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I'm helping my brother air-condition his house. Right now he has no cooling at all, because Stockholm normally isn't super hot and house AC hasn't really been a thing historically. His house is equipped with a geothermal heat pump for heating both hot tap water and the heating water that goes to radiators and convectors. The heat pump pumps its heat from a sealed circuit filled with an ethanol/water mix (that everyone calls "brine" for some reason, sometimes it's glycol based too) that goes in a long hose down the bottom of the 100m+ deep thermal well and up again. The heat pump gets brine at 6 degrees Celsius in, and it sends 4C back down the well, pretty much. 6C is a normal and good thermal well temperature where we live. The plan is to route the brine from the thermal well into the attic space, into a water-to-air heat exchanger. After this it's pretty conventional house AC I think. Brother knows electricity, I've done a bunch of plumbing (we'll use copper with mainly pressed fittings for the ethanol brine because of the fire code and probably pex for the condensation drain) but none of us have any experience with air conditioning or ventilation. I should probably mention that the point of this whole deal is to get what is essentially free cooling during the occasionally hot summer months since there's an endless supply of cool brine. The only energy costs will be the brine circulation pump and the air blower. Depending on RPM on the rotating bits it should be in the range of a few hundred Watts of power at most to get several kW worth of cold air. These kind of systems aren't unheard of here, but they're not exactly common either. The plan for the air side of things is basically a thick duct (250 mm) picking up air at a single point in a central hallway ceiling. This will be routed in a horseshoe shape round the perimeter of the attic space through a dust filter, a blower, the heat exchanger and a bunch of outlets. Where the main duct is over a room we wish to cool, we'll use a T-piece to a narrower duct (125mm) that goes into an adjustable ceiling air outlet. There will be about 7 of these ceiling outlets. The plan is to balance the airflow between the rooms using the adjustable outlets, and regulate the temperature with a single air temp sensor controlling the RPM on the air blower. The brine pump will likely run at a constant, sufficiently high RPM unless the heat pump needs the brine for making hot tap water, when there won't be any AC at all for a few minutes every now and then. It is probably possible to route the heat pump and attic air cooler in series if this turns out to be a problem but right now they are parallel, so it's one or the other (the plumber who recently replaced the 20 year old broken heat pump installed copper fittings on the existing brine circuit for this so that's the only part of the project that is done already) Parts and materials for the whole shebang should cost 3000-4000 euro or so. A few things I want to know: -Does any part of this sound dumb? -what is the easiest way to insulate air ducts to prevent condensation? -Are flexible air ducts fine or are hard ducts clearly superior? -What needs to be done to muffle the sound of the blower and the moving air? -I've always heard that pex tube/hose can stand water freezing inside it without issue. Is this actually true?
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Nov 14, 2021 10:00
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Thanks for feedback. Duct wrap might be commonly available where you live, but these things aren't really common or available here, at least not in any big box stores that cater to amateurs. I'm sure we can order it though, or worst case improvise something. There's more than one way to skin a cat, so I wouldn't be at all surprised if what's available in norther Europe is totally different than what is common in the US. I know lots of our plumbing/electrical/normal house construction practices and materials differ and it's likely that the same goes for moving air around. The reason for considering flexible duct is the space available. The house is rectangular and has what I think is called a hip roof, at least that's the shape of it. I don't know the words to describe the structure of the framing, but there's lots of lumber and zig-zags spaced about 1 meter apart going across the rectangle. We've added more insulation to the bottom of the attic and put in a floor up there for storage, and we'd like most if not all of the ducting to go past the outside edge of this floor, into the wedge where the outer roof meets the attic floor - or rather the top of the insulation, since the lack of headroom made it senseless to floor all the way out. The point is that it would be very difficult to manoeuvre any lengths over about 1.5 m of hard ducting into this space because of all the lumber holding the roof up, so using mainly flexible ducting seems attractive for this reason. As for turning the A/C brine pump off when the heat pump is making tap water my brother has assured me it's no biggie, and I have great confidence in his considerable electrical/electronic abilities. The heat pump is pretty beefy and puts out 12kW at full tilt, so hot water production doesn't take long or happen very often. It's a modern unit with RPM control on the compressor so this time of year it's mostly slowly ticking over keeping the radiators warm, but when it switches over to making hot water it goes full tilt, at least it sound like it does. Hopefully the house won't heat up noticeable when it happens. Bro will probably use an arduino to control the blower speed, I'm sure he'll program it so it knows not to to turn the blower at full blast in futile cooling attempts during the hot water making phase. We already figured we want to isolate the blower mechanically to keep vibrations local and avoid resonance. I'm not sure I've ever seen canvas connectors, but I'm sure we can find something flexible that does the job.
