12-18-09, 12:56 PM | #221 |
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Except for the "HVAC girl" I talked about previously, HVAC engineers tend to be hostile to amateurs. They often claim stuff about safety, but that is a very weak argument since automotive repair is even more dangerous (plus a mistake in automotive repair is more likely to hurt innocent others) and every automotive parts store I've been to has been very willing to help with how to troubleshoot and repair just about anything on a car, even those that are safety-related.
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To my surprise, shortly after Naomi Wu gave me a bit of fame for making good use of solar power, Allie Moore got really jealous of her... |
12-21-09, 01:27 AM | #222 | ||||||
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CN: Thanks for your excellent report...
Christian Nelson,
Thanks for your excellent report. Quote:
Now that your into the thick of winter, what is your assessment of your combo-hydronic system? Is it delivering heat to your home as you had hoped it would? What kinds of things would you do different? What did you do that was really right? Do you know what the 'degree days' are in your area? How well is your place insulated? Can you share details regarding your hydronic floor layout? Did you use a 'wet system' or a 'dry system'? More details of the radiators? The reason I'm so curious is that I'm about to put one in my place in a few weeks, and I'd appreciate any advice you have. Quote:
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A slightly different approach I am considering is to use the heat pump to extract heat from the water storage tank down to a point that would prevent the tank from freezing, in my area. Then the heat pump would switch to ground source heat extraction, until solar energy brought the storage tank up to some desirable temperature. This plan would have the advantage that the heat pump would chill the water that was flowing through the solar heat collector, giving the collector a larger delta-T, which will result in higher collector efficiency. The water-source switching can be done with electrically controlled water valves, which are used in the hydronics industry. My tests indicate that the water-source temperature has a direct, positive effect on COP... the higher the temperature, the higher the COP. But only up to a point. If the feed temperature gets too high, it can boil the refrigerant prematurely and mess up the evaporation/condensation cycle. So there's still work to do. BTW, I went to a local solar equipment trade show a couple of years ago and I told them about my idea of a heatpump-assisted solar collector, and everybody I spoke to got really excited... always a good sign. Quote:
I can tell you that the fusing process is really pretty easy, and is incredibly strong. But as I learned, you need to be able to test every weld... very important. Quote:
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I really want to hear about the foam injection scheme... Have you figured what the cost per cubic foot is? Do you have any info as to the R-value of the foam? My method of using slabs of EPS foam layered up in the wall is working, but it is a fearful lot of work. Good luck on your project! Please feel free to ask any questions and share any discoveries you have along the way. And in case you haven't noticed, there are loads of people tuning into this kind of thing. We're all in turn: scientists, grunt workers, pirates and a revolutionaries. This is exciting stuff. Best Regards, -AC_Hacker |
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12-22-09, 08:24 AM | #223 | |||||||||
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Wow, gave me homework already!
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What I did wrong.. Well, biggest one was not using oxygen barrier PEX for my infloor loops, and between base board radiators. I've worn out a couple of pumps due to corrosion in 3 years of use. I am not going to be able to pull the runs out of the concrete, so I am planning on replacing my pumps with bronze as they fail, and maybe trying to find a nontoxic corrosion inhibitor to add to the water. Another bad move was I trusted a solder joint that was blind, I saw it flow, and assumed it wen all the way around. Of course, it was right above the new boiler I installed this year, and it didn't leak until a few weeks after I had it all going great. It leaked on to the controller board, and burned it up before I discovered the issue. I ended up buying a new board for $400 (after I finally found a place willing to sell it to me) so ALWAYS check all the way around your solder joint. Get a mirror if you have to. Quote:
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12-22-09, 08:25 AM | #224 | ||||||||
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12-22-09, 08:48 AM | #225 |
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Oh, forgot to mention, the new boiler is only consuming 400 gallons, where the old one used 900 gallons of propane.
If that trend continues, the new boiler will have paid for itself in a year and a half. Now, that may be because I was seriously not running the old system right. But, I have talked to others around my area, and 2000 gallons a year isn't out of the question for most, so what I was getting last year, seems to be average for my area. I also was wrong about the frost line. For footings, it's 42" to up to code, around me, the water pipes and sewers that aren't 6 feet down freeze if you don't have good snow cover in January. I have a poorly updated blog about my house project located here: http://nelsonics.blogspot.com/ Last edited by Christian Nelson; 12-22-09 at 09:38 AM.. |
12-23-09, 03:05 AM | #226 |
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Christian Nelson,
Just a quick reply, I'm getting ready to leave town for a few days, so my time is short... Wow! Sounds like you're really taking the bull by the horns! Yeah, I think you're on the right track with the insulation. I like the idea of zero infiltration. At some point you may need to consider a heat recovery ventilator, if your house gets super tight. Regarding heat pumps, the reason I got into building mine is that I couldn't find a water-in-water-out unit that was less than 4 Tons (1 Ton = 12,000 BTU/hr). It looks like your weather conditions are quite demanding, compared to mine and your house is larger too, so you may be able to find a unit already built that would work for you, in the 4 Ton range or larger. Don't know if you read the part of my blog where I talked about using electric heaters with Kill-A-Watts attached to get precise real-time heat loss measurements. Don't know if I'd try that on a house as large as yours, but if you could measure the amount of propane you actually use an a per hour basis, as temperature fluctuates,it would be very useful information for future heating calculations. I found that the Hydronics Explorer program over-estimated my heat requirements by about 50%, which is really quite close. So, if you are able to keep your house warm with feed temperatures of 120 or less, you'd be a good candidate for a ground source heat pump, because that's pretty close to the limit of the present technology. The Japanese are working on Carbon Dioxide vapor-compression units which will reach higher temps. Some units are entering the market already. So the feed temperature is important. Better insulation means lower feed temperatures, less firewood, less propane, less Tons of HVAC, as I'm sure you know already. I think your wife deserves a shiny golden trophy... not every wife would survive such a major upgrade adventure such as your family is on. Kudos to all of you! Best regards, -AC_Hacker |
01-01-10, 11:25 AM | #227 |
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ac hacker, I have been skimming this epic thread of yours trying to find out where exactly you got that heat exchanger, I'm going to do something something similar for my ac in the house, and this will be a whole other thread but I think I'm going to add one on these to the fridge first and use the waste heat to preheat my hot water.
