Introduction
I realized those days a dual flow "homemade" which seems rather well. A small contribution to saving the planet's resources ...
It has a measured efficiency of about 65% outdoor air at 10 ° C is warmed to 16 ° C-17 ° C for an indoor temp of 20 ° C (see other measures below).
The total installation cost is approximately EUR 1000. It represents a savings of heating about 15% compared to a simple air flow but above all it brings comfort Because the air is significantly cleaner.
exchanger is a plate heat exchanger aluminum cross-flow. It was built from aluminum plates and strips bonded with adhesive polymer. There are 80 plates 350x350 mm, ie an exchange surface of 19 m2.
For those who prefer practice to theory go directly to the stages of construction photos at the bottom.
General Setup
Stale air coming from the bathroom, the toilet and kitchen in a box distribution with filter, it is then sent to a heat exchanger of aluminum (see below).
Fresh air is filtered in another box and sent in the heat exchanger where it warms. The heated air is then distributed from the interchange to the bedrooms and living room.
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Study
FlowTo estimate the number of m3 renew an hour, most theories are based on the volume of parts and their moisture. However I am convinced, like many others, that ventilation should not be based on the number of habitable m3 but the number of people and number of pieces of water .. Source polutions and humidity in a home being us humans much ..
There is an excellent analysis on the pollution human: http://www.lamaisondurable.com/2009/01/vmc-et-co2.html and http://www.canalblog. com / cf / fe / tb /? bid = 464556 & pid = 11989316
The problem is that most estimates are based on m2 or m3 of living .. including the standards of the Walloon region .. (See below pdf page 14) for a normal house but it's the same for 2 people in a big house it would be too ..
http://energie.wallonie.be/servlet/Repository/guide-mecanique.pdf?ID=10993&saveFile=true
A prerequisite is of course important that the house is sealed .. no opening at the top of the frame, no air currents in the external doors ... should not be a thermo but minimal resistance. Air is a lazy, he will always the easiest path.
A good report on this subject is also available on the website of the Walloon Region:
http://www.energie-ren.com/2009/bilan/pdfs/CETE_etude_2006.pdf Nevertheless either I renew the air of rooms and office at 45 m3 / h, the living room, kitchen and bathrooms: 75 m3 / h and the toilet 30 m3 / h. A total of 210 m3 180 m3 sucked insufler cons which makes the house a slight overpressure.
careful if you have a wood stove, it must eventually provide an additional opening for direct printing. A wood stove consumes 8 m3 per kilogram of wood Burn it is therefore about 30 m3/hr per hour expected. Either you unbalance the VMC to provide this extra air, or you are planning a direct air intake. The difference in calories that would be lost in bringing the already warmed air is negligible.
Ductwork
I noticed there were two main types of configurations VMC:- The traditional configuration sheathed T Galvanized and I will call configuration A
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- configuration with centralized distribution box I would call configuration B
Both configurations are valid but I think the configuration with distribution box that has the most advantages as I summarized below.
Configuration A is the most installed and most proven becaufe has always been used (air conditioning, ventilation of buildings ...) It is not necessarily best for a CMV turbofan Because it is more likely to have noise and pressure drop to the "T" if you do not work with some duct section sufficient in common (see orange zones) If you always work with good sections we arrive at the configuration C where there is the least losses.
configuration B is for me the one with the most advantages in VMC. This is one I used in my installation and is used by some professional installers. It is easy to install. It reduces noise and the risk of losses after the subwoofer output is not very important because the speeds are low and there are more "T" up to the mouth. There is also no risk of noise from one room to another as in a configuration A. The box in turn causes loss of course loads but still reasonable (the only figures that I found being 50Pa to 300m3 / h for a cubic box flat confotube see page 4: http://www.ventilatie.com/01/MyDocum...1_6_180609.pdf ). If flows are too high can increase even if the ducts have two arrivals per piece. This configuration can also afford to work with fans and low power without the risk of noise which makes perfect sense in the context of a CMV DF ... However it increases the cost sensitive since multiplied meters sheaths ...
