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Dehumidifier.
We've got one of those for drying clothes during the winter, but don't tend to run it in the house as a general rule.
I think at the moment, with the warm-ish days and cold nights, the air is a bit 'wetter'. It normally sorts itself out to a more acceptable level in a week or two.
I have been saying for years about getting a PIV unit installed to try to help with reducing moisture levels. We are planning on getting our hall, stairs & landing redecorated when we have an extension put in next year, so I think we will get it fitted while that's being done.
Had that deep in your bones feeling cold all evening so had to fire up the wood burner for the first time.
A hot bath is quicker and probably more efficient for that.
I think at the moment, with the warm-ish days and cold nights, the air is a bit ‘wetter’.
Unlikely. Warm, indoor, moisture laden air is just condensing on colder surfaces over night, because the nights have got colder.
We have friends who live in the foothills of the Pyrenees and they use dehumidifiers in winter as dry air feels warmer than moist air and it's very moist all year round where they live.
I think at the moment, with the warm-ish days and cold nights, the air is a bit ‘wetter’.
Unlikely. Warm, indoor, moisture laden air is just condensing on colder surfaces over night, because the nights have got colder.
Are you confusing moisture content of the air with relative humidity?
Went to bed last night and the house was 19C, woke up to a frost and the thermostat saying 17.5, feeling very smug about the cavity wall insulation we had installed back in 2019!
Heating should have come on at 17.5, but it's a smarth-ish thermostat so it doesn't come on if it's marginal and it knows the house will gain a couple of degC from sunshine, the conservatory, towel rails/hot water system.
Still tempted to get a dehumidifier and plumb it in under the stairs in the hallway. We still don't have a kitchen extractor so must produce a fair bit of humidity so that recovered heat might keep the house warm on marginal days like today?
I’m sure we’ve been over this many times in this thread already but what part of having a fire in your house is not having heating?
Depends:
Are you Ray Mears living in the woods - then it's heating.
Are you sat in a chair on your phone, charged from a plug socket? Then it's not heating, it's just middle class hygge that happens to produce heat.
Still tempted to get a dehumidifier and plumb it in under the stairs in the hallway
Oh, this is a brilliant idea. A plumbed-in dehumidifier! I could put one in the loft.
EDIT oh, apparently they have a maximum ambient temp, too hot in the loft in summer.
Went to bed last night and the house was 19C, woke up to a frost and the thermostat saying 17.5
I turned the heating off before bed last night, room temp was 19c, by morning it was down to 14c 🙁
Was fine in bed but had to boost it back up today... currently at 17.6, relative hunidity at 57%
Central heating on yesterday and again today, but I had company and was feeling a bit sniffly.
Put the CH on last night, jeez I feel such a wimp as had intended to aim for the end of the month.
Put the CH on last night, jeez I feel such a wimp as had intended to aim for the end of the month.
😀
I was hoping to hold off until November but I've had to scrape ice off the car for the last two mornings, so the heating is most definitely on.
I've got as far as bleeding the radiators (only one had air in!!) and the boiler service is booked. The dehumidifier is now on the landing when not being used for clothes drying. Was a bit nippy yesterday morning - thermometer in living room said 15.8 degrees, but by the time the sun had come out that soon went up to 18.9. Mrs Fazzini comes from the same school of CH thought as my mum did (and by default therefore me too): Cold? Put a jumper on. Still cold? Put another one on 😂
I'm going with jumpers and blankets, house temp is generally 17.5 or 18 which I think is about as low as I'd want to go.
i like to go as long as possible without putting it on, regular topic of dispute with mrs ex-punk. but tonight i'll make an exception cos my little grandaughters coming over to stay for the night and we cant be having my little sweetheart getting cold 🥰
tomorrow itll be back to an igloo.
Unless it’s for financial reasons
Mine is *very* much this
*IMPORTANT UPDATE ALERT*
First time in the loft. 50mm of insulation now topped up to 350mm.
BUT
Also noticed 3 full to exploding bin bags abandoned by previous owner. Full of Lego!!! Star Wars sets, Lego animals, bricks etc
JACKPOT
My day is made. As you were…
Unless it’s for financial reasons it seems to be a strange sort of masochism.