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Nov 14, 2021 15:59
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MRC48B posted:You get 6c back from your geo well year round? Yeah. It's deep. There's probably water flowing down there or the well would have cooled off after 20 years of use.
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Nov 14, 2021 16:00
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MRC48B posted:They take it better, but its still not good. Huh. That sucks a little bit. There's two PVC sewer vents going through the attic and I was planning to drain to either of those. If I could just run hose and allow water to block off a low point there's no risk of sewer smell entering the air. If I use something more flexible like high quality garden hose maybe I can just let it freeze in the winter. I guess a constant downslope is possible but it's more work and will take away more storage space in the attic. And I would perhaps need some kind of smell trap. Other drainage options are possible but less elegant. As for the coil freezing I doubt it's an issue. The brine is supposed to be good down to -24C which Stockholm rarely sees. The attic should be slightly above ambient due to spill heat from below, and there should be some convection of heat through the ducts as well. But maybe it's best to plan for draining the cooling circuit each fall to be totally sure. There's going to be copper tubing well away from the ducting after all.
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Nov 14, 2021 17:18
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The Slack Lagoon posted:Anyone have experience with central heat pump to warm air system in places that get below freezing? I've worked with air source heat pumps for a few years and installed two of them for my own use - one is a simple cheap air-to-air split unit, the other is an old school 13kW air-to-water system that makes radiator water and tap water for a modest house with poor insulation. What motronic said pretty much, except you have to guess about future energy costs. A good heat pump install can be expected to last 20 years or so. With U.S. electrical generation being what it is I guess natural gas prices should track electrical prices pretty well, but what with the climate crisis this might change over time. Where I live (Sweden) natural gas isn't really a thing so heat pumps are hugely popular. The air-to-air variety (usually small split units) is popular mainly as a retrofit to old houses previously heated with straight electric, but the residential houses here that have central heating are pretty much always on a water system and an air-to-water unit usually goes into those if air-source is used. Those who have the option and can afford it tend to go with geothermal heat pumps even if these have their own issues too. In new construction here geothermal heat pumps combined with water floor heating is considered the pinnacle of heating solutions. Huge surface of your radiators means lower temps on your output, which means the heat pump will perform better. Also heated floors feel good to walk on.  All air source heat pumps have a COP (coefficient of performance) graph similar to this. It varies a bit but below -15C/5F ambient or thereabout it's usually not worth it to run an air source heat pump. While the COP can still be well above 1 (depending on what temps your putting out on the other side, mainly) you'll have real issues with evaporator ice which messes up the duty cycle to the point that all pumps I've ever dealt with shut down and go straight resistive somewhere around those temps. Where I live temps that low are rare and not long in duration so assuming your heat pump is beefy enough to supply enough heat at a lovely COP when your heat need is the largest this might not be an issue.
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Nov 28, 2021 09:55
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Geothermal air conditioning project at bro's house is go! We decided to start with the brine plumbing since the blower is on back order for another month or so and the air stuff will block necessary plumbing access in the attic. Bro rented a couple of tools for the day:  Bro with beefy hammer drill to punch through the garage wall.  Press tool for copper fittings whatever this might be called in English.  The run up the facade and far enough into the attic to be workable from up top was a bit tricky and took some planning but it all worked out. Insulation, the cover and trim pieces for the conduit whatchamacallit are yet to be done though. There will be some wiring in there before that can happen.  We left things at a good place to connect to the brine/air heat exchanger in the attic - the last bit will be flexible hose and a few brass compression fittings for serviceability. The loose clamp in the picture is no longer loose. We're all hooked up to the brine down in the garage. We managed to do all the plumbing that requires the press tool which was the ambition so unless there's a leak somewhere I think today was a success. After the heat exchanger is in we'll hook up the expansion tank and the condensation drain but that's all the plumbing needed if things go to plan.
