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Tagged: decision making criteria, Heat transfer
- This topic has 17 replies, 7 voices, and was last updated 10 years, 11 months ago by Sally Blackwell.
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March 19, 2013 at 5:17 pm #1096AnonymousInactive
What is the effectiveness of heat transfer kits? They seem to work best with log burners and when the length of the transfer is minimized, because substantial heat is lost along the length of the duct. What about pumping hot air downwards? This seems counter intuitive but I have a client who is interested in pumping heat from a log burner room upstairs to a room directly below. Is this worth doing? How would it work? Would you take air from the ceiling of the top floor and then pump it down to through the floor of the bottom room? Would you not lose quite a lot of heat by doing this?
Also, does anyone have any good websites or resources on heat transfer kits?
March 20, 2013 at 11:50 am #1098Norman SmithParticipantYour comment about heat transfer kits working best with log burners is linked to the energy output of various heating appliances. Larger woodburners of 18 kW capacity and more have the ability to heat (and sometimes overheat) a living area and so have some to spare to heat other rooms in the house.
Conversely heat pumps and the like at 6-8 kW have much less output and transferring some of this to bedrooms would be at the expense of heating the living room. I have heard of people insulating the ducting to reduce the heat loss as it passes through the ceiling space. I have also seen installations where hot air is removed from the apex of a ceiling and pumped down to bedrooms at a lower level, to make its way back up – a kind of virtuous circle you could say.
There are technical reports and other information about the efficacy of these systems, in the right situation I recommend them, and did just this week. As a starting point take a look at http://www.ecobob.co.nz/forum/ForumPosts/91/Re-Heat-transfer-systems-.aspx?ShowForumPostId=2078.
Regards, Norman
March 21, 2013 at 12:05 pm #1103AnonymousInactiveIf you have any technical reports I’d keen on reading them too! Thanks 🙂
March 25, 2013 at 1:32 pm #1113Vicki CowanKeymasterWe haven’t looked at heat transfer kits in a detailed study (oh how I would like to) but from our Papakowhai Research we came to the following conclusions about when they work best:
-with a wood burner
-with insulated ducting (otherwise all the heat is lost into the ceiling)
-with the outlets going to where you want the heat (don’t heat transfer to a hallway – if you want it to heat the bedrooms put the outlets in the bedrooms – and best not too close to the door)
-with fewer rather than more outlets (1 or 2 is better than 3 or 4)
-with shorter rather than longer ducting (if you’ve got a space you want to heat a long way away from the wood burner don’t be tempted to use heat transfer)
-with a thermostat (so that they transfer heat when there actually is some to transfer) – normally you locate this on the other side of the room from the heat source
-with a grunty fan.
March 25, 2013 at 10:06 pm #1119Sally BlackwellMemberAre there summary reports from your Papakowhai research? We’ve got a whole lot of Beacon stuff in the Best Practice Library but nothing from that particular study, I don’t think.
March 25, 2013 at 10:06 pm #1120Sally BlackwellMemberAre there summary reports from your Papakowhai research? We’ve got a whole lot of Beacon stuff in the Best Practice Library but nothing from that particular study, I don’t think.
March 26, 2013 at 9:45 am #1121Norman SmithParticipantNot only are these reports available they are a superb resource which provides unique insights into ‘deep’ retrofitting.
Hi Lois, what is your definition of a grunty fan; this may present two problems (1) cost to run offsets the benefits of the heat transfer system and (2) drafts are created.
Norman
March 26, 2013 at 10:09 am #1122Norman SmithParticipantAlso meant to say that one of the problems with their performance is the cheap ducting which is standard. This slows down the air movement so by the time the air gets to its destination such as a bedroom at the other end of the hosue it has cooled down. Hence Lois’ advice to get a grunty fan! Another way to address this is to spend more to get smoother ducting, thus lowering the coefficient of friction so the air can be moved more quickly with less energy. Some better ducting is also insulated. If you do need to learn from the experience of others don’t forget the EcoBob site (see earlier posting).
Norman
March 28, 2013 at 10:31 am #1123AnonymousInactiveThanks for all the information everyone. If anyone has any study reports or reference material I’m really interested in digging deeper and learning a bit more. Cheers!
