Which ASHP are set up to cool

[davidh72]

Was over in Germany a few months ago and bought two of the proper plugs. Put into 10kw ecotherm and working well. Strangely not using it at present! If anyone wants to purchase the spare one I am up for reasonable offers. 

[Benpointer]

Apols all, I know this is a huge thread but...  what was the answer to the original question "Which ASHP are set up to cool"?

 

Also, do they all only cool through the UFH loops or can they run cooled water through fan coil unit with condensation collection?  I am worried that a cold floor on a hot humid day will just cause condensation all across the floor.

 

Apols for the dumb question - trying to understand if I need to specify a separate aircon system or I can get the ASHP to do that for me in our new-build for which we are at the early design stage .

[JohnMo]

41 minutes ago, Benpointer said:

Which ASHP are set up to cool

Most are, but you need to read the datasheet. Some need additional parts (e.g. Vaillant).

 

42 minutes ago, Benpointer said:

do they all only cool through the UFH loops or can they run cooled water through fan coil unit

Simple answer heat pump doesn't care or know what it's pump too.

 

42 minutes ago, Benpointer said:

I am worried that a cold floor on a hot humid day will just cause condensation all across the floor.

You set flow temperature according to likely dew point within the house. So if you target a house temperature of say 21-22, then your flow temp is set around that. But it is floor surface temperature that is affected by dew point. We flow at around 14 degs. No issues in 2 summers.

 

Fan coils are more effective as you can run 6 deg water through them.

[joth]

In addition to the colder flow temps, fan coils are more effective as they can dump cool air on your head (if installed in the ceiling) which then cascades down over the whole body rather than UFH which gently cools the ground your toes touch but not necessarily much more than that. Hot air rises; cool air falls

Gentle cooling under floor is still useful to temper the effects of an overheating build, but it's much less immediate or effective for cooling down an overheating person than a FCU even when running at similar temps.

 

[JohnMo]

6 minutes ago, joth said:

UFH which gently cools the ground your toes touch but not necessarily much more than that. Hot air rises; cool air falls

That is only part of the mechanism. UFH cooling works in the most part by pulling the heat from the body. The floor temp being substantially below the body temperature. So your body radiates heat to the floor.

[joth]

26 minutes ago, JohnMo said:

That is only part of the mechanism. UFH cooling works in the most part by pulling the heat from the body. The floor temp being substantially below the body temperature. So your body radiates heat to the floor.

.... which is much less effective than dumping cold air on top of the body.

 

EDIT to add: in addition, blowing air gives will windchill effect of its own. So even if the air it ~same temperature as the room it can still create a cooling effect.

 

 

Edited December 6 by joth

[yngndrw]

It's worth noting that using a fan coil unit with a heatpump also improves heating - They massively increase the effective surface area of your heat emitters.

 

On the flip side, in the UK fan coil units are incredibly expensive. We spent more on them that we would have buying a separate aircon unit. That being said, it is nice to only have a single outdoor unit and to benefit when heating.

 

I wouldn't use UFH pipes for cooling, the condensation we get on our mid-position valve and filters alone (Which are hard to insulate!) is enough to tell me that it's a bad idea. You'd be supprised at how much condensation is collected via the drain when it's running.

[JohnMo]

26 minutes ago, yngndrw said:

UFH pipes for cooling, the condensation we get on our mid-position valve and filters alone

Sorry you are not comparing apples with apples. UFH flow temps are warmer than fan coils in the cooling mode - you should be flowing a temp to UFH system, that doesn't generate condensation. At most I have seen a little dulling of the stainless steel UFH manifold at the end of cooling cycle. Never seen a drip or drip forming.

 

Why are using a mid position valve on a heat pump system? Assume you actually mean, diverter valve?

 

29 minutes ago, yngndrw said:

It's worth noting that using a fan coil unit with a heatpump also improves heating - They massively increase the effective surface area of your heat emitters.

Only when discussing radiators - not UFH. And radiators don't do cooling at all well - not really applicable to a cooling thread

[JohnMo]

47 minutes ago, joth said:

.... which is much less effective than dumping cold air on top of the body.

 

EDIT to add: in addition, blowing air gives will windchill effect of its own. So even if the air it ~same temperature as the room it can still create a cooling effect.

Not disagreeing - just adding full contextual details.

 

There are several mechanisms at play for both fancoils and UFH (cooling). Fan coils are way better if you have them, that is a given.