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Apr 24, 2022 17:03
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H110Hawk posted:
Bro's been chipping away at in in my absense:   He said it was impossible to insulate properly within the confines of the conduit (I believe it, putting on the clamps in there was tight) so there's condensation coming out onto the outer wall during operation we might have to rip that out and try filling the whole box with spray foam or something. Blower might show up in a week if we're lucky, and the last plumbing bits should show up soon as well. We have some stuff we can do in the meantime though. We need an air inlet box structure in the hallway ceiling that we've been unable to source ready made, so that will need fabrication for example. Bro is also working on temp sensors, arduinos and blower speed control but he's much better at those things than I am so I'm not really involved. The basic idea is to let the AC brine pump run at a constant speed during the summer months and control indoor temps with the blower rpm alone, but we'll see if that's too crude and needs refinement once summer comes and we're making and distributing cold air.
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Apr 28, 2022 11:05
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 The blower for the geothermal AC finally showed up! The boxes are filter (barely showing in the background), blower, heat exchanger. Duct connections are 250mm. Waiting for some rubber feet for the blower and some 250mm elbows that were forgotten but it's getting closer. Sadly none of these large air duct things are available OTC for amateurs in this country so everything needs to be ordered. Central residential AC or forced air heating systems for that matter (apart from mostly retrofitted air/air heat pump mini split units) aren't really a thing here - it's all sweating during the infrequent summer heat waves and radiators/floor heating in the winter pretty much. Parts for the smaller outlets branching off of the main cool air duct are readily available though since diameters up to 125mm are common in kitchen fans, residential mechanical ventilation and so on.  The one and only air inlet is also in place. It sits by the front door in the central hallway. It needs a nice cover plate full of holes, yet to be fabricated. The wallpaper is probaby 40+ years old and the ceiling panel is hella ugly but one thing at a time.
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May 28, 2022 12:18
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Bro and I just did a trial run of the geothermal AC hardware. There was a bunch of faffing around getting the air out of the brine plumbing, but once proper circulation was established things looked really promising. With the blower and brine pump going at full blast the temps were brine 7°C in, 9° out. Air 18° in, 12° out. With the blower at the lowest rpm the chilled air went down to 9° though I forgot to check the Δt on the brine- probably not much. I have no idea how to quantify the amount of air the blower is moving (bro probably knows the numbers given by the manufacturer since he bought the thing) but it's a lot and there's no doubt in my mind that it will suffice to cool his fairly large house plenty good. Noise levels from the blower was low, barely audible over the fridge compressor which it sits directly above. Now we need to sort out all the air ducts and insulate everything, also regulate the cooling (bro claims there'll be an app for that, raspberry pies and whatnot). Ambient air in the attic was neither hot nor humid but all exposed brine pipes saw plenty of condensation so all cool things need to be properly sorted. My overall impression is that the guts of the system seem to work just like we hoped they would which feels pretty great.
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Jun 1, 2022 22:24
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Not much to show. Today was mostly chasing air bubbles and semi-temporary wiring. I snapped a few bad pics but phone posting so can't be bothered. I'll take some pictures of the ductwork etc when we get that. Progress is pretty slow, but we work on this together a few hours a week and bro tinkers a bit on his own. As long as it works passably well before the summer heat comes it's all good. Also the attic will become increasingly unbearable, especially when dressed for working with fibreglass so there's that I guess.