C configuration would be optimal in terms of losses. It gives me a configuration optimal. But it has other disadvantages,
complicated to implement, many different sections ..
A mix of the two configurations is also possible ... to be studied case by case basis .. No configuration is really bad if the sections are adapted to flow.
Most installers keep ductwork Galva but increasingly offer networks with rigid or flexible PVC sheaths and distribution box. We can also make a distribution network with galvanized is what I would do in my new VMC construction. By cons
my box is cubic and has changes of direction at 90 ° which implies a lot of pressure drops ... best would be to build a box with optimized output at 45 ° and decreases sections. The optimized chamber should look like this:
I will publish another post about a housing allocation homemade cheap and quite effective. If you have any ideas on the subject thank you for leaving them a comment.
Pressure drop
Special attention to reduce the maximum pressure drop is also very important becaufe will reduce fan power and therefore power consumption.
I read here: http://www.camfilfarr.com/cou_fra/news/normeEN13053.cfm
that: "a filter operating at 3400m3 / h, 12 hours a day, 7 / 7 shows that : 1 Pa = 1 Euro "
We do not work with these flow fortunately ... but this is to say that the pressure losses can quickly encrypt .. do your calculations based on rates given that the VMC has two fans that run 24 hours a day ...
Then you also rely on the fact that savings on the price of the VMC less powerful if we reduce the losses ..
The calculation depends of each case. Here is mine for example. My courses in fluid mechanics is too far .. I used a free software Helios . The calculations seem to stick to reality with the exception of those in the distribution box which I think are far too optimistic ..
A calculation of losses and sizing of fans is paramount ! .. (Otherwise it probably will not get out of some mouths ...).
Filters
Beware filters .. the shorter they are more the pressure drops are high .. and will increase even faster over time will clog the filters becaufe even faster ... When I see that some have filters VMC commercial sized duct .. it's a scandal!
My distribution box also has the advantage of playing as a filter. I put a filter type G3 53x53cm! ... which is very large. There's also a box in the entrance.
A final point should not be overlooked is the noise. The noise of the VMC can not be a problem, it depends where the VMC can be placed. If it can be placed in a basement, garage or attic will win. Personally my fans are very noisy but being in the attic insulated and are connected by tubes insulating sonoflex aténuation whose sound is about 20db at 1m for most frequencies ... I almost anything faze ... he must really listen. ( I was told however that these gains tended to collapse with time .. damn!) What we hear most is the outdoor grill if the window is open ... but not like we open the window with a CMV .. AC solves the problem!
The noise gain is due to changes in speed and air direction. Below 2m / s AC is not acceptable. With the setup with subwoofer is reduced noise sensiblemement. With other configurations must be careful to "T" would be too close to a mouth.
Note on sonoflex: attention these flexible tubes have the disadvantage of causing large pressure drops at high flow rates but if flows are low there is no problem. Otherwise there is also the possibility to put only 2 m boom for insulation out of the VMC or just before the last turn or adding a silencer. I was also told that these gains tended to collapse over time ..
exchanger exchanger exchanger is a plate of aluminum cross-flow. The hot exhaust air passes over two and a plate of cold fresh air which passes in the other direction perpendicular is reheated.
exchanger was constructed from aluminum plates and strips bonded with adhesive polymer. There are 80 plates 350x350 mm, ie an exchange surface of 19 m2. The spacing between the plates is 3mm.
There are two main types of heat exchanger: cross-flow and flow against the current.
The cross-flow is an estimated yield of 50-70% against 80-95% for the current cons. I did not realize exchanger against the current because it's more complex to implement and I would not invest too much time. But now I see that it works I regret not having built a heat exchanger against the current. It would, however, probably need the fans a bit more powerful becaufe pressure losses must be higher.
The principle of cross-flow and cons current is very well explained in this scheme from the literature of NED-Air to us VMC is good ..
sources: documentation NED Air
The materials used for heat exchangers are generally PVC / PE or aluminum. The type of material has little influence on the performance of the exchanger, because the conductivity of the air gap is much smaller than the material used for the interchange. In other words, the air layer on the surface of the plate is much more insulating than the plate itself and therefore the total insulation layer plate + air + air layer is not very different with one material or another (provided that it is more conductive that the air!).
