1
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[Door opens, footsteps]

2
00:00:05,400 --> 00:00:07,144
[Creak!] [THUD!]

3
00:00:07,399 --> 00:00:10,098
[Jazzy music: 'The Russians Are Coming' - Val Bennett]
[vacuum cleaner noise]

4
00:00:10,099 --> 00:00:12,298
[Jazzy music: 'The Russians Are Coming' - Val Bennett]
[TV static noise]

5
00:00:12,299 --> 00:00:14,199
[Jazzy music: 'The Russians Are Coming' - Val Bennett]
[Steam hisses]

6
00:00:14,200 --> 00:00:16,289
[Jazzy music: 'The Russians Are Coming' - Val Bennett]

7
00:00:16,290 --> 00:00:17,889
[Jazzy music: 'The Russians Are Coming' - Val Bennett]
[sewing machine rattles]

8
00:00:17,890 --> 00:00:20,389
[Jazzy music: 'The Russians Are Coming' - Val Bennett]
[*Whoop!*]

9
00:00:20,390 --> 00:00:30,604
[Jazzy music: 'The Russians Are Coming' - Val Bennett]

10
00:00:30,605 --> 00:00:49,768
[music fades] [howling wind]

11
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Tim: Today we tend to take it for granted, living indoors at a comfortable, even temperature.

12
00:00:58,681 --> 00:01:02,912
In winter especially, central heating has really changed our lives quite dramatically.

13
00:01:02,913 --> 00:01:07,483
Without it people had to spend hours carting coal about, lighting fires,

14
00:01:07,484 --> 00:01:11,611
keeping fires going, and they still had to wear masses of clothes indoors.

15
00:01:11,612 --> 00:01:16,552
But to make a heating system that's completely automatic and reliable

16
00:01:16,553 --> 00:01:20,219
has taken an enormous amount of effort and ingenuity.

17
00:01:20,220 --> 00:01:25,170
I hope to tell you something about how these systems evolved and how they work in this programme.

18
00:01:32,009 --> 00:01:36,908
Even lighting a simple fire isn't at all easy without modern gadgets, like lighters or matches.

19
00:01:36,909 --> 00:01:41,408
One of the most effective methods used in many parts of the world is a bow drill.

20
00:01:41,409 --> 00:01:44,689
It's much better than the boy scout method of rubbing sticks together.

21
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[screechy rattle of wood on wood]

22
00:01:51,153 --> 00:01:54,303
But even this requires a lot of skill and practice.

23
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And I haven't managed to make it work myself, despite spending a whole afternoon playing with it.

24
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Even speeding up the rotation with an electric drill...

25
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[loud drilling noise]

26
00:02:06,435 --> 00:02:09,961
The friction is creating a hot powdery charcoal,

27
00:02:09,962 --> 00:02:12,950
which in theory can make a bit of tinder catch light.

28
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[drilling continues]

29
00:02:14,298 --> 00:02:18,360
This looks much more hopeful, but I've never actually managed to get a flame out of it,

30
00:02:18,361 --> 00:02:21,194
despite trying with all sorts of different types of tinder.

31
00:02:21,195 --> 00:02:24,274
Well the ancient types of civilisations, including the Romans,

32
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very sensibly never let their fires go out if they could possibly help it.

33
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[footsteps]
At first the Romans simply had a fire in the middle of their living room.

34
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The Latin for hearth is focus.  The fire was literally the focus of the room.

35
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[Romans babble to one another]

36
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[fire crackles and Romans start to cough]

37
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They probably had trouble with smoke, because the Latin for living room is atrium from 'atum', meaning black.

38
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So they started putting the fire outside, in a furnace, with cavities under the floors and in the walls.

39
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[romans babble]
The Romans were rather decadent and just as they were getting comfortable, their civilisation declined and fell.

40
00:03:05,658 --> 00:03:09,080
And houses once again became very smoky.

41
00:03:10,081 --> 00:03:13,607
The next attempt to improve matters was made by the Normans.

42
00:03:13,608 --> 00:03:18,216
They made holes in their castle walls and tried to funnel the smoke out sideways.