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Jun 1, 2022 22:57
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MRC48B posted:there are two ways to measure airflow: I actually knew about both these methods at least in theory, now that I think about it. I have access to pressure sensors (bro intends to maybe use them in concert with the raspberry pi for control) and an anemometer too. No excuse other than being pressed for time and sloppy with my language. Anyways, airflow is plentiful, we could probably get away with a size or two smaller on the blower. This is a good thing since we'll use more flexible ducts than I'd prefer, mostly because of the layout of the attic space.
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Jun 1, 2022 23:18
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A few bad pics. Bro messing around:  The white box with the little knob is some sort of temporary PWM controller he made for the blower for testing purposes. We had to disassemble some things and flip the heat exchanger around to air it out before the brine would circulate. Not shown is the expansion tank that sits above on a rafter. This is tricky to refill, and we had to pour five additional liters in it before things were done bubbling and gurgling.   These are the air outlets in the kitchen and guest bedroom. They're screwed shut at the moment but it's just an adjustable vent. There will be 7 of these in all rooms along the outer walls of the top floor of the house (double vents in the living room since it's big and facing south). A WC that's in the middle of the floor and can't be easily reached by an air duct will only be passively cooled by being surrounded by cooled rooms. The central hallway has no outlet, only the air inlet, but it's open to the kitchen and living room on either end that will have outlets. Hopefully we can get a reasonable balance between the various rooms by adjusting the outlets and also shut them in the winter to limit heat losses from the ducts which are bound to be much worse insulated than the ceiling is. Possibly some doors or inner walls will need additional ventilation so outlet air can flow past closed doors into the central hallway back to the inlet. We'll see. The brine sampled from the system doesn't freeze at the -20C found in the freezer but it can't be very far off, so we plan to automate the AC circulation pump to run to prevent frost damage in the AC plumbing if ambient air temp gets low enough for this to become a possibility - this temp is available on the internet which is easy because no wiring, although having one or two sensors locally is also a possibility. This running of the pump when it's really cold will lower the efficiency of the heat pump a tiny bit by cooling the brine some, but it shouldn't be noticable in the grand scheme of things as it's far from every winter it gets that cold. This is a chart of lowest temps measured in various months in Stockholm over the last years. -20 isn't unheard of but not exactly common either. 
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Jun 3, 2022 08:26
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Some geothermal AC progress: First of all, assuming things leads to mistakes and manuals are good to read when you don't know what you're doing.  Turns out the heat exchanger needed to be turned 80° to the right. Now it's correctly installed according to the book, the condensation drainage actually works and it purges itself from air.  Also there's now a riser and a ball valve for air purging on the exchanger outlet side of things. I can only find a single auto purge valve for this purpose that's actually rated for ethanol which costs a small fortune so it's manual for now, probably forever. The semi-insulated riser hose on the left (exchanger inlet side) leads to the expansion tank. A few millimeters of foams seems sufficient to prevent condensation on the hoses so that's good.  There are blinky lights and fancy electronics now. I have a very vague idea of how any of this actually works but bro can touch his laptop and turn the circulation pump and blower on and off as well as regulate the blower RPM.  The air duct bends finally showed up so apart from that little piece of flex hose it's now hard duct from inlet to filter at least. We also started duct insulation yesterday. There's very little locally available for the purpose apart from Armacell sheets which are awesome but very expensive at $50/m2 so we ended up using rolls of 50mm fiberglass with paper backing on one side and wrapping the ducts in that and fixing in place with tape. A very itchy job and it's not looking pretty but it seems to work significantly better than no duct insulation at all at least. I assume we'll also have to wrap the whole sausage in plastic to get a proper vapor barrier before everything is finished. It's obvious that duct insulation is critical for getting cold air to the far end of the air passage. It's working great at the outlets closest to the heat exchanger but the outlet air gets progressively warmer the further away you get, especially when the sun is shining and the attic gets very hot.
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Jun 15, 2022 09:36
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I wrapped a package yesterday. A sweaty itchy package. Seems to work though.