Lol, if it wasn't for financial reasons, my thermostat would be 19/20c, 24/7/365
The significant investment in heating and insulation etc, is also for financial reasons as in theory, over time it will payy off as it will cost 'X' less to keep the house at 'Y' temp.
Leave it off for as long into autumn as possible, again financial reasons.
my thermostat would be 19/20c, 24/7/365
I'm lucky enough mine can be 18/20/21 all the time. I still got annoyed when yesterdays cold winds blowing through London in exactly the right direction to blast through bathroom window vents cost me £4.51, my highest daily gas bill since May. And for a double whammy we we weren't in to benefit, we were standing the Velopark freezing our toes off - despite the sun -marshalling a Duathlon.
I'm using my central heating this year if needed. Kitchen is currently 11°c so I might turn it on for a few hours.
Last winter I made it to December before using my central heating. Taking the chill out of the air in the morning will probably benefit me more mentally rather than challenging myself to see how cold I can get.
Log burner will be used less this year and the money that I didn't spend on wood briquettes will go on the gas bill instead.
I'm wondering if I would benefit from another layer of loft insulation, current insulation is level with the joists..not not sure if it would affect ventilation too much?
I'm half tempted to hire a thermal camera so I can check all over the houseand I'm not just shooting in the dark, but they look to cost about £100 per day to hire...
I’m wondering if I would benefit from another layer of loft insulation, current insulation is level with the joists..not not sure if it would affect ventilation too much?
That's bugger all. My 2007 build came with about a foot of insulation, and I added another foot not long after we moved in. Quite a big difference in warmth feel, even before I was paying that much attention beyond general; but also made a huge difference to outside noise coming into the house and it's not even a noisy location.
A modern new build house will have about 400mm of insulation in the roof. I'd aim for that but be careful that you still have the loft ventilated.
Still not getting the fact that people make a significant investment in equipment to keep them warm then take great pride in not using it.
Whilst I do like to keep the bill as low as I can (better things to spend the money on), I also like to consume as little fossil fuel as I can without going full hair-shirt.
EDIT oh, apparently they have a maximum ambient temp, too hot in the loft in summer
Do you really need it in summmer...?
Do you really need it in summmer…
Yes, it can be humid in the summer as well!
I’m half tempted to hire a thermal camera so I can check all over the houseand I’m not just shooting in the dark, but they look to cost about £100 per day to hire…
You could just spend that money on more insulation instead. AFAIA loft insulation gives the biggest payback - after that probably comes walls (if you have solid 9" walls then you're a bit pooped without large expense) and windows, which are also very spendy.
Check for drafts just by checking doors and windows with an incense stick!
If your with OVO your going to see an increase in payments as they want winter paid for by the end of march rather than being spread over 12 months, that's over an £100 per month increase for me.
If your with OVO your going to see an increase in payments as they want winter paid for by the end of march rather than being spread over 12 months,
Don't they all work to end of April normally anyway?
Build up credit over summer, work through it over winter to be roughly zero balance by end of April.
so- boiler flow temperature vs length of time it takes to warm a house up to the desired temperature.
Pretty much every energy saving website says its best from an efficiency point of view to lower the flow temp of your boiler. Given that flow temp affects how quickly a house warms up, is that blanket guidance correct?
ie if at a flow temp of 60deg c it takes your house 3 hours to warm up to your desired temperature vs 1.5 hours if the flow temp was set at 70 deg c, does it still hold that the 60deg C flow temp uses less gas overall? Anyone got any good links that talk about this, or know the maths to prove it one way or the other.
Asking because this is the scenario I find myself in - 60deg c flow temp takes 3 hours to hit target temp , 70deg c takes 1.5 hours - similar outdoor ambient temperatures (1deg c) and similar starting temperature and target temperature, but which temperature uses less gas overall?
If you have a system that works at a fixed flow temperature then lowering it is going to save gas, as it’ll always be heated to that temperature (or off).
