Ducted chilled water fan coil options

[HughF]

I’m looking at throwing a ducted fan coil (extract from the hallway, return into the bedrooms) into the loft. Does anyone have any good recommendations for a unit that is quiet, has simple on/off controls?

 

Looking to add a ‘cooling’ circuit to my system as the girls in the house are of a certain age and are struggling in this summer heat. 

[JoeBano]

I was having a look yesterday for my kitchen, found theses https://theheatpumps.co.uk/products/chilled-water-fan-coil-units.html 

I have no idea how quiet they are. Might be a starting point…. 
ive got myson Ivectors in the bedrooms quieter than a normal fan blowing about, managed to keep the bedrooms at 20-21 while it was 29c outside without insulating the pipework. They are control by heatmiser fan coil stat 

[HughF]

2 hours ago, JoeBano said:

I was having a look yesterday for my kitchen, found theses https://theheatpumps.co.uk/products/chilled-water-fan-coil-units.html 

I have no idea how quiet they are. Might be a starting point…. 
ive got myson Ivectors in the bedrooms quieter than a normal fan blowing about, managed to keep the bedrooms at 20-21 while it was 29c outside without insulating the pipework. They are control by heatmiser fan coil stat 

That’s an option for sure. Replace the bedroom rads with wall mount fan coils. I was thinking a separate unit and ducting would make pipe work easier as when I replumbed I didn’t consider cooling so made a few mistakes with pipe runs and lack of zoning. Not an issue with heating but certainly an issue if I want to cool, I’d need to valve off the existing fan coils which don’t have a condensate pan, and the rads. They’re all on the same zone.

[JohnMo]

23 minutes ago, HughF said:

I’d need to valve off the existing fan coils which don’t have a condensate pan

Just run the heat pump at about 12 degs and no lower, then you don't generate condensation. My fan coil has no drain connector to the pan, no issue. If I flow at 7 degs plenty of condensation likely. Your radiators will be pretty much the same, but not really contribute to cooling. I would try before you change stuff.

[Nick Laslett]

@HughF, I’ve said this many times before, but when I first found BuildHub in 2019, my first takeaway was this overheating issue. All these well insulated houses, with high air tightness overheating in the summer. At that time it was unclear if RHI allowed you to run an ASHP in reverse. 
 

I was working in the Middle East and was thoroughly sick of air conditioning 24/7. I thought it must be possible to add enough cooling to a UK house just to take the edge off the summer heatwave, without resorting to aircon. 
 

I’m glad that fan coil units are part of the regular discussion now on BuildHub. I know this issue doesn’t affect everybody in the UK, dues to the vagaries of the UK weather. 
 

Good luck with your search to find a good solution. I’m sure members with more familiarity with the topic will be along soon. 

[MikeSharp01]

Our solution is going to be a fan coil unit in the MVHR duct to the bedrooms and only the bedrooms. Although MVHR cannot move a lot of heat about we have fitted large ducts and servo controlled dampers also limiting the fan coil to the bedrooms concentrates it, with the UFH running at the same time and the passive stack ventilation system's roof lights open I figure we will be able to keep it bearable. 

[JohnMo]

28 minutes ago, MikeSharp01 said:

coil unit in the MVHR duct to the bedrooms

So are you proposing to boost the MVHR at the same time. And running at 7 degs instead of UFH flow of 12? To make it effective? I would run two MVHR units on for bedrooms and the rest of the house.

 

Have you done the heat reduction calculations?

[JoeBano]

5 hours ago, JohnMo said:

Just run the heat pump at about 12 degs and no lower, then you don't generate condensation. My fan coil has no drain connector to the pan, no issue. If I flow at 7 degs plenty of condensation likely. Your radiators will be pretty much the same, but not really contribute to cooling. I would try before you change stuff.

I got a tiny bit of condensation on my pipe works yesterday but it was very humid. 12c flow temperature seems to be the best outcome for me. 

[MikeSharp01]

49 minutes ago, JohnMo said:

are you proposing to boost the MVHR at the same time. And running at 7 degs instead of UFH flow of 12? To make it effective?

Yes we will boost the MVHR but also restrict the rest of the house. I was going to experiment with flow temp and the flow sequence to see how it goes - so through the fan coil then on to the UFH so I can keep the UFH flow temperature within reaonable bounds or run the fan coils and UFH at different times. I did the calcs years ago, literally, some things have changed so I will do them again and see how it goes. It was never intended to be air conditioning just enough to keep the bedrooms below a bearable max and knock back the overheating days. 

[HughF]

If we get another hot spell I’ll try setting the heat pump to 12 degrees and jumper out the call for heat (why oh why can’t we get heat/cool thermostats in the UK)… see how the fan coils work.

[JohnMo]

32 minutes ago, HughF said:

why oh why can’t we get heat/cool thermostats

You can

A simple cooling or heating thermostat is a Computherm Q7RF, but a nicer and easier to use one is the Q20RF.

 

I also have a polypipe wiring centre (same as Roth badged one), that can be manually selected between heat and cool or will automatically change over with a zero volt input.

 

But I just have the call for heat/cool with a jumper in permanently. I just switch between heat or cool. Cool has a slight WC curve.