I chose aluminum for two reasons:
- lower losses. Indeed I have no cavities between my aluminum plates as found in heat exchangers PVC. The airflow therefore suffer fewer losses.
- longevity .. the aluminum more resistant to changes in t ° to moisture and frost possible condensates
Fans
Two fans of a sheath of 45 W and 65 W, which respectively rates of 260 and 340 m3 / h 0 Pa pressure. By analyzing their loss curves of pressure, I have enough speed for the load losses estimated so that's good.
Sheathing
The sheathing is made with flexible ducts isolated type sonoflex. They have the advantage of almost completely aténuer noise. However, they cause losses greater loads when working with large flows. To regulate the flow, I inserted the valves to constant air flow in such ducts:
Insulation
- I focused on a perfect insulation of pipes. (+ 6 insulated ducts cm glass wool in conduits) a picture will follow. Indeed it is not enough to have a powerful heat exchanger .. yet it is very necessary insulate ducts not to lose the precious heat recovered and to avoid condensation in the exhaust ducts ... Even if the ducts are insulated in an attic or basement, it is absurd to heat these spaces are not living spaces. By cons, if the ducts are in the envelope of the living space when it is actually not necessary to isolate.
- The housing allocation is isolated from the inside by 2 cm of polyurethane and externally.
- The windbox is not isolated because it's inutil
- exchanger and suction fan are insulated with polyurethane.
- insulfation The fan is also isolated but more for steel string and thermal issues ..
Cost The total cost is approximately EUR 1000 all inclusive (ducts, fans, vents .. and all materials) ... and a short week DIY hard ... The cost can be significantly reduced by using PVC honeycomb plates as proposed by
Antifreeze
If frozen hard, condensate can freeze on contact with indirect air entering galcial. To prevent any interchange is so stuck in the ice there are several solutions:
- draw the air inside the attic .. AC can unbalance the VMC and it must not freeze too hard in the attic
- short circuiting a portion of the outflow into the stream returning (AC polu a little air but AC heats free)
- heat the incoming air with a resistance .. AC consumes power
- decrease the speed of the incoming stream .. AC unbalance the breakdown ...
Results
I put the fan on A few days ago and it is still early to draw conclusions but I can already say that:
- air is breathable .. a feeling of home ventilated continuously without too cool which is really nice. The house is already much drier .. and one feels in the morning the air is drier. The walls being drier I guess we will also win in isolation .. nothing more conductive than the damp walls ...
- a first rough measurement gives: Internal temperature 20 ° C, 10 ° C and outside air temperature at 16 ° C insufler ...
an efficiency Thermal (Tins-Text) / (Tint-Text) = 60 ° C% pil!
rather encouraging ...
- a second measure text 10.5 ° C, held 19.5 ° C and air at 15.5 ° C has a yield of 56% a little less good but my thermometer takes forever to level ... I'll buy a thermometer worthy of the name .. text
- 13 ° C 19 ° C held tins = 17 °> 67% humidity 55% AC back; text
- 16 ° C 21 ° C held tins = 19 °> 60% Rate Humidity 58% text
- 13 ° C 19 ° C held tins = 17 °> 67% humidity 60% as yesterday morning
- text 15 ° C 21 ° C held tins = 19 °> 67% humidity 57% .. AC is confirmed, but I absolutely have to buy a thermometer more accurate .. text
- 13 ° C 20 ° C held tins = 18 °> 71% humidity 65% text
- 10 ° C kept 19 ° C 16 ° C INS => 67% moisture content 67% ( it's raining this morning) text
- 9 ° C kept 19 ° C 15 ° C INS => 60% (after an absence of a 1 / 2 day minimum heating) text
- 7 ° C 18 ° C held 14 tins C => 64% (51% humidity, am a bit cooler ...) text
- 8 ° C 20 ° C held tins 15 ° C => 58%;
- text held 17.2 7.8 ° C 13.5 ° C INS => 60% (new themometre .. not much more accurate and much slower is stabilizing ... (-!)
