[Door opens, footsteps]
[Creak!] [THUD!]
[Jazzy music: 'The Russians Are Coming' - Val Bennett] [vacuum cleaner noise]
[Jazzy music: 'The Russians Are Coming' - Val Bennett] [TV static noise]
[Jazzy music: 'The Russians Are Coming' - Val Bennett] [Steam hisses]
[Jazzy music: 'The Russians Are Coming' - Val Bennett]
[sewing machine rattles]
[Jazzy music: 'The Russians Are Coming' - Val Bennett] [*Whoop!*]
[Jazzy music: 'The Russians Are Coming' - Val Bennett]
[music fades] [howling wind]
Tim: Today we tend to take it for granted, living indoors at a comfortable, even temperature.
In winter especially, central heating has really changed our lives quite dramatically.
Without it people had to spend hours carting coal about, lighting fires,
keeping fires going, and they still had to wear masses of clothes indoors.
But to make a heating system that's completely automatic and reliable
has taken an enormous amount of effort and ingenuity.
I hope to tell you something about how these systems evolved and how they work in this programme.
Even lighting a simple fire isn't at all easy without modern gadgets, like lighters or matches.
One of the most effective methods used in many parts of the world is a bow drill.
It's much better than the boy scout method of rubbing sticks together.
[screechy rattle of wood on wood]
But even this requires a lot of skill and practice.
And I haven't managed to make it work myself, despite spending a whole afternoon playing with it.
Even speeding up the rotation with an electric drill...
[loud drilling noise]
The friction is creating a hot powdery charcoal,
which in theory can make a bit of tinder catch light.
[drilling continues]
This looks much more hopeful, but I've never actually managed to get a flame out of it,
despite trying with all sorts of different types of tinder.
Well the ancient types of civilisations, including the Romans,
very sensibly never let their fires go out if they could possibly help it.
[footsteps] At first the Romans simply had a fire in the middle of their living room.
The Latin for hearth is focus. The fire was literally the focus of the room.
[Romans babble to one another]
[fire crackles and Romans start to cough]
They probably had trouble with smoke, because the Latin for living room is atrium from 'atum', meaning black.
So they started putting the fire outside, in a furnace, with cavities under the floors and in the walls.
[romans babble] The Romans were rather decadent and just as they were getting comfortable, their civilisation declined and fell.
And houses once again became very smoky.
The next attempt to improve matters was made by the Normans.
They made holes in their castle walls and tried to funnel the smoke out sideways.
Here we've built a horizontal chimney, and you can see it doesn't really work very well.
[clank clank clank]
The hot gases from a fire naturally rise,
and so to make a chimney 'draw' it really has to point upwards.
The Normans finally realised this in the 13th Century,
when castles started to incorporate true chimneys.
By the 18th Century, chimneys were regarded as indispensable in Britain,
and hardly any buildings were put up without them.
Even Chiswick house, which was intended to be an exact replica of an Italian design by Palladio.
At the last minute, the design was modified to include 4 large chimneys on each side.
Lord Burlington had the house built, after returning from the Grand Tour of Europe
fired with an enthusiasm for Palladian architecture.
But he obviously felt that comfort was more important than aesthetics.
Although well designed open fires made houses almost comfortable,
this sort of heat was totally unsuitable for the tropical green houses that came into fashion in the 18th century.
An even heat was required for the plants that was totally smoke-free.
At first the Roman system of central heating was revived.
The only remains are these cast iron chimneys disguised as urns.
Fires were lit behind the greenhouse and smoke was drawn up through cavities in the wall.
The wall became hot, and this created the warmth the plants needed.
[footsteps on gravel] The 18th Century was also the start of the industrial revolution,
and steam power was really the miracle of the age.
So all the fires behind the walls were soon replaced by a central boiler.
And steam or hot water was fed through these enormous pipes that acted as radiators.
In fact these systems are remarkably similar to the modern domestic central heating systems.
These pipes take up much more space than todays small-bore pipes and ultra thin radiators.
