So I’m hearing that a bigger rad would help? It’s possible, there’s not a ton of room here but I could go 50% larger probably.

You could also change the type of radiator, more panels/convectors within the same length.

IANAE.

If your flow temp is 60°, you’ll never see 70° in the tank and the tank stat will just keep calling for more heat, no?

Also, Arguably you only need your tank hot water at 60-65 for Legionella pasteurisation so theres some saving to be made by reducing the temperature you store HW at and making the thermal gradient smaller.

That’s what I was aiming for, except the boiler just as a dial labeled min->max, so I’m going to have to get a thermometer out to measure the return temps. I’d presumed though it would just shut down when the load was low ( Tin + minDt -> Tout > Tset).

Trying to figure out how to set it up this winter, I’d thought of getting some Tado valves + controller for the most used rooms. But then that means I’ll need to leave at least the hallway* on dumb all the time one of them is calling for heat which seems pointless. The alternative is to go all in on the Tado system and do every radiator so they an call for heat individually and nothing needs to be always on?

*current system is thermostat and timer in the hallway and that rad turned upto max which allows me to turn off the towel rail in the bathroom which would otherwise be the ‘always on’ bit.

I’ve had to open the door in the garden office to let the heat out.
It needs a couple of minutes with the fan heater first thing to take the chill off, then warms up lovely during the morning with the sun coming through. Even on overcast day it warms up enough to not need heating.
The wife and dog have joined me down here today

Turned the heating on on 1st October. Boiler pissed itself and was promptly turned off. Plumber just been out. Various bits relating to the capture, storage and disposal of condensate now on order and won’t be here for days. Sadly, the small fortune being saved on gas is going on boiler parts next week. Costing effing money even when switched off!!

That’s what I was aiming for, except the boiler just as a dial labeled min->max, so I’m going to have to get a thermometer out to measure the return temps.

I just found that the manual for mine states the temperature range on the knob which is from 30 to 82C.

I’d turned it down to half way then turned up the hot water thermostat in the tank. The boiler fired for a bit then cut out, and the display indicated that the ‘desired’ temperature had been reached. This suggests that the burner just goes on and off, and the knob doesn’t actually reduce the flame.

But then that means I’ll need to leave at least the hallway* on dumb all the time one of them is calling for heat which seems pointless. The alternative is to go all in on the Tado system and do every radiator so they an call for heat individually and nothing needs to be always on?

Same situation as me. Apparently if you fit a bypass valve (or already have one) then you can do the all-smart-TRV system. The risk if you have all the rads shut off apparently is burning out the pump, because the water won’t flow. But I cannot see how no water at all flows, because the rads aren’t in series with each other? Unless the last rad is in series with the loop that feeds all the others? I need a circuit diagram of the plumbing.

I’d turned it down to half way

Try minimum and maximum settings (30 and 80). On my boiler there were two burner levels, on the minimum it was definitely on the slower burner and on max logically enough the higher burn. Somewher between the it transitioned but without trying the extremes you won’t know if you have two burner levels or just one. An added complication is that on the boiler I had the central heating circuit and hot water circuit had independant controls so running hot water could be made to activate either the higher or lower level of burn irrespective of what the central heating was doing. Fitting a shower head with a finer jet meant I could adjust it so it never go onto the higher burn for a shower.

@mattyfez good link, realised I’ve already been reading their website.

Another video worth watching that was mentioned in yours:

Turned the heating on on 1st October. Boiler pissed itself and was promptly turned off.

I’m half expecting that when it gets cold enough to turn on. Maybe it would be worth a turn on and bleed the rads just in case we need it at some point.

Didn’t twig that running HW and Ch together would drive it into high burn mode. Have just changed the timings in the morning to keep them separate. Probably bad science practice by changing multiple things at once but I’m trying to get a mode of operation that is efficient. Fingers crossed it all works. The MVHR system I am designing should go a way to help distribution of localised heat. Just need to find a way to make heat with spare solar leccy for the underfloor heating. Ideas welcome.

any thoughts on what the most efficient way of running underfloor heating?. we have an electric (as opposed to water) system for a garden room. A combination of an impossibly difficult to set up timer and a pretty slow to make itself known to the user nature means that we have tended to leave it on at a lowish level rather than go for periodic heating cycles – is that the best way forward even if it means consumption at peak times?

@blackhat that video I posted above should help answer your question.

@squirrelking

Blimmin heck, thats going to take some digesting, hahah!

Ah, my burner does seem to be variable after all. I tweaked the knob whilst it was running and it revs up or down on an apparently sliding scale.

I’ve turned the hot water up to 60. I don’t think we have Legionnaire’s disease in the house but there might be other nasties hanging around in there. I may insulate the airing cupboard with some boards on the walls and door to keep the heat in.

