Heating power percentage and calling for heat
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gas usage in kWh ? mine is between 42 - 50 kWh.
@andyblac
Mine is currently around the 65Kwh for 24 hrs.
I have a 3 bed detached house with a garage conversion and an extended kitchen, so 7 radiators and a towel rail down stairs, but only the 2 in the lounge and the 1 in the conversion have tado smart trvs fitted. I also have WTS in the lounge to better control the 2 rads. The lounge is assigned to my extension kit so can fire the boiler. The conversion is independent. Upstairs only the 3 bedrooms have tado smart trvs fitted in conjunction with another WTS. The ensuite and upstairs hall and main bathroom towel rail all have dumb trvs fitted. At the moment I'm trying to copy @eezytiger setup with only the lounge firing the boiler, and the other rooms siphoning off heat as required. Up until about 2 days ago I had the heating off between 2200hrs and 0730hrs. I now have the heating set back to 18c for those hrs and a daytime schedule of 20c from 0730hrs to 2200hrs. I used to have a similar day time schedule to yours ie stepped temp increases throughout the day. So far I can't say I'm using any less gas than I was before, however the house is a lot warmer all over and I know this is true because my better half has asked why the house is so much warmer.0 -
3 bed semi with solid brick walls and good double/triple glazing, doors and loft insulation.
I've been playing with temps a bit, but assume a set temp of 18C in all rooms at all times except 20C downstairs from 0700-2200 for simplicity. Also assume one room (mostly the lounge, but I think different rooms trialed) in charge of firing the boiler and remaining rooms as parasites, stealing heat when available. :-) Note that parasitic rooms may not always hit set temp. They might fall a little short, but, unoccupied as they usually are, that is fine for us.
1008 kWh gas used in November. Take off 70 kWh (equal to summer months) for HW and cooking, so 938 kWh for heating = average daily heating consumption of 31 kWh.
Details for November this year vs last below, including showers, hot water, cooking.
1st December - 46 kWh used.
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@Notascoobie thanks, @eezytiger thanks I used 918 kWh in November, minus 80kWh for cooking and showers thats 838kWh, = average daily heating consumption of 27 kWh. So little less than you, but i have since tweaked my schedules (setbacks etc) so it should be even less now.
I used 50 kWh yesterday, (got down to 0˚c in the morning), plus the cleaner left my hall door open, which caused my media room temps to drop, and it had to recover from that (my hall is always cold even though the rad has no TRV on it and is always open).
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@andyblac Not sure where I’m going wrong in the gas used for showers department! Both you and @eezytiger seem to be using much less than me on that front. I looked at my consumption for June, July and August when the heating wasn’t on at all, and was averaging 6.5Kwh purely for water heating! I we need to have shorter showers!
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@Notascoobie I've been reading this with interest and was thinking the same thing.
@eezytiger and @andyblac do you have combi boilers?
I've got a system boiler and a megaflo cylinder. 2 adults and 2 children and our water heating (and gas hob - though that's negligible) usage is anywhere from 8-10 kWh a day!0 -
@cbd20 I have an 11 year old combi. Max flow temp is currently set to 50C, but it does sometimes overshoot to maybe 52.x before shutting down. However, it only reaches that when increasing the temperature of the house. For temperature maintenance it will not rise that far.
Consequently my return temp is always kept low - temporarily touching 45C at worst case. Usually it is far lower, which keeps boiler efficiency high.
Here are my flow temperature distribution stats for today, up till 11:35. The flow has only exceeded 47C for five minutes, with a maximum of 50.15C recorded. Vertical scale is minutes spent in each temperature band.
Return temps for today, showing only 11 minutes above 40C and a max of 42.25
Very efficient.
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Yup your combi vs my system + megaflo setup explains a lot of our DHW difference I suspect.0
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@eezytiger When you mention the minimum burn time could I check how this works. Does this mean that if only 0.1oC is needed Tado will fire the boiler for 4 mins even if it only needed 2 mins. Does it close the TRV's at 2 mins and then run the boiler for further 2 mins using the bypass?
