Energy myth-busting: Is it cheaper to have heating on all day?

Spies

Turned my flow down to 55c but rooms still hitting target, I imagine that's due to the milder weather right now more than anything. 

BUFF

Cardew said:

The vast majority of those who log in to this forum want to know the answer to question posed on page one of this thread ie,

Energy myth-busting: Is it cheaper to have heating on all day?

The last 20 pages of this thread will leave them totally confused; if they bothered reading that far. The answer is NO albeit there are 4,873 caveats to consider.

The next question to be posed is to ask if it is possible to jump from an aircraft at 18,000 ft without a parachute and survive. I contend the answer is NO but Nicholas Stephen Alkemade would not agree!

I raise you Vesna Vulovic https://en.wikipedia.org/wiki/Vesna_Vulović.

The thing is that the simplistic question doesn't take into account individual cirumstances & the cheapest way to run may also come with other implications that many people are unwilling to put up with.

richardc1983

Spies said:

Turned my flow down to 55c but rooms still hitting target, I imagine that's due to the milder weather right now more than anything. 

Turn it down some more. Particularly with it being mild. 

Ultrasonic

I've turned my heating off now but as I rather suspected I have ended up using more gas today by virtue of leaving my heating on continuously rather than switching it on and off manually as I normally do. Over the day I used about 26 kWh of gas vs 22 kWh last Saturday, when it was considerably colder outside. I had the water temp set to 40°C until early afternoon but then changed it to 45°C which did a better job of being able to maintain the thermostat temperature of 18°C.

orrery

richardc1983 said:

Spies said:

Turned my flow down to 55c but rooms still hitting target, I imagine that's due to the milder weather right now more than anything. 

Turn it down some more. Particularly with it being mild. 

Our discussions seem to take a very simplistic view of how the average boiler works. My Vaillant can be turned down to 50C but everything goes pear shaped fairly quickly: it rapidly reaches 50, starts to modulate back, once it modulates down to its lowest level (5kW) it will continue running until the flow temperature reaches 7C above the set temperature (so 57C if set to 50) and then is shuts down. After a short timeout, it tries to re-start and will almost certainly have to shut down almost immediately (the startup sequence tests at full power).

It is far better to have a reasonable flow temperature (62 to 70C, depending on the season) and use a controller that uses proportional control to ensure the return temperature is kept low - that way you get the benefit of a high flow temperature when you need it and the economy of always being in condensing mode and ensuring that the boiler doesn't short-cycle.

I use a Tado controller that allow unlimited temperature segments, but even the Honeywell controller I retired years ago did a passable impression of a proportional controller.

The first thing that I'd recommend anyone to do is to get a couple of electronic thermometers with long wire probes (as cheap as chips on ebay) and monitor flow and return temperatures side by side, get a comfy chair and a book and sit by the boiler to find out what it is really doing.

[Deleted User]

BUFF said:

Deleted_User said:

There's lots to consider, and in my opinion the answer is not as straightforward as just leaving your heating system tick over day in day out.

correct, it's going to be different for every house/system & person (convenience/comfort are usually considerations as well as simply lowest running cost).

Deleted_User said:

For instance where is your ground floor room stat installed, many homes have them installed in the hallway which might be the coldest part of the house, therefore the stat is constantly switching on your boiler to heat up the whole of the house even though it's only the hallway that might be the coldest, so if you have no rad stats fitted in your rooms you will be burning gas for the fun of it trying to heat up the hallway which might not even have a rad there, so the stat will be asking the boiler for heat but it might take forever for the stat to benefit from the heat.

Correct room stat location is very important, for an efficient heating system to work correctly.

Yes, but if you know your system you learn how to offset. e.g. my roomstat is in the kitchen which is the coldest room in the house - setting the roomstat to 14.5 there will get me 16C in the rooms.

Deleted_User said:

Towel rads, very nice to look at but do absolutely nothing to warm up a bathroom, yes they get extremely hot to touch, but offer no ambient temperature whatsoever.
If you have towel rails in bathrooms with stats fitted it will be a waste of time.
Towel rails are only good for 2 things, warm/dry your towels and they look nice.

Sorry but I totally disagree with this. My 1800h x550w white ladder rail is rated for ~3000btu & the bathroom can be the hottest room in the house.
Metallic plating or towels over (rather than in front of) will reduce output significantly.
Because I run lowish flow temps mine doesn't get extremely hot to touch - hot, yes, but not extremely.

I think when someone purchase a towel rail they tend to get a bit side tracked by the BTU figures and think matching the BTU of the conventional rad they are replacing will provide the same ambient temperature as the conventional did.

A conventional radiator and a more modern towel warmer/rail are two completely different items !

The clue is in the products name ;
A radiator is manufactured to radiate heat into the room it is placed.
A towel warmer/rail is, just that, a towel warmer.

I totally agree you can get towel warmer/rails with a very high BTU, even matching or exceeding your conventional radiator, but that's where the similarities end.
The radiator is designed to use the BTU that it outputs in a totally different way to that of a similar BTU produced by a towel rail.
One will radiate, the other will not, or at least not anywhere near the way a conventional radiator does.
It's simple physics.
The radiator has a larger surface area hence more heat to radiate.
The towel rail loses the surface heat that it produces almost immediately due to the single tubing.
Yes the tubes get hot, very hot sometimes, but that heat is not being radiated like a conventional radiator.

Many years ago when central heating as we know it was introduced in UK homes, the radiators that we see in our homes were manufactured in such a way that they would radiate the heat in the rooms they were placed, the design has never altered , apart from when then the manufactures realised that they could make the radiators even more efficient by using thinner steel and adding convector fins to throw the heat even further into the room, this design is still with us today.