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Jun 20, 2022 07:31
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El Mero Mero posted:Came across this heat pump start-up company earlier today and I'd be curious what folks in here think about it. It's sorely tempting to me since we have a perfect window for it. I'm not proficient in moon units and had to google that 9000 btu is 2.6kW, but that system is essentially the same as what I installed in the house I'm in right now, in that the entire refrigerant loop with all the associated doodads sits outside and all that comes inside is water. What I installed is a 13kW air-to-water heat pump that makes radiator water and tap water, no cooling at all since it only runs the refrigerant "backwards" when de-icing the evaporator. It wouldn't surprise me if the beating heart in that little window unit is a highly conventional Copeland scroll compressor though since that's all I've ever seen on any residential use heat pump I've ever looked at closely. In the Euro market I'm used to a heat pump is a heat pump and the manus mostly compete with name recognition, modern looking designs and fancy apps since their guts are all the same regardless of brand. The only real innovation in the last 20 years is variable RPM compressors which that unit seems to have. The biggest quirk with using water as a heat carrier in a system apart from the added complexity of a water circulation pump and one extra heat exchanger is that you're bringing water outside. This means there's a risk of freezing said water and destroying expensive plumbing bits if something goes wrong (like a blown fuse on a really cold day or something). If you live in a place with cold winters and plan to use this thing for heating as well as cooling I would look into what the manu has done to mitigate that risk. I'm sending hundreds of liters of radiator water out to the heat pump so antifreeze liquid isn't a realistic option for me but maybe they do that? I'd also look into how efficient the unit is C.O.P-wise compared to a similarly sized more regular (i.e. no water involved) mini split. I'd guess it's bound to be worse but probably just a little.
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Jun 29, 2022 08:12
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An AC is a heat pump that pumps heat from the inside to the outside. A fridge or freezer works the same way. A heat pump is a heat pump that pumps heat from the outside to the inside. They are all the same only configured to accomplish different tasks. Sometimes they can reverse the flow of the refrigerant to run the other way. This is especially common if they are heat pump heat pumps. Air source heat pumps (which is what we call an AC that makes the outside colder) create lots of condensation on the evaporator side of things if the air that is to be conditioned has certain conditions.
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Jun 30, 2022 22:27
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Geothermal AC trip report: There was a bit of a heat wave last week. Bro was out of town for a few days, came home and turned on the AC. The temp graph from his bedroom looks like so:  It clearly works at cooling the house more or less as intended. We were puzzled at the lack of condensation last time we worked on the thing, but the humidity up to that time had been pretty low. This week the weather turned muggy and the flaws in the unfinished installation have become very apparent. Ain't nobody wants to work in the attic when the sun is shining, but the insulation is very nearly finished (hopefully). Wherever it isn't done it gets real sweaty. The biggest mistake was the connection between the drain hose and the heat exchanger condensation tray which was only finger tight, so a bunch of water leaked out there when the dripping started in earnest. Enough to soak through the 40 cm or so of fiberglass insulation as well as the inner ceiling. Oops. Luckily the insulation in new and clean so there's little risk of anything nasty growing in there before it dries out with a bit of forced ventilation.
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Jul 3, 2022 17:40
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I forgot, I have some very rough performance numbers: Power consumption at full blast is about 260W; 170W on the blower, 80W on the brine pump and 10W on control. Airflow is roughly 200 l/s which google says is about 420 cfm. When cooling a hot house (say 27°C) the thermal output is about 3.4 kW. If the house is at a more comfortable 22°C the output drops to 2.6 kW or so. Probably not sufficient for a house of the same size in Phoenix or something, but it seems to be about right for Stockholm.
