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How Condensing Boilers Work - Plumbing Tips

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- [Announcer] Plumberparts.co.uk
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- Hello and welcome to this
week's plumberparts.co.uk video.
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Today I'm gonna tell you all
about condensing boilers.
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For the purposes of today's
video we're going to use
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Grant Vortex Combi condensing boiler.
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This is the outdoor model as well.
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All I'm gonna show you in this video
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is the burner at the bottom,
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the primary heat exchanger
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and the secondary,
condensing heat exchanger.
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The first thing you
should know when comparing
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a condensing boiler to a
standard conventional boiler
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is that the heat input is very
much the same at the bottom.
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Roughly 250 to 350 degrees C.
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This is the burner, we're just
gonna pop out the bottom now.
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This part here is what inputs the heat
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at the start of the heating process.
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This burner here is likely to be fitted
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with a small nozzle that atomizes the oil,
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much like putting your finger
over the end of a hose.
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There's two electrodes that light that oil
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and that's what inputs the heat
into the combustion chamber
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and the heat exchanger
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for transferring heat into the water.
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Now I've got the burner out,
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we can have a look at the
primary heat exchanger.
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To do this remove this
front panel just here.
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So first we have the
primary heat exchanger
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which is set up
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in a group of baffles, that all slide out
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when they need to be cleaned.
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Burner fan is down in here
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so hot air, which is heated
by the burner at the bottom,
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goes though these convector fins
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and tries to keep the heat in this area
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for as long as possible
to allow the hot water
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to take heat away and
off to the radiators.
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Let's take a closer look
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at the primary heat exchanging
baffles of this boiler.
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Right, so here we have the
primary baffle area just here.
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Now remember, most boilers,
especially quite old ones,
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the baffles are really just a metal plate
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usually just about three of them
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they're at a slight angle one, two, three
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and then that flue gas
goes off out to atmosphere
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never to be gotten back again.
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Often at about 250
degrees flue temperature.
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Have another look at these here,
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this is only the start of the
heat exchanging possibilities.
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So firstly the hot gases
come up through here,
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round here, up through
this small hole here,
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like so, goes round this part here.
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Up here,
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and is again forced round
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another area.
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Round here, around the back here,
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up here, round here, round here
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and then finally out the front
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where it then goes up to
the condensing chamber.
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You have two columns
like this so straightaway
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without there even being a condensing part
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the actual standard primary heat exchanger
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is already miles more efficient.
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Because it keeps the heat in
there for as long as possible
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to allow the water a
chance to collect heat
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from that and take it
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So, heat comes out of our
two little holes at the top
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goes around, through this condensing area.
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Each one of these tubes points downwards
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and has a small, spiral fin
that goes down the middle.
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As it condenses it goes down,
causes condensed droplets.
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The condense itself is
taken away in a drain
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and disposed of safely.
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So that's the first major difference
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between a conventional boiler
and a condensing boiler.
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Most condensing boilers
are gonna be more modern
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and the primary heat
exchanging area at the bottom
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is gonna be better designed
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and have much better
capability in taking heat away
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into the water and off to your radiators.
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Secondly, we have, obviously the top part
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is the condensing chamber.
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How they work that's different.
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Most conventional boilers have a flue
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that comes out the top of the burner
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and a return that comes in the bottom,
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because generally the bottom is colder.
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So, cold water comes back
from the heating system
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in the return, is heated
up through the chamber,
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and then goes out through the
flue, back off to the rads.
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That doesn't happen with
a condensing boiler.
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The return goes into the
condensing chamber first
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picking up latent heat
from the flue gases.
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Then it goes in at the bottom
of the primary heat exchanger
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and out.
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So effectively you have two
heat exchanges instead of one.
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Right, let's just slow
down for a sec, okay?
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We'll have a quick look firstly
of a conventional boiler.
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So, we have our heat input
of 300 degrees at the bottom,
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our standard baffles,
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we have our return coming
back from the heating system.
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That water picks up that heat,
goes out through the flue
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300 degrees starts off around here
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and we lose about 250
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off to atmosphere, out through the flue.
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A condensing boiler has the
same heat input at the bottom
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has more modern baffles and
a condensing chamber on top.
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This time the return
comes back from the system
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into the connecting chamber first
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and picks up latent heat.
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Now, the reason it condenses is,
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if you imagine you breathing
on a window on a cold day
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it will condense onto that window.
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So, as cold water comes back
into this really hot area
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it will condense through here
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and a little condense
drain will take that off
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and safely dispose of it.
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After going through
this condensing chamber
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return flows down into the
bottom of our primary chamber
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takes up this heat here and
then goes off back to the system
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This time, our flue temperature
will be about 55 degrees C.
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So that shows that you
have the same heat input
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at the bottom as a conventional boiler
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but you save all this energy
because so much extra heat
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is being extracted and put into the water
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that goes off into the radiators.
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Remember, there are
two much more efficient
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heat exchanges here.
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Even when the boiler is not condensing
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because sometimes when the
return temperature is warm
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it won't condense it will
always be a lot more efficient.
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I hope you found today's
video interesting and helpful.
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If you think we haven't covered anything
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or you think we should have
done something slightly better
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please do contact us on our YouTube.
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And as ever, don't forget to subscribe.
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See you soon everyone, have a great time.
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Bye.
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