43
00:03:19,317 --> 00:03:24,144
Here we've built a horizontal chimney, and you can see it doesn't really work very well.

44
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[clank clank clank]

45
00:03:46,853 --> 00:03:50,904
The hot gases from a fire naturally rise,

46
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and so to make a chimney 'draw' it really has to point upwards.

47
00:03:54,702 --> 00:03:58,988
The Normans finally realised this in the 13th Century,

48
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when castles started to incorporate true chimneys.

49
00:04:06,318 --> 00:04:10,613
By the 18th Century, chimneys were regarded as indispensable in Britain,

50
00:04:10,614 --> 00:04:13,105
and hardly any buildings were put up without them.

51
00:04:13,106 --> 00:04:20,109
Even Chiswick house, which was intended to be an exact replica of an Italian design by Palladio.

52
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At the last minute, the design was modified to include 4 large chimneys on each side.

53
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Lord Burlington had the house built, after returning from the Grand Tour of Europe

54
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fired with an enthusiasm for Palladian architecture.

55
00:04:36,639 --> 00:04:40,446
But he obviously felt that comfort was more important than aesthetics.

56
00:04:43,713 --> 00:04:47,661
Although well designed open fires made houses almost comfortable,

57
00:04:47,662 --> 00:04:53,690
this sort of heat was totally unsuitable for the tropical green houses that came into fashion in the 18th century.

58
00:04:53,691 --> 00:04:58,944
An even heat was required for the plants that was totally smoke-free.

59
00:05:00,235 --> 00:05:03,572
At first the Roman system of central heating was revived.

60
00:05:03,573 --> 00:05:08,283
The only remains are these cast iron chimneys disguised as urns.

61
00:05:12,365 --> 00:05:17,499
Fires were lit behind the greenhouse and smoke was drawn up through cavities in the wall.

62
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The wall became hot, and this created the warmth the plants needed.

63
00:05:28,647 --> 00:05:34,899
[footsteps on gravel]
The 18th Century was also the start of the industrial revolution,

64
00:05:34,900 --> 00:05:37,884
and steam power was really the miracle of the age.

65
00:05:37,885 --> 00:05:42,535
So all the fires behind the walls were soon replaced by a central boiler.

66
00:05:42,536 --> 00:05:48,712
And steam or hot water was fed through these enormous pipes that acted as radiators.

67
00:05:48,713 --> 00:05:53,958
In fact these systems are remarkably similar to the modern domestic central heating systems.

68
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These pipes take up much more space than todays small-bore pipes and ultra thin radiators.

69
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But the principle is really exactly the same.

70
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[ticking]
This is a steam powered clock I made for a health food shop a few years ago.

71
00:06:17,579 --> 00:06:20,412
The positions of the weights show the time,

72
00:06:20,413 --> 00:06:23,427
and every hour they are wound up by a steam-powered piston.

73
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It taught me a lot about the problems of using steam

74
00:06:28,410 --> 00:06:33,933
One of the worst is scale. The high temperatures tend to increase the effect,

75
00:06:33,934 --> 00:06:38,764
and even using a water softener, scale causes all sorts of difficulties.

76
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[steam hisses]
for a start it's very difficult to regulate.

77
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[clanking] On this valve for instance there's a very very slight adjustment

78
00:06:45,797 --> 00:06:49,924
between it not providing enough steam, so the piston doesn't work at all,

79
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and providing too much so it whizzes up and down at an alarming rate.

80
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[clanking]

81
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It's all timed so the winding finishes exactly on the hour and the whistle blows.

82
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[winding finishes]
[low whistle]

83
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Steam heating remained popular in America for large buildings,

84
00:07:26,693 --> 00:07:32,751
but hot water systems have far fewer problems, and quickly replaced steam for domestic use.

85
00:07:35,453 --> 00:07:39,605
Commercial exploitation of central heating for private houses

86
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didn't really start until the 1920s.

87
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At first it was only installed in luxury houses.  But it quickly spread to the mass market.

88
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First being incorporated on a wide scale, in the new suburban housing estates in the 1930s.

