Fancoil plan P (yes, there’s been lots of iterations….)

[G and J]

Given the recent warm weather it's not terribly surprising that bedroom cooling has been exercising our grey cells.  (I wonder if there's a correlation between time of year for design and later overheating issues?)

We are committed to ASHP (with some cooling capability) running wet UFH downstairs and electric UFH in all bathrooms, with electric points in case but otherwise no heating provision upstairs.  But we also want cooling in the bedroom.

The most sensible option for us appears to be a single fancoil unit in our bedroom itself, probably built into the ceiling, but I thought it prudent to ask you guys for a sanity check - not on me, I failed that long ago - but on the plan/placement.


The thinking is:

The fancoil location is good for pipes inc. the condensate drain, and is away from the bed and behind a wall to help with the noise.

Under normal conditions the fancoil will be dormant and not needed for heating though it could of course be turned on to heat.

Under mildly warm conditions front and rear windows will be opened to deal with the excess heat.

When running the fancoil will push through a lot more air than the MVHR.

When in overheat conditions the doors to the bedroom and ensuite will be closed, as will the windows, and the MVHR will keep the air fresh without carrying away all the cool air.  


So folks, is the above a good plan? 

[JohnMo]

I would do a simple wall mount one. Panasonic, Cool Energy or Myson are good ones. Condensation drain, yes if flowing 5 Deg water. But if the water is going through the UFH also a flow temp of 14ish would be better to keep away from condensation issues in the floor. If you don't involve the floor in the flow path you will need a 50 plus litre buffer also to stop short cycling. Our summer house fan coil has been running for the last 6 weeks, pipes not insulated and no condensate drain, zero drips.

 

Just run the pipes from your UFH manifold as a separate loop.

[garrymartin]

It's where you see them in most hotels. Dropped ceiling in the entryway to the room with access hatch and then the grille at the end so it's pushing into the room rather than down from above.

 

Here's a few images I have saved in the little "FCU" knowledge base for inspiration...

 

 

 

[JohnMo]

Our Myson in the summer house. Big one and 4 pipe K2 heat exchanges piped in series, so I can run the same flow temps as UFH 

[G and J]

2 hours ago, JohnMo said:

I would do a simple wall mount one. Panasonic, Cool Energy or Myson are good ones. Condensation drain, yes if flowing 5 Deg water. But if the water is going through the UFH also a flow temp of 14ish would be better to keep away from condensation issues in the floor. If you don't involve the floor in the flow path you will need a 50 plus litre buffer also to stop short cycling. Our summer house fan coil has been running for the last 6 weeks, pipes not insulated and no condensate drain, zero drips.

 

Just run the pipes from your UFH manifold as a separate loop.

I did wonder if that would be enough to cool the bedroom sufficiently.  I kinda thought well, a drain won’t cost much to allow for condensate if used that way, and allowing for a zone valve to be able to be added later if needed to isolate just the fancoil would be easy too. 
 

As for the volumiser, if five days a year for a few hours a day the heat pump ran short cycles would that matter?

[G and J]

2 hours ago, garrymartin said:

It's where you see them in most hotels. Dropped ceiling in the entryway to the room with access hatch and then the grille at the end so it's pushing into the room rather than down from above.

 

Here's a few images I have saved in the little "FCU" knowledge base for inspiration...

 

 

 

In the 90’s I used travel lodges a fair bit and these ideas have reminded me of them.   I can never remember hearing the airflow or being much too hot in summer either.   Winter was different, they used have the heating on crazy.  
 

So I’ve unconsciously been inspired by a cheap roadside hotel chain.  Outstanding!  😕 

[G and J]

2 hours ago, JohnMo said:

Our Myson in the summer house. Big one and 4 pipe K2 heat exchanges piped in series, so I can run the same flow temps as UFH 

So I need to find one that fits above our bedroom door…

[JohnMo]

5 minutes ago, G and J said:

As for the volumiser, if five days a year for a few hours a day the heat pump ran short cycles would that matter?

