Green Building Forum - Oh, I get it now.. Wed, 06 May 2026 14:54:08 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 Oh, I get it now.. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226598#Comment_226598 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226598#Comment_226598 Sun, 05 Jul 2015 08:20:15 +0100 cjard
But I get it now, the intention is that this is an ASHP that is mounted inside an MVHR instead of a heat exchanger.. The ASHP takes heat from the air that is going out to the world and being exahusted, and stores it in water, rather than a simple cross flowing matrix taking heat from the outbound air and storing it in inbound air

I do wonder whether it is more effective, could the ASHP wih the addition of electrical energy establish a steeper delta t and recover more heat from the outgoing air, store it in water, which could then be used to heat more the inbound air via a device something like a car radiator. Of course effective is a question of what you pay and what you get.. Assuming the fan that pushes the air in the MVHR is the same, you then have the added cost of running an ASHP compressor or heat pumping technology, so does it transfer more heat for the extra money? Is it also more flexible in that in summer the hot water generated can be used as hot water for cleaning etc rather than heating house air, when a normal mhr switches to bypass and just loses it]]> Oh, I get it now.. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226599#Comment_226599 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226599#Comment_226599 Sun, 05 Jul 2015 09:41:13 +0100 SteamyTea There is a thing called entropy.
This is a measure of the order, or disorder of molecules.

If you measure the temperature of something, what you are really doing is measuring the average speed of all the molecules.
As it is an average, some molecules will be slow moving, others fast moving, this translates to the energy levels.

What a heat pump does, is capture the energy in the faster moving molecules by, in effect, slowing them down, and taking that energy to somewhere else (your water).
You can, if you like, think of it as having a box of energy, and squeezing the box smaller. The only thing that changes is the volume. Then the Boyle's law can be used to calculate the new temperature.

In Physics, there is a thing called 'conservation'. All this means is that you can reshuffle things, but you end up with the same quantity. The law's of indices and Algebra (rearranging equations) are useful mathematical tools here.

So lots of small is equal to a small amounts of lots.

Don't get temperature an energy mixed up. Energy used to be called heat, which is very annoying these days.
I blame the post modernists.]]> Oh, I get it now.. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226600#Comment_226600 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226600#Comment_226600 Sun, 05 Jul 2015 10:03:04 +0100 Ed Davies
There are some who get good results from them, e.g., a chap on the Navitron forum at the north end of Skye (no, not Skyewright) but his is a bit of special case as he pre-warms his incoming air by running it along the glazed ridge of his adjacent workshop (if I remember the details correctly).

There have been others (Nibe (sp?)) in housing association-type properties which have been the source of major complaints. It's difficult to know what's really going on, of course, but the response from the manufacturers at least makes sense - AIUI they say that the users aren't using the things properly; that they should be left running continuously rather than being switched on and off like gas central heating as running them at high power off cool inside air is very inefficient.

I'm not sure that trying to extract more energy from the exhaust air of MVHR makes much sense in Britain. An efficient MVHR should be exhausting air which is only a couple of degrees warmer than the outside air so there's little gain to be had in terms of sensible heat. In a dry climate the exhaust air might have significantly more water vapour than outside air and so usable amounts of latent heat but in Britain in the heating season the outside air is likely to be pretty damp anyway.

Dry continental air might be different. Perhaps that's why the Ecocent comes from Austria (I think).]]> Oh, I get it now.. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226607#Comment_226607 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226607#Comment_226607 Sun, 05 Jul 2015 16:23:26 +0100 Yanntoe
The Ecocent unit seems to take warm and possibly humid air from the room in which it sits and extract energy from it which is then stored in (hot) water. The cooler drier air is then released back into the interior of the building.
This would seem like a good idea for a well insulated room which gets warm due to eg a boiler/hot water tank, especially if this is also an area used to dry clothes/wood/dog etc.
In this situation wouldn't the external humidity be less relevant, particularly as an alternative to MVHR?
The Ecocent appears to be available as a stand alone heat exchange unit for connection via a coil to a separates water cylinder or as part of an integrated ASHP/cylinder.
In a room with e.g. a balanced flue boiler, there would be no need for an external air supply so in the heating season the dehumidifying effect would be undiluted by external humid air, heat would be available from the waste heat from the boiler/cylinder, and at a time of low PV output, hot water would be produced from a relatively low electricity consumption using waste heat. As a bonus you'd get a dry dog.

