Fancoil - Best invention ever no contest!

[Dave Jones]

36C outside yesterday. The aquarea purring away at 16c (ramping up/down automatically to keep the right side of the wet bulb). walking into the ground floor is like walking into a fridge even theough its 21, the ufh loop does its work.

 

The bedrooms though with the panasonic fan coils are sitting at 21 while the bathroom and landing are 26/8. 

 

CoP is reported as 27, although i guess its not setup for cooling ? Free anyway with the mega excess of solar.

 

 

added the new 2025 model into the loft and also included the condensate drain, this is the largest unit they do and the heat exchanger is about 80cm wide so should  be a beast for cooling.

 

[haythorn_1]

Where did you buy the fan coils from?

[Dave Jones]

huws grey ordered them in.

[Alan Ambrose]

How noisy do you find these?

[Ben1984]

I am currently trying to work out a spec for our fan coils, wondering if you can help with a couple of questions please:

I can get away with relatively small units if i size them for heating - is it worth oversizing them for cooling and/or quieter operation?
Is there any meaningful difference between a ceiling and wall mounted unit in terms of performance (assuming everything else is equal)?
I am currently planning to have 1 unit in each bedroom - should I consider adding 1 or 2 units downstairs in the main living space? EDIT: For clarification I will have UFH throughout the ground floor, the fan coils would simple add some extra cooling in the summer.
 

Edited Monday at 14:12 by Ben1984

[JoeBano]

32 minutes ago, Ben1984 said:

I am currently trying to work out a spec for our fan coils, wondering if you can help with a couple of questions please:

I can get away with relatively small units if i size them for heating - is it worth oversizing them for cooling and/or quieter operation?
Is there any meaningful difference between a ceiling and wall mounted unit in terms of performance (assuming everything else is equal)?
I am currently planning to have 1 unit in each bedroom - should I consider adding 1 or 2 units downstairs in the main living space?
 

. 

I’ve got myson ivectors (1000x600) fan coil units, 

1930’s detached outside walls insulated to 0.3 U-value. Running a flow temperature -2 35c on lowest fan speed nice and quiet. Now it’s 32c outside running it at 15c just above dew point and its fan speed 3 to keep 21c. So If you are thinking about cooling more than heat, insulated pipe work to run lower than dew point or bigger units if you can’t insulated pipework. These Panasonic units are a nice looking unit, some are nasty out there. 

[JohnMo]

30 minutes ago, Ben1984 said:

can get away with relatively small units

Generally no, they are sized the same as radiators in a lot of respects. So during heating the cooler the flow the bigger the radiator or fan coil is going to be. Cooling is the same the warmer the flow the bigger they need to be. A unit with a water flow temp of 7, will be half the size compared to one flowing 14 degs, in rough terms. You need to read the datasheet and size accordingly. But a fan coil is generally a lot smaller than a radiator of the same output.

[Dave Jones]

45 minutes ago, Ben1984 said:

I am currently trying to work out a spec for our fan coils, wondering if you can help with a couple of questions please:

I can get away with relatively small units if i size them for heating - is it worth oversizing them for cooling and/or quieter operation?
Is there any meaningful difference between a ceiling and wall mounted unit in terms of performance (assuming everything else is equal)?
I am currently planning to have 1 unit in each bedroom - should I consider adding 1 or 2 units downstairs in the main living space? EDIT: For clarification I will have UFH throughout the ground floor, the fan coils would simple add some extra cooling in the summer.
 

 

dont need downstairs the UFH loop keeps it like a fridge.

 

get the larger of the three and leave them on auto 24 x 7, no more noise than a typical indoor AC unit. 

 

If its put up with a fan or 32C i know which i'll pick!

[Ben1984]

12 minutes ago, JoeBano said:

. 