 

But if you don't have them, cannot justify the costs or you are retrofitting a HP and cannot justify moving away from UFH. When UFH is in cooling mode, it does make a warm house feel cooler, even if actual air temp is quite high. But also allows cools the house down quickly (compared to not having cooling) when the sun goes away.

[Benpointer]

Am I right in thinking that a fan coil will have its own condensation collection and therefore require a drain connection?

 

Also, that a fan relies on an external feed of hot or cold water to do its work - so it's effectively a radiator* with a fan?

 

(* I use the term 'radiator' in the CH heating sense.)

[JohnMo]

9 minutes ago, Benpointer said:

so it's effectively a radiator* with a fan

Sort of, but looks more like a car radiator that a house radiator.

[yngndrw]

28 minutes ago, JohnMo said:

Sorry you are not comparing apples with apples. UFH flow temps are warmer than fan coils in the cooling mode - you should be flowing a temp to UFH system, that doesn't generate condensation. At most I have seen a little dulling of the stainless steel UFH manifold at the end of cooling cycle. Never seen a drip or drip forming.

You're right, but the issue is that underfloor temperatures must be much higher - So high that I'd question the amount of energy it can transfer.

 

For example, using an online dew point calculator, with an air temperature of 23C and a relative humidity of 70%, the dew point is 17.2C so a maximum temperature delta of 5.8C in that example. In our system, the cooling flow temperature is set to 9C so the temperature delta would be 14C for the same example. That difference in temperature delta is really enormous and it would be worse if you were more conservative with the numbers to ensure that you avoid condensation. If the flow temperature has to be in the 20C+ range, I'd seriously question the effectiveness.

 

28 minutes ago, JohnMo said:

Why are using a mid position valve on a heat pump system? Assume you actually mean, diverter valve?

We use an additional mid-position valve to switch between underfloor + fan coil (For heating) and just fan coil. (For cooling) When we designed the system, we were unsure whether or not we wanted to use the fan coil units for heating but in hindsight, it was silly to even consider that. We could have gotten away with just a 2 port valve to block the underfloor circuit and a relay to invert the "cooling" signal - That would have also helped reduce the condensation as cold water wouldn't be flowing through the valve

 

28 minutes ago, JohnMo said:

Only when discussing radiators - not UFH. And radiators don't do cooling at all well - not really applicable to a cooling thread

We have underfloor heating as well, adding the fan coils made a massive difference. Our heat curve setting is currently 0.2 with the fan coil fans on very low. (They are inaudible) It's worth noting that our fan coils are oversized, they can dump over 5kW each with the fan turned up. That's one of the major benefits, the forced convection from the fan makes them extremely efficient even when the fan is on low.

 

 

12 minutes ago, Benpointer said:

Am I right in thinking that a fan coil will have its own condensation collection and therefore require a drain connection?

It depends, some fan coil units (At least, the ones sold in the UK) are designed specifically for heating and therefore don't have a drain pan. Make sure you find one with a drain pan (Sometimes it's an optional extra) if you're going to use it for cooling and yes this will need to be connected up - Ours just goes to a pipe outside and drips onto the floor.

 

12 minutes ago, Benpointer said:

Also, that a fan relies on an external feed of hot or cold water to do its work - so it's effectively a radiator* with a fan?

 

(* I use the term 'radiator' in the CH heating sense.)

Yes that's exactly right. It's a high-density radiator in a box with a fan and a drain pan. They should be dirt cheap, but as they are quite rare over here they cost a fortune. Sometimes they come with extras such as valve sets and auxiliary electric heaters (Ours did as our supplier didn't know what to order, he'd never seen one before despite working in the HVAC industry) but you can remove all of that.

Edited December 6 by yngndrw

[yngndrw]

Just to add, one option if you don't have the space for ducting a regular fan coil unit is a vertical unit with a casing such as the Daikin FWL-DAT range. These are essentially just forced convection radiators, complete with drain pan.

[JohnMo]

52 minutes ago, yngndrw said:

For example, using an online dew point calculator, with an air temperature of 23C and a relative humidity of 70%, the dew point is 17.2C so a maximum temperature delta of 5.8C in that example

Sounds about right

 

53 minutes ago, yngndrw said:

That difference in temperature delta is really enormous

It is, but so is the surface area available. Our house about 192m² so that approx 6kW of cooling power. A set of fan coils may be slightly more effective and targeted, but my heat pump only puts out 6kW of cooling power. As I said above fan coils are better than UFH, and UFH takes the edge off and allow quicker recovery to normal temps.

