FCU Location and Dimension Practicalities

[puntloos]

My current forerunner is the M25DA R32 Coolant FCU from Mitsubishi -spec attached (link). They have multi. models but  I've put in blue the sizes pertaining to this one.

The specs say "WxDxH - 790x700x200"

 

Height: I don't care *too* much about the width and depth but am I correct that this device will fit in a ceiling void of 210mm? Or will for example pipes coming out of the thing need more space above, to the side, below? I don't see any of this, but I can certainly imagine pipe runs will need to be planned somewhat carefully.

 

Overall size: I have a ceiling void of 210mm: (ignore the cold bridge, that's another matter)

 

 

 

But more specifically, I want:
One FCU to service my livingroom (adjacent) to limit noise generated

-> Can I put the livingroom FCU in the office, or will that not matter - since the 'output' still is a direct opening

-> Should the FCU air output "point" at the livingroom (#2) ? Or input and output parallel to livingroom(#1)?

 

One FCU to serve the office

- Can put it anywhere in principle, but where would you actually put it? Note the shaft to the ASHP etc is in the top left corner.

 

The networking closet air extract

Needs to go from the closet to the shaft. Under the FCUs (eating into cupboard)? Or should we pipe around it? Through it, perhaps?

 

Air that goes *into* the FCU

Where does this air come from? I imagine i have to supply the air from the loft (from shaft) or can we use the office air? (Underpressure doesn't seem good?)

 

 

Perhaps take a look at the attached image: (I'm drawing them below the actual ceiling so you can see what's going on)
 

 

 

SEZ-M-R32-annotated.pdf

Edited December 9, 2021 by puntloos

[joth]

One trick is to lower the ceilings in an ancillary space (e.g. the Hall if it had standard height ceiling) and then put the FCU in the doorways into the important rooms, so it spits into the room through a wall, often via a vent above the doorway. In practice I think this means placing the lintel high (if it's a supporting wall) so the door is full height of the room, then framing it out below the FCU to build out the door frame.

This has the added benefit of making the living areas feel bigger as you enter them as you're coming in from the lower ceiling corridor into the taller room.

 

Obviously need to take care about sound leakage through the big hole poked in the wall.

 

Hotel rooms are often built this way too (lowered ceiling in the "lobby area, example) around the door, bathroom, minibar before entering the room itself, and continental apartments often are too.   Or using a dropped pelmet around a room.

 

I think in your plans, you could consider lower ceiling in the office (or an area of it) and have the FCU blow into the living room from there. (Need to check the return airflow path is sufficient for that / might have to duct both the intake and supply paths)

 

FCUs work in recirculating mode. In general, if putting the FCU "in" the room it serves, it draws intake air directly from that same room and vents back out into it, generally one or other would be ducted to try and get the in and out vents far enough apart to perturb enough air that the whole room cools down. Putting the MVHR outlet / fresh air supply close to the FCU intake means the FCU has added benefit of moving the fresh air around the room too. (I can show you all of this on a super scale model in an office near Kings X, if we're ever in that area around the same time ?)

 

Take a look at "linear slot diffusers", these can make for a stylish  feature. If they continue unbroken along and edge of a room, it doesn't even stand out as M&E services at all. 

https://www.pinterest.com/rmurphy1981/linear-slot-diffusers/

 

[puntloos]

4 hours ago, joth said:

One trick is to lower the ceilings in an ancillary space (e.g. the Hall if it had standard height ceiling) and then put the FCU in the doorways into the important rooms, so it spits into the room through a wall, often via a vent above the doorway. In practice I think this means placing the lintel high (if it's a supporting wall) so the door is full height of the room, then framing it out below the FCU to build out the door frame.

This has the added benefit of making the living areas feel bigger as you enter them as you're coming in from the lower ceiling corridor into the taller room.

 

Obviously need to take care about sound leakage through the big hole poked in the wall.

 

Yes this is one of my main questions, does all the noise come out of the 'diffuser' (as you pointed out below) anyway, or is the entire thing the noise-box and having it on the other side of a wall will be a big benefit?

 

4 hours ago, joth said:

 

Hotel rooms are often built this way too (lowered ceiling in the "lobby area, example) around the door, bathroom, minibar before entering the room itself, and continental apartments often are too.   Or using a dropped pelmet around a room.

Yeah I've seen this. Surprisingly elegant way to hide things. But I'm not sure I even need it with my fairly generous void.