89
00:08:01,683 --> 00:08:05,905
Since then, many different types of central heating system have been developed.

90
00:08:05,906 --> 00:08:09,159
but the hot water and radiator type has remained the most common.

91
00:08:09,160 --> 00:08:12,052
And it is this that I am going to concentrate on in this programme.

92
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It's basically very simple.  Water is heated in a boiler by a fire,

93
00:08:17,610 --> 00:08:20,383
and the exhaust gases go up the chimney.

94
00:08:20,384 --> 00:08:24,480
The hot water is pumped through a series of radiators,

95
00:08:24,481 --> 00:08:28,206
and eventually returns to the boiler to be reheated again.

96
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[hissing noise]

97
00:08:30,812 --> 00:08:33,947
The pipes round the boiler do look a bit complicated:

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There's one pipe to a tank in the roof, to fill the system with water.

99
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There's also a vent pipe, which lets the water inside expand as it heats up,

100
00:08:43,580 --> 00:08:46,973
and lets water and steam out in case it boils.

101
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Here we've deliberately overheated the system, and the steam harmlessly comes out of the vent.

102
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While fresh water comes in through the feed pipe, to stop the boiler boiling dry.

103
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Of course this doesn't normally happen, and the boiler is

104
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actually rather inaccurately named, as the water's never intended to boil.

105
00:09:07,932 --> 00:09:10,901
Most boilers also provide the hot water for the house,

106
00:09:10,902 --> 00:09:16,040
and this creates even more pipes that we've left out on this model...

107
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Here, Rex has made a transparent radiator, so you can see what happens inside.

108
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The hot water, fresh from the boiler, builds up at the top.

109
00:09:27,916 --> 00:09:33,639
And then as it gives out its heat, slowly falls until it goes through the outlet and back to the boiler.

110
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Although radiators are simple things, they can stop working.

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[Air hisses from bleed valve]
Air can become trapped inside, and this stops the circulation.

112
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This is why radiators have bleed valves on top.
[louder hiss as water squirts from valve]

113
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Radiators can also corrode,

114
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in this old radiator you can see how much debris has accumulated.

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[scraping]
The corrosion insulates the water inside the radiator,

116
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and reduces its efficiency at giving out heat.

117
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Modern systems usually have chemicals added to the water to reduce the corrosion.

118
00:10:08,023 --> 00:10:12,306
Of course all the radiators, and other bits and pieces, are joined together by copper pipes.

119
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There are two common sorts of connector, used to join the pipes together.

120
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This sort's called a compression fitting, and it's rather ingenious.

121
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Inside are these soft copper rings called 'olives'.

122
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And when I tighten the nuts up, this squashes the olives against the pipe,

123
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and makes the joint watertight.

124
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If a joint like this leaks, you can often stop it by just tightening up the nuts a bit.
[ratchet noise]

125
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You can see the solder inside this sort of fitting. It's called a Yorkshire connector.

126
00:10:54,560 --> 00:10:57,734
The end of the pipes are first coated with flux...

127
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Then, when the joint is heated, the flux cleans the metal

128
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and the solder flows out and seals the joint.
[roar of blowtorch]

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These fittings are cheaper than compression fittings, but if a joint like this leaks it can be tricky,

130
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because it has to be completely dry before resoldering.

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This is a basic solid fuel boiler.

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It's simply a coal fire surrounded by a jacket full of water.

133
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A sort of double-bowl shape.

134
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It's designed so as much heat as possible is transferred to the water,

135
00:11:45,171 --> 00:11:48,561
although the top of the boiler has to be left open or the fire wouldn't draw properly.

136
00:11:51,111 --> 00:11:56,098
This boiler is probably only transferring about 50% of the fire's heat to the water.

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The other 50% is wasted up the chimney.

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[footsteps]
An ingeniously simple way of heating a whole building

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from a single coal fire, without a boiler was used in the Danish war office.

140
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[clanking]
Cannon balls were heated in a basement stove until red hot.

141
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[wheels rattling]
They were then carried to every room and deposited, glowing, in the fireplaces several times a day.

