Fan Coil Units for use with a (cooling) ASHP

[joth]

8 hours ago, Dan F said:

 

If you have the spreadsheet you can make "cooling load" appear by enabling "mechanical cooling" (N29).

 

 

May not be suitable, but if i) you are building to PH standard ii) have PHPP with cooling load iii) having a heat pump, then worth considering.

 

 

I posted about this elsewhere, but for me this was the most disappointing aspect of PHPP: it only considers the building as a whole, not room by room requirements. You can do "critical room" heating load, but not cooling.

Overall our house is absolutely fine for not overheating, but our bedroom is still a problem. An MVHR  cannot keep up with moving the heat of 2 humans, so overheating is (eventually) guaranteed without some additional measures. 

If you're happy to sleep with the window and/or door open, then there's much less to worry about, but I don't because my sleep is easily disturbed by noise, and a large part of going Passive was I bought into the idea it would drastically improve sound proofing. 

Edited September 14, 2021 by joth

[Omnibuswoman]

1 minute ago, joth said:

If you're happy to sleep with the window and/or door open, then there's much less to worry about, but I don't because my sleep is easily disturbed by noise, and a large part of going Passive was I bought into the idea it would drastically improve sound proofing. 

 Yes, this is the issue. HWMBO is a very light sleeper and needs both quiet and darkness to be able to sleep well. So we never sleep with the windows open even in a heatwave. I’ve taken to sleeping in another room with the window open when we have a spell of super hot weather. 
 

We were hoping to overcome this in the new house with a combination of metal roller shutters over the bedroom windows, à la most European countries, plus some in-room cooling we can deploy ahead of bedtime (too noisy for sleep). 

[Omnibuswoman]

@joth have you built yet? Is the soundproofing level what you had hoped?

[joth]

Just now, Omnibuswoman said:

@joth have you built yet? Is the soundproofing level what you had hoped?

Yes moved in in Feb

 

Soundproofing is almost what we hoped for. Still get a faint rumble from passing goods trains (one or two a night), last week's Grand Designs says the solution to that was to build on top of a rubber mat foundation. That was never going to happen in a retrofit!!

 

The main killer of soundproofing though is having to leave a window open overnight. That means we hear almost constant train noise. 

 

The one other weird one is metal guttering  really picks up a dripping noise from the tiles and transmits through the joists  straight into the bedrooms. I may stuff some sort of fine mesh into the gutter as a drop diffuser. 

[Omnibuswoman]

Ahhh interesting. I’m quite deaf so little of this stuff even registers with me!
 

Our plot is already going to be pretty quiet (in my view) as it’s two houses back from the road, in a small village. But next door may get planning permission for five new houses, which will mean months if not years of construction work nearby. At 8am on a Saturday morning we may well be glad of the high levels of soundproofing!!

 

 

[Omnibuswoman]

5 hours ago, Omnibuswoman said:But next door may get planning permission for five new houses, which will mean months if not years of construction work nearby. At 8am on a Saturday morning we may well be glad of the high levels of soundproofing!!

 

 

News flash - I’ve just read that the planning application has now been refused again (fifth submission) so this may well not be an issue for us after all!! The local Neighbourhood Development Plan had set the area as being outside of the village boundary (the dividing line being our garden wall), and this was relied upon to decline it. 

[puntloos]

Just a note here that I found these fan coils:

 

Carrier Idrofan 42EP - 156mm (oops, not 150..) in-ceiling fan coil.

https://www.carrier.com/commercial/en/fi/products/air-treatment/hydronic-terminal-units/concealed-and-ducted-fan-coil/42ep/

http://eto.carrier.com/litterature/sdd/7579247.pdf

 

[Blynchy]

This was a fantastic thread with some great info. I was stuck trying to figure out what heating I was going to install upstairs but now I have my answer as I was looking for coolign as well. I have two quick questions for @joth

1. How are you controlling the hot water heating element and the cooling?  Do you have a 3 way valve separating the hot water tank from the buffer? and if so what controls that valve. 

