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  #1  
Old 02/08/07, 02:11 PM
 
Join Date: Oct 2006
Location: Alaska
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setting up radiant floor heating with HOT WATER HEATER

Yes, I have searched the archives and I am reading them. One person mentioned doing a system as I am proposing (Maura at http://www.homesteadingtoday.com/pri...d.php?t=105288) so hopefully she will post here again with more details or PM me. Here's what I have, folks.

I am in Southcentral Alaska. I live in a rural area. I am off-grid on a solar system with back-up generator and batteries. The house is about 2,000sf on 2 levels, with all modern amenities. We have oil heat in the house now using two Toyostoves. They work but they don't put heat where we want it so we are always running ceiling fans, etc. and having to leave bedroom doors open. In anticipation of this, we planned for a supplemental or secondary heat system (if it works well, it may end up as our primary heating system).

So, we ran hot water capable PEX and separate thermostat wires in several different zones under the subfloor as a staple up system and insulated with reflective bubble sheets to reflect the heat up and then used bat insulation to fill the voids before drywalling. We have a very deep basement-like crawlspace so we terminated all the PEX runs there. We have plenty of room to install a system here and all of our mechanical components are here except the electrical breaker box. it is high and dry and vapor barriered so no issues there. We also ran power from the electrical breaker box to the same area in the crawl to power the system on a dedicated circuit. I believe we have 6 zones.

We would be using either a propane or an oil-fired hot water heater, NOT a boiler (unless you guys talk me out of it, lol). We were going to put in a fairly small HWH along the lines of 20 gallons or so but not sure what size is needed for sure. Whatever we use, it can't be electric (I don't think) as we are off-grid with pretty high usage already. So then the non-electric HWH would be vented directly out of the crawlspace above the foundation, of course. We only have to worry about national basic life/safety and plumbing codes for bank financing, there are no local building codes. To date, everything we've done has been inspected and approved.

We would be using WATER (probably distilled to keep it from being contaminated or high in mineral content), not glycol, in the system. I already have some parts on hand from a guy that engineered a system (without the how-tos of course) using black iron pipes (which I think is a BAD idea for water pipes long-term) and a big, expensive boiler that I found out right quick was a model with a bad reliability history. We took back the boiler before ever unwrapping it and haven't done any work on the system since. We got a bid for an oil-fired boiler from another company that was WAY TOO HIGH and then I started reading about hot water heaters and how and why they work better, especially for closed-loop systems as we plan to use.

What we need to do now is figure out how to build a manifold type system and set it up for a closed-loop system with a hot water heater. I've read a lot on this but seen no real diagrams and shopping lists of parts with a good how-to. I've been to the book stores and the libraries and I can't find the two books that have been recommended in the past on other websites. Don't ask me what they're called now as I have forgotten since it's been a while.

What I am looking for are some caveats and info. from people that have done this using a hot water heater for this application or from those that know about this sort of set-up. I would also like a diagram or even some step-by-steps of how this is supposed to look and work and what materials I need to get the system running.

Thank you in advance.

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  #2  
Old 02/08/07, 02:42 PM
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many people to propane on demand hot water heater with a small brass pump to circulate the hot wter the pump is put to a thermostat

other wise a regular tank hot water heater would work but you need a tank above the cold side to drain back into if it is a glosed system

or my many people i know have hot water heat systems that use a regular hot water (boiler) it is called that but is not realy a boiler as it does't make steam some propain some natural gas

my aunt has her boiler in the garage and it keeps it heated in the 40's or better all the time a cousin has his on the closed in porch.

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  #3  
Old 02/08/07, 03:24 PM
 
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Location: Foyil,Ok
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We will be using radiant and geothermal to heat the house. After your radiant is installed/hooked up you might price geothermal and see if it would be too expensive to add.

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  #4  
Old 02/08/07, 03:33 PM
 
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Location: Alaska
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geothermal - don't think that's available/possible here...??

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  #5  
Old 02/08/07, 03:34 PM
 
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Location: Alaska
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I have looked into the tankless idea (we have one for our domestic potable water and love it) but have read they don't hold up well to this sort of sytem???

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  #6  
Old 02/08/07, 03:36 PM
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Have seen it done several times, but it will have to have water feed, expansion tank, back flow preventer, pump/s, bleeders and generally the most of the same components as a small boiler.
Might want to price it both ways.

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  #7  
Old 02/08/07, 03:52 PM
 
Join Date: Oct 2006
Location: Alaska
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Since I can get a HWH very inexpensively compared to the boiler, and since they are supposed to handle this system better, that's where we were leaning. The boilers alone are upwards of $4K here. I would get the best HWH I could find and afford (recommendations or warnings of ones to avoid?). I don't mind setting up all the extra components you mention hunter63, just need to see some diagrams and a few comments on how tos.

