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Forum Index : Other Stuff : Electric hot water systems

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MacGyver

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Joined: 12/05/2009
Location: United States
Posts: 1329
Posted: 09:09pm 14 Jun 2009
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I'd like to do a little FYI here:

As far as a heat pump being "green-friendly" hogwash! Think about how
it works. First off, gas, coal or some other primary fuel is burned to
create steam, which in turn is used to create electricity for the grid.

Next, the compressor in the heat pump creates high-pressure gas, heat
and a low-pressure place (evaporator) to make things work. My point in
all this is it's a waste of resources.

IMO heat should come from its primary source (gas, wood, coal, etc.)
Electricity should come by means of a passive collection system (wind,
solar, etc.) that converts the energy to a more useful form.

Also, a heat pump will "heat" to the same degree it will "cool" in reverse.
What that means is if the outside temperature gets cooler than the heat
pump can cool warm air, it heats no further. That means if the
temperature inside your house gets below about 41 degrees, you'd better
own a thick overcoat.

The waste heat from compressing the gas inside the unit is miniscule
when compared to other, less complicated-schemes to gather heat.

I say use a concentrated, tracking solar collector (coming soon to my Web
site) for heating water and your house or work shop. Use PV or several
other mechanical means to create useable electricity and put your efforts
after capturing all the free stuff first! Spend the same amount of time and
effort it would take to capture the waste heat from your heat pump
building something closer to its primary energy source, that's all.

Okay, I'm finished.
:O)

Edited by MacGyver 2009-09-03
Nothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
 
petanque don
Senior Member

Joined: 02/08/2006
Location: Australia
Posts: 212
Posted: 05:19am 16 Jun 2009
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Perhaps the main advantage of making a heat pump compulsory is that it will make evacuated tubes look like good value.
 
MacGyver

Guru

Joined: 12/05/2009
Location: United States
Posts: 1329
Posted: 06:28am 25 Aug 2009
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Oztules:

From your reply on page 1: "a good ole solar refrigerator"

Do you have an Internet link for this? I'm assuming it is an 'absorption' unit
and likely uses ammonia and water, but I'm interested in learning more none
the less.
Nothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
 
MacGyver

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Joined: 12/05/2009
Location: United States
Posts: 1329
Posted: 07:07am 25 Aug 2009
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Okay. Since this is in the "Other Stuff" category already, I know a great
way to make a very efficient, gas-fired water heater, if anyone is
interested:

A quick note before I begin: This is cool for those who live out in the
boonies like on a farm, but I wouldn't use it to replace my existing water
heater in any home I was considering offering for sale in the near future.
That being said, here we go:

I make small steam engines as a hobby and often use what is termed a
"fire-tube boiler". All this is is (that looks funny, but it's the way I would
"say" it if I were speaking) a cylinder with ends and a bunch of tubes
running through the thing, welded at each end to the end plates. The end
plates are also welded to the cylinder. I usually use either copper or brass
for the cylinder and always use soft copper for the tubes. Fire (heated
air) flows through the small tubes.

The more (copper tubes) the merrier! What "I" do is manufacture a bunch
of tubes of 3/8" into a bundle and "twist" the bundle so all the tubes
touch. I make the bundle large enough to "just fit" into the cylinder
tightly. The ends of the tubes are way longer than the cylinder and the
reason is, I pinch off the ends, then weld (braise) the whole bunch
together forming end caps on the cylinder.

When it cools, I test it through the inlet and outlet fittings with air under
water (look for bubbles) and when I'm sure it's got no leaks, I grind off
the tubes up next to the end caps on the cylinder opening them up again
on each end. It's a lot of work, if you haven't already guessed!

I try to make the "boiler" no larger than about 3" wide and about 10 feet
long. There is an inlet and outlet fitting, one on each end. One lets cold
water in and the other lets hot water out.

How it works:

Water flows "around" the little tubes within the cylinder; fire flows
"through" the little tubes and the heat is transferred to the water.

I make a small METAL fan (squirrel-cage design), which sits at one end of
the 'boiler' and I place a SMALL gas flame array at the other end. I spin
the fan and it SLOWLY draws the heated air through the little tubes. To
make it efficient, I try to pull the heat through so the exhaust
temperature of the heated air is close to the temperature of the water
inside the boiler.

The trick here is to go slowly, both with drawing the hot air through as
well a with supplying it with water. If you want to run the water fast, like
for a shower, just make the tube really, really long (like 20 feet long!).

I found that if I use ALL the heat from as much flame as it takes to fry an
egg, it'll heat my water to hotter than I can put my hand into comfortably
and use only a tiny bit of fuel. Neat, huh?