I’ve got myson ivectors (1000x600) fan coil units, 

1930’s detached outside walls insulated to 0.3 U-value. Running a flow temperature -2 35c on lowest fan speed nice and quiet. Now it’s 32c outside running it at 15c just above dew point and its fan speed 3 to keep 21c. So If you are thinking about cooling more than heat, insulated pipe work to run lower than dew point or bigger units if you can’t insulated pipework. These Panasonic units are a nice looking unit, some are nasty out there. 

Thanks, I'm currently looking at concealed units - I can get a 5KW unit that has a grill measuring ~900mm x 200mm that should (in theory) meet the heating requirements of the room or I can spend an extra ~£250 and get a 11KW unit with a grill that measures 1600mm x 200mm. Trying to decide if it's worth paying more and getting a larger unit with noise and cooling in mind.

[Dave Jones]

the issue you will have is running the ASHP cold enough for those industrial size units will be waaaaay to cold for the UFH loop. will get condensation everyhere, any missing lagging and it will be dripping out. The dew point today for us is 21c and you can feel the humidity, still ok at 17c flow temp though as its only peking for a few hours.

[Ben1984]

Has anyone on here run water below dew point (~7 degrees) through their fan coils? - The reading/research I've done suggest most people run it around 14/15 degrees. I am happy to insulate the pipework to the fan units, but I think I'd still be a bit concerened about dew forming in voids if I ran it at 7 degrees

 

[Ben1984]

1 minute ago, Dave Jones said:

the issue you will have is running the ASHP cold enough for those industrial size units will be waaaaay to cold for the UFH loop. will get condensation everyhere, any missing lagging and it will be dripping out. The dew point today for us is 21c and you can feel the humidity, still ok at 17c flow temp though as its only peking for a few hours.

Why would I need to run the ASHP at a colder temperature for a larger unit? I was under the impression that I could achieve more cooling with a larger unit without reducing the flow temperature. 

[Dave Jones]

though you were on about running it 7c below dew point ?

[joth]

14 minutes ago, Ben1984 said:

Has anyone on here run water below dew point (~7 degrees) through their fan coils? - The reading/research I've done suggest most people run it around 14/15 degrees. I am happy to insulate the pipework to the fan units, but I think I'd still be a bit concerened about dew forming in voids if I ran it at 7 degrees

 

Yes I originally ran my FCU at those sorts of temps, while all the pipework is well insulated the snag is all the valves, pumps, mag filter, flow sensor etc etc. There's a lot of extra "gubbins" inline in an ASHP install (at least, there is in mine) and it's really onerous so lag all those components, not to mention makes maintenance of them harder. And even when I tried I found condensation was forming due to tiny gaps and then e.g. the pump gate vales starting to corrode over.

So on balance I now just run mine at dew point. (some stuff still gets a little glistening with beads of sweat but no river of condensate running everywhere)

 

19 minutes ago, Dave Jones said:

waaaaay to cold for the UFH loop

This point was easily avoided in my installs: ecodan has two zones with independent setpoints, using an electronic mixing valve, so with the loxone load/weather curve the UFH generally ticks over at 18C flow temp while the FCU at around 12C (due to GF not needing as much cooling as upstairs)

 

[joth]

One thing to note is sizing depends on the air source going into the FCU.

My 2 FCUs are in the loft, so pulling fairly warm air in summer (and cold in winter, if I ever used them for heating. I don't). So my FCU have higher realized output power than if the air coming into it was already "pretty cold". (Output power is determined by the delta between air inlet temp and the water temp, and air flow rate).

If you have the FCU in the room being cooled, and down at floor height (where air is naturally cooler anyway) it will not have as much effective output than if you are drawing in hotter air from higher up. Hence why split aircon units are normally installed up high. (but rads installed down low) 

 

 

Edited Monday at 15:08 by joth

[Ben1984]

Thanks Joth, some useful insight. I was very sceptical about putting water through the FCU below dew point and it sounds like I was probably right to be.

I think I will go for ceiling or concealed wall (mounted high up) units in the 5 bedrooms and rely on the UFH downstairs for cooling. Aiming to run everything at the same temperature (~15 degrees for cooling and ~40 degrees for heating).