I have set my Vaillant 938 at the lowest output of 6KW. I use eBUS and have the flow temperature set in the Vaillant at between 40-45oC.
I presumed my system was going in to anti-cycle due to the return temperature being exceeded, and had done something similar to you by setting all bar one TRV to independent. However, I find the the boiler short cycling too.
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@gary333 Your question is a bit beyond my knowledge, but I would think that a two minute burn is almost completely worthless, because you'll mostly be heating the pipes under the floors and so little will make it to the radiator(s) to do useful work and change the room temp. Maybe if it was the closest radiator to the boiler there would be a minimal benefit, but if that tiny bit of heat is to be shared between multiple radiators or has to travel all round the house to reach the needy rad then......
I suppose that without range rating, and the boiler burning at full chat, it might just do something useful, but not at 6 kW, or even my 9 kW.
This is why I found Tado's short burns of 4 minutes "relay closed", creating 3:40 minutes of gas burn, so completely useless. 4 minutes (3:40") at 9 kW is not going to do as much work as 4 minutes (3: 40") at 24 kW.
I've had my minimum burn duration raised to ten minutes, somewhat arbitrarily, which compensates for my reduced boiler output. So a 10 minute burn (- 20 seconds activation time) consumes 1.8 kWh of gas. A 3:40 burn would be about 0.6kWh and a two minute burn (- 20 seconds activation time) would be like lighting a match. ;-)
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@cbd20 yes Baxi Combi 836, another tip I have worked out is, if you need to bump your heating say by 2˚c, try setting it to bump by 1˚c blocks,
ie if you want to bump by 2˚c in the morning do it in 2 time block by 1˚c each, the first block being 45mins before, this uses less gas see graph below, i wanted to bump by 2˚c so i created a 1˚c bump for 45 mins before the main bump time block. This helps the demand be lower and save gas!!, as the excess heat from the rad from the short high demand helps room heat up.
before bump split:
after split, the 1st bump is taken care of by 1 bar demand, followed by the 2 bump both with shorter high and slightly longer mid demand, but short overall time to bump.
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@cbd20 , I've got a Worcester bosch 38cdi classic combi boiler. It's 7 years old and I've range rated it down as low as I can. I've also got the domestic Hot water temp at 50c, can't really reduce that any further or it's not hot enough at the taps.0
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@eezytiger , just taken this picture of my smart meter monitor. You can see 3.318kw. This is what my boiler is using to maintain the lounge/dining room at 20c. It’s doing a pretty good job with the temp ranging between 19.8c and 20.2c. However what I don’t really know is how long that boiler burn lasts, and how often it happens. I am assuming if for example the boiler were to be fired up for a full 24hrs at 3.831kw then my gas used would be 24 x 3.381 = 81.144Kwh. Now I know my boiler isn’t firing 24/7, so can’t really fathom why after 15hrs I’ve used 42.99kwh, and will probably end up at my usual 65 to 70 KWh for the 24hr period, and that’s not a kick in the pants off the 81.144Kwh for a theoretical 24/7 boiler burn.
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@Notascoobie I find the easiest way to monitor how my boiler has been functioning, other than staring at live data, is to look at the half hourly data from my supplier or a third party app, but this is only available the following day.
Given that HW and cooking are small and infrequent bumps in consumption the patterns in the boiler firing are simple enough to see. If you have a fixed power output, as I do (9 kW) then you can easily turn consumption numbers into burn time. If your boiler is modulating variable output then it's not possible to do this, but it is still useful, in my opinion, to see the energy usage patterns. Boiler power is far less interesting, other than to confirm that range rating is working.
e.g. 4.5 kWh consumed in a 30 minute window means the boiler was on solidly for 30 minutes. A ten minute burn should be 1.5 kWh etc.. You will note from the graph below that there is often a clear 30 minute gap between ignitions, so isolating each burn is relatively easy. Many of mine, whilst maintaining temp rather than increasing it, are 1.8 kWh at a time, followed by a gap. Assuming boiler output to be exactly 9 kW, the 1.8 kWh burns imply a burn time of 12 minutes.
