Hey there guys, Paul here from Theengineeringmindset.com. In this video we are
gonna be looking at FCUs. FCU stands for fan coil unit. Now fan coil units are very common in all types of buildings
from offices, bars, canteens, even some homes. And maybe apartments will
have a fan coil unit in them. Fan coil units are used to condition the local air to suit the
temperature requirements of the immediate space. So as you can see in this model here, we've got this space here and there's a fan coil unit in there. With the duct work going off
to feed the various parts. And then on the fan coil
unit, we've got these two. We've got these pipes running to it, which are the cooling
and heating coils inside. And the air, which has
been supplied to there, has been treated and distributed through these local duct works, to supply the required air.
So in this building model here, you can see we've got the main AHU here and that's supplying fresh
air through this main duct all the way along to the rooms. And branches will come off of this and they will feed fresh
air into the space. Each space will need a certain amount of fresh air per hour
entering into the space. So you'll have a brunch coming off and that will feed the
fresh air into them. So this fresh air is
directed into the back, the inlet of the fan coil unit. And it's usually not connected though, there's a gap in between. There is a reason for that,
which we'll look at later. And so that fresh air enters into the box, it gets sucked inside here. As a fan, we'll have a
look inside that shortly and that air gets heated or cooled and pushed out through these
diffuses into the space.
Now some of that air will recirculate up through the false
ceiling through those grills we looked at and back into this box here, whereas some of the air will be picked up into this return duct and that
will be sucked by a fan here and pushed out of the building. So the fan coil units are
located up in the ceiling. So this is a false ceiling
in a typical office. And here you can see these diffuses, these are the supply diffusers
so that treated tempered air is being supplied into, this office here, right, can circulate there and
all of it gets sent back up through these return grills. If that false ceiling wasn't there, it would look something like this. So here we got a fan coil unit. And we've got these, the duct work, which is supplying the air. These are also diffuses,
they're just slightly different from the square ones we
saw just a second ago.
So this fan coil unit is
sucking up all the air in this space and it's
passing it across here. There's a fan inside and
it's pushing across a heating and cooling coil, which treats the air to the right temperature that
it's set to for this area. And that area is then pushed
out through these duct works to be supplied out
through these diffusers, just where they're required. So this is the supply duct here. And as you can see, the
fresh air is coming in and is entering into the space above this false ceiling here
into the void above them. Now this fresh air enters
into the fan coil unit, and passes through the
fan as a filter, etcetera. We'll have a look at
that in the moment also. Once the air is treated to
the temperature it requires, it's then pushed out through the diffusers and out into the space that
pushes the air in the room, the dirty and the kind of used air up and that will then push this
through the return grill and back into the ceiling void.
Now that air is mixed
again with some fresh air and pushed through. So that loop continues. Meanwhile, some of this
returner enters into this void, is actually sucked up by this duct here. So any air that makes it to
this part will be sucked out and that will be pushed
out back out to atmosphere. Let's just have a look
inside a fan coil unit to see some of its components. So if we remove the lid, we can have a look at
inside of the fan coil unit. And as you can see, it's
actually fairly simple in design. So this is the air inlet, so it comes through this face here. This is just a removable filter.
The filters look something like this. They can just be pulled off
and they can just be cleaned or they can re replaced and that just tries to stop
the dust and stuff coming in, because that's going to be sent out through the local duct
work around the office. So the filters are just
there to try and clean some of that and remove the dust. Once that air is pulled
through the filters into the space here, it
enters into the fans.
Now in the fan coil unit
you can have just one fan, then maybe two fans and maybe three fans. There could be more, but
two fans is fairly common, in fan coil units. So driving these is a small
motor in the middle there. So that motor there is
just located in the middle and that is connected to the
fan blades inside the fans. Now these fans are usually quite small, maybe around 80 Watts
or something like this.
And they've got this
shaft through the middle. And so, on this you can
connect multiple fans. So you might have some fan blade cage here and another one on this side, they could even be extended
to have a third cage on there as well. So that air is then forced
by these fans out here. And then into this box here, this part here contains the
heating and cooling coils. Now the heating and cooling coils, they just heat the air up or cool it down depending on the requirements
for the local environment, you may have just one coil in there.