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[clunk]

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00:12:24,625 --> 00:12:28,551
This was possibly the first ever coal-fired central heating system,

144
00:12:28,552 --> 00:12:31,506
and remained in use until about 1900.

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Man: Ahhh!

146
00:12:34,366 --> 00:12:39,568
Although coal was the first fuel to be used, today oil and gas fired boilers are more common.

147
00:12:40,163 --> 00:12:43,057
Oil fired boilers are a bit more complicated.

148
00:12:46,381 --> 00:12:52,244
This is the wall flame type, and the oil comes in right at the bottom, under an electric motor.

149
00:12:52,245 --> 00:12:57,414
This is the shaft of the motor, and as it whizzes round and round,

150
00:12:57,415 --> 00:13:01,990
the centrifugal force pushes the oil outwards and upwards through these tubes,

151
00:13:01,991 --> 00:13:04,611
and it comes out the end as a fine spray.

152
00:13:07,731 --> 00:13:12,150
This spray is ignited by an electric spark.
[*bzzzt* of sparking]

153
00:13:12,151 --> 00:13:17,114
[roaring of flame]

154
00:13:17,115 --> 00:13:21,843
Oil fired boilers like this, tend to be less wasteful of heat than solid fuel.

155
00:13:23,519 --> 00:13:26,532
[sparking and flame continues]

156
00:13:26,533 --> 00:13:31,710
The water being heated sits between the double walls of the boiler, just like in the coal one.

157
00:13:34,083 --> 00:13:39,174
Rex uses the spark units from these boilers to create the Jacob's Ladder effect

158
00:13:39,175 --> 00:13:44,237
you sometimes see in films as part of Frankenstein-style laboratories.

159
00:13:44,238 --> 00:14:03,511
[buzzing noise]

160
00:14:03,512 --> 00:14:05,477
Back to central heating boilers...

161
00:14:05,478 --> 00:14:11,558
Gas was first used only for lighting, and the original gas lights were just holes in the pipes.

162
00:14:12,059 --> 00:14:15,170
Gas mantles weren't discovered until the 20th Century.

163
00:14:15,171 --> 00:14:20,080
These early gas lights weren't very effective, but they were a bit brighter and less messy than candles.

164
00:14:20,581 --> 00:14:27,006
But then in 1855, Professor Robert Wilhelm von Bunsen published his findings

165
00:14:27,007 --> 00:14:30,921
on the effects of mixing air with the gas before it was burnt.

166
00:14:30,922 --> 00:14:39,322
And this, his Bunsen burner, the gas comes out of a little nozzle and goes up a tube

167
00:14:40,423 --> 00:14:46,730
[click] And a variable amount of air can be drawn in through the side of the tube.

168
00:14:46,731 --> 00:14:48,838
[roaring of bunsen burner]

169
00:14:48,839 --> 00:14:51,854
As the air is added the gas burns more efficiently,

170
00:14:51,855 --> 00:14:56,018
and the yellow colour, caused by the unburnt particles of carbon, disappears.

171
00:15:00,966 --> 00:15:07,030
With this temperature probe, you can see that this is the gas burning alone,

172
00:15:07,031 --> 00:15:13,293
and when I add the air, the temperature goes up quite dramatically.

173
00:15:13,294 --> 00:15:16,379
I can see the tip of the probe getting red hot.

174
00:15:17,005 --> 00:15:20,651
And for the first time, this made it practical to use gas for heating.

175
00:15:20,652 --> 00:15:23,408
[Music]
# happy in the morning,

176
00:15:23,409 --> 00:15:25,720
# as the water's hot.

177
00:15:25,721 --> 00:15:28,102
# We can bath an army,

178
00:15:28,103 --> 00:15:30,055
# The Ascot does the lot.

179
00:15:30,056 --> 00:15:32,769
# Happy after breakfast,

180
00:15:32,770 --> 00:15:34,679
# cos the water's hot.

181
00:15:34,680 --> 00:15:36,644
# Dirty, greasy dishes,

182
00:15:36,645 --> 00:15:38,905
# Are left without a blot.