I don't think the live power output shows the picture of how the energy is delivered over the course of an hour or day. Also, over 3 kW is more like the requirement for a whole house to be maintained, not a single room. Then again, if that's your lowest boiler output, you wouldn't expect to see anything less, other than zero.
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@eezytiger The Bright app can get your readings for the same day (with about an hour delay). if you have SMETS2 meters. Refreshing the app now I can see my usage up until 3pm.
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@gary333 OK. I do have the Bright app and also the Glow IHD, which is supposed to improve the interface with Bright, but my meters are SMETS1 and this seems to create some limitations.
I've just opened Bright and there is no gas data at all for today in the app, despite the IHD being bang up to date.
Loop is doing a much better job - just a couple of hours behind.
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@eezytiger On my app I have to scroll down from the top near between where it says "gas" and the date. It seems to refresh the data after 30 seconds or so. Like you say though, maybe the SMETS1 might not be as capable.
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@gary333 Unfortunately a forced refresh does not help. I've had a ticket outstanding with support for ages. I've seen up to date data on very rare occasions, but that is the exception. So it can be done. I don't understand why it is so hit and miss. We're talking one successful refresh per month, if that.
Yet Loop, without an expensive third party IHD, does a much better job.
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@eezytiger Are your meters on the DCC as yet?
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Just been reading through this whole conversation again from the start. I spent a scintilating hour this afternoon watching my boiler behavior whilst looking at the room heat demands on my tablet and recording the boiler burn times and flow temperature changes as shown on the boiler front display (Yes, sad...I know!). Anyway, I started my observations at 1500hrs, just as the boiler was finishing a burn cycle. Over the next hour this is what I observed:
Time Flow temp at start & end of burn Burn duration Room temp & Heat demand bars
1505 35c rising to 45c 3 mins 20c and 2 wavy lines
1515 35c rising to 46c 2mins 30 secs 20c and 2 wavy lines
1555 29c rising to 41c 3 mins 15 secs 20.2c and 1 wavy line
1605 36c rising to 45c 3 mins 20c and 2 wavy lines
I should also add that the pump was running continuously for the duration, albeit at varying speeds. Does The above seem like a normal operating regime? This was the two radiators in my lounge which are tied to a Wireless Temp Sensor calling for heat/Firing the boiler. I do have a further 4 SRTs and another WTS in different rooms, but these are all independent and set at temps above the lounge so as always to be open to accept heat. And another 5 radiators and 2 towel rails with either dumb TRVs or no TRVs, always ready to accept heat. I have no way of knowing how much, if at all the 2 SRTs in the lounge opened(or not) for each heat demand. Any thoughts anyone?
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well I think I have finally found the best schedule, only used 40kWh of gas yesterday.
This time last year:
Yesterday:
17˚c overnight, then 07:00 17.5˚c for 45mins, then to day temp of 07:45 18.5˚c, 16:00 to 19˚c, 18:30 19.5˚c, 21:15 20˚c (final increase as some family members stay up till late some times, plus this helps overnight temp before setback has to kick in), 21:30 back to 17˚c
bumping in small increments to evening temp, seemed to use less demand and thus less gas, as going from 18.5˚c to 20˚c used way more gas.
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Could someone keep me right on my understanding or indeed lack of understanding about this scenario please.
If I have 2 smart TRVs in a room with a wireless temp sensor and an extension kit connected to my boiler as the zone controller. If I were to replace the 2 smart TRVs with dumb TRVs, and open them up fully, would the Wireless Temp Sensor be able to demand the boiler to fire up, (via the extension kit) or is it not capable of doing that? If it can, I’m struggling to see why I wouldn’t be better doing so and eliminate this issue of ‘is the srt open enough or not’ or am I missing something blindingly obvious?
ps. Are you able to set up a schedule for a wireless temp sensor the same as you can for an srt?