Finding the right point is a bit on an experiment. When I had a system like this, I just started at 70 and lowered it by one degree each day until I felt it was heating up at an acceptable rate and cold achieve the set point.
If you’ve got a system that modulates the flow temperature and/or has weather compensation then it’s more about the heat curve (which dictates that flow temperature given an external temperature and a set point) and a max flow temperature. Because the system will adjust the flow temperature within the bounds determined by the heat curve. In this case you want to be starting high and then lowering to where it can achieve the set point. If it’s too low, and can’t achieve the set point it stays on and burns more. If it’s too high, it’ll overshoot and can get into cycling on/off, not condensing and lowering efficiency like that.
TL/DR - start high, and lower it very gradually till you’re not comfortable, then raise it a touch.
does it still hold that the 60deg C flow temp uses less gas overall?
In principle yes up to a point, because the cooler your flow temp the cooler the return temp and more heat is extracted from the gas; the less heat is leaving your house via the flue.
However it's complex because your radiators can shed a certain amount of heat from the water which depends on their temperature (and that of the rooms) and your boiler has a lower limit on the amount of gas it can burn. Mine is shite and has a minimum of 9kW which is more than the radiators can get rid of at 50C or even 60C. BUT the flow water starts off cold. So it puts in 12kW (the max) but the water doesn't reach 60C straight away, it takes a while to warm up, during which time the house is also getting warmer even before the flow temp is reached. When it is, if the house still isn't up to temp, the boiler will start cycling. If this happens on a 3 minute cycle or more, it's not too bad for efficiency, but if it's every 30s then it reduces efficiency. So the lower flow temps are more efficient but that could be off set by short cycling.
Depending on your boiler it might have a variable output pump, and it might be controlled by the boiler itself (mine isn't). A good modern boiler can have a nice low flame and a slow pump which means that the water hangs around in the radiators long enough to get nice and cool so the return flow temperatures are nice and low, and it could be super efficient. So in that situation you want to set the flow temp as low as you can so that the house gets warm - after all, it might be losing heat at 3kW on a cold day but if the boiler is throttled down and only producing 2kW of heat, you'll get cold.
Mine is always producing a minimum of 9kW so I have to work out how to get that heat out of the water and into the house. I've had to fit bigger radiators for this purpose and it has helped a fair bit. Eventually the boiler cycles, so when it gets colder I may need to turn up the temperature so that more heat is output. However, the flow temp would increase by 10C and the return temp by say 8C (because more heat is dumped at a higher temperature) but the return temp would still increase, and that is what reduces efficiency.
Also, if you are running lower temps it takes longer to heat up so you may well be better off not letting it cool down as much overnight - they call this the 'set back' temperature. I have now gone with a set back overnight of 16 and daytime of 17.5, and the span on the thermostat is 0.5C. Because it's warmer for longer in theory you would lose more heat but this could be offset by more efficient running. And you can get away with a lower temp too whilst still feeling comfortable. You aren't just warming the air with your heating you are warming everything in it - floors, furniture etc. So if you let it get cold overnight and the floors get cold, the boiler will work hard in the morning to get the air warm and switch off but the floors/chairs etc will still be cold so you will want a higher air temp to feel comfortable. If you keep it largely the same temp all the time it will feel warmer even at a lower air temp setting.
Got it?
I didn't even know they made combi boilers with such a low output as 12kw.
Most are 24-30kw heating for a 3 bed 2 bath house.
What make/ model is it? Surprised it's not firing constantly if it's modulating as well . Even a low modulating model will run down to 1/3 so it would only be generating 4kw , across an entire house.
Mine isn't a combi, I have a water tank. It's the smallest boiler in the range, but they all have the same minimum flame so the 35kW one modulates down to 9kW, but so does my 12kW one. And 9 is too much.
Modern ones can modulate down to like 1.5kW which would be perfect for us.
I've no idea what I'd do with 35kW. I guess it would heat the circulating water up almost instantly then throttle back to the same figure.
Most are 24-30kw heating for a 3 bed 2 bath house.
Most combi boilers just surely.
Heatings off tonight but the stoves on.
