Fan Coil Units for use with a (cooling) ASHP

[-rick-]

6 minutes ago, Ommm said:

Something I couldn't work out... in the absence of external cooling, would a standard dehumidifier help here?  If the room is a closed system isn't it just putting more heat into it? Or is it that the reduced humidity will reduce the 'feels like' temperature more than the extra heat?

 

It's maybe not the most efficient way to organise things, but only really needed for extended heatwaves. Reducing the humidity will definitely affect how it feels, but also lower the dew point that would allow you to drop the water temp running through the floor without worrying about condensation, so you could get more cooling from that system.

 

6 minutes ago, Ommm said:

I have my fan coil swapped for a radiator set up.  It's ok but not brilliant, room temps about 23 when it's 32 outside, some of which is just from the masonry rather than the fan coil. One thing I hadn't realised is that the pipes run through the loft which is a lot hotter than the house, so my 15C flow is causing sweating at the uninsulated pipe clamps and that's dripping onto the ceiling below... I shall have to repaint, but it's probably still worth it for the cooling.

 

Time to insulate those pipes! Waste of money heating/cooling the loft.

[G and J]

I think it’s my turn to ask a dumb question.  (When one has a talent one should use it!).

 

What’s is the issue with condensation?

 

I get that condensation on a tiled floor would not be good.  I’m not trying to cool the floor that much.

 

I also get that condensation on a concealed pipe would not be good, rotting the timber nearby.

 

We are seeing condensation on our manifold when I run the ASHP  at too cool a flow temp.  (OK there’s another question there but our heat pump is doing odd stuff, appearing unwilling to ‘get out of bed’ for flow temps above f cold, so cooling needs to be in ‘hard’ bursts, but that’s another question).

So we run our heat pump, have a nice coolish slab, get condensation on the manifold, so what?  It’s all stainless and brass and plastic, I can put a towel under it to catch the drips, so where’s the harm short term?

 

One day, I’ll have fitted a fan coil upstairs (having major issues finding a ceiling mounted one), and the heat pump control will be sorted so it does moderate cooling so we’ll avoid condensation that way and I can box in the manifold safe in the knowledge that it’s not dripping.  
 

But for now I need to burst cool the slab as that’s what the heat pump wants to do, so is it ok to accept condensation on an exposed manifold during a heatwave?

[NCXo82ike]

1 hour ago, Ommm said:

Something I couldn't work out... in the absence of external cooling, would a standard dehumidifier help here?  If the room is a closed system isn't it just putting more heat into it? Or is it that the reduced humidity will reduce the 'feels like' temperature more than the extra heat?

 

I have my fan coil swapped for a radiator set up.  It's ok but not brilliant, room temps about 23 when it's 32 outside, some of which is just from the masonry rather than the fan coil. One thing I hadn't realised is that the pipes run through the loft which is a lot hotter than the house, so my 15C flow is causing sweating at the uninsulated pipe clamps and that's dripping onto the ceiling below... I shall have to repaint, but it's probably still worth it for the cooling.

So yes the dehumidifier would increase heat by its power consumption: ~200w. So counter-productive. Quite possibly the decrease in internal RH would allow the floor temp to drop lower and the increase in system performance overall.

 

Looking at Messana who still hydronic systems to rich Californians, the dehumidification is a well advertised component. 

[JohnMo]

19 minutes ago, G and J said:

OK there’s another question there but our heat pump is doing odd stuff, appearing unwilling to ‘get out of bed’ for flow temps above f cold

That is just a set up issue, are you running a fixed flow rate? Hydraulically separated etc. what heat pump?

 

21 minutes ago, G and J said:

nice coolish slab, get condensation on the manifold, so what?  It’s all stainless and brass and plastic, I can put a towel under it to catch the drips, so where’s the harm short term?

That is generally ok short term, but if your heat pumps decides to latch on and over long period can lead to condensation on floor surfaces and lead to slips and falls.

 

 

[-rick-]

23 minutes ago, G and J said:

What’s is the issue with condensation?

 

AFAIK the concern is mainly structural damage caused by damp. But also a concern that a damp area might be make a good home for mould.

 

23 minutes ago, G and J said:

So we run our heat pump, have a nice coolish slab, get condensation on the manifold, so what?  It’s all stainless and brass and plastic, I can put a towel under it to catch the drips, so where’s the harm short term?

Short term none.

 

Long term, maybe there's more condensation that you don't see that will cause damage given enough time.

[Wil]

I’m running everything, rads and UFH, at 18 today and most of the rads are sweating buckets. Where it’s an issue there’s a towel on the floor under the rad.

 

Irritatingly I have a 10kW FCU to put in the loft but it’s sitting in the spare bedroom on my ‘to-do’ list.

 

We’re night purging hard, then sealing up and running as above for these couple of days.

Edited 13 minutes ago by Wil

[G and J]

11 minutes ago, JohnMo said:

That is just a set up issue, are you running a fixed flow rate? Hydraulically separated etc. what heat pump?

It is a setup issue and I’ve had some input from Maxa technical and am seeking more.   
 

We have a Maxa heat pump, single zone, UFH only at present, no volumisers or any other unnecessary gubbins.

 

13 minutes ago, JohnMo said:

That is generally ok short term, but if your heat pumps decides to latch on and over long period can lead to condensation on floor surfaces and lead to slips and falls.

 

We won’t be getting into the realms of damp floors.  
But what does “latch on” mean?