Blimmin heck, thats going to take some digesting, hahah!

Yeah, there is a bit of maths used to justify the theory but it looks sound enough to me. You don’t really need to understand that bit IMO, just the conclusions.

Jesus wept ive just got he predicted costs for this winter. bills going u 3 to 4 fold!!

molgrips

Same situation as me. Apparently if you fit a bypass valve (or already have one) then you can do the all-smart-TRV system. The risk if you have all the rads shut off apparently is burning out the pump, because the water won’t flow.

Didn’t you say previously on this thread that you have some towel radiators without TRVs? If that’s the case, then as long as you don’t close the lockshield valves on these rads, then they act as your bypass valves.
This is how the radiator in our bathroom is set-up (and I think it’s quite standard), so there’s an flow bypass built-in.

We stuck the heating on last Thursday in the evening; mainly because the towels in the bathroom weren’t drying (might have to investigate a towel radiator with electric functionality, so we can pop it on when the heating is off) at some point.
It was on for an hour and the house got too hot (thermostat on 19, now reduced by a degree).
Since then, we had 30mins on Fri, 15mins on Sat and apart from that it’s not come on again.

I am looking into other options for the winter when I am working from home. We don’t have a smart set-up, and I don’t want the entire house being heated when we could restrict it to my small office.
How do the costs of an oil-filled radiator stack-up compared to having the boiler running to heat the whole house? I’m guessing it would be cheaper, but need to do the sums.

Didn’t you say previously on this thread that you have some towel radiators without TRVs? If that’s the case, then as long as you don’t close the lockshield valves on these rads, then they act as your bypass valves.

Yes, and also hallway rads, but they are dumping heat into the hallways and bathrooms that I don’t want to heat cos I’m not in there. Ok so the bathrooms will need some heat to dry them out and the hanging towels etc, but not hallways.

might have to investigate a towel radiator with electric functionality, so we can pop it on when the heating is off

You can get hybrid towel rails that are like HW ones but also have an electric heating element. I want some of those because towels still need drying in the summer.

How do the costs of an oil-filled radiator stack-up compared to having the boiler running to heat the whole house?

Well, our boiler is 12kW I just found out. An oil rad to heat one room is what, 2kW? So there’s 6x the heat output. The boiler isn’t 100% efficient but in theory and ideal conditions it is close, being a condensing boiler. That’s 6x the output, but at 8p/kWh vs 50p for my electricity, that’s about the same. So you’d have to decide if the boiler was on for the same amount of time as the radiator. To be honest, it sounds pretty comparable.

You could also consider that gas might be 6x cheaper but it could be heating more than 6x the volume.

Ok so the bathrooms will need some heat to dry them out and the hanging towels etc, but not hallways.

Dry air is more efficient .. unless the moisture has somewhere to go from the bathroom

molgrips

Well, our boiler is 12kW I just found out. An oil rad to heat one room is what, 2kW? So there’s 6x the heat output. The boiler isn’t 100% efficient but in theory and ideal conditions it is close, being a condensing boiler. That’s 6x the output, but at 8p/kWh vs 50p for my electricity, that’s about the same.

I am not sure the calculation is as easy as that, is it?
Our boiler is 30kw, but looking at the manual it says that CH output is fully modulating from 6.1 to 24.2KW, while for hot water it can fully modulate up to a max of 30.3kw. (Our boiler was serviced today, so i had already dug the manual out).
So presumably, it isn’t always pumping out 24.2kw when the heating is on although I don’t know how it determines where to run within that output range? Max output with larger delta T, and then reduced output as delta T approaches set T, to avoid over-shoot?
Dunno.
Not a lot of info about this kind of thing on the Ideal website although just found a couple of articles on other sites I will read while eating my lunch.

8p/kWh vs 50p for my electricity, that’s about the same.

Why is your electricity 50p/kwh?

The cap seems to have set it at about 35p/kwh.

Yes, and also hallway rads, but they are dumping heat into the hallways and bathrooms that I don’t want to heat cos I’m not in there.

@molgrips check that video above that I posted, it makes a very good argument (technically and economically) against isolating individual rooms unless they are remote or insulated form teh rest of the house.

Didn’t you say previously on this thread that you have some towel radiators without TRVs? If that’s the case, then as long as you don’t close the lockshield valves on these rads, then they act as your bypass valves.
This is how the radiator in our bathroom is set-up (and I think it’s quite standard), so there’s an flow bypass built-in.

Yes also, but we never use the main bathroom, we’ve got an en-suite where the towel rail is on the HW circuit. So if we close don’t close the valve on that it’s heating a room with no one it it. Instead I’ve set the TRV in the hallway to max (~28ish?) so it never closes before the thermostat on the wall (19C) has switched the boiler off.