Heating has kicked in a couple times the last week or so mostly as the kiddos room has dropped below the set point when at -2 outside temp.
Put CH on just for an hour tonight mainly as I have manflu. The wad I spent on the loft in April seems to be working as the house is really retaining the heat.
ie if at a flow temp of 60deg c it takes your house 3 hours to warm up to your desired temperature vs 1.5 hours if the flow temp was set at 70 deg c, does it still hold that the 60deg C flow temp uses less gas overall? Anyone got any good links that talk about this, or know the maths to prove it one way or the other.
Asking because this is the scenario I find myself in – 60deg c flow temp takes 3 hours to hit target temp , 70deg c takes 1.5 hours – similar outdoor ambient temperatures (1deg c) and similar starting temperature and target temperature, but which temperature uses less gas overall?
Think of it as a thermodynamic system.
Energy in = energy out
Energy out = conductivity x surface area x differential temperature x time
Therefore any time spent at a lower temperature is reducing your energy bill.
It's also why letting the temperature drop overnight is cheaper, because those hours the house is at a low temp overnight it's losing less energy than it would if it was warm. Also why dropping the thermostat by 1C saves about 10% off the bill, it's on average ~9C outside, average thermostat is ~19C, knock 1C off that, the temp differential drops by 10% and you're reducing the energy transfer by 10%.
Unless it’s for financial reasons it seems to be a strange sort of masochism.
Why am I being kink shamed?
Until then though, I just don't feel 'cold'. I can quite happily sit around the house down to about 15-16C and if I feel cold then I get up off the sofa and do some batch cooking, tinker in the shed, go for a ride, etc.
It’s also why letting the temperature drop overnight is cheaper
That's the simple model. But there are multiple other factors that might mean that's not then case.
That’s the simple model. But there are multiple other factors that might mean that’s not then case.
Unless your boiler/system is massively inefficient, combined with a house that didn't lose much heat then it holds true. For Joe Blogs in a normal house with normal gas (or electric, or oil, or LPG, or wood fired) heating it's correct.
It won't be true if you have storage heaters (obviously, that's their whole principal). And might not be true if you have an ASHP and underfloor heating and a discounted night rate (because that's potentially a wet storage heater with an efficient daytime mode). But for the other 90% of housing* it'll hold true.
*Not a made up stat for once on the internet, 5% are on storage and 5% are on "other" which I took as ASHP. https://www.statista.com/statistics/426988/united-kingdom-uk-heating-methods/
@mattyfez the thread has moved on a bit but that amount of old, scraggy-looking fibreglass is about what we had when we moved in over 15 years ago.
I added some newer stuff over the top. if I remember correctly 200mm thick.
I suppose it made a difference. Awkward getting the insulation under the cables but otherwise OK.
My cost of electricity fell below 5p per kWh between 02:30 and 05:30 so the underfloor in the kitchen and the oil rad in the bedroom came on between those times this morning.
It definitely makes a difference and combined with the stove I don't need to burn any oil quite yet other than for hot water.
Unless your boiler/system is massively inefficient, combined with a house that didn’t lose much heat then it holds true. For Joe Blogs in a normal house with normal gas (or electric, or oil, or LPG, or wood fired) heating it’s correct.
Sums?
My cost of electricity fell below 5p per kWh between 02:30 and 05:30 so the underfloor in the kitchen and the oil rad in the bedroom came on between those times this morning.
It definitely makes a difference and combined with the stove I don’t need to burn any oil quite yet other than for hot water.
Did the same this morning, we've an oil filled radiator set up to take advantage of the plunge pricing.
Did the same this morning, we’ve an oil filled radiator set up to take advantage of the plunge pricing
I think there's more on the way with this wind!
I've got more WiFi plugs arriving so I'll put one on the heater in my office and maybe another somewhere else as well!
I turned mine back on a couple of days ago after I got home from work and it was still 15c in the house, it's been nice waking up to a 20c house these past couple of mornings. In hindsight though I should have dusted the rads first, bit of a pong for the first hour of them coming on
Unless your boiler/system is massively inefficient, combined with a house that didn’t lose much heat then it holds true. For Joe Blogs in a normal house with normal gas (or electric, or oil, or LPG, or wood fired) heating it’s correct.
