Fan Coil in Loft

[Mr Blobby]

Has anyone on here actually installed an FCU like this (or similar unit) in the loft, for cooling, connected to an ASHP and with the exhaust grill in the ceiling?

 

 

 

If so then please tell me more about the install and what is needed.  

How is the FCU ducted to the exhaust vent?  

Did you install it vertically?  

Did you use ducting from the FCU to the grill in the ceiling?

 

Some pictures would be lovely.

 

[JohnMo]

Watching with interest

[Nickfromwales]

12 minutes ago, Mr Blobby said:

Has anyone on here actually installed an FCU like this (or similar unit) in the loft, for cooling, connected to an ASHP and with the exhaust grill in the ceiling?

 

 

 

If so then please tell me more about the install and what is needed.  

How is the FCU ducted to the exhaust vent?  

Did you install it vertically?  

Did you use ducting from the FCU to the grill in the ceiling?

 

Some pictures would be lovely.

 

The loft is within the heated, airtight envelope, ya? 

[IanR]

26 minutes ago, Mr Blobby said:

Has anyone on here actually installed an FCU like this (or similar unit) in the loft, for cooling, connected to an ASHP and with the exhaust grill in the ceiling?

Thinking about it, but not done yet.

Have you got a reason for wanting to take air from the loft and circulate it to the room below?

Typically you'd recirculate the air within a closed off room, ie. inlet and return into the same volume. It's not going to be powerful enough to cool/heat the whole house with a single unit.

Edited Wednesday at 18:17 by IanR

[Mr Blobby]

15 hours ago, Nickfromwales said:

The loft is within the heated, airtight envelope, ya? 

 

Yes, warm airtight loft.  

Plenty of room to install a pair of these in the eaves, one over each SW facing bedroom that are most likely to overheat.

I think taking the intake air from the loft will be ok, as it would mean only one grill in the ceiling, and easy access to change filters. 

 

The supplier tells me the FCU in the above image can only be installed horizontally because of condensate tray (although I would be running above dew point).  

 

15 hours ago, IanR said:

Have you got a reason for wanting to take air from the loft and circulate it to the room below?

 

I don't really want to build a bulkhead like a premier inn bedroom.  I would prefer a single exhaust grill in the ceiling facing downwards.  This would leave the FCU higher in the loft which would also  make for an easy connection from FCU condensate drain to the pipe connected to the condensate drain in the MVHR, leaving the option to run below dew point, should I ever wish to do so.

 

15 hours ago, IanR said:

Typically you'd recirculate the air within a closed off room, ie. inlet and return into the same volume. It's not going to be powerful enough to cool/heat the whole house with a single unit.

 

This is a good point, the air in the loft being potentially warmer than the target bedroom.  This is not really to cool the whole house as we have cooling in the slabs and some external blind and solar glazing.  But I am concerned about two SW bedrooms that may be at risk of solar gain overheating. 

 

Maybe building a bulkhead is easiest.  Otherwise the challenge is connecting ducting from hotizontal FCU in loft to a single grill in the ceiling. It would be a 90 degree angle and about less than 1 metre length.

Has anyone done this or similar?

Edited Thursday at 10:00 by Mr Blobby

[Nickfromwales]

6 minutes ago, Mr Blobby said:

I think taking the intake air from the loft will be ok, as it would mean only one grill in the ceiling, and easy access to change filters. 

It’ll feck your MVHR flow up quite a bit? You’re suppose to recirculate the air in the room, boss

 

Last one I did this on I installed 2x 92mm Ubbink radial runs to letterbox sized extract points (22x 225mm) with one in each far corner of the room vs 100% of the airflow at the one vent (for sound mostly, but also for more even flow of the cooled air throughout the room). The bedrooms with direct cooling had a communal attic space with vaulted ceilings, so the idea was to have the FCU grille in the vertical wall direct off the FCU, flow the air in at the top and let it blanket down, across the whole bedroom, and then exit via the 2x letterbox grilles (I installed these at socket height to blend in a bit).

Using a transfer grille in the landing outside of the bedrooms could see air from bathrooms being pulled towards this, with positive air being forced out of the MVHR inlet. Not. A great idea to not have these properly recirculate, and I wouldn’t do this if it was my own job. 
Maybe create a pelmet, and use that as the hidden extract point? Without being there it’s a bit sketchy to advise obvs…

[IanR]

Have you got the install instructions for the FCU you have imaged?