I Then surisolé pedestals with 6 cm of polyurethane and bought two new temperature sensors and an anemometer Testo. I will publish new measures soon:
Premiere measure:
- text -2.1 ° C, held 15.4 ° C, 9.8 ° C INS => 68%
efficiencies announced by the manufacturers of VMC are measured under optimal conditions at the outlet of the heat exchanger ... I measured under more adverse: the air temperature outside the chamber air inlet, the inside temperature on arrival at the interchange in the chamber and the temperature distribution in a mouth insulfée blowing
- few drops of condensate out of the heat exchanger ... no condensation in the housing allocation. Yesss!
- to measure the beginning I first used an anemometer to home Décalton which gives only very approximate measures ... I then bought an anemometer testo 410 much more accurate, which gives me speeds that correspond to the calculated flow rates.
- powers measured fans. P = U * I * cos (phi) (fan => cos (phi) ~ = 0.7) and measured with a Amperemeter I + / - 50 and 35 W consumed. We need a power meter to know the exact phase shift.
Grounds
VMC I cobbled this for several reasons:
- limited access to the attic making it impossible to move from a CMV commercial
- scalable and robust system. the only thing that I will eventually replace in the future is a fan .. filters s'ecrasseront slowly saw their sizes and are easy to replace.
- house well insulated but not K45 impossible to have the premium
- price (all inclusive ducts, materials, Ventilos ...) for 1000 Eur. The VMC cheap trade does not break enough and have even less efficient exchangers. And anyway nothing but the VMC is already costing more than 1000 usd
- fun, challenge and pride of the builder! ... (Do not launch into the adventure if you do not tinker !) ...
Other similar projects
- Jean-Pierre has built a base plate exchanger plastic packs:
http://www.autoconstruction.info/La-fabrication-d-un-recuperateur.html - Joel began construction of an interchange at current aluminum cons:
http://www.autoconstruction.info/Fabriquer-un-recuperateur-de.html - Mission Project "troglodyte" was also made with a CMV-based exchanger plate packs, he also did a great calculation of pressure drops very instructive
http://missiontroglo.canalblog.com/archives/ventilation/index.html
Detailed description and photos
Construction of the interchange
Collect aluminum plates and strips cut to proper size. I bought the plates from a wholesaler in my area http://www.ironsaleeurope.be/index_fr.html (very cool ..) A cartridge of adhesive polymer Tec 7 should suffice. 
The plates are bonded with adhesive polymer (Tec7). I did some tests, cold welds and other adhesives are not enough Resita (the worst being the Soudal) ..
3mm shims are placed in order to obtain a pressure throughout the plate.
must be glued to the plates under pressure for 24 hours.
Tabs are placed at the corner of the cube corners to seal the heat exchanger in its box and increase strength. The cube is strapped to secure the corners. The leading edges of the plates are contoured to the mill to reduce losses.
Count 4-5 h to complete the cube ... Best is to do 3-4 x not to let the glue dry before putting too much pressure.
cabinet exchanger
exchanger is placed in a wooden box. The box is sealed with rubber sheeting (aquaplan.be) and rubber bands.
The pecking rights are screwed to the fitting of the ducts.
A release is scheduled for condensate recovery. 
Housing Allocation and filter
The chamber air distribution collecting stale air is also built of wood and insulated to prevent condensation of the air before it enters the heat exchanger.
To have easy access to the filter, I made a hinged lid with style tie trunk.
The airtight lid is secured by rubber bands (a groundsheet cut)
Assembly and installation Seen necking access to the attic (45x45cm) everything has been done in pre-fabricated and assembled on site.
Do not forget the condensate ...
Although seal it with silicone joints between plates and adhesive tape to ensure airtightness.
I finally installed the caissons, the heat exchanger and fans as shown in figure above.
And here's the result ... a picture with the insulation will
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