Sums?
U value x Wall area x Delta T
you cant adjust your wall area so the only two ways to reduce heat loss are to reduce U value or Decrease Delta T
so assuming your U value doesnt change over night - the higher you keep delta T the more heat your losing.
I think there’s more on the way with this wind!
I’ve got more WiFi plugs arriving so I’ll put one on the heater in my office and maybe another somewhere else as well!
Fingers crossed for a particularly breezy winter 😀
Yes I know the physics thanks but that's not the whole story as I said. How does having to run your heating* flat out for 2 hours in the morning change its efficiency? How much warmer does the air have to be when the floor and furniture is cold in order for people to feel comfortable?
* by this I mean your specific heating in your house
the thread has moved on a bit but that amount of old, scraggy-looking fibreglass is about what we had when we moved in over 15 years ago.
Sorry to derail a bit again, but I've been looking at loft insulation to layer on top of the existing stuff, I'm lookin at probably 30m2, probably more like 25m2 actually accounting for leaving a gap around the edges
https://www.diy.com/departments/diall-insulation-roll-l-6m-w-0-37m-t-100mm/3663602481812_BQ.prd
This looks interesting as its non itchy, but £10 per m2 is crazy compared to what I presume is the nasty itchy stuff at £2.25 per m2
Is there such a thing as reasonably priced insulation that doesn't require wearing a hazmat suit? lol!
Honestly at that price I'd wear the suit. You can buy disposable ones, get some gloves, glasses and a mask - it's cheap as chips and you won't be up there long.
Yes I know the physics thanks but that’s not the whole story as I said. How does having to run your heating* flat out for 2 hours in the morning change its efficiency? How much warmer does the air have to be when the floor and furniture is cold in order for people to feel comfortable?
There is no magic woo, it's just the first law of thermodynamics.
If you lose less energy, you don't have to put as much in.
If it takes you 2hours of heating to warm it up in the morning, then the boiler would have to run more than 2 hours overnight to maintain it.
The only fly in that over simplistic ointment is boiler efficiency under different loads. But even if the boiler is more efficient at low loads (probable), it's in the order of ~10% different.
In order for it to me more efficient to heat the house 24h/day from a conventional gas/oil boiler or normal electric rads, you would need a system that:
1) lost very little energy at all (thus you get no benefit from the reduced dT, which is a bit like saying you found £20 note that you dropped earlier, it's not actually a benefit).
2) a heating system whos efficiency dropped massively as the load increased.
1 is rarely true, 2 isn't true of most gas boilers (a condensing boiler is about 15% more efficient at 5% than it is flat out, and as you yourself pointed out, most boilers don't go below about 30-50%.
* by this I mean your specific heating in your house
I'm not going to leave my heating on all night burning money to win an internet argument.
But here's an illustration, assume it's 8C outside and heating is set to 18C to make dT = 10C.
Heat flux (im eliminating area for simplicity) is assumed to be 0.5kWh/degC*hour
Over 10 hours that's 10C x 0.5 x 10 hours = 50kWh energy.
Let that drop to 15C inside and the heat lost is only 7 x 0.5 x 8, plus 10 x 0.5 x 2 = 28 + 2.5 = 38kWh
You can complicate that simplification with a specific heat capacity and mass of the building to give a temperature profile as a curve etc, but the end result would be similar.
I think there’s more on the way with this wind!
Tonight from 23.30 - 05.00 looking like near to 0p/kw. Pity I've not switched my energy supplier yet 🙁
I’m not going to leave my heating on all night burning money to win an internet argument.
I'm not asking you to. However, in my experience in my house, leaving it "on" all night but setting it back a degree or so means it never actually fires unless it's a properly cold night, but it does mean that in the morning it can bring the house up to temp quite quickly. If you've been following - in my house, the minimum output of the boiler is above the radiator output so we kind of need to get the rooms heated up before the short cycling happens which requires a certain temperature and it also needs the house to not be that cold to begin with.