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Jul 4, 2022 09:04
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IOwnCalculus posted:I've been watching you post for a while now and somehow I only just now realized that your plan all along was literally just using the brine to cool a heat exchanger and not using it to cool the hot side of a regular heat pump. That's awesome. This type of system is actually called "free cooling" in Swedish since the C.O.P is so high it is almost free! As I've mentioned previously, residential AC is very uncommon here since the climate doesn't really require it historically, but with climate change and modern architecture with lots of glass this is slowly changing. It's fairly common in larger buildings though - hospitals, office towers, large industries, big box stores and the like. There's a practically limitless supply of cool water at the bottom of the large lake where Stockholm gets its tap water so there's a few limited grids around the city for district free cooling, though it's nowhere near the coverage of the district heating grids. My local hospital is pretty far away from this lake so when they expanded with a new wing they drilled hundreds of geothermal holes under it to sort both heating and cooling. In essence they store summer heat in a large chunk of bedrock and re-use it in the winter. Pretty clever. In bro's case I assume his geothermal hole is "wet" and has water flowing past it since it still puts out good temps even though it's several decades old, but in case it is a dry hole a nice side effect of his system would be slowing down the heat pump cooling of the rock around the hole and prolong its life a little. Measuring anything related to heat in tons of all things is just  to me but hey whatever works for you.It would have been possible to install a system 2-3 times as powerful as we did (there is a real limit to brine flow because of the diameter of the hose loop in the well) but we made an educated guesstimation and figured this size would be reasonable. Also the most economical, compact and easy to install - it is a retrofit after all. Only time will tell but early results indicate we got it about right. If it can't quite keep the entire house at 21C during the worst heat wave in history it will still keep things cooler and drier than at the neighbor's house at least. Bedrooms where it's most important can be given priority too of course. In my house I have zero active cooling which is the norm. If there's a heat wave I can always leave my top floor bedroom for the relatively cool comfort of the basement for a time. Right now I'm sitting in front of an open balcony door for ventilation with a screen door installed to keep bugs and the neighbor's evil cat out. It's a cool 22C outside today. Not quite like in Phoenix. It will be interesting to experiment with flow settings and see what happens at lower speeds on blower and pump. I'd hazard that we'd get 80% of max cooling on 50% of the electricity use making the C.O.P even more bananas. The noise levels at full blast is quite tolerable as it is but less noise and more efficiency is of course always more better.
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Jul 5, 2022 08:38
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Huh. Makes about as much sense as calories I suppose.
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Jul 5, 2022 12:44
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glynnenstein posted:I don't know if I'd call duct work easy. I suppose flex duct is easy, but with rigid back when I was helping out with residential installs a couple decades ago, we never regretted paying a few hundred to have a sheet-metal guy do that stuff for us. There's an art to doing it fast and neat. Not to mention that ducts are often in very inconvenient locations. But arguably there's an art to doing anything fast and neat, and for a DIYer air ducts are easy to comprehend in how they function and pretty safe if you mess up - not like plumbing with potential for major water damage or electrical things with fires or electrocution as worst case scenarios.
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Aug 5, 2022 16:44
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blindjoe posted:I havent figured out how adding mass to the resistor makes it more efficient. I guess the idea is that the energy stays in the oil instead of venting out of the room?
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Aug 16, 2022 19:27
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There will be condensation. When it's cold enough ice will form. How much depends on ambient temperature and humidity. The heat pump will periodically de-ice itself as a part of normal operation when the sensor values indicate this is needed. You don't have to think about it apart from periodically checking that the outside unit's drainage isn't clogged. Depending on the surroundings som heat pumps tend to ingest leaves and such and if so you'll have to unclog more frequently. I give mine an annual inspection so I'll remember but it's too frequent.
Invalido fucked around with this message at 11:25 on Sep 6, 2022 |
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Sep 6, 2022 11:05
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jailbait#3 posted:Does anyone have experience with hybrid (air-to-water and air-to-air) heat pumps? My house is pushing 120 years old and has a 100k BTU, 85% efficient boiler that's nearly 40 years old. The thought of putting good money into a new gas unit kills me. If I'm spending on a heat pump, why not get A/C too, right? But the house has no ducts, and heats with cast iron rads that are now crazy oversized since the house has had major insulation upgrades over the years. I keep the valves throttled down on most of them. Together with my brother I've retrofitted an old house that used to be straight resistive with an air-to-water heat pump, so I guess I know some, at least about the air-to-water side of things. It's a 13kW thermal output unit that feeds two isolated tanks, one for heating water and one for tap water. It's a relatively old unit that we bought as a complete installation package for a ridiculously low price used with almost no hours on the compressor. It has no RPM control on the compressor like modern ones do, so both storage tanks are necessary to limit the start frequency. It's been working flawlessly for more than a few years now. MRC48B posted:their performance is kinda crap. Convectors are useful too and have huge effective areas in a relatively small volume. They can be ceiling mounted and can also be used for cooling (at least commercially this is pretty common where I live) though I have no real experience with this.