But the principle is really exactly the same.
[ticking] This is a steam powered clock I made for a health food shop a few years ago.
The positions of the weights show the time,
and every hour they are wound up by a steam-powered piston.
It taught me a lot about the problems of using steam
One of the worst is scale. The high temperatures tend to increase the effect,
and even using a water softener, scale causes all sorts of difficulties.
[steam hisses] for a start it's very difficult to regulate.
[clanking] On this valve for instance there's a very very slight adjustment
between it not providing enough steam, so the piston doesn't work at all,
and providing too much so it whizzes up and down at an alarming rate.
[clanking]
It's all timed so the winding finishes exactly on the hour and the whistle blows.
[winding finishes] [low whistle]
Steam heating remained popular in America for large buildings,
but hot water systems have far fewer problems, and quickly replaced steam for domestic use.
Commercial exploitation of central heating for private houses
didn't really start until the 1920s.
At first it was only installed in luxury houses. But it quickly spread to the mass market.
First being incorporated on a wide scale, in the new suburban housing estates in the 1930s.
Since then, many different types of central heating system have been developed.
but the hot water and radiator type has remained the most common.
And it is this that I am going to concentrate on in this programme.
It's basically very simple. Water is heated in a boiler by a fire,
and the exhaust gases go up the chimney.
The hot water is pumped through a series of radiators,
and eventually returns to the boiler to be reheated again.
[hissing noise]
The pipes round the boiler do look a bit complicated:
There's one pipe to a tank in the roof, to fill the system with water.
There's also a vent pipe, which lets the water inside expand as it heats up,
and lets water and steam out in case it boils.
Here we've deliberately overheated the system, and the steam harmlessly comes out of the vent.
While fresh water comes in through the feed pipe, to stop the boiler boiling dry.
Of course this doesn't normally happen, and the boiler is
actually rather inaccurately named, as the water's never intended to boil.
Most boilers also provide the hot water for the house,
and this creates even more pipes that we've left out on this model...
Here, Rex has made a transparent radiator, so you can see what happens inside.
The hot water, fresh from the boiler, builds up at the top.
And then as it gives out its heat, slowly falls until it goes through the outlet and back to the boiler.
Although radiators are simple things, they can stop working.
[Air hisses from bleed valve] Air can become trapped inside, and this stops the circulation.
This is why radiators have bleed valves on top. [louder hiss as water squirts from valve]
Radiators can also corrode,
in this old radiator you can see how much debris has accumulated.
[scraping] The corrosion insulates the water inside the radiator,
and reduces its efficiency at giving out heat.
Modern systems usually have chemicals added to the water to reduce the corrosion.
Of course all the radiators, and other bits and pieces, are joined together by copper pipes.
There are two common sorts of connector, used to join the pipes together.
This sort's called a compression fitting, and it's rather ingenious.
Inside are these soft copper rings called 'olives'.
And when I tighten the nuts up, this squashes the olives against the pipe,
and makes the joint watertight.
If a joint like this leaks, you can often stop it by just tightening up the nuts a bit. [ratchet noise]
You can see the solder inside this sort of fitting. It's called a Yorkshire connector.
The end of the pipes are first coated with flux...
Then, when the joint is heated, the flux cleans the metal
and the solder flows out and seals the joint. [roar of blowtorch]
These fittings are cheaper than compression fittings, but if a joint like this leaks it can be tricky,
because it has to be completely dry before resoldering.
This is a basic solid fuel boiler.
It's simply a coal fire surrounded by a jacket full of water.
A sort of double-bowl shape.
It's designed so as much heat as possible is transferred to the water,
although the top of the boiler has to be left open or the fire wouldn't draw properly.
This boiler is probably only transferring about 50% of the fire's heat to the water.
The other 50% is wasted up the chimney.
[footsteps] An ingeniously simple way of heating a whole building
from a single coal fire, without a boiler was used in the Danish war office.
[clanking] Cannon balls were heated in a basement stove until red hot.
