This guy killed entire Tado value proposition
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@eezytiger , you're pretty much down on your gas usage across the board there on last year! I am very jealous of those numbers! My 21.95Kwh for today does include 2 showers this morning, but we are electric for cooking so no gas use there. This is my gas usage for October....so far!
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@Notascoobie Without looking back at last year's October weather, I suspect it's a bit milder this year. Also, whilst I did fit Tado on 7th October last year, I was running it in numpty "out of the box mode" instead of optimised as it is now. Furthermore, I've learned a lot about running the boiler more efficiently, so output is dialled way back (9 kW fixed instead of 24 kW modulated) and with target flow temperature set to 50C currently (which it has seldom reached so far this season) so return temps are super low and efficiency about as good as I can expect from this 11 year old boiler.
As temperatures drop I may have to revisit boiler settings, but for milder weather so far it appears to be paying off.
Apart from Tado and my new boiler skills I also had a major revision to glazing last year, replacing 33 year old aluminium framed double glazing with acoustic uPVC double glazing on the south side and uPVC triple glazing on the north and east. Plus new exit doors. Oh, and the 33 year old TRVs fitted prior to Tado were all seized and completely defective, which is what led me to replace them with Tado in the first place.
Taking everything into account my gas usage has dropped massively this year compared with last.
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@eezytiger , I've pretty much replicated your operating mode today in an effort to see how it pans out over the next few days. I've reduced the power output of the boiler in CH mode down to 30% which I belive is about 9.4Kw. I watched what was happening at the boiler this morning as the heating switched on. The burners fired up and the flow temperature went up to 52c. It sat there for about 15 mins then the burners switched off but the pump continued running. Flow temperature started to drop down over the next 10 mins to 41c, at that point burners fired up again and flow temp rose again to 52c. Burners then shut down again after about 10 mins. Now I'm no expert, but isn't that the boiler cycling? And isn't that to be avoided? Do you have any idea how long your boiler has the burners on for?0
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@Notascoobie For my system I'm using relay control between Tado and the boiler. Tado seems to switch the boiler on in multiples of ten minutes. Today it was on solidly for 30 minutes from 07:00, raising flow temperature slowly from overnight 20C to 46C before shutting the boiler off. The boiler flow limit is 50C, so this was never reached. It was Tado calling the shots.
Later on, at 08:00 and again at 08:20 it looks like the boiler fired up again, but only briefly. Tado said it was "heating", but I do not know why, as the bathroom was already above set temperature. Seems like a Tado error to me.
Regarding your own setup, it's hard to diagnose from my end. Two things come to mind.
Firstly, the difference between your overnight temperature and daytime target might be greater than mine and it simply needed a lot more oomph to close the gap. It may also be that you have a bigger property to heat.
Secondly, maybe you had fewer radiators requiring heat, or smaller radiators, and so the output from the boiler could not be dissipated as quickly as the boiler was supplying it. I have set temperature differentials for my radiators such that there will usually be several, possibly all of them, open for heat when the bathroom fires the boiler. In other words, the bathroom has the lowest temperature target of all rooms. Other rooms are either equal to or higher than the bathroom. They may not reach their set temperature, but the rads are open and ready to dissipate heat whenever the boiler is on.
There are more things to consider with your setup. Are you using relay control or Opentherm? What is controlling the boiler flow temperature (limit)? Did Tado shut off the boiler or did the boiler make the decision to shut off?
By the way, pump overrun is completely normal after the burner shuts off. Mine always runs on for five minutes, even if the burner only lights for a single minute.
So, I have no concrete answers for you. Your property (size, insulation, temperature targets, radiator sizing, boiler specs, boiler control) are very unique to you. I'm not a heating engineer, but I've refined my setup to suit my needs and the limitations of my boiler, rads etc.. I think you will have to fine tune things to suit your environment as precisely as I have.
