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Old 07-17-13, 03:17 PM   #51
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The parts are copper, so they will quite easily exceed $100 unfortunately.

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Old 07-17-13, 04:39 PM   #52
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The parts are copper, so they will quite easily exceed $100 unfortunately.
Plastic, especially thinner plastic is not too bad once it comes up to temp. It's interesting to note how well plastic HXs work in HRVs.

It would be unfortunate to pass on this project because of cost.

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Old 07-17-13, 05:02 PM   #53
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I've never seen a plastic drain heat exchanger design, what are you proposing?
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Old 07-19-13, 12:35 AM   #54
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Quote:
Originally Posted by AC_Hacker View Post
Plastic, especially thinner plastic is not too bad once it comes up to temp. It's interesting to note how well plastic HXs work in HRVs.

It would be unfortunate to pass on this project because of cost.

-AC
Interesting.
Perhaps the outside sleeve could be plastic, even if it is a poor heat exchanger ?
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Old 07-19-13, 08:41 PM   #55
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Interesting.
Perhaps the outside sleeve could be plastic, even if it is a poor heat exchanger ?
Well, the outside sleeve would be great, especially if it was a terrible conductor. If you make one copper and the other plastic, there could be problems with different expansion rates.

But the thinner the material, the less resistance it has to heat flow. I was actually thinking about the inner sleeve being plastic.

There has been a lot of machinating about aluminum vs. plastic for a HX in the HRV thread. Interesting to read.

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Old 07-20-13, 08:01 AM   #56
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My very first solar water heater used black plastic tubing in a drain back configuration - disaster! Here's why.

Built a box with glass and insulation, put in the plastic tubes, etc - all along ideas used at the time (1978). Used a "drain back" configuration so that it was simple and would only turn on if the heater thermostat detected warmth. then circulating pump turned on.

Had a simple heat exchanger (coil of copper) in an insulated tub.

One sunny day the main power went off to the area and after an hour it turned back on. The water went up into the VERY hot collector and immediately flashed into super heated steam. Melted every one of the black plastic heat exchanger tubes.

I rebuilt with type M copper tubes . . . .


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Old 07-20-13, 01:44 PM   #57
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My very first solar water heater used black plastic tubing in a drain back configuration - disaster! Here's why...
Good info for solar heat collectors, but this thread is addressing the recovery of heat from shower water, so the disaster scenario that you have described will not happen in a shower.

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Old 07-25-13, 04:13 PM   #58
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Quote:
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The efficiency is in the long term cost, IF you can get the cheap panels.

An it appears the day of the cheap panel isn't here yet..

I just got off the phone with the dealer and it turns out that Solar Panels : Solar Panels Direct $1.74 per watt
is pulling a bait-n-switch with their shipping cost.

It was:

$58.80 USD 4 $235.20 USD
Shipping and handling $101.74 USD
Total $336.94 USD

And now, they want $240 for shipping. More than the price of the panels..

I think maybe I'll wait until they have $1-a-watt panels at Lowes..
Thread got off topic, but I was just browsing around this thread and some others on build it solar. Noticed this for 95cent/watt solar panels. I have not looked into availability or shipping cost.
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Old 07-25-13, 07:10 PM   #59
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Quote:
Originally Posted by gt390 View Post
Thread got off topic, but I was just browsing around this thread and some others on build it solar. Noticed this for 95cent/watt solar panels. I have not looked into availability or shipping cost.
Home - American Solartechnics, LLC.
Yeah, somehow this thread lost it's way. 95 cents a watt sounds really good to me.
Plus, I'm only about 215 miles from the dealer in Maine. I could drive up there.
215 mi, 3 hours 36 mins on I-95 N. I could build a giant PV farm in my back yard!
I would never see the fry pan coming towards my noggin..

I just looked at Home Depot and found $1.36 per watt.
Grape Solar 235-Watt Polycrystalline PV Solar Panel-GS-P-235-Fab1 at The Home Depot
Lower than I expected to see..

PV prices are coming down into the DHW heating range.
My PV DHW stuff is still working surprisingly well, considering the way it's wired up.
Summer sun is keeping my A7 ASHP from getting much chance to run.

Today was rainy, so it should run after my shower this evening.. At least an hour.

Thanks for posting. I will alert my local buddies. One friend is getting ready
to retire up in Maine, and he might be very interested in some cheap PV.

Anyways, here's my current solar hotwater hack.. Currently using about 7 cents a day off the grid..
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Last edited by Xringer; 07-25-13 at 07:21 PM..
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Old 09-25-13, 12:18 AM   #60
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I've been working on an new way to control when the A7 (ASHP) runs.
It was on a timer that enabled 120AC to the A7 in the early afternoon.
In the hopes there was a lot of sunshine during the morning hours.
Now, I'm working on using a micro controller (CAI) to monitor
the water temperature, solar conditions etc, to optimize performance.

During the last 5 or 6 days, that I've been working on the CAI programing,
all my time has been spent on other stuff and the A7 has been unplugged..

Meaning, we've been using nothing but solar PV heated hot water!
It's not boiling hot, but it's doing the job, this week..

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