[wheels rattling] They were then carried to every room and deposited, glowing, in the fireplaces several times a day.
[clunk]
This was possibly the first ever coal-fired central heating system,
and remained in use until about 1900.
Man: Ahhh!
Although coal was the first fuel to be used, today oil and gas fired boilers are more common.
Oil fired boilers are a bit more complicated.
This is the wall flame type, and the oil comes in right at the bottom, under an electric motor.
This is the shaft of the motor, and as it whizzes round and round,
the centrifugal force pushes the oil outwards and upwards through these tubes,
and it comes out the end as a fine spray.
This spray is ignited by an electric spark. [*bzzzt* of sparking]
[roaring of flame]
Oil fired boilers like this, tend to be less wasteful of heat than solid fuel.
[sparking and flame continues]
The water being heated sits between the double walls of the boiler, just like in the coal one.
Rex uses the spark units from these boilers to create the Jacob's Ladder effect
you sometimes see in films as part of Frankenstein-style laboratories.
[buzzing noise]
Back to central heating boilers...
Gas was first used only for lighting, and the original gas lights were just holes in the pipes.
Gas mantles weren't discovered until the 20th Century.
These early gas lights weren't very effective, but they were a bit brighter and less messy than candles.
But then in 1855, Professor Robert Wilhelm von Bunsen published his findings
on the effects of mixing air with the gas before it was burnt.
And this, his Bunsen burner, the gas comes out of a little nozzle and goes up a tube
[click] And a variable amount of air can be drawn in through the side of the tube.
[roaring of bunsen burner]
As the air is added the gas burns more efficiently,
and the yellow colour, caused by the unburnt particles of carbon, disappears.
With this temperature probe, you can see that this is the gas burning alone,
and when I add the air, the temperature goes up quite dramatically.
I can see the tip of the probe getting red hot.
And for the first time, this made it practical to use gas for heating.
[Music] # happy in the morning,
# as the water's hot.
# We can bath an army,
# The Ascot does the lot.
# Happy after breakfast,
# cos the water's hot.
# Dirty, greasy dishes,
# Are left without a blot.
# Cleaning house has no more fears,
# The Ascot's waiting there.
# Saving money, sighs and tears,
# And endless wear and tear.
All: # Happy in the evening,
# As we know we've got,
# Water, water everywhere,
♪ And always boiling hot. ♪
Tim: The Ascot works on exactly the same principle as the modern gas central heating boiler.
These sorts of boilers do look much more compact than other types,
and that's because instead of a large water jacket, a small amount of water
flows continuously through these pipes above the flames, getting hotter as it goes.
These fins help transfer heat from the flames to the pipes.
It also all looks rather more flimsy than other sorts of boilers.
But this is because gas burns with a much cleaner and less corrosive flame than anything else,
and so the metal just doesn't need to be so thick.
And the thinner the metal, the less energy that's wasted heating it up every time the boiler comes on.
[unscrewing screws]
The gas comes out from this row of jets...
And then it draws air into these tubes. Just like in the Bunsen burner.
And then it burns in this array of flames...
[roaring of burning gas]
Man gas boilers have a balanced flue. This is basically just a hole in the wall.
And, the air comes in through this hole, goes round the outside, and up through
the middle of the boiler, and then the exhaust gases come out through the same hole.
Unlike the Norman horizontal chimneys, this actually works,
because the whole unit is totally sealed, and the pressure of
of the air coming in, exactly equals or balances the pressure
of the exhaust gases coming out.
And this is why it's called a balanced flue.
It often seems rather wasteful when you feel all the heat coming out of one of these things when the boiler's on.
But in fact gas powered boilers are really quite efficient, and
up to 3/4 of the heat of the fire is transferred to the water.
In an open fire only 1/4 of the heat may be transferred to the room,
and 3/4 of it may be lost up the chimney.
But of course you don't notice that because your chimneys are usually out of reach.
The most common sort of electric heating doesn't use boilers at all.
