://www.heatgeek.com/how-to-test-and-set-your-pump-speed/
employing return/outgoing temperature monitors, it was interesting to see Vailants can give you this data. https://www.youtube.com/watch?v=S3Px81qU06k

smart move seems to be getting that data and then having a pump which will adjust(reduce) the flow when some radiators are off seem more important than installing remote control TRV's,
it's not hard to just manually turn off the heat in the rooms you don't use, or adjust the bedroom valves a couple of times a day
 
I have turned the heating down on my boiler but the water I have to keep at 60. I have no idea if there's any dead legs in this house as it's pretty old and the previous owners seemed slap dash in how they did things.

That said they at least got a very efficient combi put in but seeing as the shower didn't even have its own isolator switch till we moved in I can't really take the chance.
 
jpaul said:
Like the other combi thread you need the Tado eu digital interface to get it to modulate the boiler.
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Thats what I initially thought however I don't think its the case. I could instead fit a simple 2 wire outdoor weather compensation sensor, and this alone will allow my boiler to modulate. So if its that easy, why don't the manufacturers specify it as mandatory?
 
danlightbulb said:
Thats what I initially thought however I don't think its the case. I could instead fit a simple 2 wire outdoor weather compensation sensor, and this alone will allow my boiler to modulate. So if its that easy, why don't the manufacturers specify it as mandatory?
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Personally I think until the recent bat**** crazy price rises not many people really cared. Maybe things will change going forward.
 
Yes depending on boiler I can that I can see an independently connected weather comp, might give some economic master control setting of max outgoing boiler temperature, even if tado interface just turns the boiler on/off.

again you really need outgoing/return temp data to see what is happening during use, when some zones are off.
when we have just 20% of the radiator on in the house I suspect return temp will be inefficiently nearly matching outgoing.



what I'd read after other thread https://community.tado.com/en-gb/di...dulation-on-worcester-bosch-38cdi-classic-erp
 
IvanDobskey said:
I set my CH flow temperature to 55c (was previously set to 75c). Will see how it behaves when it eventually comes on. Although I think 55c seems too low and may struggle to warm our reasonable sized four bed detached. Boiler is a valiant condenser combi.
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How did you get on with this? I did the same and although it heated up all the rads it wasnt hot enough to heat the rad in the hall where the thermostat is so the heating was on for much longer than last year which would only get worse as we go further into winter

Ended up putting up to 65c which is still 10c less than what it was on previously and now hot enough to heat the master radiator
 
Relentless81 said:
Ended up putting up to 65c which is still 10c less than what it was on previously and now hot enough to heat the master radiator
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Unfortunately not condensing mode though. How can people get round this issue? If <55 is not hot enough to warm up the house, how are you supposed to use condensing mode?
 
danlightbulb said:
My understanding is you need a flow temperature of <55 to get the boiler to condense.
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Mine was that it was the returning temp that got it to condense, maybe you're right. Perhaps someone can confirm. Even so nothing I can do about it, I need the master rad to warm up otherwise it will run for hours more than it did previously
 
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danlightbulb said:
Unfortunately not condensing mode though. How can people get round this issue? If <55 is not hot enough to warm up the house, how are you supposed to use condensing mode?
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The simple answer is... you don't. Not at first. But that's where OpenTherm comes in - you'll start off on a high setting, and OpenTherm reduces the flow temperature as you get closer to the thermostat set point, ensuring you get back into the condensing temperatures.
 
squerble said:
The simple answer is... you don't. Not at first. But that's where OpenTherm comes in - you'll start off on a high setting, and OpenTherm reduces the flow temperature as you get closer to the thermostat set point, ensuring you get back into the condensing temperatures.
Click to expand...
BUt what if its really cold and your rads cant get the house warm enough, i.e more heat is being lost than you can input.
 
danlightbulb said:
My understanding is you need a flow temperature of <55 to get the boiler to condense.
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No. Your return temp needs to be under 55oC so the supply temp can be any temp depending on how efficient your radiators are at putting the heat out.

A very efficient system might have a flow of 67oC but, as the water heat is transferred to the rooms via the radiators (thereby cooling the water itself), the water temp at the return point to the boiler may be 50oC meaning condensing occurs.
 
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