183
00:15:38,906 --> 00:15:41,381
# Cleaning house has no more fears,

184
00:15:41,382 --> 00:15:43,662
# The Ascot's waiting there.

185
00:15:43,663 --> 00:15:45,956
# Saving money, sighs and tears,

186
00:15:45,957 --> 00:15:48,286
# And endless wear and tear.

187
00:15:48,287 --> 00:15:50,013
All: # Happy in the evening,

188
00:15:50,014 --> 00:15:52,364
# As we know we've got,

189
00:15:52,365 --> 00:15:54,741
# Water, water everywhere,

190
00:15:54,742 --> 00:15:57,432
# And always boiling hot. #

191
00:15:57,433 --> 00:16:01,654
Tim: The Ascot works on exactly the same principle as the modern gas central heating boiler.

192
00:16:01,655 --> 00:16:05,292
These sorts of boilers do look much more compact than other types,

193
00:16:05,293 --> 00:16:08,861
and that's because instead of a large water jacket, a small amount of water

194
00:16:08,896 --> 00:16:13,483
flows continuously through these pipes above the flames, getting hotter as it goes.

195
00:16:13,484 --> 00:16:18,244
These fins help transfer heat from the flames to the pipes.

196
00:16:19,924 --> 00:16:23,858
It also all looks rather more flimsy than other sorts of boilers.

197
00:16:23,859 --> 00:16:28,743
But this is because gas burns with a much cleaner and less corrosive flame than anything else,

198
00:16:28,744 --> 00:16:31,656
and so the metal just doesn't need to be so thick.

199
00:16:31,657 --> 00:16:37,303
And the thinner the metal, the less energy that's wasted heating it up every time the boiler comes on.

200
00:16:40,003 --> 00:16:48,349
[unscrewing screws]

201
00:16:48,350 --> 00:16:52,253
The gas comes out from this row of jets...

202
00:16:56,646 --> 00:17:02,739
And then it draws air into these tubes. Just like in the Bunsen burner.

203
00:17:02,740 --> 00:17:06,701
And then it burns in this array of flames...

204
00:17:06,702 --> 00:17:11,360
[roaring of burning gas]

205
00:17:15,827 --> 00:17:20,940
Man gas boilers have a balanced flue. This is basically just a hole in the wall.

206
00:17:20,941 --> 00:17:25,598
And, the air comes in through this hole, goes round the outside, and up through

207
00:17:25,599 --> 00:17:29,982
the middle of the boiler, and then the exhaust gases come out through the same hole.

208
00:17:29,983 --> 00:17:34,381
Unlike the Norman horizontal chimneys, this actually works,

209
00:17:34,382 --> 00:17:38,060
because the whole unit is totally sealed, and the pressure of

210
00:17:38,061 --> 00:17:41,688
of the air coming in, exactly equals or balances the pressure

211
00:17:41,689 --> 00:17:44,260
of the exhaust gases coming out.

212
00:17:44,261 --> 00:17:48,074
And this is why it's called a balanced flue.

213
00:17:48,075 --> 00:17:53,304
It often seems rather wasteful when you feel all the heat coming out of one of these things when the boiler's on.

214
00:17:53,305 --> 00:17:57,080
But in fact gas powered boilers are really quite efficient, and

215
00:17:57,081 --> 00:18:00,727
up to 3/4 of the heat of the fire is transferred to the water.

216
00:18:00,728 --> 00:18:05,615
In an open fire only 1/4 of the heat may be transferred to the room,

217
00:18:05,616 --> 00:18:08,309
and 3/4 of it may be lost up the chimney.

218
00:18:08,310 --> 00:18:12,092
But of course you don't notice that because your chimneys are usually out of reach.

219
00:18:12,093 --> 00:18:17,627
The most common sort of electric heating doesn't use boilers at all.

220
00:18:17,628 --> 00:18:21,903
[rapid bubbling and boiling]

221
00:18:21,904 --> 00:18:26,622
Rex: By placing this hot brick in the cold water you can see the energy stored in the brick.

222
00:18:26,623 --> 00:18:30,634
This is basically the principle behind electric night storage radiators.