March 28, 2013 at 11:11 am #1130Norman SmithParticipantI don’t have such a report in my system but its always possible BRANZ or Consumer have covered it or a Masters student somewhere made this the subject of their thesis. If you have time a serious iterative literature search would be the place to start.
In looking for the definitive statement I find its always important to see what the principal product suppliers are saying, e.g. Mitre 10, Bunnings and Plcacemakers. e.g. http://www.mitre10.co.nz/how_to_guides/interior/heat_transfer_kits_guide/. Among other things they are often the source which in the first instance the public go to, and listen to, when they have a problem. They are there to sell products but that is not to say its deliberately misleading, if not always the full story.
I believe one of the roles of home energy advisers is to act as moderators who have the knowledge to tell the other side of the story, particular when households are bombarded with TV advertising about miracle energy saving products – surely coming soon when autumn arrives! As a matter of interest, as a frequenter of hardware outlets for many years, the arrival of these huge outlets has also meant the severe dumbing down of staff. It’s not their fault but the staff there don’t know nuffink.
Of course Janet the other question is — what is the issue your client is looking to address? You said they were interesting in pumping heat, but what is the problem? Not sure if you have been to have a look at your client’s house; are they too hot in the lounge, too cold in ther bedroom, is the issue dampness or asthma? Its always possible they sought to address the presenting problem and with limited knowledge and reached a conclusion the solution was heat transfer kits when it might not be.
Cheers, Norman
April 4, 2013 at 1:12 pm #1143Paul HansenParticipantThe thing to keep in mind here is you can get a Lada system, a Toyota Carolla or a Rolls Royce when it comes to Heat Transfer. The above comments are correct in that you don’t want to be considering any system that does’t have insulated ducting, this is common sense, they will also give a quieter run as the insulation will dampen noise. If air quality or respiratory issues are of concern there a good and bad filters for these systems as well. Medical grade F7 filters will take alot of pollens, dust etc out of the system and these DO NEED maintaining to achieve perofrmance.
The other thing to keep an eye on in any system is the quality of install. Ducting comes in set lengths. This needs to be installed in as straight a lines as possible between the source room and the outlets. Cheap systems with quick cost cutting installs will not trim ducting but simply coil up excess in your roof space. Each coil will contribute to killing the systems efficiency. Smooth interior linings of the ducting also add to efficiencies. Quality fans (read GRUNTY) also contribute. Hanging the fans via super strong polypropelene (DANBAND) will give you vibration free running. this stuff is rated for 90kgs, so doesn.t look much but works well. Chain hangers or fan units sitting on a building structure element will end up with annoying running noise coming through the ducts.
We see thousnads of these units installed while we are insulating houses and like I stated there are Lada’s, Rolls Royce’s and everything in between. Some of the install quality is appalling to level where ducting is not secured to fan units or inlets/outlets therefore making the system next to useless regardless of actual quality as well as sucking in stale roof space sir. Filters not installed or installed badly, fan units resting on timber and metres of not needed ducting lying about the roof space.
Advice is to check the quality of the unit you buy or is being installed on your behalf, check the quality of the install at completion and query post install maintentance or call backs. If a company is not interseted in post install advice or maintenance they may not be worth the time in the first place.
April 4, 2013 at 9:39 pm #1146Norman SmithParticipantThanks Paul, your coal face experience is very helpful.
In your experience does the same issue of quality of installation apply to heat recovery and ventilation systems such as DVS and HRV? I’m not talking about the pros and cons of positive pressure systems versus those with true heat exchangers – that’s another story – but how they are installed. Good, bad and ugly.
Norman
April 8, 2013 at 11:29 am #1147Vicki CowanKeymasterI’ll try and find the report, but I think when we got BRANZ to look at positive pressure systems there were installation issues with some of them. Of course maintenance was also a major issue – no one seems to replace the filters, and some of the photos of what they looked like in the ceiling were fairly yucky.
April 11, 2013 at 10:59 am #1151Sally BlackwellMemberIf you find this Lois, or if anyone else has got anything relevant, please upload it to the best practice library. Link on the Right Hand bar.
Thanks!
April 22, 2013 at 11:04 am #1232Jo WillsParticipantLoving this post, thank you to everyone contributing, this is great, and extremely useful!
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