 

If you have UFH already moving to cooling with a heat pump is zero cost option, which makes the house more comfortable than it would otherwise be. Adding fan coils can make a more comfortable house, but at a cost. If starting from a blank sheet, install fan coils.

 

56 minutes ago, yngndrw said:

If the flow temperature has to be in the 20C+ range

Why would need to be that high? We flow between 12 and 14. The heat pump will generally cycle. Running for about 40 mins. Manifold does get just below dew point, as I see dulling of bright stainless. But not enough to bother about. To get floor surface temp to 17 you have to flow cooler than that.

[SteamyTea]

2 hours ago, joth said:

EDIT to add: in addition, blowing air gives will windchill effect of its own. So even if the air it ~same temperature as the room it can still create a cooling effect.

Only if you have excess moisture to remove.

[JohnMo]

With a fan coil running for long durations how do you manage indoor humidity levels in winter, if using for heating. I know some expensive versions of A2A are connected to allow fresh air in to prevent humidity dropping too low. If we get a prolonged cold snap heating with UFH and have MVHR ventilation we can get as low as 35% humidity.

[jack]

3 hours ago, yngndrw said:

I wouldn't use UFH pipes for cooling, the condensation we get on our mid-position valve and filters alone (Which are hard to insulate!) is enough to tell me that it's a bad idea. You'd be supprised at how much condensation is collected via the drain when it's running.

We run water through our UFH at around 15 deg C and get a breath of condensation (not enough to drip) on the metal parts of the UFH manifold. From memory, that gives us a floor surface temperature of around 19 deg C.

 

Although the air temp tends to still be quite warm during long hot spells, walking around in bare feet or socks seems to cool me down out of all proportion to the amount of contact area with the floor. Walking into the house on a hot day feels like walking into a cave. Lying down on the floor when you get back after exercising in hot weather is absolute bliss!

This is all downstairs. There's no cooling upstairs, and during longer periods of hot weather, I do wish we'd installed some form of cooling, whether fan coils or aircon.

 

The other thing that I think is even more important is insect screens. Even during very hot weather, most nights the temperature outside drops well below the interior temperature. If we had insect screens we'd be able to open all the windows upstairs and let out a lot of the heat that's built up during the day. Retrofitting insect screens is on my increasingly long list of things to do.

[yngndrw]

I think one takeaway from this conversion is that the whole subject is extremely variable due to personal comfort preference, building types, sun load etc. We all seem to be having different experiences and setting it differently!

 

1 hour ago, JohnMo said:

With a fan coil running for long durations how do you manage indoor humidity levels in winter, if using for heating. I know some expensive versions of A2A are connected to allow fresh air in to prevent humidity dropping too low. If we get a prolonged cold snap heating with UFH and have MVHR ventilation we can get as low as 35% humidity.

We don't, the plan is to install MVHR which I think will resolve it. Warm air can hold more moisture so if the heating is on and you're constantly exchanging the air with outdoor fresh air, you should always be removing humidity. If the humidity drops too low, you could always use a humidifier.

 

That's the thing with air tightness and insulation, it's really about control. They allow you to then manage the temperature/humidity/air quality yourself, but that still requires something to make the change you want.

 

1 hour ago, jack said:

We run water through our UFH at around 15 deg C and get a breath of condensation (not enough to drip) on the metal parts of the UFH manifold. From memory, that gives us a floor surface temperature of around 19 deg C.

 

Although the air temp tends to still be quite warm during long hot spells, walking around in bare feet or socks seems to cool me down out of all proportion to the amount of contact area with the floor. Walking into the house on a hot day feels like walking into a cave. Lying down on the floor when you get back after exercising in hot weather is absolute bliss!

This is all downstairs. There's no cooling upstairs, and during longer periods of hot weather, I do wish we'd installed some form of cooling, whether fan coils or aircon.

 

The other thing that I think is even more important is insect screens. Even during very hot weather, most nights the temperature outside drops well below the interior temperature. If we had insect screens we'd be able to open all the windows upstairs and let out a lot of the heat that's built up during the day. Retrofitting insect screens is on my increasingly long list of things to do.

If you have roof windows, most manufacturers offer some form of insect screen for them so that could be an option.