Get the flow temperature correct you can leave the heat pump to manage cycling based on demand. You can set a very simple WC for cooling. Mine is 14.5 at 30 OAT and 15 at 20. The heat pump senses return temp and starts compressor based on need. Sun comes out  return temp rises heat pump compressor starts.

 

13 minutes ago, G and J said:

did wonder if that would be enough to cool the bedroom sufficiently.

That's all @Dave Jones is using and says his bedroom remains well cool. This our summer house, you can clearly see when the sun came out with a steep rise in temp and equally quick drop in temp.

 

 For comparison the house (temperature sensor in hall) house is just UFH cooling. The real spike in the living room is much bigger, but the cooling effect similar.

 

 

[JohnMo]

8 minutes ago, G and J said:

So I need to find one that fits above our bedroom door…

Look at Cool Energy web site

[garrymartin]

25 minutes ago, G and J said:

So I need to find one that fits above our bedroom door…

I'm not at the stage of needing to actually find a UK supplier, but Daikin advertise these from their UK site...

 

https://www.daikin.co.uk/en_gb/products/product.html/FWXM-ATV3R.html

 

Also, @joth has mentioned these before - think he has them...

 

joth on buildhub - "Mitsubishi is my M&E guy's go to make, but now we've agreed cooling is legal he's thinking Panasonic is better as it multiple flow temperatures and better cooling modes." - https://www.shopclima.it/en/panasonic-paw-fc-d15-aquarea-compact-fan-coil-with-left-side-connection-1-5-kw.html (which are actually https://www.systemair.com/en/products/air-conditioning/fan-coil-units/syscoil-comfort?sku=374272, even Panasonic notes in their literature that they don't manufacture them...) 

[JohnMo]

32 minutes ago, garrymartin said:

1 hour ago, G and J said:

 

I'm not at the stage of needing to actually find a UK supplier, but Daikin advertise

I found the following two important parameters you need to be able to adjust:

Fan starting temperature for cooling and heating. This is the water flow temperature being detected by the fan coil to give a permission for the fan to start. Not all units have these as adjustable, so worth checking. My default settings were 15 degs for cooling and 32 for heating. These were reset to 18 and 21.

 

I found some cheaper units were factory set to 35 for heating only. 

 

Also check the flow output at different flow temperatures, once you get to UFH flow temp the output of fan coils drops. My unit can do 6.5kW a delta 50, at delta 10 it's closer to 1kW.

[Dave Jones]

putting a ceiling cassette makes a whole bunch of more work, getting it airtight into the cold loft etc.

 

id put as fancoil unit higher up on a wall if your stuck for space. As long as you have good airtightness and leave the bedroom door closed  our bedrooms were at 19/20 with outside at 30 and flow temp of 16.

 

All free as there is excess of solar when its really hot!

 

I did test one of the bedrooms by turning it off and it got to 25 by dusk. Within 90 mins that room was at 19 when i turned it back on.

 

The main problem with them, apart from cost, is once you have them you can never go back.

 

[joth]

18 hours ago, garrymartin said:

I'm not at the stage of needing to actually find a UK supplier, but Daikin advertise these from their UK site...

 

https://www.daikin.co.uk/en_gb/products/product.html/FWXM-ATV3R.html

 

Also, @joth has mentioned these before - think he has them...

 

joth on buildhub - "Mitsubishi is my M&E guy's go to make, but now we've agreed cooling is legal he's thinking Panasonic is better as it multiple flow temperatures and better cooling modes." - https://www.shopclima.it/en/panasonic-paw-fc-d15-aquarea-compact-fan-coil-with-left-side-connection-1-5-kw.html (which are actually https://www.systemair.com/en/products/air-conditioning/fan-coil-units/syscoil-comfort?sku=374272, even Panasonic notes in their literature that they don't manufacture them...) 

That quote about Mitsu vs Panasonic is 5+ years ago so no idea how it applies today. I've worked with 4 different Ecodan 8.5kW installs though, so can vouch it works fine for cooling.