On a tankless, wouldn't it always be running since the circulation pumps would always be pushing water in/out of it and thus triggering the heating mechanism?

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  #8  
Old 02/08/07, 04:21 PM
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i have seen this done many times in my opinion a water heater does not make water hot enough to heat efficiently especially in colder climates

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  #9  
Old 02/08/07, 05:02 PM
 
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Location: Alaska
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mtman - I've heard this concern before but keep reading from people that have done it that that isn't true. ??? They all advocate for lower water temps (like 100F instead of 130F) but most water heaters I've seen *can* go as high as 140F. I think the other thread to which I linked talked a bit about this too - something about it's not necessary to have the water so hot and may make the floor uncomfortable?? Not sure that would be the case here though, where we have subfloor, underlayment, then flooring on top of the PEX.
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  #10  
Old 02/08/07, 05:09 PM
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My buddy just put in PEX in his cabin on KGB (mile 10). The boiler was set low and it would not heat. He called out one of the senior plumbers from Gold Star and the guy said that it had to be set higher. I believe it is at 180 degrees. I do not know how you could set it up with a hot water heater. His pump was more expensive but I believe that it is much more energy effecient.

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  #11  
Old 02/08/07, 05:51 PM
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Location: Northern Michigan (U.P.)
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My neighbor created a radiant heating system that works good. He uses clear plastic pipe under the subfloor, held in place with aluminum reflector sheets. His operating temperature is around 100 degrees F. That's a lot cooler than I'd expected. His system has a hot water storage of 20,000 gallons, so he doesn't have to fire up his wod boiler often. So, based on that, I'd say you could run your propane water heater at a low setting. Your system would have to be non-pressure, open system, to prevent blowing your lines.

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  #12  
Old 02/08/07, 05:53 PM
 
Join Date: Jun 2004
Location: Wyoming
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Our on demand propane water heater heats both our radiant floor and all domestic water. It is an open system that we installed and plumbed ourselves. We are on well water and installed a water softner.

Small home 1200 sq feet. Two zones.

Ask away and if I can help I will.

Jill

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  #13  
Old 02/08/07, 05:55 PM
 
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Also! I run the water at 110 most of the time and up to 140 when exteremly cold. I ususally do not run it higher than 110.

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  #14  
Old 02/08/07, 06:33 PM
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Quote:
Originally Posted by painterswife
Also! I run the water at 110 most of the time and up to 140 when exteremly cold. I ususally do not run it higher than 110.

thats what im talking about colder climates call me old school i dont think water heaters are made for that
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Old 02/08/07, 06:43 PM
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You can try this site, examples of piping systems.
http://www.parkerboiler.com/presenta...hwp/sld001.htm

Wirsbo is a maker of pex and heating systems.
Might want to get to their web site. Don't know if the publish them on line but,
there are calculations that have to do with length/ size of tubing vs sq ft, vs floor temp/flo rate/btu's given up etc.

mtman is correct water, heaters weren't made for this, but I have seen some in action, as supplemental heating

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  #16  
Old 02/08/07, 07:14 PM
 
Join Date: Jun 2002
Location: Idaho
Posts: 4,332

We're about to put in a system using a water heater. I went to Radiantec and they were very helpful. They have a system that uses your potable water for heat so there is never a chance of stale, bacteria laden nasty stagnant water gathering in the pipes. The water also can help cool the house a little in the summer.


He quickly steered me away from an on demand heater. His explanation was that they operate at a set, high btu. If you turn on a faucet to wash your hands, it blasts full power until you get done washing. Lots of heat just went up the flue. he told me to shop for the highest efficiency (within reason) propane heater I could find locally. 40 or 50 gallon will be plenty big enough. He will be supplying all the pex and fittings and pumps and controls. I checked locally and he beat the local tubing price.

The schematics and diagrams and instructions included in the quote package make it look very simple to hook up.

No, I don't work for them but I am about to be a customer.

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  #17  
Old 02/08/07, 07:22 PM
 
Join Date: May 2003
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As with any heating system, the source of the heat must meet or excede the demand. The BTU requirement for the house must be determined before proceeding with the selection of the device/size to be used.

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  #18  
Old 02/08/07, 07:52 PM
 
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Location: Wyoming
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Quote:
Originally Posted by mtman
thats what im talking about colder climates call me old school i dont think water heaters are made for that
I ran it the first year with a regular hot water heater(tank) no problems and we get -30 here.
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  #19  
Old 02/08/07, 07:56 PM
 
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Location: Wyoming
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"He quickly steered me away from an on demand heater. His explanation was that they operate at a set, high btu. If you turn on a faucet to wash your hands, it blasts full power until you get done washing"

Not quite correct. My on-demand only heats the water to the proper temp. It modulates the heat form a low of 17000 BTU's to 140,000 BTU's. The warmer the water coming back the less BTU's used.