I'm trying to operate my heating as though I have a heat pump. I'm really testing whether my radiators and insulation of the property can work with low flow temperatures. Of course, October temperatures are no real test at all, but I'm tweaking and refining as I experiment and learn. So far I am happy with the way things are shaping up. The real test will be in January though.0 -
Thanks for that detailed reply @eezytiger . We do obviously have some system differences. My property is a 3 bed detached with a lounge/diner, an internal garage conversion to a study/family room, and a recently extended kitchen/diner. We also have a down stairs utility room and cloak room. Upstairs isthe 3 bedrooms, 1 of which has an ensuite, and the main bathroom. House was built in 1997. We changed to a Worcester 38cdi combi about 6 years ago. New upvc double glazing was put in about 10 years ago along with injected cavity wall insulation. I have recently brought the loft insulation up to 450mm. All in all I think the house is as well insulated as I can make it. We do have a lot of radiators mind you. 7 rads and a towel rail down stairs, and another 5 rads and another towel rail upstairs, so 12 rads and 2 towel rails in total. I replaced relay control with modulated control last year, and as I mentioned earlier I've reduced the power output of the boiler to 9.4Kw this morning. My CH flow temp seems to max out at about 50-55c and the front dial is set to just below 3(max is 6). Domestic Hot water temp is set to50c. I'll stick with the changes I've made today for a bit and see how it pans out. Must admit though that even the wife has commented this morning that the house feels a lot warmer than usual. Anyway, thanks for all your help.1
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Interesting thread you've started here @eezytiger
I've run tado on relay with a (basic) weather compensating Viessmann for the last 10 years. Dumb TRVs throughout.
I've spent a lot of time attempting to optimise the (fixed gradient) WC curve, and it's currently set to 70C flow at -10C outside. So pretty much condensing all the time.
I now have 2 tado room stats as I've just upgraded to a v3+ and through an unintended quirk of the installation process, it's running alongside my existing v1. So V3 is sitting in the hallway (good indicator of overall house temperature) and temp sensor for v1 is in the lounge (higher heat loss due to lots of glass, but for reasons you gave above, not the best place to site the stat for whole house). In practice, this means the V3 drives the whole house heating, but if that goes off and the lounge drops faster, the V1 will put the heating back on.
It's all on a single zone (despite the two stats) again, for the reasons you give above (emitter area). TRVs create some floor zoning, in that the first floor TRVs are around 18C and the (most unused) second floor are set to around 16C. This doesn't seem to create a noticeable 'heat drag' through the floors.
The house is old and fairly large and whilst some windows are DG, the ground floor is largely SG. As we don't plan to stay here for much longer, there's no ROI on upgrading the windows (would need to be bespoke timber period as we're in a conservation area), for little saving on heat loss.
I've experimented with constant circulation at a fixed set point, but found that uneconomical given our property characteristics. I now run a small (2-3C) set back with programmed ramp up (not tado Early Start, which doesn't work so well, particularly with the new V3+).
The house does cost a small fortune to heat in these ridiculous times, but since installing the new boiler, TRVs and tado (and DG on the upper floors and enhanced roof insulation), I've brought the energy usage down by around 65% from when we bought the place.
As you're likely already aware, if you're able to install weather comp with your boiler (particularly if it's advanced WC), then I think you'll have yours completely nailed. Even basic weather comp will save you seasonally adjusting the flow temp on your boiler.
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@DM932187 That's no point in bothering with weather comp for *my* boiler. With 9 kW minimum output and typical UK temps it cannot modulate the flow to low temperatures. So long as the boiler is lit the flow temp continues to rise.
I've tried eBus control three times in the past year and all I see is extremely low and unachievable flow temp demands (such as 33C). The boiler just sails past the set temp until it shuts off. My boiler design does not continue circulating water and topping up the heat occasionally. Once it shuts off the burner there is a five minute pump overrun and then a period of more minutes (the lower the flow temp the more the minutes) spent in anti-cycling mode, where the boiler will not fire again.
https://myboiler.com/vaillant/vaillant-ecotec-boiler-anti-cycling-time/
So, for *my* boiler it's back to relay switching and a manually set flow temp. It was 50C in autumn, now it's 55C. That still keeps my boiler very comfortably in condensing mode, with headroom to spare.
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@eezytiger Hmm, tell me more.
My Viessmann has a relatively poor modulation ratio and minimum output is around 7kW. It can modulate down to about 30C minimum, below which it cycles. However, there are rarely days when we need the heating that aren't cool enough to require a flow temperature much below 30C. Even then, although the boiler will cycle the burners to maintain say, 25C, it will probably still cycle less than tado's relay 'modulation', and when the burners cut out the pump overrun doesn't kick in unless there's also no call for heat from the stat. The burners switch off, but there's still (warm) water flowing around the system (until it cools enough again to trigger the burners). Even when tado does switch the system off, the overrun will be overtaken if there's another call for heat from the stat opening the circuit valve.
Now of course, your boiler is different and so is your property. With ours, we have no difficulty with a circa 20C delta T, which helps keep the burners ticking over.