[HughF]

Interesting thermostat, cheers. Shame my wife wouldn’t be able to use that - we run a nest for that very reason (peak ergonomics imho)
 

Remind me again if you could be so kind what heat pump you’re using?

Edited Monday at 06:30 by HughF

[JohnMo]

32 minutes ago, HughF said:

Remind me again if you could be so kind what heat pump you’re using?

I'm using a Maxa 6kW R32 ASHP. It's a pretty simple ASHP.

[JoeBano]

10 hours ago, HughF said:

If we get another hot spell I’ll try setting the heat pump to 12 degrees and jumper out the call for heat (why oh why can’t we get heat/cool thermostats in the UK)… see how the fan coils work.

I’ve got heatmiser fan coil stats do cooling and heat. Need 3 pole relay to get it to work because I’ve got a 4 pipe buffer setup. 

[HughF]

49 minutes ago, JohnMo said:

I'm using a Maxa 6kW R32 ASHP. It's a pretty simple ASHP.

A good unit if I recall (I remember reading the manual from cover to cover)

[JohnMo]

5 minutes ago, HughF said:

A good unit if I recall (I remember reading the manual from cover to cover)

Simple but good controls easy to adjust, but it's a derated larger unit, so depth of modulation is a little limited, which is a downside, but managed to get it to run as I want it to.

[HughF]

I’d like mine to have a little more options for cooling (dedicated cooling zone valve output for example, dedicated cooling call instead of a combined heat/cool call), but it does what we need

[HughF]

Hmm…. A dedicated call for cooling you say?

[dpmiller]

yep, that contact overrides the current mode set in User Mask, according to Chris...

[kevinm]

We are in the final design stages of a passive-certified timber frame house. Cooling was a big focus for us.

 

All south and west windows have external venetian blinds. This will cut the solar gain.

 

We looked at mhrv cooling but concluded it was a waste of time. You would do well to get 800w of cooling without running your fan at a noisy speed. If you cool your mhrv aggressively, you then have to insulate your mhrv ducts, or you will get condensation on the outside. Also with most mhrv systems, you dont have individual room control. This is important, as rooms' cooling demand changes throughut the day, especially without external shading.

 

We are going with fancoil units made by systemair. They have a large range of fancoils. We are going with a combination of ceiling casettes, hidden ducted and wall mounted units. This gives individual room control of the cooling.

https://www.systemair.com/en-ie/products/air-conditioning/fan-coil-units

I cant see them on the UK website for some reason. SystemAir Ireland have said they can order whatever fancoil I want on a supply-only basis.

 

One consideration with active cooling the house is that you will want to close the mhrv summer bypass once the house gets cooler than ambient so that you are not dunmping all your nice cold air outside. It will also help to dehumidify the air coming in by pre-cooling it.

[HughF]

2 hours ago, dpmiller said:

yep, that contact overrides the current mode set in User Mask, according to Chris...

Perfecto…. He’s at installer show this week so I’m not bothering him with questions.

 

So a/c linkage is a simple call for heat/cool with the ambient switching taking care of changing from heat to cool. The dedicated cooling call is just that and the same for heating call?

Edited 1 hour ago by HughF

[JohnMo]

15 minutes ago, kevinm said:

Cooling was a big focus for us

Did you not consider just doing UFH (cooling) for the main parts of the house and/or a simple fan coil for the bedrooms. We get huge amounts of solar gain, which you shouldn't in a certified passivhaus. We were cooling at 10 degs outside if the sun was out in April mainly because the sun setting to west circumvents the roof overhangs. 

 

UFH (cooling) works well for us. Even if internal air temperature is high it feels way cooler and as soon as solar gain stops air temperature is pulled down to normal levels really quickly.

 

Are you not spending many thousands of Euro needlessly? Isn't the point of passivhaus you don't need to really cool or heat? If you need to actively cool doesn't your energy consumption exceed the passivhaus requirements?

[kevinm]

1 hour ago, JohnMo said:

Did you not consider just doing UFH (cooling) for the main parts of the house and/or a simple fan coil for the bedrooms. We get huge amounts of solar gain, which you shouldn't in a certified passivhaus. We were cooling at 10 degs outside if the sun was out in April mainly because the sun setting to west circumvents the roof overhangs. 

 

UFH (cooling) works well for us. Even if internal air temperature is high it feels way cooler and as soon as solar gain stops air temperature is pulled down to normal levels really quickly.

 

Are you not spending many thousands of Euro needlessly? Isn't the point of passivhaus you don't need to really cool or heat? If you need to actively cool doesn't your energy consumption exceed the passivhaus requirements?

We did but there were a few reasons that we decided not to. 

• With the house being timber frame, there were concerns from the architect with regards to hidden condensation (particularly on the undserside of the screed upstairs)
• With the ufh pipes in the insulated raft (no screed downstairs). Response times would be very slow.
• We want the fan coils as much for humidity reduction as cooling, cooling the ufh provides no dehumidification. Running the fancoils at low water flow temp and low fan speed will dehumdify the air without cooling the room excessivly. We are ~25km from the Atlantic, and 150m from a 3 km2 lake, so high humidity is an issue with warm weather.

Edited 35 minutes ago by kevinm