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Old 04-18-13, 02:14 PM   #401
Fornax
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Hi All,

It's been a while since I posted but there are so many details that it would be a very long post.

So instead I'll start with a simple write-up summing up some of my experiences so far, not very organized. A great chance for you all to ask about points of interest on which I can give details.

I 'fired up the engines' on january 9th when I got all the ducts more or less connected so I had the airflows. Back then none of the ducts were insulated so a lot of heat was exchanged with the surroundings (the unheated shed).

I kept the apparatus running since, aside of short intervals when I needed to disconnect ducts or disassemble the HX-core. Since 'launch' I properly routed all ducts and insulated them, also applied dustfilters.

- Since starting the HRV the windows stayed closed, which greatly increased comfort in the livingroom since the lowest 2 feet weren't so cold anymore.
- We did turn on the heating higher than in previous winters (ohh, bad).
- We used around 15% less NG on heating than in 2012 calculated on heating degree days, even with the heating set to higher temperatures.
- With the central heating running less the rooms upstairs were noticably colder.

- Old Air Out is drawn out from the kitchen, right underneath the ceiling. Here the temperature could reach 28C with 3 pans on the furnace while preparing food and as a result the Fresh Air Out (blowing fresh air into the livingroom) could reach a whopping 24C. As a result I turned down the thermostat half an hour before cooking, otherwise it would get way too warm in the livingroom :- )

- The Fresh Air In blowing air into the livingroom created a strong airflow sticking to the ceiling, untill reaching the opposite wall right above the couch. While sitting on that couch a noticable draught was felt. I modified the inlet to create a more diffuse airflow.

- With the larger amount of air ventilated the inside air feels much fresher and there appears to be less dust settling on furniture and such.

- I don't have good temperature measurements. I only have 2 simple thermometers on which I can guestimate values by half a centigrade. This makes calculating the efficiency of my HRV a bit tricky, especially since temperaturedifferences are quite small. Best I can say is that it's between 65 and 75%.
Yesterday I ordered a buch of digital thermometers from DealExtreme. Alas the weather is improving and the heatingseason is comming to an end, oh wait, that is a good thing!

- Designflaw: The square area of my filters as applied now is too small, clogs up relatively fast causing imballance between the 2 airflows.

- Designflaw: Negative pressure on both channels in the HX-Core. The core _will_ leak so it must be: draw stale air and push fresh air through the HX-Core. (Observeable while cooking, and you don't even need a lot of garlic.) That way the leaking will be from the fresh to the old air, so the incomming air to my livingroom will be 100% fresh.

So on my to-do list are:
- make seperate filterboxes.
- relocate the fan in the fresh air channel so it pushes air into the HX-Core.


I did make another modification to my HX-Core and I can say the fans I choose are working lovely. More on that later though.

Fornax


Last edited by Fornax; 06-28-13 at 02:39 PM..
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Old 04-18-13, 02:48 PM   #402
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Hey, this is great news, Formax!
Today, as I was coming back from work, I was wondering what happened to this thread, and I was planning to give some info, too. So I guess you have beaten me on time
As for me, I dismantled everything last week, now it's quite warm and I will soon need my balcony to be ready for having dinner outside, so I put everything back in my garage.
It's also good to hear that you are happy with the motors. Did you managed to get some current consumption data, too?
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Old 04-18-13, 03:29 PM   #403
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Heya Kostas,

As for the fans, yes I have some data. A few weeks back I connected them to my kill-a-watt so I can monitor their combined powerconsumption.

According to their specsheet in the lowest setting (of 3) they are said to use 8 watts. What I measure right now is 34 watts though for the two combined.
To me this is plausible since the fans have to overcome the load of the dustfilters and the HX-core. I can also see when the filter(s) are getting poluted, powerusage will climb up slightly to 36/37W.

Earlier I mentioned to you the fans are very silent. And indeed they are when they need not overcome any resistance. As they are now they do make some sound, comparable with any whole-house-ventilator.

To me this is not a problem, the fans are located in a different room and the sound through the ducting is only noticeable when you know what to listen to. (The HD in my mediaplayer is louder).

Together for both fans the use of electricity is about half of that of the single whole-house-fan that was installed 30 years ago, still a win-win situation.
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Old 04-18-13, 03:55 PM   #404
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Nearly 40w / 24h use (worst case) means aprox 1Kwh/day, that's almost €6/month, at least here in Italy. Not bad at all, a better living surely worth it!
Thanks for your feedback, Fornax
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Old 04-18-13, 11:23 PM   #405
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Thanks for the data!
Quote:
Originally Posted by Fornax View Post
According to their specsheet in the lowest setting (of 3) they are said to use 8 watts. What I measure right now is 34 watts though for the two combined.
To me this is plausible since the fans have to overcome the load of the dustfilters and the HX-core. I can also see when the filter(s) are getting poluted, powerusage will climb up slightly to 36/37W.

Earlier I mentioned to you the fans are very silent. And indeed they are when they need not overcome any resistance. As they are now they do make some sound, comparable with any whole-house-ventilator.
When you install larger filters the resistance should drop, and with it the noise and power consumption.
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Old 04-30-13, 02:31 PM   #406
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I aquired and installed 4 thermometers with good resolution so now I have somewhat reliable numbers on how my HRV performs.

The thermometers I got are discussed here

It turns out my HX-core is not as efficient as I expected/hoped it to be. A good thing though is that my FAI (Fresh Air In) is preheated for free by my crawlspace so the low efficiency of the HX-core didn't leave me with cold fresh air when it was freezing 15 degrees centigrade last winter : ) The lowest FAI I measured back then was around +12C.