On our coldest nights, with the heating off entirely, we drop about 5C overnight. To put this back when people get up in the morning we had to get the heating to run for an hour - but floors and seats are all still cold. Just as it got up to temp everyone left and the heating went off again. So it really was a huge waste of energy to have it on in the morning at all. But then if we didn't turn it on we'd have a freezing house.<br /><br />The fact the temperature is even most of the time and the walls and furniture etc are all maintained at temp is the reason we can set the thermostat to 17.5C and be perfectly comfortable. If the fabric of the house is cooled to 14C and then heating comes back on set to 17.5 it feels freezing.
But here’s an illustration
Yes, that says that a warmer house loses more heat - we know this. What you're not taking into account is how your boiler is working. A short cycling boiler loses a lot of efficiency. When you're outputting your 9kW of heat, where's it going? If the air gets warm, the heating goes off but the mass of the house could still be cold.
All I'm saying is that there's a lot you're ignoring. This is why we have 'smart' heating controllers that test everything out to learn the optimum parameters for your house and setup based on weather, and how often the user calls for more heat etc - because you can't predict it simply.
Sounds like you could do with bigger radiators rather than just burning lots of fuel (but efficient) for the sake of it.
Pity I’ve not switched my energy supplier yet
Ufh, bedroom heater, Tumblr drier are on and the oven is cleaning itself.
Meter said we were using 10kWh when I last looked!
All this flow temp talk, which I admit I've only really skin read, does it apply to (modern) oil boilers too? If it does I'll read it in more detail.
Not as much, because they don't have the condensing part.
Sounds like you could do with bigger radiators rather than just burning lots of fuel (but efficient) for the sake of it.
Ah, I'm not burning fuel for the sake of it. I'm aiming to find the cheapest way to be the most comfortable, which in my case means a relatively high 'set back' temperature of 16C. I mean you appreciate I'm not leaving the heating burning away at 21C all night right?
But yes I do need bigger radiators. I installed three last month, will probably do the rest next month.
mines a condenser - ive had it for 12 years i would not consider it modern
at the same time theres only 1 or 2 on the market that can modulate so its a law of diminishing returns but you can reduce short cycling to large degree.
but bigger radiators are king. most of my rads are at least double the size the rooms need for this reason - our kitchen diner has 3 large double - and its not a huge room but due to surface area available it removes plenty heat from the system and ensure that my return temp is correct + my house heats quickly for low oil use and limited short cycling.
Yes I agree there. We had tiny rads all round. There were three without TRVs in the hallway and two landings which were 40 or 60cm single panel. We replaced the bottom one with a 140cm single and now a 160cm double. Will replace the rest of the singles with slightly wider doubles, as space permits.
Even then the ballast rads (without TRVs in the hallways) won't be anywhere near enough to dump the heat, so the TRVs and the main thermostat need to be balanced so they all heat up together. Kinda helps that the rad in the hallway with the thermost is now the last one in the loop so the other get heat quicker. When their TRVs turn off it puts more heat in the hallway so the main stat turns off after the rooms get warm.
I'd like a bigger rad in the kitchen/diner but it would be in the way so I was considering kickboard radiators.
mines a condenser – ive had it for 12 years I would not consider it modern
Ours is a Greenstar Danesmoor External, fitted a couple of years ago, I dunno if it's a condensor or not, guess I could find out.
but bigger radiators are king. most of my rads are at least double the size the rooms need for this reason – our kitchen diner has 3 large double – and its not a huge room but due to surface area available it removes plenty heat from the system and ensure that my return temp is correct + my house heats quickly for low oil use and limited short cycling.
Ah, this is interesting. In one of our rooms there's two rads, both TRV'd, and I've turned one of them off as the room heats fine without it, thinking this would save fuel - would I be better leaving it on?
In one of our rooms there’s two rads, both TRV’d, and I’ve turned one of them off as the room heats fine without it, thinking this would save fuel – would I be better leaving it on?
If they are both on a TRV then turning one off makes no difference - with the same flow temp, you'd heat the room faster but the TRVs would turn off earlier.