It could just be a cooling coil or it could just be a heating coil. Or you may have both of them like this, where the air can be heated or cooled. So these coils are fed, say this one's the heating coil here. So this is fed hot water from the boiler. And this coil here's the cooling one. So this is fed cold
water from the chiller. We just changed the view there. And so now the air is coming through here and imagine it's coming
towards the screen. So if this was the heating coil, then hot water is going to be entering through this pipe here and it makes its way all the way around. And as it does so loses some of its heat or if it was a cooling coil eve, as well as that loses
some of its thermal energy and transfers that over into the air, which is being forced,
out towards the screen. And that's what changes
the temperature of the air.
Now if you are cooling the
air, using a cooling coil, then you are gonna generate
quite a bit of condensation. So as that warm air is being
picked up from the space and being pushed by this
fan into the heating and cooling chamber and
when it hits the coil, it's gonna start to
condense if you're cooling. So this water, which will run off and it'll collect in this
drip tray at the bottom here. And so you also need a pipe
work, to take that water away. And in the right months,
in the summer for etcetera, in the UK, that's really
gonna be quite a lot of water you're generating. But after the air has
passed across these coils, it enters into the discharge plenum. And this is what is connected
to the local duck work and to the diffusers. So, you may have many holes on here and these will all be
sent off through duct work out to where it's required. This is how the fans will
look in the real world. So here we've got the two fan
chambers mounted to one motor and here we've got just a single fan with its very own motor.
Now the cooling coils, whether
heating and cooling coils, do not necessarily have to
be on this side of the fan, it kind of varies by manufacturer. So these coils could
also be before the fans, so that the air is coming in, passing through the filter, passes over the coils fast and then is sucked by
the fans and pushed out. But this is a very common example. Now I've put in this model
that there are the coils and that there's water
passing through these to keep up the temperature as required.
You may also find that there's
an AC unit or refrigerant, doing exactly the same job as this one. And the heating one
could be electric also, it usually depends on the size and location of the fan coil and the room. But this water type is very
common in large buildings, especially office buildings. So looking at this schematic here, of how the fan coil unit works, we've got the main AHU over here and that's supplying the air
down through these ducts, and it's supplying each of the rooms. Now, not all of the fan coil units will have this fresh air duct to them. You can see this one
here does not have that. However, each room will
have a fresh air connection because there is a requirement
obviously for each room to have a certain amount
of fresh air per hour. So that fresh air is supplied in, you can see in this example, it's coming through this duct
here and this is the filter. This is the inlet for the fan coil unit, so it's not connected and that air will be blown onto here, but also into the void.
That filter can just be removed. You can see here it's
slightly not joined there, so this can just be pulled off or slid out depending on the design and
that can even be cleaned or just thrown away and
replaced with a new one. It could be a slightly
different view there. So again, we got the fan coil unit there with the air entering and this is the fresh
air being supplied here.
And the tempered air is leaving and coming up through these ducts here. You can also tell it's tempered
by these colored arrows here pointing the direction of
the flow and indicating that the air could be hot or cold. Now on the coils, if they are supplied by hot or chilled water, then as you can see here, so we've got the border, which is feeding into
the AHU for the main one. And it also has a flow and return pipe that runs along the ceiling and connects and branches off
to each of the fan coil unit. There's also a chiller and
this is providing chilled water off to the main AHU and then down into each of the fan coil units as well.
So up in the ceiling, you're gonna see a lot of pipes like this. So here you can see we've
got the heating flow. So that's going this way in
the direction of the areas, the color bands also indicate this. And then we've got the returns, once that has given up its heat, that comes back and heads back to the boiler again on this one. So we've got the chilled water flow, so it's flowing in this direction. Think the areas actually wrong there. And then with the chilled
water return here as well. So this is going to the fan coil units and this is returning
and going the chiller and these connections
look something like this, where they're connecting
off into the cooling coils and you can see here, then
just branching off there from the main risers that
pass it along the ceiling.
And these are just branching off and feeding into the fan coil unit. Now the main AHU that's
supplying all the fresh air, for the building into the spaces, this does not necessarily
have to have these additional requirements in there for
heating and cooling coils, it could just be 100% fresh air being pushed in and pushed out. So it could be something just like this, where the air is passing straight in off into the spaces and
that air is then picked up and sent and pushed out of the building. You'll probably just have some filters on the supply there though, but you're still gonna have
your connections to the chillers and the boilers feeding off
onto the fan coil units. Unless of course your cooling is supplied by a refrigeration unit and
the heating could be electric.
Okay, that is it for this
video on fan coil units. Thank you very much for watching. I hope you've enjoyed this
and this has helped you. If it has, don't forget to
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