You dont see convector fins on your towel rails, why ? Because they wouldn't be of any use as the heat is lost through it's design. 

At the end of the day it's all down to choice.
As I've previously said, we have towel rails in our bathroom & ensuites, they were installed as a cosmetic choice, they get hot, sometimes a bit too hot, but we knew when having them installed that the ambient room temp would significantly drop compared to when the rooms had convectional rads.

I dont want to steal this thread from the original subject so we'll have to agree to disagree.

Ultrasonic

Deleted_User said:

The clue is in the products name ;
A radiator is manufactured to radiate heat into the room it is placed.
A towel warmer/rail is, just that, a towel warmer.

I totally agree you can get towel warmer/rails with a very high BTU, even matching or exceeding your conventional radiator, but that's where the similarities end.
The radiator is designed to use the BTU that it outputs in a totally different way to that of a similar BTU produced by a towel rail.
One will radiate, the other will not, or at least not anywhere near the way a conventional radiator does.
It's simple physics.
The radiator has a larger surface area hence more heat to radiate.
The towel rail loses the surface heat that it produces almost immediately due to the single tubing.
Yes the tubes get hot, very hot sometimes, but that heat is not being radiated like a conventional radiator.

Conventional 'radiators' predominantly heat by convection not radiation.

My suspicion as to why some find towel rails underwhelming is that I'll bet they heat the room far less effectively when covered up by towels, just as a conventional radiator probably would.

As above though, my bathroom is very effectively heated by my towel rail and I can easily make it the warmest room in the house using this.

Spies

Today's experiment of turning the boiler down further has been ruined by having a shower, so gas usage is obviously higher! 

BUFF

Deleted_User said:

BUFF said:

Deleted_User said:

Towel rads, very nice to look at but do absolutely nothing to warm up a bathroom, yes they get extremely hot to touch, but offer no ambient temperature whatsoever.
If you have towel rails in bathrooms with stats fitted it will be a waste of time.
Towel rails are only good for 2 things, warm/dry your towels and they look nice.

Sorry but I totally disagree with this. My 1800h x550w white ladder rail is rated for ~3000btu & the bathroom can be the hottest room in the house.
Metallic plating or towels over (rather than in front of) will reduce output significantly.
Because I run lowish flow temps mine doesn't get extremely hot to touch - hot, yes, but not extremely.

I think when someone purchase a towel rail they tend to get a bit side tracked by the BTU figures and think matching the BTU of the conventional rad they are replacing will provide the same ambient temperature as the conventional did.

A conventional radiator and a more modern towel warmer/rail are two completely different items !

The clue is in the products name ;
A radiator is manufactured to radiate heat into the room it is placed.
A towel warmer/rail is, just that, a towel warmer.

I totally agree you can get towel warmer/rails with a very high BTU, even matching or exceeding your conventional radiator, but that's where the similarities end.
The radiator is designed to use the BTU that it outputs in a totally different way to that of a similar BTU produced by a towel rail.
One will radiate, the other will not, or at least not anywhere near the way a conventional radiator does.
It's simple physics.
The radiator has a larger surface area hence more heat to radiate.
The towel rail loses the surface heat that it produces almost immediately due to the single tubing.
Yes the tubes get hot, very hot sometimes, but that heat is not being radiated like a conventional radiator.

Many years ago when central heating as we know it was introduced in UK homes, the radiators that we see in our homes were manufactured in such a way that they would radiate the heat in the rooms they were placed, the design has never altered , apart from when then the manufactures realised that they could make the radiators even more efficient by using thinner steel and adding convector fins to throw the heat even further into the room, this design is still with us today.

You dont see convector fins on your towel rails, why ? Because they wouldn't be of any use as the heat is lost through it's design. 

At the end of the day it's all down to choice.
As I've previously said, we have towel rails in our bathroom & ensuites, they were installed as a cosmetic choice, they get hot, sometimes a bit too hot, but we knew when having them installed that the ambient room temp would significantly drop compared to when the rooms had convectional rads.

I dont want to steal this thread from the original subject so we'll have to agree to disagree.

I used to sell radiators for 1 of the largest manufacturers in Europe, I think that I understand how they work
I disagree with your explanation of radiation between a panel rad & a ladder/towel rail - a panel rad & a rail rated at the same BTU do output equally, it's actually measured/tested in laboratories for certification. They will be different physical sizes for the same output though depending upon design (e.g. a single panel 1800x500 radiator would probably output ~50% more than my 1800x500 ladder rail).
Adding more panels or fins similarly allows for higher output in the same physical dimensions of height & width. Convection & how heated air circulates in a room is a different argument.

N.B. that I called mine a ladder rail & not a towel rail. I also caveated plating them or hanging towels directly over them as either (or worse, both) will significantly decrease output for a given size. My towels hang in front of the ladder rail.

BUFF

richardc1983 said:

Oh the old my d£¥k is bigger than your d£¥k comment. There's plenty of people in sales selling products they know nothing about. Heat pumps and boilers being one of them. That comment just makes you look arrogant as if the other person is wrong.

A towel rail does not convect in the same way a panel rad would hence why they are slower to warm up a room, just like any radiator where something is placed over the top of the fins you disrupt the air flow. 

& what if he is? They are tested for certification - surely empirical evidence trumps opinions?

I never said that a ladder/towel rail convects at all (although they do albeit not as much as with fins) ... If you have a typical UK sized bathroom, an appropriately sized (output) ladder rail not covered up will heat it perfectly adequately & as quickly as an equivalent output single panel radiator.