However, with bigger (or more) the return flow is cooler which helps condensing. It also means you can run lower output (aka flow) temps which, if you have a modulating boiler, will result in more efficient running; and also result in lower flow temps which helps if you have a condensing boiler.
So in short yes, more/bigger rads is better.
So in short yes, more/bigger rads is better.
But only if you have a condensing boiler?
Hmm well - it would also work if you can turn the flame down on your boiler. A larger heat exchanger extracts more heat, which is fairly intuitive, but if you make the flame smaller then the heat exchanger becomes effectively larger. A modulating gas boiler does this for you to a greater or lesser extent. Now the oil boiler IHN mentioned does apparently have a temperature control; not sure if it makes the flame smaller or just shuts itself off when hits the temp. Probably the latter.
If you don't have a boiler that can reduce its flame, then more rads would allow the return temp to be lower; but this would make the flow temp lower as well since the flame is only adding X amount of heat to the water. That would mean that the boiler would be less likely to short cycle before the house warms up. More rads means more heat is extracted from the water, for the same temp - therefore if the boiler can only put in X and the rads can extract X it won't short cycle whilst the house is heating up.
So yes, more rads is still better. How much better? Well, it depends.
No. In all cases a bigger emitter allows a smaller ∆t and greater efficiency.
Its why heat pumps like underfloor heating the best.
That would mean that the boiler would be less likely to short cycle before the house warms up
In all cases a bigger emitter allows a smaller ∆t and greater efficiency.
And why are these a good thing? (Genuine question, not arguing it cos I have no idea). If the answer is "read the rest of the thread you lazy get", then fair enough:-)
Ours is a Greenstar Danesmoor External, fitted a couple of years ago, I dunno if it’s a condensor or not, guess I could find out.
IIRC All domestic boilers have to be condensing now, so your one will be.
And why are these a good thing?
Your radiators get water in at a certain temp, say 60C, and it exits at a lower temp cos it's cooled down - and transferred heat to the air in your house. Ideally the water exiting would be about 40C, then that means the return temp to your boiler is 40C. Then it goes through the flames and heats back up to 60C and so on.
If your rads are too small, then the water doesn't have time to cool down by 20C on its way through, which means that it might come back to the boiler at say 45C. But it still picks up another 20C on the way through the flame at 1000C whatever, so then it's 65C on the way out. And next time it's 70C and so on. If your boiler is set to shut off at 70C it will then shut off but the water is still being pumped around. So the flow temp drops quickly down to say 50C at which point the boiler goes 'oh that's too cold' and turns back on again. and so on.
The rapid turning on and off of the boiler is inefficient and can wear it out prematurely. The solution to this could be to restrict the flow of water (or turn the pump down) so that it moves more slowly through the radiator and does cool down. But then, because you are putting not much water through, the amount of heat being emitted is a fair bit lower.
Big rads mean your water can flow through it quickly enough, and still cool down. More heat is extracted from the water which means more heat into the room. So it'll heat up quicker, and the boiler water will stay at the right temp.
Looked at another way - radiators have a rated heat output. A small single panel is about I dunno, 500W, a big double panel 2,100W, at a particular temperature. If your rads are too small, the sum total of their output could be less than the boiler's minimum output, so the flow water gets too hot and the boiler shuts off before your house is warm and the situation above happens.
The rads output more heat if they are hotter (of course) so with smaller rads you can run the system hotter. You might not prevent it short cycling in theory, but your house may get warm enough before it starts. But when running high temps you won't be condensing.
Short cycling - where the boiler turns off and on every minute or less, is very inefficient. Not exactly sure why, maybe a bit of gas is wasted as it lights up, dunno.
Ta. And boggo (big) rads aren't that expensive either, right?
Actually, a follow on question. Say I put enormous radiators throughout the house, what would happen if the water returning to the boiler was at, say 20deg?
And, they'd need to be carefully balanced, right? Because otherwise the heat might have been taken out of the water before it got to the radiators at the end of the chain?
Actually, a follow on question. Say I put enormous radiators throughout the house, what would happen if the water returning to the boiler was at, say 20deg?