 

Does in not install 180º from the way it is pictured, inlet at the horizontal and outlet at the vertical?



You mention keeping above dew point. What kW of cooling are you expecting from a 14°C water feed?

 

They're really for single room recirc.

My loft is the warmest place in the house, often around 26°C. I think you'll be warming the bedrooms below rather than cooling.

Edited Thursday at 10:04 by IanR

[Nickfromwales]

1 minute ago, IanR said:

Have you got the install instructions for the FCU you have imaged?

 

Does in not install 180º from the way it is pictured, inlet at the horizontal and outlet at the vertical?



You mention keeping above dew point. What kW of cooling are you expecting from a 14°C water feed?

 

They're really for single room recirc.

The airflow would be reversed to what you’ve shown here? Cooled air is always sent out high?

[Mr Blobby]

18 minutes ago, IanR said:

 

Does in not install 180º from teh way it is pictured, inlet at the horizontal and outlet at the vertical?

 

I think that's actually the right way up, the intake sucks air in at the bottom and spits it out the front.

 

18 minutes ago, IanR said:

You mention keeping above dew point. What kW of cooling are you expecting from a 14°C water feed?

 

Not much, but hopefully better than just slab cooling, esp in bedrooms with solar gain and carpets on the floor.  And we are in Northern Ireland where it rarely gets above 23C on a summers day.

 

I'm getting the impression that pelmet is the way to go here 🤪

Edited Thursday at 10:20 by Mr Blobby

[Wil]

I’m also considering this (and this company) but was going to install above the ceiling rather than create a bulkhead. My requirement is primarily heating but cool at high temp (above dew point) would take the edge off in summer. Use MDF to form plenums for the supply/ extract from the room.

 

My experiments with various fan rads have shown that fan noise in bedrooms is totally unacceptable- even the motorised TRVs are annoying.. So the aim is to get this outside the rooms acoustically and potentially have some sort of baffle for the fan noise (which just adds complication and is the reason I haven’t progressed. Plan is to hang the FCU on catenaries to avoid vibration.

[crispy_wafer]

Slightly different take, I've installed a couple of ducted FCU's in the loft space and one in the base of a cupboard, supply and extract ducting traversing loft spaces and eaves to the bedrooms and downstairs.  Mine are A2A rather than A2W units though.

[joth]

19 hours ago, Mr Blobby said:

Has anyone on here actually installed an FCU like this (or similar unit) in the loft, for cooling, connected to an ASHP and with the exhaust grill in the ceiling?

 

 

 

If so then please tell me more about the install and what is needed.  

How is the FCU ducted to the exhaust vent?  

Did you install it vertically?  

Did you use ducting from the FCU to the grill in the ceiling?

 

Some pictures would be lovely.

 

Yes, this will be the fourth summer running it.

It's a systemair FCU rebranded as Panasonic. Ducted into linear supply grills in three bedrooms.

All documented and photos in the OG FCU thread here

 

Linear grills

 

 

I had a custom output  plenum made for the FCU by ductstore.co.uk

 

 

Edited Thursday at 13:12 by joth

[Nickfromwales]

3 hours ago, Wil said:

I’m also considering this (and this company) but was going to install above the ceiling rather than create a bulkhead. My requirement is primarily heating but cool at high temp (above dew point) would take the edge off in summer. Use MDF to form plenums for the supply/ extract from the room.

 

My experiments with various fan rads have shown that fan noise in bedrooms is totally unacceptable- even the motorised TRVs are annoying.. So the aim is to get this outside the rooms acoustically and potentially have some sort of baffle for the fan noise (which just adds complication and is the reason I haven’t progressed. Plan is to hang the FCU on catenaries to avoid vibration.

Remember that the airflow rate will be quite high for cooling, think of every hotel you’ve stayed in, so audibility will be something you won’t obliterate.

[Mr Blobby]

On 06/03/2025 at 13:10, joth said:

 

I had a custom output  plenum made for the FCU by ductstore.co.uk

 

 

Your pic above is very neat.  Two of these (intake and exhaust) in each room would be great as an alternative to a pelmet, but how did you connect this grill(s) to the plenum?  

Do you have any pics of the ducting in the loft?  Did you buy all the ducting and grills from ductstore.co.uk?