2.In the summer, how quickly can heat pump go from heating to cooling operation? Does it bring up the hot water tank to temperature and then switch to cooling if necessary. I presume there is a bandwith of temperature on the hot water tank?

 

I was at the Self Build show in Dublin this weekend and spoke to a few manufactures about this idea and they were all very much against it and against underfloor cooling. To me they don't seem to understand the engineering and are just trying to flog heat pumps as easily as possible. 

[joth]

18 hours ago, Blynchy said:

 

1. How are you controlling the hot water heating element and the cooling?  Do you have a 3 way valve separating the hot water tank from the buffer? and if so what controls that valve. 

 

The buffer (LLH) feeds two circuits (GF UFH and FF FCU) each with their own circulation pump, so it's just a matter of turning on/off the relevant circulation pump, which the FTC6 manages itself. Originally I just looped the FCU fan off the zone pump, but I have a more elaborate independent variable speed control from Loxone setup now. (So in winter I can drive extra ventilation even when the zone isn't running). One snag with this is the ASHP primary pump seems powerful enough to push a slug of very hot water through the LLH and into the FCU even when the zone isn't active, e.g. when transitioning in/out of DHW mode. This maybe in part as they used a crumby mid-position valve for the heating/DHW change over, which I'll probably replace when I change the buffer for a larger one.

 

 

18 hours ago, Blynchy said:

 

2.In the summer, how quickly can heat pump go from heating to cooling operation? Does it bring up the hot water tank to temperature and then switch to cooling if necessary. I presume there is a bandwith of temperature on the hot water tank?

 

The FTC6 has a very manual switch from heating to cooling mode, so I just change it over twice a year.

It switches from DHW heating to zone cooling fine modulo issue mentioned above that I'm sure the mid-position valve has some latency/let through that means it is doing pointless work cooling the UVC for a short time, or vice versa. Unless you have an ecodan the challenges will be different depending on the exact install.

Also in summer I don't use ASHP for DHW that much as the solar divert to immersion heater does most the work.

 

 

18 hours ago, Blynchy said:

I was at the Self Build show in Dublin this weekend and spoke to a few manufactures about this idea and they were all very much against it and against underfloor cooling

 

Yeah having done it I have some sympathy for their view. On a standard (non passive) house, cooling via UFH is probably not going to achieve much and it takes a lot of effort to totally insulate all pipework and components to ensure no condensation drips anywhere. If you want really effective cooling a separate a2a heat pump is going to work much better and probably now cost that much more, once installing FCUs per room is taken into account.

I'm still improving ductwork and buffer tank to try and see if I can get mine at better efficiency this summer. The heating has just stopped coming on, so now is the time for system changes!

 

 

 

[puntloos]

On 14/03/2022 at 14:35, joth said:

Yeah having done it I have some sympathy for their view. On a standard (non passive) house, cooling via UFH is probably not going to achieve much and it takes a lot of effort to totally insulate all pipework and components to ensure no condensation drips anywhere. If you want really effective cooling a separate a2a heat pump is going to work much better and probably now cost that much more, once installing FCUs per room is taken into account.

I'm still improving ductwork and buffer tank to try and see if I can get mine at better efficiency this summer. The heating has just stopped coming on, so now is the time for system changes!

 

That's the design I'm going with, because indeed the extra price for a secondary device is "okay" in the great scheme of things - for me at least. FYI my current device cost list. Fully separate A2A with four FCUs adds maybe 10,000 and suddenly you will be pretty much guaranteed you can cool and heat your way out of any spikes in a very responsive way. No idea what the impact will be on the installation cost but I imagine it isn't going to break the bank by itself. 

 

One important thing to design properly is that you don't want the two systems fighting each other (A2A cooling and A2W heating your room)

 

Edited March 17, 2022 by puntloos

[Ommm]

Just to note that I've written some notes on how to enable cooling on Grant Aerona3 ASHPs:

https://github.com/aerona-chofu-ashp/docs/blob/main/guides/cooling.md

 

I've only tested it, haven't plumbing in cooling for real yet.  The main blocker is noisiness of FCUs (one resident is ultra noise sensitive) and so I'm trying to design a system to be as quiet as possible.  This may require some 'creative' design and experimentation, which I have more scope for on my A2W system than a traditional A2A system.  Will have to see what they can tolerate.