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01-02-10, 01:15 AM | #228 | |
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Where to get Heat Exchanger...
Joe,
Welcome to the conversation! Quote:
If your circulating fluids are clean and in closed loops, you should have no problem with 'fowling', which seems to be the biggest potential problem with brazed plate heat exchangers. If you try to buy them from a reputable outfit that is in the business of selling heat exchangers, you'll have to pay with your arm, your leg, and your first born... However, if you do a search on ebay and use a term like "brazed plate", you will find many people selling them, some at prices that are sure to fit your budget. The next problem will be to determine the size you need. In this post, you'll find a discussion regarding selecting a heat exchanger, or in engineering, "sizing" a heat exchanger. I plowed through quite a few web sites and poured over many tables and created this formula: Heat = ((width) x (length) x (# of plates - 2)) x 1950 [* NOTE: a previous version of this formula had 5000 as the last term. Subsequently I have come to realize that the formula overstated the capacity if the heat exchangers, and I have changed the multiplier to 1950, which produces more reliable values *] ...where:
You might need to play around with it a bit to get what you need. So for instance, if you hooked a Kill-a-Watt to your refrigerator, and found that when it was running for several minutes, it was consuming maybe 400 watts, you'd convert the watts to BTUs like this: BTUs = Watts x 3.412 = 400 x 3.412 = 1364.8 BTU So, you want a heat exchanger that was at least this size or larger. If I looked on ebay, I see a small 10 plate exchanger for $45, not too bad. It is 7.52 inches long = 0.6267 ft it is 2.87 inches wide = 0.2392 ft Plugging that info into the formula I created goes like so: Heat = (0.2392 * 0.6267 * (10 - 2)) x 1950 = 2338.54 BTUs This would be nearly twice what I need, so the heat exchanger would work well for my project. The particular heat exchanger in the link has this fitting info: Fittings Available: All 4 ports: 1/2" Male NPT All 4 ports: 3/4" Male NPT All 4 ports: 1/2" Female NPT All 4 ports: 3/4" Female NPT All 4 ports ... NPT means that it is pipe thread on all connections. This is good for water, good for beer, but not so good for refrigerant, which spends it's life searching for ways to escape. The kind of connections you want on the refrigerant side are called "sweat" fittings. which would suggest sweat soldering, but remember that refrigeration connections want to be brazed. If you keep searching, you will find the size you want, with the connections you want, at the price you want. Good luck! Best regards, -AC_Hacker Last edited by AC_Hacker; 01-10-11 at 07:30 PM.. |
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01-02-10, 04:24 PM | #229 |
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Great info as usual, I can find the NPT ones all day long, but the problem I'm having is finding one with sweat fittings. I didn't know if you had found a good supplier for them or not.
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01-02-10, 06:54 PM | #230 | |
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Heat Exchangers
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I don't know how carefully you searched... Did you try searching the supplier's "store" in addition to the ebay posts? Might help. If you find a supplier or two or three that seems reasonable, you might even send them an email... never hurts. They just might have exactly what you want, or it might be coming in soon, or maybe they could order it for you. Long as you're at it, you might see if they can get a 5-plate exchanger, since the 10-plate was over-capacity. Could save you some money too. As a final desperate measure, you might try to make your own heat exchanger, probably not brazed plate, that's pretty sophistocated. But check this one out: Soft copper tube inside soft copper tube, the picture tells the story... This style is called tube-in-tube. It would be a real crap shoot knowing how much tube to use. You could always make one and just try it out. A lot of good stuff gets made that way. If it was me, I'd start with five feet of tube. When I tried my first Brazed Plate lash-up, I had no idea if it would work or not, I just hacked it together and tried it out. Worked good. Then I studied up on capacities and all that and found out that I could hardly have been closer. Best of luck! Regards, -AC_Hacker Last edited by AC_Hacker; 01-02-10 at 08:40 PM.. |
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Tags |
air conditioner, diy, gshp, heat pump, homemade |
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