I'd definitely run constant circulation on mine if it weren't for the relatively high heat loss. Far quieter/comfortable than the relay nonsense (which with the new v3 seems unfathomably intent on holding the house temp 0.3C below the set point, which the V1 never did)
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@DM932187 My boiler is rated for 9-24 kW. I've range rated it to the minimum, so it can only ever put out 9 kW, or 0 W.
It's just gone 10:00 and my total gas used so far is 29 kWh since midnight. That includes a shower of c.1 kWh. So my heating needs, averaged over the last 10 hours are 2.8 kWh per hour, or 2.8 kW. If it hadn't been for a one degree heating ramp at 07:00 the average need would probably be closer to 2 kW.
Since my boiler cannot output less than 9 kW (apart from 0 kW) it only needs to be lit for 20 minutes per hour or even less to maintain status quo. There is no other possibility - for *my* boiler. It is oversized and that's the price you pay for having a sub-optimal boiler installed.
What I need is a boiler that can run all day at under 3 kW. Much less than that in autumn/spring. Veissman have such options in their latest boilers. WB can go as low as 3.2 kW, but that's really more than many would need for most of the year in South East England. I don't know what other brands can offer, but in this modern, enlightened age, less is more. Low and slow is the way to go.
It's the power output that's the problem. The flow temps inevitably are forced up and up by the excessive power.
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Well, you're on about half of mine there, @eezytiger!
I hadn't fully appreciated you'd taken the max output down to the minimum, and so I now totally get where you're coming from. With an average of 2kWh, moving to WC would give you marginal gains at best and as you say, would require a new boiler if you (rightly) want modulation, which is an investment that would take you a very long time to recover.
Simple WC would possibly still work, but you would get some more cycling of the burners. Marginal gains though at your current levels of consumption, so likely best to wait until you need to replace anyway (as you'll know). At that point, I'd personally go with a V200 range boiler. You can bin off tado completely at that point, as you can run the 200s 24/7 with parallel shifting for set back.
Oversized boilers are a sad fact of UK installation. Mine's up to 26kW and like you, I make the best of it. Somewhat unfortunately (for me at this point), Viessmann boilers are bulletproof, so I'll not be needing to replace before we leave this leaky old shed of a house.
I'll not be letting the Mrs convince me to buy a 'period' property again. At least not unless it's in need of a full gutting and therefore floor to ceiling retrofitting programme. And a new v200.
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Sorry, @eezytiger, one other (genuine) question if I can.
Why would you rate it to the minimum and turn off the modulation?
And a follow-up...
Doesn't the boiler self-limit based on demand, so will only use it if you needed more than 9kW - e.g. to heat water?
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@DM932187 My next "boiler" will probably be a heat pump, but hopefully not for another decade, so long as my current boiler continues working. By that time the decision will probably be taken out of my hands by legislation or punitive gas (CO2) taxation.
Right now my electricity costs more than five times as much as gas per kWh on my tariff so I'm happy enough with my present, imperfect, system. I'm sure that will change down the line.
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@DM932187 Hot water demands are not affected by range rating. That's only for CH.
The only reason to ever need more than 9 kW for central heating my home would be if all the insulation vanished overnight, we saw Arctic temperatures or I let the system go stone cold overnight (or whilst on holiday) and wanted to rapidly heat it from cold.
I have essentially been trying to operate my system as though I actually had a heat pump, within the constraints of my boiler. So, low power, minimal or no overnight setback, just a steady drip feed of warmth to the whole house 24x7.
It is really a test to see if my radiators would be up to the task of working with a heat pump or if it would be a wholesale change of everything to make the move.
I keep records of daily gas consumption going back a few years, thanks to my smart meter. The highest gas usage day was in February 2021, when I used 130 kWh in one day. Averaged over the day that's 5.4 kW. On the worst day on record. Since then I've improved home insulation, installed Tado (previous TRVs were 33 years old and no longer exerted thermostatic control) and learned a lot about running the boiler more efficiently.
A 5 kW heat pump would probably be sufficient. So should a 5 kW boiler. I do not need 9 kW, never mind 24.
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Understood. All very good points @eezytiger. Thanks for sharing your thoughts.
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i've just checked the spec of my boiler - Alpha eTec 28
- Heating output range: 4.3 – 26.1 kW
- Max hot water output: 28.3kW
- Max DHW flow rate: 12.1 litres per minute
looks like changing from relay to opentherm (which i'll be doing once i've completed the rest of the upgrades) will help with efficiency.
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