[joth]

9 hours ago, Ommm said:

Just to note that I've written some notes on how to enable cooling on Grant Aerona3 ASHPs:

https://github.com/aerona-chofu-ashp/docs/blob/main/guides/cooling.md

 

I've only tested it, haven't plumbing in cooling for real yet.  The main blocker is noisiness of FCUs (one resident is ultra noise sensitive) and so I'm trying to design a system to be as quiet as possible.  This may require some 'creative' design and experimentation, which I have more scope for on my A2W system than a traditional A2A system.  Will have to see what they can tolerate.

Nice write up!

 

"the ASHP is set to require a dry contact (between terminals 24 and 25) on the control PCB to activate cooling mode"

 

That's quite funny you had to disable this dry contact option - it's a nice option to have, and I really wish the ecodan FTC6 supported this as then I could have my home controller (Loxone) automatically switch the unit between heating and cooling as needed, rather than have to do it manually. Still it only needs toggling twice a year so I'm currently OK living with that.

 

[joth]

9 hours ago, Ommm said:

The main blocker is noisiness of FCUs (one resident is ultra noise sensitive) and so I'm trying to design a system to be as quiet as possible. 

IME The main issue will be the air flow noise, rather than the FCU motor. You can locate the FCU some distance away and isolate it from vibration, but the challenge is the quantity of air movement needed for any effective heat transport is always going to have some noise with it. Largest duct sizes you can manage and oversized grills and plenums is the best shot I'd imagine.

 

[Ommm]

5 hours ago, joth said:

IME The main issue will be the air flow noise, rather than the FCU motor. You can locate the FCU some distance away and isolate it from vibration, but the challenge is the quantity of air movement needed for any effective heat transport is always going to have some noise with it. Largest duct sizes you can manage and oversized grills and plenums is the best shot I'd imagine.

 

 

Agreed. The main issue with wall-hung FCUs (either radiator style, or traditional A/C wall units) seems to be that they try to pack everything into a small package, which means forcing air at moderately high pressure through relatively small apertures.  Whereas I'm looking at 200mm ducts, which means it may be possible to dial down the fan speed to keep the airflow noise down.  Also avoiding flexi ducting should help.

 

However many of the basic heat exchanger boxes don't have good datasheets so it's hard to know the relation between airflow and cooling power.  Might just have to experiment.

[offthepiste]

Am I mad? I am considering using radiators for cooling.

 

We will be relatively airtight and insulated with an MVHR and ASHP with UFH on the ground floor with low temperature, e.g. yet to be decided but probably aluminium, radiators on the uppers floors. Radiator pipework will be plastic and located in underfloor / ceiling voids.

 

Googling around and reading through this post, including https://github.com/aerona-chofu-ashp/docs/blob/main/guides/cooling.md I see comments regarding condensation and effectiveness.

 

Has anyone got real life experience of this or has a strong view against such an idea?

 

Cheers ... enjoy the hot weather whilst it lasts!

[Ommm]

You’re mad, but not for the reason I expected.

 

 I’ve been playing with 80mm fans on top of radiators with the ASHP on cooling. The problem was not condensation (which isn’t very bad) but limited surface area and lack of convection. They don’t really cool at all.

 

The convection issue is the fatal flaw. In heating systems you feed the radiator with hot water at the bottom. The hot water rises and, at the other end the cold water sinks. The outlet from the radiator is the cold water from the bottom of the other end, resulting in the heat evenly distributed across the radiator. 

 

 When you use the same setup for cooling, the cold water stays at the bottom, and the hot water stays at the top. Hence you get a strip of cold maybe 6” high at the bottom as the water passes from inlet to outlet and the rest is cool but not cold. Condensation only forms on that strip. When putting a fan on top you’re mostly passing air over the cool part, and the cold part is untouched. If you put the fan at the bottom the condensation drips on it. The radiator fins also aren’t very fine and so you’re mostly sucking air past the radiator (I can’t seal well enough to go from only the closed part of the fins). Result is a cold wet radiator but not troubling the room air very much at all.