Code:
FAI     OAO    OAI     FAO              %efficiency
T1      T2      T3      T4              IN      OUT
15,5	17	19,7	18,3		67%	64%
15,8	17,7	21,4	19,6		68%	66%
15,5	16,7	19	17,8		66%	66%
15,9	17,5	20,9	19,2		66%	68%
These measurements are taken when the system had been in a steady state for a while (Central heating off, no cooking, no direct sun in the kitchen).
Values are also adjusted from the raw readings to the actual temperatures, oh, in degrees celcius.

One can see the calculated efficiency is quite consistent.. and low. Only 66% where one would expect a counterflow HX to perform better than this.
Also IN and OUT are the same which means both flows appear to be balanced nicely. I asume this indicates that my fans are working fine and I made the right guesses when choosing diameter of ducting.

So I have a working HRV that even my wife is appreciating by now. Now I need to think about what is wrong with the HX-core and how to improve it using what I have. I have some ideas but no rush, heatingseason is over.

Fornax
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Old 05-10-13, 03:39 PM   #407
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Testing post for the first time.
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Old 05-10-13, 03:48 PM   #408
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Default Commercial or DIY HRV for a cottage in California?

OK, my test worked so here goes...

Greetings everyone! I'm a new member and I think it took me four hours to go through all of the posts going back more than three years! I commend and thank all of you for keeping the conversation going for so long with such camraderie and enthusiasm.

I have a few comments before I introduce my own situation with HRVs. First, if any of you who have successfully built working devices are interested, I encourage you to post detailed instructions on instructables.com, or some similar site, where many more people will be able to access them easily. Second, it would be great if someone compiled an "HRV lessons learned and great links" thread. The bottom line is that the vast amount of information in this thread is too dispersed and difficult to access, considering the digital age that we live in.

Regarding HRV designs, I don't have much to add to the conversation (at least not yet), but I did come across some materials that I don't think have been mentioned here. There are three different types of signage material similar to coroplast, but with aluminum on the exterior instead of plastic (the corrugated core is still plastic). These are called Alumalite, D-lite, and Econo-lite, Unfortunately, they are all rather pricey, but they would probably offer somewhat better heat exchange than coroplast.


My situation is the following: I live in Berkeley, CA and I have a 300 square foot cottage in my backyard that is a converted garage, and which I rent to a single person. The climate here is very mild and on the cool side, known for our foggy summer mornings. In the winter, the daily temperature generally goes from 4-13 C and in the summer from 13-22 C. The cottage is an uninsulated, concrete block building (except the roof is insulated), that has one large space with a kitchenette, and a small, separate bathroom. In its present state, the cottage is very inefficient in terms of heating (it's heated with a modern natural gas space heater).

I'm planning to add insulation and drywall to the West and North walls, and possibly make the South wall into a Trombe wall (it has very good solar exposure), put in double paned windows and add a layer of insulation and laminate flooring on the concrete slab. The cottage tends to be damp, especially in the rainy season, and that's why I want to put in an HRV. Since the space is only 300 square feet, I think the HRV only needs to have a flow rate of 20 cfm or so.

My quandry now is whether to buy a unit or go DIY. All of the commercial HVRs that I have come across are much too big for such a small space. Through this thread, I learned about the Panasonic WhisperComfort™ Spot ERV. It has a very low flow rate, low energy consumption and it's very reasonably priced. However, it is an ERV, so my concern is that it will not remove enough of the excess humidity that I want to get rid of. I spoke to a sales rep at Panasonic today, and he said that the Whispercomfort would only pull moisture out of the interior air when the humidity is higher indoors than outdoors. That sounds pretty good to me, but I'm not sure. Perhaps I should start by measuring the indoor and outdoor humidity over a period of time. Can any of you shed some light on this issue? Most of the info I've seen online, as well as in this thread, pertains to places with more extreme climates than what we have, so I need help conceptualizing how this ERV would perform in my situation. If I can get to a place of feeling like the Panasonic will do a good job, then I'll probably buy one. But, I don't want to make that investment and then find that the cottage is still too damp afterwards.

On the DIY side, I really like the results that some of you have gotten with your HVRs. My main two concerns are that I have so many other projects brewing that adding the HVR would be burdensome (I want to have a working HVR within six months). I also wonder whether a DIY HVR would be reliable in the long term. Also, I am not living in the cottage, and I don't want our tenant to be too much of a guinea pig, especially since ventilation does affect one's health. If I decide not to go DIY for the cottage, I still have the option of making one later for my clothes dryer exhaust (another great idea from this thread!) If I do go DIY for this project, I also wonder how to size the heat exchanger.

Thanks, in advance, for your advice!
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Old 05-10-13, 05:13 PM   #409
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Quote:
Originally Posted by WattWatcher View Post
... it would be great if someone compiled an "HRV lessons learned and great links" thread. The bottom line is that the vast amount of information in this thread is too dispersed and difficult to access, considering the digital age that we live in...
WattWatcher,

Thanks for your post. I think your idea of a 'lessons learned' thread is one that is very much needed, and there's probably no one better suited for that project than you, since you recognized the need and have just read the entire thread.

It would be helpful to everyone if you took that on. As you can see, many people have done considerable research and also have done hands on work which they were so generous to document and share.

Your authorship of that thread would be would be a generous contribution on the very same scale.

Best of Luck,

-AC
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Old 05-11-13, 03:51 PM   #410
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Ventilation will keep indoor humidity down if the outdoor dew point temperature is at least 20 deg F lower than the inside temperature. For example, the outdoor dewpoint right now is 58 deg F at the Oakland airport. If the indoor temperature is below 78 deg F, the house will be humid inside. If the house is poorly ventilated, it will be even more humid inside.

If the outdoor dewpoint reaches 70 deg F, the house will be a swamp inside. The solution is a dehumidifier. No need for ductwork, just put it anywhere in the house and set it for about 50% RH.

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