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Oct 21, 2022 04:11
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It was properly cold for Stockholm for most of December and bro's geothermal A/C system isn't finished. There was a cold downdraft from the big hole bringing air up into the attic. After thinking about more complicated solutions for a few minutes this is what I came up with: Apart from a form fitting winter plug that's not a plush shark from IKEA there needs to be some kind of cosmetic grate or mesh blocking that gaping hole, but sheet metal full of holes which was plan A is proving surprisingly difficult to find in sufficient dimensions, so the gaping hole is still there several months later. It's 600x600mm so it's a standard panel size for air stuff but it's a commercial size where things aren't really available to amateurs. Bro seems fine with the hole and the shark so I guess it's down to me to find some junk that can be modified to suit. Louvres or slats would work too I guess but ideally they should be at a 45 degree angle to the hole in order to block the sightline effectively from the parts of the hallway where your head is likely to be, and building such louvres nicely seems like a complicated and time consuming nightmare project to me. Same goes for drilling holes in my own sheet of metal. Metal with a nice hole pattern is probably still ideal since this part sits before the air filter so it's bound to get dirty and should be made with ease of cleaning in mind. The search continues.
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Dec 23, 2022 08:57
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His Divine Shadow posted:Yeah, it goes by a temperature curve instead. And it works real well, the curve is also adjustable. I have a suspicion that this type of setup can fail a little when it's real windy, at least in houses that aren't super controlled airflow-wise - have you ever noticed it gets a bit cold when it's blowing hard outside? On my one and only heat pump install I did for myself I regulate on a combination of outside air temp/curve and the return temp from the radiators, based on advice from a graybeard with lots of experience and I'm real happy with how it works. The wood stove or sunshine through windows will make the thermostats on the radiators in the affected rooms limit the water flow there but the heating water return temp still gives good feedback to the heat pump brains about how the colder rooms are doing. Not workable in a hot air system of course, but I've heard plenty of people having trouble finding the perfect place for a single electronic temp sensor in their homes.
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Mar 17, 2023 18:02
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I would assume that as long as the total area of all holes where air can get into of the attic are at least as large as the area of the fan blowing air out of the attic you should be alright? E: I'm also intrigued by the idea of a house fan. I live in a 3-story souterrain house without AC where the lowest lever/semi-basement is pleasantly cool, while the top floor where the master bedroom is gets pretty toasty right about this time of year. It's not super obvious how I would manage airflow neatly though since all outer walls and floors are reinforced concrete. Attic roof is wood and so are the gables up there though, but the only easy air path into the attic is though the hatch. I suppose I could just leave that cracked open during the summer and simply install a fan blowing air either out the gable or through the roof, that shouldn't be too hard to do and would draw cooler air into the bedrooms up there at least. Worth looking into I think. Invalido fucked around with this message at 15:41 on Jun 21, 2023 |
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Jun 21, 2023 15:22
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MRC48B posted:I prefer not glued, for disassembly for cleaning. the drain is at zero pressure, so it shouldn't leak even without glue. ymmv. Where I live gluing pipes of any kind isn't a thing for some reason. Anything under pressure used to be metal, now PEM or PEX is common and you can't glue that poo poo anyways. PVC is standard for drains though, the parts look like this:  That little rubber seal is enough to stop the zero pressure poop water from leaking, can still be disassembled for cleaning. A plumber's trick I've learned is to use a little soap as lube, makes the parts slide together easier.