 

 So unless you’re willing to turn your radiators upside down in the summer I don’t think they’re going to work.

[SteamyTea]

18 hours ago, Ommm said:

The convection issue is the fatal flaw.

Isn't this why we use pumped system and gravity systems these days?

[offthepiste]

Hi @Ommm did conclude I was mad. So option is possibly adding a cooling unit as part of MVHR.

 

Current plans are Zehnder ConfoAir Q600 with Enthalpy (have been flamed already on this!) and therefore considering ComfoCool Q600 as add on. May either do it now or design for it later.

 

Has anyone got any recommendations for radiators? My guess is that they will be aluminium as we will operate at low temperature. GF will be UFH throughout. ASHP will be a Viessmann split unit.

[Ommm]

4 hours ago, SteamyTea said:

Isn't this why we use pumped system and gravity systems these days?

There aren't generally pumps inside each radiator, which is what you'd need to avoid stratification.  Of course the pump is moving water around the system, but that doesn't distribute heat/cold across the surface of the radiator - we rely on convection inside the radiator to do that.

 

To do it for cooling, you'd either need a radiator with inlet and outlet plumbed at the top (cold water sinks, pushing up hot water) which would be no good for heating, or you need a serpentine tube making the radiator a long pipe run rather than a vertical body of water.

 

For example this is sold as a 'transmission cooler radiator' for a car:

https://www.amazon.co.uk/Transmission-Cooler-Auto-Manual-Radiator-Converter/dp/B08JGQQLYY/

and it doesn't matter which way it's mounted as the fluid flows through the whole loop.  A central heating radiator isn't like that - you can 'short circuit' from inlet to outlet and bypass most of the water inside.

[joe90]

48 minutes ago, Ommm said:

it doesn't matter which way it's mounted as the fluid flows through the whole loop. 

But, mounted “portrait” you will have problems getting the air out of it 🤷‍♂️

[Ommm]

3 hours ago, joe90 said:

But, mounted “portrait” you will have problems getting the air out of it 🤷‍♂️

Well yes, which is why they normally have an enormous fan mounted behind them :-)

[joe90]

10 hours ago, Ommm said:

Well yes, which is why they normally have an enormous fan mounted behind them 🙂

But a fan will not remove water just move the heat faster.

[Nickfromwales]

21 hours ago, SteamyTea said:

Isn't this why we use pumped system and gravity systems these days?

Not relevant, as this is heating which has always used circulation pumps. Gravity has been for feed and expansion only. 

[joth]

Small update on my FCU install: yesterday I finished installing one of the bedroom ducted plenums and grills.

It was a pig of a job to do. Wish I'd done it during the build rather than thinking "oh that will be easy to retrofit".

But I'm pleased with the result.

 

Just 3 more to go!!

 

This one: https://www.ventilationland.co.uk/product/35035/slot-diffuser-with-3-adjustable-slots-of-1000-mm.html - along with the plenum, costs more than the FCU  🙄

[Nickfromwales]

1 hour ago, joth said:

Small update on my FCU install: yesterday I finished installing one of the bedroom ducted plenums and grills.

It was a pig of a job to do. Wish I'd done it during the build rather than thinking "oh that will be easy to retrofit".

But I'm pleased with the result.

 

Just 3 more to go!!

 

This one: https://www.ventilationland.co.uk/product/35035/slot-diffuser-with-3-adjustable-slots-of-1000-mm.html - along with the plenum, costs more than the FCU  🙄

I went with 2x regular MVHR ceiling valves with 2x lower extracts in 225x25mm, each with their own 92mm ducts on a previous install. Was a little less ‘prominent’ than that one.

I do accept that the “joy of cool” will soon allow you to forgive and forget anything perceived as conspicuous though, as at that point it’ll defo be your best friend.
 

I do, personally, like quite a cold bedroom. When staying in hotels I always ring ahead and ask for the heating to be off in my room.