DIY ventilation heat exchanger

[Piwoslaw]

Fornax & Kostas: One more HUGE thanks for building your recuperators and for sharing the details here. The step-by-step write-up is priceless for any would-be DIYer with less than ideal manual skills

I would like to ask if both of you could share the cost of your setup with us. If possible, please break it up into individual items, like how much for the HX core(s), the cabinet, the fans, ductwork, any random stuff.

[kostas]

Thanks Piwoslaw, it was a pleasure sharing
I would like to wait a while for a step-by-step guide as I am still heavy-testing the machine, that's to avoid giving wrong instructions to the people. But I promise I will do it

Speaking of costs and efforts, here is a short list:

PP core: total 9 sq meters €40 (including machine cutting)
Aluminum core: 70 pieces 30x30cm cut out of used printing plates (a friend of mine who works there gave them out for free), 20 min of machine cutting by another friend hammer smith (that cost me a bottle of Cabernet Sauvignon )
Motors €40 each
220v Speed selector €17 (a theft!)
Polystyrene sheets €10
Plywood sheets reclaimed from used pallets at my work.
90° Aluminum profiles €13
Aluminum tape €7
Screws and nails €3
Isolated ducts reclaimed from other works (another friend, thermal technician this time)
Cables, plugs and every other stuff already had it in my lab.

Total: €170

Total working hours: 49

Working period (not including reading, learning, drawing concepts and thinking endless nights!): from July to December.

Hope that helps and.... to be continued!!

[Fornax]

Piwoslaw, thanks for your thanks : )

In a separate thread I'll document my entire build (in the near future), when it's completely finished.

I can say a few things now though. The Apparatus is working, and it is working well.
The WSF-score is good so far: This morning she said the inside air is good, like as if windows were open the entire night, but with the windows closed, also less cold. Around lunchtime she fired up the deepfrier, without turning on the cookinghood. No smell of fat in the livingroom. Dinnertime: cook & bake dinner, no smell in the rest of the house (livingroom). I quote my wife: "We don't need the cooker-hood anymore."

After about 1 day of the apparatus working, and the windows closed, I can state the obvious: the central heating is running less than before, and that is a good thing! (My particular setup saves natural gas and coin.)

Now onto the heat recovery, this is less than I expected.
Temperature in the livingroom is 20C, FAI (Fresh Air In) (warmed up by the HRV) is 18 or 18.5C. This sounds fine but OAO (Old Air Out) is extracted right underneath the ceiling at 22C. So the apparatus is working fine, the FAI is comfortable but the efficiency is way lower than I estimated it to be. This means my heatexchanger is not working like I expected it to do.

As for buildingcosts I guess mine did cost around 800 euro so far, this does exceed what I estimated by 50% Things are cheaper in the USA plus we have 21% VAT here. So for building contraptions like these we can equall dollars to euros.

A whole-house HRV installed by a commercial party would have cost some 2000,- to 6000,-. At this moment the HX is performing under par but we are happy with how the apparatus is working.

I do need to investigate why the apparatus is not as efficient as I estimated it to be, at the moment it is at around 75-ish%. (Kostas' cores are much larger, both of them.) so perhaps it is working well for it's size (in which case I undersized it.)

The temperature of the FAI is fine but I am cheating: the cold FAI is coming from our crawlspace which is much warmer than the outside air.

[Piwoslaw]

Originally Posted by Fornax

I quote my wife: "We don't need the cooker-hood anymore."

Not sure if this is technically possible in your house, but maybe the HX could be hooked up to the cooking hood so that it sucks up the stale air directly from the kitchen?

[Gasper]

I gave up on DIY heat exchanger, for now. But I did all the piping to 7 rooms and it cost me around 700 €. I am thinking of buying a cheap ERV unit from china (Holtop) for less than 500€ with digital controller. The only draw back is that the motors use 105 W for 150 m3/h at 75 Pa.

[Gasper]

4. post, don't allow links

[Gasper]

.. and the 5. post with ...

[Gasper]

Here are some of my observations:

There are two types of exchangers:
- HRV - heat recovery ventilation - the exchanger is made of aluminium, coroplast or plastic. Temperature efficiency can be over 100% if there is high humidity in indoor air. The draw back is that latent heat is not transferred, and in cold winter the air coming into the house will have extremely low humidity. And if you are changing 1/2 of house volume per hour you can expect room humidity <30%. Of course if you live in a humid climate with not so low temps this type of exchanger is very good. You also need a water drain from the exchanger.

- ERV - Energy recovery ventilation - The exchanger is made of paper or rotary air-to-air enthalpy wheel. The point is that latent heat (humidity) is also transferred, the temperature efficiency is normally <80%, but this type of exchanger will maintain room humidity around 40%-50% almost under all conditions in winter. The exchanger doesn't need water drain. You can DIY this type of exchanger from card board:
cheap easy living - Air to air heat exchanger
Izdelava kartonskega izmenjevalca | PodSvojoStreho
The recuperator from last link is working well for 2 years with no problem, no it's not mine.

[kostas]

Originally Posted by Piwoslaw

Not sure if this is technically possible in your house, but maybe the HX could be hooked up to the cooking hood so that it sucks up the stale air directly from the kitchen?

Negative, fat and oil contained in the cooking air will rapidly dirt and obstruct the HX cores.
There are some cooking hood models that include a small HRV inside, but are way too expensive.

[Daox]

Originally Posted by Gasper

Here are some of my observations:

There are two types of exchangers:
- HRV - heat recovery ventilation - the exchanger is made of aluminium, coroplast or plastic. Temperature efficiency can be over 100% if there is high humidity in indoor air. The draw back is that latent heat is not transferred, and in cold winter the air coming into the house will have extremely low humidity. And if you are changing 1/2 of house volume per hour you can expect room humidity <30%. Of course if you live in a humid climate with not so low temps this type of exchanger is very good. You also need a water drain from the exchanger.

- ERV - Energy recovery ventilation - The exchanger is made of paper or rotary air-to-air enthalpy wheel. The point is that latent heat (humidity) is also transferred, the temperature efficiency is normally <80%, but this type of exchanger will maintain room humidity around 40%-50% almost under all conditions in winter. The exchanger doesn't need water drain. You can DIY this type of exchanger from card board:
cheap easy living - Air to air heat exchanger
Izdelava kartonskega izmenjevalca | PodSvojoStreho
The recuperator from last link is working well for 2 years with no problem, no it's not mine.

If you're in a cold climate you will have problems with your HRV or ERV freezing and eventually plugging up from what I've read. This is why some units have a resistive heating coil in them to preheat outdoor air when needed.