Bypass valve seems to be the right tool for the job.

Why is your electricity 50p/kwh?

The cap seems to have set it at about 35p/kwh.

I’m not Molgrips, but I’m with Good Energy, which is one of the companies exempt from the cap. As of this month, what GE are terming ‘The Government Energy Price Guarantee’ will kick in. Our unit costs will now be

Gas 12.6p
Electricity 49.7p

I knew that going with a renewable energy provider would be a bit more expensive, but….ouch

Fortunately we’re a low-use household so even at those prices we shouldn’t be much over £200 a month. But still… I’m not a high earner! And this hurts!

Heatings on full blast. The f****s have over £800 of MY MONEY in their bank account and cant/wont refund it, so Im just going to spend it for them – oh! and they put up my direct debit by £20. I get the uplift in direct debit, but trying to get that much money back from them has proved to be a total nightmare as you just cant get through (Scottish power). So at current prices I should get a week of 20C then its back to cuddling up with the dog and the cat.

So presumably, it isn’t always pumping out 24.2kw when the heating is on although I don’t know how it determines where to run within that output range?

Presumably by varying the burner heat output based on the return flow temp. I’m not sure mine does this, but it seems like such an obvious thing to do I can’t imagine why it wouldn’t.

I need to go back through the manual.

EDIT this is getting a bit silly now and I’m sure any plumbers are laughing their heads off, but I’ve found out that boilers can be modulating, whereby they do vary the burner according to the heat demand which must be measured as I said by the inlet temperature. This article says that a modulation ratio of 1:6 is average for a modern boiler i.e. it can vary between say 5 and 30kW, but in my manual it says it only varies between 9.3 and 12kW which is shit. But this may be a function of it being small.

Heatings on full blast. The f****s have over £800 of MY MONEY in their bank account and cant/wont refund it, so Im just going to spend it for them

That’s daft. Just cancel the DD for the next 4 months or whatever it is.

Why is your electricity 50p/kwh?

Octopus standard variable tariff. 16p 12am-7am, 41p at other times. I’m assuming that’s ex vat.

A couple of interesting points from that video, relating to me:

1. The graph he shows of boiler efficiency vs load – this is another picture of the same thing:

Given that my boiler has such poor modulation* it cannot run at less than 77% load so would revert to being an on-off boiler, and that could drop the efficiency off a cliff. My radiator is only rated at 780W, so even at max power that would represent about 8% of the minimum modulating output so that would mean at most less than 50% efficiency and the boiler would be cycling on and off all the time. Conversely, from the graph a proper modulating boiler would be quite happy at that load and maybe even near peak efficiency.

2. Our house deviates a lot from the theoretical house in his example (which he does acknowledge, to be fair). Where I sit all day is on the top floor and is always much warmer than the kitchen two floors below where it’s coldest. That said, point 1 above means that heating only this room on gas with my current boiler is a non-starter. I could well be better off with an electric rad.

3. I could still go for smart TRVs, but only to turn the rooms a bit during the day. So it’d save some but not tons.

4. I really need to figure out what the boiler is doing when it’s heating the house and the hot water. Turning the output down manually will increase the efficiency, but if I go below 60 I can’t heat the hot water to the sanitary temperature. This is presumably why better boilers have two outputs. And if the hot water is on, and the bottom of the tank is nearly at 60 but the boiler output temp is nearly at 60 then it won’t dump much heat out of the heating coil and the return temps won’t be very low. So again I might be better off heating with electricity overnight. I’ll try and invest in some sort of temperature probes for the in and out pipes.

5. My heating design is utterly shit. There are a hundred or so houses on this street, I bet no-one else has thought about it in this level of detail. They’re probably all on the original boilers and will be chucking tons of money away. Not because the boiler itself is nominally inefficient but because the systems haven’t been well designed or configured.

* The modulation is specified as being between 9.3kW and 12kW but it also says the output temperature can be as low as 30. Does this mean that it reverts to on-off mode if you specify a really low temp? I think it probably does.

@molgrips …have a read of this online article I found earlier

HeatGeek link

Your boiler does sound very small for a 3-storey (presumably 3 or 4 bedroom?) house. That will be partly because you have a tank, so are not having to heat water ‘on-demand’.

From that article – yes, the degree of modulation will vary based on the size of the boiler & smaller ones can’t modulate as much.
And yes – it will cycle on & off to simulate a lower modulation level if needed (like PWM control for LEDs etc).

Regarding the set temperatures – yeah, our boiler (Ideal Logic Max C30) has two temp dials – one for HW & one for CH.