Or are we discussing another system?

As I need a drying room and it happens that this will be an insulated "plant room", which will contain my boiler, cylinder, wet clothes , often wet dog, and wood for the fires, the Ecocent idea seems to be a better option than a single room 'MVHR unit.
Could it be?]]> Oh, I get it now.. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226610#Comment_226610 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226610#Comment_226610 Sun, 05 Jul 2015 19:07:36 +0100 Ed Davies Posted By: YanntoeThe Ecocent unit seems to take warm and possibly humid air from the room in which it sits and extract energy from it which is then stored in (hot) water. The cooler drier air is then released back into the interior of the building.You could be right but my understanding was that the air from the Ecocent unit is normally exhausted from the building.

The Nibe devices (which are like big Ecocents but feeding to the central heating system rather than directly into a cylinder are intended as the primary heating system for well-insulated houses.

In this situation wouldn't the external humidity be less relevant
Possibly, but the situation which cjard mentioned was extraction of extra energy from MVHR exhaust air. In that case, comparison with extraction of energy from general outdoor air (ie, a normal ASHP) is relevant.]]> Oh, I get it now.. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226612#Comment_226612 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226612#Comment_226612 Sun, 05 Jul 2015 19:21:58 +0100 Yanntoe Just checked, and the Ecocent units can take air from, and exhaust into the same (or other)room rather than outside.
This is from their brochure ....

"Cooling in the re-circulating air mode (picture 3) The Ecocent can extract warm air and place cooled, dehumidified, outlet air back into the same room – this is perfect for cellars and gymnasiums"

I'm interested because I originally thought that a single room MVHR unit might suit my needs, but this looks, potentially, better.

Perhaps something for cjard to have a look at.]]> Oh, I get it now.. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226617#Comment_226617 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226617#Comment_226617 Sun, 05 Jul 2015 21:04:35 +0100 cjard
I'm not immediately motivated to think that a HSHRHP could meet my heating needs.. My father in law is keen on an ASHP, I'm happy to see how his works out (he has the semi on the other side) before fitting one]]> Oh, I get it now.. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226627#Comment_226627 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226627#Comment_226627 Sun, 05 Jul 2015 23:07:43 +0100 ringi
Spend the money you save on improving the fabric of the building and PV.]]> Oh, I get it now.. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226633#Comment_226633 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226633#Comment_226633 Mon, 06 Jul 2015 08:32:22 +0100 Chris P Bacon
I looked at installing something like this when I was building but could never find any proper details on their de-frosting/frost protection capabilities if used with an outside air supply. I have since come across the CTC Ecowater which can operate down to -10ºC and has properly documented frost protection and PV integration. Had I known about it at the time I would most probably have installed it.

My idea was to install about 12m² of home made solar air panels on the inlet to provide some preheating and reduce to risk of needing to defrost.

I think the ultimate solution would be to use Solar air/PV hybrid panels to preheat the supply and power the unit. In summer there is the probability that the pre-heated air would be above the higher limit of what these units are designed for so it might be useful to have the option to have supply and exhaust within the house at those times to provide some useful cooling.]]> Oh, I get it now.. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226634#Comment_226634 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226634#Comment_226634 Mon, 06 Jul 2015 08:36:55 +0100 Chris P Bacon Posted By: cjardOh, I've kinda decided on my heating device- I don't really have the budget for anything renewable in the first year so I'm looking at either just an immersion and a big tank (plug solar in later) or a combi boiler (boo hiss)