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@Notascoobie simple answer is yes it would, just Tado˚ TRV's give you better control of the exact temps, dumb TRV's is just a guesstimate on the dial.
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@Notascoobie unless you just had the wireless temp sensor and no other Tado devices, every time there was a call for heat from anywhere in the house your radiators in the room with just the wireless temp sensor would heat up.
You don’t set schedules for Tado devices, you set them for rooms.0 -
@andyblac , @johnnyp78 , thanks for the quick responses. I originally purchased tado to be able to individually control temperatures in different rooms. However as energy costs increased, it made less economic sense to have individual rooms calling for heat and firing the boiler to heat 1 room. So I I changed my mode of operation to having the living room with its 2 SRTs and Wireless temp sensor being the only room that was able to fire up the boiler. The SRTs in another 4 rooms are set to independent and any dumb TRVs are opened up full. However, having adopted this mode of operation - which appears to work pretty well - has me questioning why I need all the tado equipment as I no longer have any rooms other than the living room able to call for heat. Then there is also this issue with the SRTs perhaps not opening up enough at times. Also, something else I noticed yesterday was that when the living room was showing 1 or 2 wavy lines in the app, so demanding heat, the boiler wasn't always firing up, I don't know why not. Anyway, makes me wonder if I wouldn't be better doing as I suggested earlier, or even going back to my original boiler controls.0
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It really does sound like you'd be no worse off with the proven technology of the original controls, as they typically function in that way. Tado adds a measure of remote control, maybe slightly beter scheduling, boost options, and the ability to microzone, but with it comes unreliability, batteries to replace, etc.0
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Having read thru the instruction booklet for my manufacturer controls, it appears they provide load compensation, modulation, and flow temp control, so not too shabby. Perhaps having range rated the boiler output down and adjusted the max flow temp and domestic Hot water temp, reinstating the original controls may well be the way to go.0
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Hi all! I have a Worcester Bosch Greenstar 38CDi combi boiler and Tado thermostat with 8 Tado smart TRVs. My Tado system is wired to my boiler using the eBUS (BB) connections and my boiler has a minimum central heating output of 10kW. I’ve been trying to optimise the settings on my boiler and Tado system recently as I noticed the boiler was short cycling significantly due to the high minimum output. I’ve found the following settings have really helped:
- Range rate the boiler to minimum output
- Set maximum CH flow temperature to 65deg (4.5 on the dial)
- Set the pump map to Variable - Low (setting 5)* this has been key to keeping the flow temperature to a minimum and reducing short cycling.
- move thermostat to living room and zone all downstairs TRVs to the thermostat
- set one or two of the bedroom TRVs (coldest north facing rooms) to call for heat. All other TRVs upstairs are set to ‘not assigned’ (ie they can’t call for heat)
- set all to early start.
This seems to have had the following affect:
- 3 wavey lines - boiler fires up and stays on for 30mins or so warming up the radiators until Max flow temperature is reached. The pump then continues to flow until the flow temperature reduces to say 50 deg. The flame then burns as needed but usually for at least 15 mins at a time.
- 2 wavey lines - if the flow temperature is currently less than 50 deg, the flame burns until this temp is reached (usually 10mins or so) then the pump continues to run for say 15mins.
- 1 wavey line - the pump runs and radiators are just warm.
I can’t see that I’m using any less gas, but the stress on the boiler is a lot less and the short cycling has stopped. Temperatures seem to be a lot more stable and regulated.0 -
@MattyD1984 , how did you adjust your pump setting?0
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On my boiler it has a service button with a spanner icon. If you hold this for 10 secs it takes you to the service menu. You should be able to do something similar with most other boilers. If you search for the Engineers service booklet for your specific boiler it should give you instructions on how to do it.0