[rapid bubbling and boiling]
Rex: By placing this hot brick in the cold water you can see the energy stored in the brick.
This is basically the principle behind electric night storage radiators.
In this particular radiator we've cut away so you can actually see the element.
At night, the element heats up and transfers its energy into the bricks,
and they charge up, very very hot indeed.
And the following day, they can give out the stored heat
throughout the on-peak period, when electricity is a lot more expensive.
[bubbling quietly]
Tim: Every sort of central heating system needs controls
to turn it on and off according to the temperature and the time of day.
Thermostats, which control the temperature, are really quite simple devices.
They're basically bi-metallic strips.
This is a giant one we've made, and it's steel on one side, firmly fixed to brass on the other.
If I heat it up, the metals expand at a different rate,
and so the strip bends.
This is a thermostat out of an actual central heating system,
and you can see the bi-metallic strip inside.
And as the temperature warms up, the strip will bend
and make an electrical contact, which turns the system off.
And then as the temperature falls, the strip bends back and switches the system on again.
Besides thermostats, central heating systems also need timers,
so that the heating only comes on at times of the day when it's needed.
These are basically clocks, with a dial that goes round once a day.
Pushing a switch on and off as the pins pass.
This one's switching it on... [click]
This one's switching it off... [click]
Simply moving the pins, sets the switching times.
Digital electronic timers, which do the same job, appeared a few years ago,
but they haven't completely replaced the dial type.
Just as with watches, the digital ones can switch the times more precisely,
but they're rather more fiddly to set.
But the overall efficiency of a central heating system depends
mainly on how well the house is insulated.
Without insulation, about 30% is lost through the roof,
25% through the walls, 20% through the windows, 15% through ventilation and 10% through the floors.
[van engine] [people babbling] Tim: Roof insulation is obviously the most important improvement.
But double glazing is also quite effective, simply because it also stops draughts,
and these can cause greater heat losses than everything else put together.
[footsteps of workmen]
[van drives off]
[engine noise]
Ever since the building regulations were modified in 1980,
every new house that is put up, has had to be very thoroughly insulated.
These houses have a timber frame, the black exterior is just a weather-proof paper on top of plywood.
Inside there's the wooden framework that carries the weight of the house.
[construction noises]
To provide the insulation, a 4" blanket of fiberglass is stapled over the plywood.
Once the insulation's in place, the interior walls are finished off with sheets of plasterboard.
[hammering]
The outside is finished off with a fascia of bricks.
These keep the house weatherproof, but don't actually carry any load.
[builders chat to one another]
Besides the insulation, there are some other simple ways of reducing the heat losses.
Like including porches to reduce the draughts every time the front door is opened.
Some architects have also experimented with more extreme ideas.
like making the windows smaller and non opening, with energy-efficient air conditioning instead.
Woman: Oh! I can't see, it's too dark to read.
Tim: But the small windows can make these houses rather dark and depressing.
And the lack of natural ventilation can also make them rather smelly.
It can also cause dampness and rot.
[tiles falling] [building collapses]
It's easy to forget just how energy-efficient old houses can be.
Suffolk farm houses for instance.
They had highly insulated roofs - thatch,
and they were generally built facing South, complete with porches.
[sliding noise]
They even had a sort of primitive central heating system.
They were all centred around massive central chimney blocks.
Usually weighing more than the rest of the house put together.
This acted like a giant storage radiator.
So keeping one good fire alight, would warm the whole chimney block.
Enough to take the chill off all the adjacent rooms.
People did have to wear more clothes, but at least the house was never stuffy.
And next to the central fire could be quite cosy.
It all did have a sort of elegant simplicity about it, that a modern system lacks.
But of course modern central heating systems can heat houses to much higher and more comfortable temperatures.
And they're generally automatic and avoid the labour of keeping fires going all the time.
The only problem, is like all technology, it can sometimes go wrong.
[hissing water]
[Jazzy music: 'Take 5' - Dave Brubeck] [hissing water]
[Jazzy music: 'Take 5' - Dave Brubeck]