You can get Ecocent type units in a 300 litre capacity for not a huge amount more than a decent tank of the same size and they can be used with other forms of heat supply rather than just their in-built ASHP. Given the choice again I would have installed one rather than the "normal" 300 litre tank which I did.]]> Oh, I get it now.. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226636#Comment_226636 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226636#Comment_226636 Mon, 06 Jul 2015 09:38:19 +0100 gravelld Oh, I get it now.. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226640#Comment_226640 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226640#Comment_226640 Mon, 06 Jul 2015 09:46:32 +0100 Chris P Bacon Posted By: gravelldCould you run ducts from wet rooms back to the room/cupboard with the ecocent in it? Therefore using its de-humidification abilities.Yes but your ventilation system should be doing that, plus you will be extracting heat from your bathrooms when you should really be adding it...]]> Oh, I get it now.. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226641#Comment_226641 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226641#Comment_226641 Mon, 06 Jul 2015 09:59:26 +0100 gravelld
If you mean MEV or hole in the wall extractors, well at least by ducting to the Ecocent you are recovering the latent heat in the water vapour?]]> Oh, I get it now.. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226673#Comment_226673 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226673#Comment_226673 Tue, 07 Jul 2015 05:35:44 +0100 cjard
If there's an MVHR recovering heat from all over, and an eco cent sucking air from the tops of vaulted ceilings/hot laundry rooms (I have both) and maybe drawing outside air through the back of solar panels thereby cooling the panels/utilising some built up heat etc, and a system boiler or solar topping up the water tank wherever necessary, and underfloor heating running away constantly keeping things warm, plus use of dhw.. Then it can all come to a balance?

i get that the MVHR is primarily about ventilation and heat recovery is a bonus, is the suggestion that the MVHR should be left to do its thing on the lower levels and have the eco cent drawing air from the highest part of the heated envelope and dumping the exhaust outside in winter or inside in summer for some useful cooling?

Just not sure what your ideal setup would have been, Chris p]]> Oh, I get it now.. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226674#Comment_226674 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226674#Comment_226674 Tue, 07 Jul 2015 05:41:26 +0100 cjard
In terms of boilers, I've been looking at the rinnai hd50 because it drives me nuts that combos cannot operate two outlets at once, so my solution is to go for a bigger combi, that can still modulate down. Rinnai also tout it as being compatible with a cylinder in the circuit, can have preheated water, solar thermal or PV immerrsion etc and sell all the gubbins for it so right now I'm wondering if my house has any use for an eco cent..]]> Oh, I get it now.. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226677#Comment_226677 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226677#Comment_226677 Tue, 07 Jul 2015 08:49:47 +0100 Chris P Bacon Posted By: cjardhave the eco cent drawing air from the highest part of the heated envelope and dumping the exhaust outside in winterIMO you should not take a feed from inside and exhaust outside as you will unbalance your ventilation/de-pressurise the house.

At any one time you should have both feed and exhaust from inside or both feed and exhaust from outside, never a mix of the two.

In a low energy house the only time of year that I would see it making sense to feed and exhaust within the house is around now in very hot weather where the house may be up to 25ºC and the unit could provide some cooling effect.

Where the Ecocent falls down for me is that it's minimum operating temperature is 0ºC so therefore not viable to use feeding from outside during the heating season.

There are alternatives available such as the CTC Ecowater or the Ochsner Europa 323 DK which are safe down to -10ºC which make them viable to use with an external feed in the winter months (although the COP is probable pretty poor at such low temperatures at least you know you are not going to freeze your evaporator and probably destroy the unit if it gets cold outside).

In order to help the COP of the unit you could perhaps take the feed via a solar air panel or a (well ventilated) conservatory.]]> Oh, I get it now.. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226731#Comment_226731 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226731#Comment_226731 Wed, 08 Jul 2015 12:41:36 +0100 cjard
http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13459&page=1#Item_18


Overall - the earlier comment about the ESP Ecocent 300 with its heat pump being the same price as a 300 litre akvaterm solar plus, is reasonably accurate.. I'm just not sure if there's any true benefit over getting a cheaper thermal store in a house that has an MVHR (as scavenging 'waste' heat is the MVHR's secondary job and a job a good one should be good at), unless one is looking for a reasonable way to generate hot water in the non-heating season when it could be viewed as a house cooler - if it costs £500 more than an equivalent TS, how many summers of cooling my house (and should the MVHR summer bypass not be enabled?) and generating hot water as it goes, is it going to take to pay that back?]]> Oh, I get it now.. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226856#Comment_226856 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13490&Focus=226856#Comment_226856 Fri, 10 Jul 2015 23:19:36 +0100 ringi Posted By: cjardll boilers that are highly efficient, have flue gas heat recovery? Surely a boiler is a flue gas heat recoverer.. It burns gas generating massive flue temperatures and then uses it to heat water, recovering heat from the burnt gas in the process.


No, "flue gas heat recovery" is where the warm flue gases are used to preheat cold mains water. The issue is that the return temp from the PHE in a combi is too high to get much condensing of the flue gases. Also often the return from the heating system is also too high.]]>