223
00:18:30,635 --> 00:18:34,469
In this particular radiator we've cut away so you can actually see the element.

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At night, the element heats up and transfers its energy into the bricks,

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and they charge up, very very hot indeed.

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And the following day, they can give out the stored heat

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throughout the on-peak period, when electricity is a lot more expensive.

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[bubbling quietly]

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Tim: Every sort of central heating system needs controls

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to turn it on and off according to the temperature and the time of day.

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Thermostats, which control the temperature, are really quite simple devices.

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They're basically bi-metallic strips.

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This is a giant one we've made, and it's steel on one side, firmly fixed to brass on the other.

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If I heat it up, the metals expand at a different rate,

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and so the strip bends.

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This is a thermostat out of an actual central heating system,

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and you can see the bi-metallic strip inside.

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And as the temperature warms up, the strip will bend

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and make an electrical contact, which turns the system off.

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And then as the temperature falls, the strip bends back and switches the system on again.

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Besides thermostats, central heating systems also need timers,

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so that the heating only comes on at times of the day when it's needed.

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These are basically clocks, with a dial that goes round once a day.

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Pushing a switch on and off as the pins pass.

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This one's switching it on...
[click]

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This one's switching it off...
[click]

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Simply moving the pins, sets the switching times.

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Digital electronic timers, which do the same job, appeared a few years ago,

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but they haven't completely replaced the dial type.

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Just as with watches, the digital ones can switch the times more precisely,

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but they're rather more fiddly to set.

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But the overall efficiency of a central heating system depends

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mainly on how well the house is insulated.

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Without insulation, about 30% is lost through the roof,

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25% through the walls, 20% through the windows, 15% through ventilation and 10% through the floors.

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[van engine] [people babbling]
Tim: Roof insulation is obviously the most important improvement.

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But double glazing is also quite effective, simply because it also stops draughts,

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and these can cause greater heat losses than everything else put together.

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[footsteps of workmen]

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[van drives off]

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[engine noise]

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Ever since the building regulations were modified in 1980,

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every new house that is put up, has had to be very thoroughly insulated.

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These houses have a timber frame, the black exterior is just a weather-proof paper on top of plywood.

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Inside there's the wooden framework that carries the weight of the house.

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[construction noises] 

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To provide the insulation, a 4" blanket of fiberglass is stapled over the plywood.

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Once the insulation's in place, the interior walls are finished off with sheets of plasterboard.

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[hammering]

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The outside is finished off with a fascia of bricks.

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These keep the house weatherproof, but don't actually carry any load.

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[builders chat to one another]

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Besides the insulation, there are some other simple ways of reducing the heat losses.

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Like including porches to reduce the draughts every time the front door is opened.

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Some architects have also experimented with more extreme ideas.

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like making the windows smaller and non opening, with energy-efficient air conditioning instead.

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Woman: Oh! I can't see, it's too dark to read.

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Tim: But the small windows can make these houses rather dark and depressing.

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And the lack of natural ventilation can also make them rather smelly.

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It can also cause dampness and rot.

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[tiles falling]  [building collapses]

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It's easy to forget just how energy-efficient old houses can be.

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Suffolk farm houses for instance.

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They had highly insulated roofs - thatch,

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and they were generally built facing South, complete with porches.

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[sliding noise]

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They even had a sort of primitive central heating system.

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They were all centred around massive central chimney blocks.

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Usually weighing more than the rest of the house put together.

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This acted like a giant storage radiator.

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So keeping one good fire alight, would warm the whole chimney block.

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Enough to take the chill off all the adjacent rooms.

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People did have to wear more clothes, but at least the house was never stuffy.

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And next to the central fire could be quite cosy.

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It all did have a sort of elegant simplicity about it, that a modern system lacks.

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But of course modern central heating systems can heat houses to much higher and more comfortable temperatures.

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And they're generally automatic and avoid the labour of keeping fires going all the time.

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The only problem, is like all technology, it can sometimes go wrong.

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[hissing water] 

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[Jazzy music: 'Take 5' - Dave Brubeck]
[hissing water]

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[Jazzy music: 'Take 5' - Dave Brubeck]