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  #20  
Old 02/08/07, 08:03 PM
 
Join Date: Jun 2004
Location: Michigan's thumb
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We bought our stuff from Radiant Tec. Their website is www.radiantec.com Another company, formerly associated with Radiant Tec is Radiant Company, www.radiantcompany.com You can go to my website, www.thumbknitting.com and click on housebuilding to see photos of our system in the making.

If you use a regular hot water heater, you will be using the same water that you use in your faucets. The PEX is much smoother than metal pipes and you shouldn't have trouble with minerals. Many of them are lost at the bottom of the HWH anyway. We have a lot of minerals in our water also. Our local building inspector made us use a closed loop system. This required buying an expensive HWH, one in which the floor water passes through a loop inside the HWH, so that the potable and floor water never meet. It is not as efficient as using a normal HWH and an open loop. I think it is a 30 gallon tank, it's whatever size those monsters come in. Think about how much hot water your family needs for bathing and cooking, etc.

I don't know how cold it gets in south central Alaska, but in floor heat has been used in Scandanavia for a decade or too, and I believe it gets pretty cold there. We are in Michigan and the temp rarely drops below -10. Our house stays as toasty as we like, but we also have thick insulation and high quality windows.

If you go to Radiant Tec, they will send you a packet of information which diagrams everything. They will help you determine how much PEX you need for your location and at what temp the water should be. A normal hot water heater should be able to supply enough heat for any installation.

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  #21  
Old 02/08/07, 08:12 PM
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Location: Canada
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hoofinit,
I heat a portion of my basement with sub floor radiant heat that is circulated off off the outside wood funace boiler system. Temp coming in to the floor is 180. It's below frost line ground basement level, so that rises to about 100F. It thermally rises to the house floor. That house floor is about 75. The air temp in the house is 70, though I do have a heat exchanger within the forced air furnace that will kick in for demand when needed to maintain 70 air temp in the house. It's all wood heat operated. The only electric is from the 1/12 low wattage used on the circulating pump to push the 180 water line heated liquid (water) under that part of the flow. Works great, but it's not operated at all by the hot water tank. My hot water also is heated from the wood boiler outside with a heat exchange unit designed for that purpose. I get very hot water. It's more than 140 and uses no electricity. Been running that system for years now. love it.

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Old 02/08/07, 09:00 PM
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Location: Forests of maine
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We are using a series of seperate water heaters.

A propane water heater, 40 gallons and rated at 40,000 btu set at 120 degrees.

Then an electric water heater, also 40 gallons and set at 90 degrees. If the water in the loop ever drops to 90, meaning that the propane heater can not do the job, then the electric will turn on.

We also have plumbed in the loop for adding a wood-fired cookstove with water heater. So one day we will be able to heat the water via wood.

But then again we are here in sunny Maine

It is only -2 today.

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  #23  
Old 02/08/07, 10:32 PM
 
Join Date: May 2002
Location: Kitsap Co, WA
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Here's some pics of what I have. i probably can't answer any questions because I am seriously underslept and brain dead. It works fine. I have a strawbale house, as you can kind of see. Never did put the last coat of plaster on that wall thar...



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  #24  
Old 02/08/07, 10:47 PM
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I know here in Ontario we wouldn't try to heat a 2000 square foot house with a water heater. It's not the temp of the water rather the recovery rate of the system. A water heater isn't very efficient as a heat source compared to a boiler anyhow. Think 78-80 eff for the water heater and 85-93% for a boiler. The boiler will give you your DHW too. The boiler should cost about 2-3 times more than the water heater so about an extra 1000-2000. Trouble with the water heater is it must have everything else the boiler would need (as Hunter says) but it will likely only last 10-15 years, the life span of a good boiler is measured in decades. So you'll save every year over a water heater and its going to far out last a water heater, and it's actually going to heat the house, where as i suspect the water heater is going to come up short.

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  #25  
Old 02/08/07, 11:24 PM
 
Join Date: Oct 2006
Location: Alaska
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Still reading & catching up but here area a few comments.

The diagrams I have seen are all for the tubing - I don't need that part now, I already used them and we're done with the tubing (mostly).

I did have a BTU calc done on the house when SBS tried to sell me that awful boiler system. My hot water heater plan should work fine for this and most HWHs sold around here are often set to 140F permanently.

Also, remember that I already have 2 Toyostoves - 1 on each floor at 30,000BTUs each. They will stay or if we replace them we will put equal output oil drip stoves that don't require electricity to fire. In any event, we will have two heating systems and I can't imagine that even with a HWH we'd have trouble heating the place between the two systems. I have, however, read that rapidly changing the room's temperature or constantly fiddling with the thermostat does not make a radiant system happy.

