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Old 03-23-13, 03:55 PM   #11
michael
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Myself! We have the land area here, and I'm building a small (1200 SF) house on the lot across the lane from us, so I want to put a system in both places. I will hire help from time to time, but I want to be responsible for the work and workmanship. Besides, I enjoy working; I don't enjoy watching. We'll see what kind of song I sing after I've dug a kilometer's worth of trenches.

If you search E-Tech W102 heat pump, the top hit just now was "www.etechbyaosmith.com/com_waterheating.html". The page is new, but the product may be on the verge of a revival. I have the catalog and owner's manual for the heat pump. It's odd that one or two don't show up on eBay or somewhere.

I have some questions and thoughts about source loops, so I'll be back on this or other threads. Besides, I've got days and days of reading ahead...mm

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Old 03-23-13, 03:57 PM   #12
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Ahhh! Remember, that was a 1984 price!
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Old 03-23-13, 06:06 PM   #13
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Michael

Good going. You will see some of my posts on the manifesto. We as well had the oil thirsty hot water heaters suppling or home for heat. The hot water was circulated in our concrete floor via 5/8 dia Kitec, Nice stuff but like the poly B you have, it has been discontinued.

The system worked extremly well but the price of oil OUCH. We have installed solar hot water with Geo-thermal back-up and it has me and my family grinning ear to ear. We are in Canada and it can get a little cold but the geo-thermal just hums away. It operates sometimes continuously and in fact losses a little ground when the outside temps drop harshly. This is the 3% that AC-Hacker is talking about.

Your in-floor Poly B sounds perfect it will perform well at the lower supply temp. 85-110 Deg F.

For our area here the rule of thumb for the ground loop is 600 ft for each ton of heat-pump. Your milage may very. The nice thing is if you over install too much ground loop its a good thing. Higher efficiency.

We even went so far as to install our own homemade Geo-thermal heat pump in my shop. I installed 4 tons of loop and started with a 2T pump. Its working OK and saving some serious cash. The shop temp is between 14-18 deg C running full out. Fine for the shop.

Your install can be amazing. I'm on the edge of my seat imagine, a heat-pump powered with a 5.5 Kwh solar array. Thats holy grail stuff. My 2T unit is only 1500 watts 1.5 Kwh.
6 hrs of run time as the sun is powering the array warming your concrete floor. WOW

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Old 03-24-13, 02:11 AM   #14
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Hello randen, When you write "the ground loop is 600 ft for each ton," what sort of 600 ft do you mean? What width of trench, and what configuration of pipe in the trench? Straight pipe side by side or separated by the width of the trench or above and below? Half, third or quarter pitch slinky if slinky at all. Is the 600 ft the length of the trench or the length of the pipe in the trench. I'm thinking of the bore hole style where you may have a 200 ft deep hole, but you'll end up with 400 ft of pipe. A half pitch slinky in a 3 ft wide trench might take 12-13 ft of pipe to travers 18 inches of trench including the return pipe. The number of ways the source pipe can be installed is a little challenging.
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Old 03-24-13, 06:42 AM   #15
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The first thing I would say is that the tubing spacing should allow you to run 85F-90F water and still heat the place well. You cannot have a high worst case deltaT to over come like in the north. This will only have to raise the temp 30F-40F worst case.
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Old 03-24-13, 11:10 AM   #16
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Michael

I don't proffess to be an expert on the subject but a bore hole can be expensive if you don't have the room and I'm not sure of the ratio of piping because you may enter the water table somewhere in your depth and this may reduce the amount of piping (depth)required.
For our installation in my area I did ask around. A reliable installation for a trench here is 6 ft below ground in a 4 ft wide trench two loops not getting any closer than 2 ft apart each tube. The tubing was 3/4" HDPE designed for that application and welded connections. The installers had cautioned about the slinky installations, although the amount of tubing that goes into the trench gets used up the fact that for many feet of tubing are essentually overlapping and its not as good as having a minimum of 16" of dedicated zone of earth for heat collection. Now again this may be a specific detail for our harsh climate. We are subject to some wind swept areas that the ground will freeze down to 4 ft below grade. You may be able to source enough heat 1 ft below grade because your milder climate has injected enough heat into it.

I would check around locally. its a lot of time and money to not have your loop installed correctly.

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Old 03-24-13, 11:47 AM   #17
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Good information. Thanks. I only mentioned a bore hole as an example. It's not what I intend to do. The amount of red tape in this county for a drilling permit is prohibitive for me. It's a very water sensitive area, and the burden of proof that I wasn't drilling wells would be too great, so that approach is not being considered. I took a years worth of temperature samples at the surface, 20", 40" and 60" down in the area where the source pipes will go. I put four sensors in a piece of 3/4" pvc pipe, capped the lower end, filled it with dry sand to keep the sensors in place and give conductivity, put a u-bend on the top to keep water out, and recorded the temperatures every night for a year. The upper sensor varied between 48 and 73. We're close to the Pacific which is a great stabilizer of the local temperature. The lower sensor varied between 55 and 64. The sensor at 40" below the surface varied between 52 and 65. It seems to me that 48" deep wd be just fine for the source pipes. I'm imagining I can dig a narrow slot type trench four or more feet deep and bury the loop with the return portion in the bottom and the out going portion of the loop perhaps 2.5' down with each loop being about 300' long in a 150' trench. At 2' apart, I have room to install ten loops for a total of 3000' of collector pipe for a 2.5 ton heat pump. Perhaps that's far more ground source pipe than I need, but in order to find out, I'm installing one such loop which I'll connect to my small E-Tech heat pump, and monitor the rate at which I can extract heat. It should give me sufficient data in order to design the heat exchanger we need. mm
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Old 03-24-13, 01:28 PM   #18
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Quote:
Originally Posted by michael View Post
...I took a years worth of temperature samples at the surface, 20", 40" and 60" down in the area where the source pipes will go. I put four sensors in a piece of 3/4" pvc pipe, capped the lower end, filled it with dry sand to keep the sensors in place and give conductivity, put a u-bend on the top to keep water out, and recorded the temperatures every night for a year...
Hmmmmmm......

"You might be an ecorenavator if you take a year's worth of readings of ground temps before you start digging."

This info is solid gold.

Can you put this data online or in graphical form?

This is the kind of thing everybody ought to do if they're considering a GSHP.

You clearly have GSHP Fever, and there's only one cure...

Best,

-AC
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I'm not an HVAC technician. In fact, I'm barely even a hacker...
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Old 03-24-13, 02:14 PM   #19
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A question for AC: I have many related questions and topics I'd like to discuss, but would it be better for me to switch from this thread to the Manifesto thread to keep all the relevant stuff in one place? You know your way around this forum, and I'm an absolute newbie, so I could use a little guidance. Also, this thread has morphed from one about my little heat pump being directly connect to a radiant floor system to one about heat source design. I don't mind moving through lots of topics, but I don't want to run against the practices of this forum.

And, I'll work on getting the ground temp data in some sort of graph or chart. Right now it's in pencil on a ledger sheet along with air temp outdoors, in my attic, and water heater run time on a daily basis. mm
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Old 03-24-13, 04:26 PM   #20
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Michael does the E-tech HP xfr heat from input water to output water within the unit or does it require buffer tanks on the side from which to exchange?

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