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Aug 22, 2023 06:00
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Most of my air source heat pump experience is on the air-to-water side of things, where resistive backup is cheap and easy. Since you already have a system for moving hot water around and turning it into a hot house, the resistive element itself is small, cheap and simple thing sitting somewhere central, almost an afterthough, factory installed inside the hp on every unit I've ever worked with. Most people here who run air-to-air heat pumps have mini split style pumps, and their backup is usually resistive heat distributed throughout their space. I've never seen a central ashp, but forced air heat distribution isn't really a thing where I live. I assume the heat coil is just a simple box containing something similar to any other resistive air heater (only bigger), sitting inline in the ductwork somewhere close to the heat pump itself? 3k sounds like a lot for such a device but things cost money, and with install with electrical and whatnot maybe it's totally fair. My impression is that in the mini split market at least, Mitsubishi is a brand associated with high quality and long service life FWIW.
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Feb 14, 2024 06:30
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All I can tell you for reference is bro's replacement of his geothermal heat pump. He got a 16kW output variable speed unit with an internal hot water reservoir. Pretty much a straight swap labor-wise, but with a few pipe mods including deleting the old external hot water tank and a junction installed on the brine lines going to and from the thermal well meant for the AC system we built a few years back - I think he paid something like €12k total. Everything has gotten more expensive on this side of the Atlantic too so I don't doubt it would cost more now than it did four years ago.
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Feb 26, 2024 11:08
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Motronic posted:R-454B is pretty much gonna be the thing for residential fixed install cooling. I'm not questioning your knowledge about this, but I'm seeing a lot of buzz about R744 (CO2) systems. Not much available in the market though from what I can tell, a few industrial units and a couple of residential sized Mitsubishi models. From what I've gathered it's high performing in most applications and doubtlessly environmentally and fire safe, but more expensive to build for due to higher pressures.
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Apr 2, 2024 10:03
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8 dollar multimeters work, but IMO the sweet spot for cheap multimeters is in the € 20-40 range. If you want maximum ease of use get one that's auto-ranging (i.e. one where there's just one knob setting for all kinds of DC voltage or whatever, not several) Something like this one maybe? https://www.amazon.com/Neoteck-Mult...147&sr=8-5&th=1
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Apr 5, 2024 07:00
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H110Hawk posted:Do not buy a $8 multimeter. If you use them subtly wrong they simply explode in your hand. Has this ever happened to you or are you making poo poo up? The worst I've ever done as an electrically curious pre-pubescent sprout was frying my dad's analog meter by using the current setting in error. A puff of magic smoke wafting from the plastic case and an angry father were the only consequences IIRC. I'd rather fry a cheap one than a nice Fluke or something until I figure out that the "A" settings is advanced mode. My shittiest cheap multimeter sucks, but it's in a plastic case and the probe leads have insulation and it is embossed with a consumer protection agency logo if you're into that sort of thing. It's just annoying because the probes kind of suck and it's not auto-ranging and the continuity beep is really faint and it's hard to hang it up on stuff when working but it's still really useful in that it tells me answers to basic questions like "is this connected to that" or "is there any voltage here" or "will touching this thing hurt/kill me" or "how should I wire up to this switch" or "do I need to replace these alkaline batteries" or "which way does this diode go again" and such, which is 98% of my multimeter use.
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Apr 5, 2024 16:14
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I've only watched a little but this video seems like a reasonably good a place to start https://www.youtube.com/watch?v=0loXukB302Q
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Apr 5, 2024 16:30
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Fluke makes great multimeters no doubt, I just hope they don't throw away their well earned stellar reputation by enshittifying themselves like so many other tool companies have done in the last couple of decades. I'm on team "every household should have a (reasonably) cheap digital multimeter" myself - It's just one of those things that are so incredibly useful in this world, I don't understand how people get by without them (and at least a basic understanding of electricity). Then again people without basic tools or know-how throw away lots of easily fixable things because they can't do even the most simple diagnostics. Bad for the wallet, bad for the planet - multimeters for everyone! Then at least when they call me because their car won't start I can ask them what the battery voltage reads. (I have a nice one with fancy features and a USB interface I've never used, a cheap one and a small one I got specifically to bring on motorcycle road trips)
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Apr 5, 2024 17:42
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