I have talked to the Radiant Tech guys too. They are very nice but sure want to sell you a lot of components that cost too much to ship to me. Still haven't seen good diagrams for the manifold & plumbing set-up that starts at the heat source and ends at the outputs.

With regard to blowing the lines on a closed system - isn't that what an expansion tank is for? Or would that not work for a closed system as it may still be overloaded/impractical to get a big enough one affordably?

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  #26  
Old 02/08/07, 11:38 PM
 
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lonelytree that was one of the reasons that boilers aren't recommended - they must be kept at high heat. I can't recall for sure what the other reasons were but it seemed to me that there was something with them breaking down mechanically from the constant cycling of the hot/cold water.

We *can* do an open system but thought it would be simpler & better long-term to do a closed system filled with distilled water. We have EXCELLENT water (had a comprehensive well test done recently) with only slight iron sediments (between 5 and 10 micron size) that we filter out with a simple in-line filter as soon as it leaves the pressure tank. We also don't want to have issues of running the well pump a bunch for this but I'm not sure how an open system works anyway, does it discharge water anywhere? One issue I could foresee with an open system and a well is potential back-up of expanded hot water/air (even with an expansion tank?) into the well...?

I also want to repeat - we already have a tankless HWH for potable water. We do not want to mix the two supplies. For one thing, if we lose heat we don't want to lose water (at least while we fix it).

Good insights here, keep them coming...

I will need to find that website I found a while ago that had a really good explanation of why HWHs work and boilers aren't recommended and let you guys pick at it. Also, I will have to post the one (may be the same) that talks about the "don't mess with the thermostat" issue.
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  #27  
Old 02/09/07, 01:50 AM
 
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Location: NC
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Hot water wood stove

I have a hot water wood stove. It holds 500 gallons of water.WE circulate the water thru a raidiator in the furnance. THe thermostat tells the fan when to blow the warm air to all the rooms in the house.I keep the water temp about 150 degrees.It also heats all of our domestic hot water for the house.

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  #28  
Old 02/09/07, 03:20 AM
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Maybe you're thinking about thermal shocking a boiler? It's just needs a minor mixing valve to ensure the return water is no more than 20 degrees lower than the supply. I can't say for Alaska or if you care but oil fired DWH can not be used exclusively for heat they must have a sink or somethign attached to the system to be within code, here at least. Maybe that's not an issue in Alaska. You did use air barrier PEX?

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  #29  
Old 02/09/07, 10:43 AM
 
Join Date: Jun 2004
Location: Michigan's thumb
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We bought all of your system from radiant tec, which is maybe why we have the diagrams for all things. I'll see if we still have it- but we had a fire and we might not.

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  #30  
Old 02/09/07, 03:33 PM
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We have a closed system, natural gas, sealed combustion commercial water heater, high efficiency. Fluid mix is 50:50 distilled water and the pink glycol stuff. Parts & PEX by Wirsbo, which, I believe, is now called UPHONOR. Loops are not more than 250, fairly evenly divided. We have 6 zones (2100 sf total), one supplying a heat loop to a hot water maker tank. Each zone has a manifold (with supply & return orifices equal to the number of loops it is feeding)

IT IS ABSOLUTELY CRITICAL THAT THE MANIFOLDS BE ABOVE THE FLOOR YOU ARE HEATING. One of the functions of a manifold is to help adjust pressure within the loops of the zone you are heating, as well as be a possible place to bleed off the air that creeps in. Air travels up, and if you put the manifold below the loops you will develop air locks and have a disappointing heating system within 5 years. (we have a beautiful natural resource building with infloor heat in our county, the design is poor, the manifolds are upside down at the bottom of the loops, and the ladies restroom temp was 48 degrees during a warm December...)

(Yes, even closed systems will develop air in them.) You will want a pressure tank (I think on the return side of the heater/boiler.) Yes, the fluid temp is set for 180 degrees, and no, floors don't get too hot...75 is about right & it is soooo nice.

When my hubby, a mechanical engineer, designed our system, he was able to get a design cd & catalog direct from WIRSBO. Do a lot of research & reading. Journal of Light Construction in this months issue had an article about heating a 2000 sf, 2 story house in coloroado with an on demand heater. Another source of good info is PM magazine (?) it is for plumbing & fluid engineers.

Don't take unrecommended shortcuts. I have a friend whose hubby built an outdoor wood furnace for their infloor heat. When the electrician was over helping him, the system started knocking. Her hubby went to check on it when it blew. Parts of that furance & copper were found 100' away. He was able to dodge behind a pickup, & escaped injury. He hadn't bothered to build in any pressure relief valves.

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