Still not entirely sure how to size the units in the bedrooms if they are primarily there for cooling, i'll speak to some of the companies selling them.

[JohnMo]

9 minutes ago, Ben1984 said:

40 degrees for heating

That is pretty hot for UFH, unless you are a retrofit or batch charging on a smart tariff. Its still pretty hot. I would be running a weather compensation curve.

[Ben1984]

2 minutes ago, JohnMo said:

That is pretty hot for UFH, unless you are a retrofit or batch charging on a smart tariff. Its still pretty hot. I would be running a weather compensation curve.

Interesting, I thought that was quite cool! This is obviously something else I need to look into! I have no idea what a "weather compensation curve" is. 

[JohnMo]

5 minutes ago, Ben1984 said:

weather compensation curve

Basics are the colder it is outside the hotter the flow temp you have and vice versa. I find it regulates house well, there are no thermostats used for heating or cooling. Only deviation from that is if I have excess solar PV I have a smart relay set a second set point on the ASHP to add 3 degs to WC curve in heating and remove 1 Deg to cooling.

 

As an example, my WC curve runs from 20 degs outside with a flow temp of 25, then at -9 outside I flow 32.8 degs.

 

Reality is at about 10 degs average outside the cooling goes on. So I run either cooling or heating only.

[Ben1984]

22 minutes ago, JohnMo said:

Basics are the colder it is outside the hotter the flow temp you have and vice versa. I find it regulates house well, there are no thermostats used for heating or cooling. Only deviation from that is if I have excess solar PV I have a smart relay set a second set point on the ASHP to add 3 degs to WC curve in heating and remove 1 Deg to cooling.

 

As an example, my WC curve runs from 20 degs outside with a flow temp of 25, then at -9 outside I flow 32.8 degs.

 

Reality is at about 10 degs average outside the cooling goes on. So I run either cooling or heating only.

Thanks, it makes perfect sense.

I am slightly surprised that you can achieve ~20 degrees internal temperatures when it's -9 outside with a flow temp of just 32.8 degs.

I've had a few quotes for ASHP ,they have all been working off 45 degree flow - If I run it on a WC I assume I would need more pipework in my UFH and a smaller ASHP?

[JohnMo]

35 minutes ago, Ben1984 said:

am slightly surprised that you can achieve ~20 degrees internal temperatures when it's -9 outside with a flow temp of just 32.8 degs.

Our floor area is 192m² and we have a heat demand of 3.5kW, so it's really a huge radiator. We only have about 600m of pipe in the floor, at around 300mm spacing.

 

Generally when you get to low outputs from UFH pipe spacing makes very little difference to flow temperature required, but it does change reaction time. But running low and slow and on all the time reaction time is not really a factor that is important.

 

35 minutes ago, Ben1984 said:

smaller ASHP

No, you size the heat pump based on kW required. Flow temp really has a big impact on running costs, with heat pumps the lower the flow the better.

Edited Monday at 20:31 by JohnMo

[Ben1984]

10 minutes ago, JohnMo said:

Our floor area is 192m² and we have a heat demand of 3.5kW, so it's really a huge radiator. We only have about 600m of pipe in the floor, at around 300mm spacing.

 

Generally when you get to low outputs from UFH pipe spacing makes very little difference to flow temperature required, but it does change reaction time. But running low and slow and on all the time reaction time is not really a factor that is important.

 

No, you size the heat pump based on kW required. Flow temp really has a big impact on running costs, with heat pumps the lower the flow the better.

Thanks (again). I thought i'd got my head around the ASHP/heat calculations but I clearly have more to learn.

I worked out my heat loss to be in the region of 6.5KW (internal floor area of 390m2) allowing another ~2KW for hot water and adding on a bit extra I thought I would need an 8-10KW ASHP. But the quotes I'm getting from installers are for 12-18KW ASHP's. I thought this was because they were assuming a flow temperature of 45 degrees, but your post suggests that isnt the case.

 

I'm still as confused as I was when I strated researching this! I will re-visit this tomorrow.