If the water returning is quite cool, it's unlikely the water exiting the heat exchanger is massively hotter unless the flow is really restricted, it's all the same water circulating reasonably quickly. The boiler just dumps some heat in it and passes it on, it can't hold it until the output temp has reached a set level.
And boggo (big) rads aren’t that expensive either, right?
No, not at all. Replacing our 60cm singles with 60cm doubles (type 21) costs £55 each I think. The 160cm one was maybe £120 IIRC. It would have cost £500 to basically double the rad area in our whole 3 bed house.
it’s all the same water circulating reasonably quickly.
You can control how fast it circulates. My 12kW boiler can raise the temp 20C at best - in fact, there is meant to be a limit on this, you need a minimum flow and there is consequently a maximum recommended temperature increase. It can be less if the flow is faster.
Condenser boilers use the heat still in the exhaust gas to add heat to the return water from your central heating ring main . Via a heat exchanger. This is where a lower water return temperature is most beneficial. As the TD is greater more wasted energy in the gas exhaust can be utilised.
The drawbacks are the boiler still needs to get the output temperature to around 65c to heat your rads , and then the air next to the rads. So modulating , condenser boilers which can go down to 3 or 4kw can heat an entire house if big enough rads are correctly balanced via the locksheild so flow and energy transfer takes place effectively. By adding another heat exchanger the rise in temperature can be reduced making the boiler cheaper to run .
Short cycling is the boiler firing for less than a minute , then off again, then on again a minute or two later etc This is bad for the longevity of the internals. The h.e gets alot more expansion and subsequent contraction movement potential causes cracking , valves and solenoids cycle more frequently, electrodes and transformer does more work.
What you want is a boiler which fires up on full chat for maybe ten minutes then starts to reduce the flame by turning down the gas.like boiling a pan of water , alot of energy to get to boiling , then a tiny amount to keep it there. Allowing the primary and secondary he to get to operating temp and staying there. With just the gas solenoids and pump and exhaust fan running constantly. Then after a few hours the system shuts down and goes through a cooling cycle with the fan and pump to gradually remove the heat .
Older system get hot spots caused by rust build up in the primary from the rads and insufficient inhibitors and calcium carbonate in the secondary from hard water.
The drawbacks are the boiler still needs to get the output temperature to around 65c to heat your rads , and then the air next to the rads.
No, you can run the temps lower than that. Mines set to 50C currently. It may need to be higher when it's colder, that's what weather compensation is for; it also depends on your house which is what the learning algorithms in Nest are for.
You can't really heat your hot water when the flow temp is that low though. I use cheap overnight electricity for that.
Yes ,
As you have previously posted, a 50c output temperature takes 2hours in the morning to get all your house warmed through, including the soft furnishings. That's with outside air temperature still relatively mild .
Drop the outside air temperature by 5c, and in the real world people want heat way quicker than 2 hours , more like 20 mins as they are up and about then leave for work. So most people run the CH system from 0600 - 0800 , then off.
With the 50c , low flow , throttling back scenario you run, your house gets comfy as everyone leaves for school and work. So you either turn on the heat earlier or run a higher boiler output temperature. I know you are optimised for your own particular circumstances but for the people still going to work all day it's a higher work load for less time for the boiler. It might cost more to run but alot of people don't care, they just want to be warm as they grew up in painfully cold , damp houses and don't want to put their kids through the same, or see being warm as a right , or a status symbol. Even if they can't afford it.
As you have previously posted, a 50c output temperature takes 2hours in the morning to get all your house warmed through, including the soft furnishings.
Don't think so, I am running 50C because I have an overnight set back temp only 1.5C lower than the daytime. If I let it get cold overnight then yes 50C would not be enough. But I believe the house is more comfortable this way and it's cheaper, for us. The high set back temp is part of the low and slow strategy.
I like being warm too btw. Point is that 18C in a house that's already warmed through at 18C is a lot more comfortable than 18C when the whole house was 14C an hour ago.
You must be cold?
You must be cold?
Nah, I've got a woolly jumper and a hot water bottle