 

Another Daikin option is now available here: https://www.oceanairuk.com/product/daikin-fwp-2-pipe-medium-static-duct-fan-coil-unit-2-61kw-6-47kw/ 

It's actually the FWP-CT now, not -AT. (I swear these manufacturers much change model numbers more frequently than they sell units lol.)

 

 

This is the MSRP for the naked 2-pipe FCU, just takes mains input and (I believe) a 0-10V signal to control speed -- it's inverter driven so very fine grained controlled over speed vs the old 3-speed coils, which is great for anyone like me integrating it with advanced controls (e.g. Loxone). Per JohnMo comment, I put separate thermistor on the flow pipework to shut off the fan if there's a slug of warm water in the pipe (i.e. when switching from DHW reheat back to cooling)

 

But agree with Dave Jones that putting a concealed ducted unit is a lot of extra work, and especially so if retrofitting them like I did. If you can figure out a plan for the condensation drain and don't object to the aesthetic, wall mounted is a much more sensible way to go. The unit is actually inside the room being serviced, so ~100% efficient whereas the ducted ones always loose a bit of efficiency to air leaks, and the pipework and heat exchanger itself sitting inside a non-serviced space.

 

 

Edited August 19 by joth

[joth]

Ha OK actually read the OP now, rather than just the post I was tagged in 

 

@G and J is this a 2-story building, with bedroom(s) on the 1st floor?

Don't underestimate the effort it takes to add one FCU to an otherwise simple ASHP+UFH install. If you run the FCU on its own, it will have a much lower emitter size (and water volume) than the UFH so you're very likely to create short-cycling on the heat pump. Further if you run it as 2 zones you'll now need 3 circulation pumps, low loss header and electronic mixing valve (per Ecodan MIs at least, fairly typical) vs just one pump directly driving the UFH. And you lose some amount of cooling when the system switching to DHW and back. And you have to meticulously insulate all the ASHP pipework to avoid condensation (or only run it at 15+ degrees, which looses a heck of a lot of the cooling capacity which in turn increases risk of short cycling)

If doing it all again I'd look very seriously at adding a separate A2A system for the bedroom. While it maybe a bit more in materials, it really isn't that much, and the installation cost may actually be less simply because it's such a well known process to install a mini-split a2a. Can still use the ASHP for slab cooling, but this is then a very simple control system.

And this way you get two separate systems so still have some heating/cooling even if the other breaks.

Worth a look at least

 

 

[G and J]

1 minute ago, joth said:

Ha OK actually read the OP now, rather than just the post I was tagged in 

 

@G and J is this a 2-story building, with bedroom(s) on the 1st floor?

Don't underestimate the effort it takes to add one FCU to an otherwise simple ASHP+UFH install. If you run the FCU on its own, it will have a much lower emitter size (and water volume) than the UFH so you're very likely to create short-cycling on the heat pump. Further if you run it as 2 zones you'll now need 3 circulation pumps, low loss header and electronic mixing valve (per Ecodan MIs at least, fairly typical) vs just one pump directly driving the UFH. And you lose some amount of cooling when the system switching to DHW and back. And you have to meticulously insulate all the ASHP pipework to avoid condensation (or only run it at 15+ degrees, which looses a heck of a lot of the cooling capacity which in turn increases risk of short cycling)

If doing it all again I'd look very seriously at adding a separate A2A system for the bedroom. While it maybe a bit more in materials, it really isn't that much, and the installation cost may actually be less simply because it's such a well known process to install a mini-split a2a. Can still use the ASHP for slab cooling, but this is then a very simple control system.

And this way you get two separate systems so still have some heating/cooling even if the other breaks.

Worth a look at least

 

 

Yep, two storey our bedroom upstairs and not huge solar gain as not huge windows and few south facing.  I’m now erring towards a single zone UFH and fancoil run just above dew point as per @JohnMo.  So at least I’ve got someone to blame lol

 

I could mount an A2A cooling unit in our cold loft, I guess I’d worry about noise and servicing it, as it’ll be a crawl through fink trusses by the time I’ve laid all the insulation up there with some crawl boarding on top.  

[joth]

21 hours ago, garrymartin said:

Here's a few images I have saved in the little "FCU" knowledge base for inspiration...