 

 

4 hours ago, joth said:

 

I think in your plans, you could consider lower ceiling in the office (or an area of it) and have the FCU blow into the living room from there. (Need to check the return airflow path is sufficient for that / might have to duct both the intake and supply paths)

 

FCUs work in recirculating mode. In general, if putting the FCU "in" the room it serves, it draws intake air directly from that same room and vents back out into it, generally one or other would be ducted to try and get the in and out vents far enough apart to perturb enough air that the whole room cools down. Putting the MVHR outlet / fresh air supply close to the FCU intake means the FCU has added benefit of moving the fresh air around the room too. (I can show you all of this on a super scale model in an office near Kings X, if we're ever in that area around the same time ?)

Ha, not anytime soon I'm afraid!

But indeed if it's 'recirculating' then of course again drawing one room vacuum doesn't seem optimal  It seems more logical to indeed have the fresh air come from there.

 

4 hours ago, joth said:

 

Take a look at "linear slot diffusers", these can make for a stylish  feature. If they continue unbroken along and edge of a room, it doesn't even stand out as M&E services at all. 

https://www.pinterest.com/rmurphy1981/linear-slot-diffusers/

 

 

Yeah these look great, something like that sounds very good. Thanks for the tips. 

[joth]

17 hours ago, puntloos said:

Yeah I've seen this. Surprisingly elegant way to hide things. But I'm not sure I even need it with my fairly generous void

 

Couple thoughts:

- the closer the tolerance on anything, the greater the risk it doesn't work in practice due to unforeseen whatever. A contractor will always charge more contingency on very tight tolerance work, or try and pass on extra costs if it doesn't work out, or bodge something inelegant

- ideally you need enough space to ensurr the fcu is hung on tension rods to reduce vibration transfer to upstairs, and to ensure it is perfectly level so the condensation tray clears properly

- the condensate needs additional vertical drop below the FCU so the horizontal drain pipe can be angled downwards slightly, to drain reliably. The nearest the FCU is to a vertical waste pipe the easier this drain run will be (less slanting drop required)

If really stuck you can use a condensate pump, but that feels like defeat to me

 

Edited December 10, 2021 by joth

[puntloos]

On 10/12/2021 at 08:56, joth said:

 

Couple thoughts:

- the closer the tolerance on anything, the greater the risk it doesn't work in practice due to unforeseen whatever. A contractor will always charge more contingency on very tight tolerance work, or try and pass on extra costs if it doesn't work out, or bodge something inelegant

- ideally you need enough space to ensurr the fcu is hung on tension rods to reduce vibration transfer to upstairs, and to ensure it is perfectly level so the condensation tray clears properly

- the condensate needs additional vertical drop below the FCU so the horizontal drain pipe can be angled downwards slightly, to drain reliably. The nearest the FCU is to a vertical waste pipe the easier this drain run will be (less slanting drop required)

If really stuck you can use a condensate pump, but that feels like defeat to me

 

 

These are very good points, thank you. I think that with my current FCU type being 200mm and my void 210mm I can stuff it in there but actually not do any of the hanging and draining you mentioned.  

 

Instead, perhaps lowering my office ceiling by perhaps 5cm might give me the space I need to put the 2 FCUs in there elegantly.

[puntloos]

A bit of an update here:

 

The Mitsubishi FCU in question is below: 

 

My read is that from the drain pipe, which sits at 170mm from the top of the device, needs a 1:100 slope (1cm down for every 100cm)

And, my ceiling void, being currently 210mm, will therefore have 40mm (210-170) fall. 40mm fall means 4000mm distance can be traversed.

 

But guess what, even as it stands, the current designed drain run is more than 4m: (sadly the drain output is as indicated in the picture below:)

Is that correct? If carefully installed of course, as per @joth point, a 4m drain would leave 0 room for any imperfections. Instead, perhaps at least I'd need to create a new drain in the center pillar - that would reduce drain run to 3m.. 

 

 

[TonyT]

Condensate pump can collect and pump a longer distance if required.

 

[puntloos]

One thing I'm still considering is noise levels. The FCUs are "pretty quiet" - 30db on max, 25 on min. But straight above your head... i'm not sure if it's ideal (my town is fairly quiet).

 

- How long can an air outlet pipe be without trouble?

- Will the air outlet pipe still be the major source of the noise? Or will moving the main device into the office be a big noise improvement?

 

 

[puntloos]

Quick ping - How long can the exhaust and intake pipes be to a device like this?

[TonyT]

Have a look at DW144 use in conjunction with manufacturer info.