[Benpointer]

I'm learning a lot here, thanks all!

 

What happens to the MVHR when you are operating the UFH in cooling mode?  Presumably it has to still run, to remove the excess humidity.  Does it switch to summer bypass?  And would it in fact be better if it didn't, if the air outside is hotter than the air inside, it would be quite nice to exchange that heat from the intake to the exhaust.  

 

Too many questions buzzing round my brain!

Edited December 6 by Benpointer

[yngndrw]

3 minutes ago, Benpointer said:

I'm learning a lot here, thanks all!

 

What happens to the MVHR when you are operating the UFH in cooling mode?  Presumably it has to still run, to remove the excess humidity.  Does it switch to summer bypass?  And would it in fact be better if it didn't, if the air outside is hotter than the air inside, it would be quite nice to exchange that heat from the intake to the exhaust.  

 

Too many questions buzzing round my brain!

All theory as we haven't got an MVHR yet, but yes I think you're right that it depends on how well your cooling is doing:

ng is doing:

- If the indoor air is warmer than the outdoor air (I.e. Your cooling is not doing enough), then you'd want to use the summer bypass to bring in cooler air.

- If the indoor air is cooler than the outdoor air (I.e. Cooling is going well), then you'd want to use the regular heat exchanger to pre-cool the incoming air.

 

Summer bypass is often an optional feature for which you pay more money, so if you can do without it you'd save some money.

 

Either way, if your house has good air tightness then you'd want to maintain the ventilation to control humidity.

[Benpointer]

8 minutes ago, yngndrw said:

All theory as we haven't got an MVHR yet, but yes I think you're right that it depends on how well your cooling is doing:

ng is doing:

- If the indoor air is warmer than the outdoor air (I.e. Your cooling is not doing enough), then you'd want to use the summer bypass to bring in cooler air.

- If the indoor air is cooler than the outdoor air (I.e. Cooling is going well), then you'd want to use the regular heat exchanger to pre-cool the incoming air.

 

Summer bypass is often an optional feature for which you pay more money, so if you can do without it you'd save some money.

 

Either way, if your house has good air tightness then you'd want to maintain the ventilation to control humidity.

Both the MVHR units we have had in the past had automatic summer bypass included by default. 

 

The issue is "If the indoor air is warmer than the outdoor air..." that's precisely when summer bypass doesn't operate (at least as far as I am aware) because 95% of the time you want to keep that indoor air warmth to cut heating costs.

[jack]

1 hour ago, yngndrw said:

If you have roof windows, most manufacturers offer some form of insect screen for them so that could be an option.

 

That's the plan, in conjunction with screens in at least the bedrooms to encourage stack ventilation (assuming I eventually manage to fix the electric rooflight opener - yet another thing on the to-do list).

[jack]

12 minutes ago, Benpointer said:

Both the MVHR units we have had in the past had automatic summer bypass included by default. 

 

The issue is "If the indoor air is warmer than the outdoor air..." that's precisely when summer bypass doesn't operate (at least as far as I am aware) because 95% of the time you want to keep that indoor air warmth to cut heating costs.

 

Summer bypass also takes into account the outdoor air temp. The settings on ours let you set the exterior temp above which the summer bypass will operate (if the indoor air temp is higher than the outdoor temp).

 

Ignoring summer bypass, MVHR tries to maintain any temperature difference that exists between the inside and the outside.

If you have the heating on in winter, or the cooling on in summer, such that you've pushed your house temperature up or down in a direction that makes it more comfortable than the outside temperature, then you want the MVHR operating in its normal (non-bypass) mode. It will stop your hard-won heat/coolth from being lost to the outside through ventilation.

 

In summer, when the temperature outside drops below your house's internal temperature (in the evening, say), but is still above a threshold temp, the summer bypass kicks in. Instead of operating to maintain the temperature difference, the MVHR ejects warm air from the house and draws in cooler air from outside.

 

32 minutes ago, Benpointer said:

What happens to the MVHR when you are operating the UFH in cooling mode?

 

Nothing special happens. Assuming it's cooler inside than outside because of the operation of the UFH, then the MVHR will try to maintain that temperature difference.

 

Some people turn down the ventilation rate when it's very cold or hot outside. That reduces energy losses due to the large temperature difference between the inside and outside. It also reduces how much moisture is taken out of the air in winter. Overventilation when it's very cold can result in very low humidity inside.