Worth watching!

* The modulation is specified as being between 9.3kW and 12kW but it also says the output temperature can be as low as 30. Does this mean that it reverts to on-off mode if you specify a really low temp? I think it probably does.

Presumably it’s intended to run nearly flat out until all the rads are upto temperature and it senses that the return temp reaches it’s set point (or when modulated to it’s minimum the outlet temp is over the set point, effectively the same thing).

Looking at that graph unless you had all smart TRV’s (or turned 90% of the house off) then I can’t see how any system would drop to ~10% load for very long. Presumably in our ‘dumb’ systems the heating comes on and takes a while to heat up ~10 radiators, then they start switching off at the TRV, 9,8,7,6, which speeds up as the boiler is now sending it’s full power to fewer rads, 5,4,3,2,1 then switches off. Being able to run at 10% load would only work if the heating was on 24/7 so the demand at any instant was only a small amount for one room at a time. And I doubt you’d recover that last 5-10% efficiency Vs extra lost heating the house all day.

Also:
That graph ignores the 3rd axis which would be the water set point temperature, it’ll obviously be more efficient to run a boiler with a higher temperature differential to the water (both in the radiative and condensing sections).

I googled my boiler as a matter of interest. Worcester GreenStar 400. Output varies from Max 30Kw down to 3Kw.

https://www.worcester-bosch.co.uk/professional/products/boilers/greenstar-4000

It was fitted in July and replaced a 40 year old Baxi. Hardly used the heating mode yet but using approx half the gas for hot water. New boiler Combi – heat on demand – old boiler – hot water tank. Interesting to see the winter bills. Though better controls and doubled loft insulation will play a part as well so savings won’t be purely the new boiler.

Not putting the heating on – how’s it going…?

Turned air source heat pump off in January so no central heating/hot water. Been doing fine as it’s not been that cold, although I have a multi fuel stove in living room so obviously that’s fired up in the afternoon and loaded up at night, tiny 1bedroom bungalow so it’s ok at the moment. Got my electricity use down to an average of 2.5kw a day or £1.15 ish or 850kw/year. If I ran the air source heating/hot water It uses near enough 4000kw/year according to previous bills due to non insulated and draughty housing association bungalow so nope…….not using it.

My bastard smart heating system has been smart enough to stop my heating from turning on. Got elderly relatives arriving today so spent an unpleasant hour at lunch pairing thermostats to RF receiver (again), uninstalling and reinstalling app (again) and linking Wi-Fi up (again).

I googled my boiler as a matter of interest. Worcester GreenStar 400. Output varies from Max 30Kw down to 3Kw.

Mine is a Greenstar 4000, but its only 15kw because I’m running a system boiler because I like to have a tank. The benefit is the new circuit controls and integral pump are covered in the warranty now too, and because its all managed by the boiler it should in theory help with efficiency.

AFAIUI, modulation is achieved by the gas valve. The new greenstars can modulate every 10%. The previous ones were 50% or 100%.

Starting to think we should bin off our boiler (put in by the previous owner in 2017 and underpowered) and fit a modulating one with more headroom. With underfloor heating going in and a larger tank fitted this year the existing one is not the best*.
After about a week of having the dial turn down to about 40% from about 80, the water in the tank is noticeably cooler which is subsequently making us use more hot water. I was going to turn the temp up a touch on the tank to make it go further but as we are now not even reaching the current setpoint…..

*We need to move it anyway. A replacement should allow us to make better use of our heat generation.

I didn’t use my Central heating until November 1st last year. So hopefully I’ll manage to make it beyond that date this year.

All this talk of boilers is just about gas-fired ones, anyone got any tips for optimising an oil-fired one? It’s brand-spanking new, one of these:

https://www.worcester-bosch.co.uk/products/boilers/directory/greenstar-danesmoor-external

What’s all this talk of modulation and condensing? Our 35year Stelrad Ideal Sprint is still going strong. It might not be as efficient but it’s easily fixable (don’t worry I don’t touch the gas side) and parts are still available.
Thankfully our main heat source is a Greta approved massive Coalbrookdale Stove thats been lit a few times recently.

I had an idea.

I’ve now learned I need my boiler output temp on a lower value for more efficiency due to the boiler itself, the size of the rads and the fact I have a well insulated house in a mild location. But I also am now concerned about bacteria in the HW tank and with a low temperature from the boiler I might not be able to get the water hot enough.

So I think I will set the water temp to a modest value, but use the immersion heater on a timer just before the off-peak period ends to get it nice and hot. I’ve just switched to an EV tariff with 7.5p/kWh overnight charging, that will make it fairly cheap. I think the immersion heater has a fixed temperature of 60C or something sanitary.