 

Those are great diagrams of a simple concept I've explained many times in words and bad pictures haha

Do you have a link to this knowledge base? 

Thx

 

[joth]

2 minutes ago, G and J said:

Yep, two storey our bedroom upstairs and not huge solar gain as not huge windows and few south facing.  I’m now erring towards a single zone UFH and fancoil run just above dew point as per @JohnMo.  So at least I’ve got someone to blame lol

 

If you are happy to self install (or can find someone else competent enough to do it professionally) this will work, just bear in mind if doing it above dew point it's much more of a low-and-slow cooling power rather than the icy hurricane-on-demand you can command on an a2a. 

And always run UFH+FCU together to minimize short cycling.

 

 

 

[garrymartin]

2 minutes ago, joth said:

Do you have a link to this knowledge base?

The knowledge base I referred to is my own. I use a package called Obsidian to create a Personal Knowledge Management (PKM) system for all sorts of things, but I have a dedicated one for everything related to the (hopefully) future build.

 

Those particular images came from this site though https://www.hotelsuniversity.com/hotel-hvac-systems-what-are-my-options-part-2/

[mjc55]

1 hour ago, garrymartin said:

The knowledge base I referred to is my own. I use a package called Obsidian to create a Personal Knowledge Management (PKM) system for all sorts of things, but I have a dedicated one for everything related to the (hopefully) future build.

 

Those particular images came from this site though https://www.hotelsuniversity.com/hotel-hvac-systems-what-are-my-options-part-2/

 

Looks interesting.  Was thinking that I need something to link together thought processes and checklists that I currently use Excel for.

 

Big learning curve or something that is easy to d/l and run with?

[garrymartin]

1 hour ago, mjc55 said:

 

Looks interesting.  Was thinking that I need something to link together thought processes and checklists that I currently use Excel for.

 

Big learning curve or something that is easy to d/l and run with?

Super easy to start with and you can get as complicated and complex as you like through add-ons.

 

I mostly keep it super simple - it's just text, images, and inline documents with various links externally and internally to the PKM.

 

[Bancroft]

21 hours ago, garrymartin said:

Super easy to start with and you can get as complicated and complex as you like through add-ons.

 

I mostly keep it super simple - it's just text, images, and inline documents with various links externally and internally to the PKM.

 

 

Oh great, I came here to do some research on heating/cooling and now you've got me heading down an Obsidian rabbit hole...🤦‍♂️

 

[JohnMo]

8 minutes ago, Bancroft said:

 

Oh great, I came here to do some research on heating/cooling and now you've got me heading down an Obsidian rabbit hole...🤦‍♂️

 

Don't do it, you will spend too much time looking at stupid computers and get nothing real done. 

 

I pretty much took the opposite approach, research, decide, put on plan. Freeze that bit of the plan. Otherwise procrastination takes over. Stopped looking on here once build started to stop any tangents.

[garrymartin]

43 minutes ago, JohnMo said:

I pretty much took the opposite approach, research, decide, put on plan

Whilst I need to get planning permission first before I can start thinking about a plan, that's pretty much my approach.

 

Each of my "research" notes has a section at the top for "design decisions". At the point I go to plan (or to discussions with specialists to create the plan), I'll just take the design decisions as they stand at that point in time.

 

In the meantime, I have the opportunity through research (including here) to refine my understanding. My heating and cooling section is a great example where I'm constantly adding research and important little pieces of information, experience, or wisdom. The "design decisions" start with "Expensive fabric = cheap heating" and "Simplest system possible, even if that means a little more complication/cost in installing it in the first place" for example.

[G and J]

On 19/08/2024 at 09:46, joth said:

And always run UFH+FCU together to minimize short cycling.

That’s how we will start, and hopefully stay.

 

If faster cooling is needed the valves and a volumiser will be added laterer.

[joth]

1 hour ago, G and J said:

If faster cooling is needed the valves and a volumiser ** will be added laterer.

** ..and lots of insulation / condensation management... 

Good luck, however it goes!