A little note of caution here: If you use 'soft solder' instead of brass
braising rod to hook things up, it's okay; just don't let your heater run out
of water. If that happens, you'll wind up with a mess as the heat will melt
the solder and the thing will fall apart!

EDIT: I forgot to mention, this rig operates in a HORIZONTAL position,
not vertical. It'll work vertical, but lying down makes more efficient use of
the heat source. (9-1-09) :O)Edited by MacGyver 2009-09-03
Nothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
 
AMACK

Senior Member

Joined: 31/05/2009
Location: Australia
Posts: 184
Posted: 11:08am 25 Aug 2009
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I have a quantum hot water heater ( Heat pump ) It works well but there is some noise. I have and still am doing home reno's and changed a few things to move the system to a spot that the noise would not have any effect.

When we installed the system we got a rebate of $600 from the gov and have to put up $2600 of our own money. then 12 months latter they put the rebate up to about $2600. I seen an advert that you can now get the system installed for $400. DAM,

The other idear i have was to make a stainless tank to replace one lenght of flue in a wood heater that we use to heat the house. This wood heater goes 24 hours a day in winter and I think the heat going up that pipe is a big loss. I would like to heat water and pump it around to radiator's in each room of the house. My plan was to send the water back to the hot water unit and past it throgh the tank from one side and out the other.
I have spoken to a plumber and he was not sure it it would work but I can not see why not.
The water in the system would be moved by a 240 volt 15 watt pump that moves about 13 lt per min. The System is closed loop untill you turn the hot tap on. At this time the water that feeds the hot water system would come from the ratiator system circuit and be pre warmed by the fire. ( around 50 0C ) I think by passing the water through the hot water system the tank sould use the heat ( eg Hot water rises cold water drops to the bottom of the tank) When the cold watewr drops it should be moved to the wood heater and warmed up and sent back around. I have planed on two releaf valves on e on the heat tank on the wood heater and the second on the hot water unit.
The system should work as the water in the hot water tank will not get over 56 oC as that is all it will heat too.

If there is any hot water experts out there let me know. I do have detailed plans that I have drawn up and I do have some plumbing back ground but not thermal knowlage..

andy
*Note to self

1. Make it thick

2.Make it heavy.

3.Make it stronger than it should be.

4. Don't rush the first job as the second job will cost more and take mor
 
MacGyver

Guru

Joined: 12/05/2009
Location: United States
Posts: 1329
Posted: 03:49am 02 Sep 2009
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I'm a plumbing contractor in real life. I've been at it since I was 15.

At any rate, what you are attempting to do will work, but there are several
hurtles you'll have to jump.

First off, the system should be either active (pumped) or passive (gravity).
It will likely not work both ways. If your idea is to wrap soft copper
around the stainless steel exhaust tube from a fireplace, that will work,
but stainless is not good transferring heat. If as you said in your post,
you want to manufacture a tank as an intermediate in the flu; good luck.
I hope you are an excellent welder and own a heli-arc rig.

If you're bent on making a tank, be sure the bottom is concave and the
top is convex. Any other design will buckle and leak. There's a reason
water heaters are shaped the way they are.

If you want to do hydronic heating, the water should be separated from
the domestic or "potable" water. It would be good also to mix in
something to resist corrosion as well as an anti-freeze agent. I don't
know how cold it is where you live, but my guess is it probably freezes
pipes. If that's the case, you'll have to build a sensing system so your rig
doesn't freeze if not in use. If it freezes, it'll create a leak(s).

If I were you, I'd go back a couple of posts and take a look at my little
"fire-tube" boiler tutorial. It wouldn't have to be that fancy, but like I
said, the more tubes, the merrier. At any rate, if it were me in your
shoes, I'd use a METAL squirrel-cage fan and draw burning wood stove
exhaust through whatever I was trying to secondarily heat. This makes
efficient use of your waste heat and is very simple to build.

If you want more information, just ask.

Oh, something I forgot to say in my previous post is that the "fire-tube"
boiler I made for heating water is operated in a HORIZONTAL position.
This orientation makes more efficient use of the heat being drawn
through the thing.Edited by MacGyver 2009-09-03
Nothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
 
AMACK

Senior Member

Joined: 31/05/2009
Location: Australia
Posts: 184
Posted: 10:12am 02 Sep 2009
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Thank MacGyver Something to think about..

*Note to self

1. Make it thick

2.Make it heavy.

3.Make it stronger than it should be.

4. Don't rush the first job as the second job will cost more and take mor
 
Bryan1

Guru

Joined: 22/02/2006
Location: Australia
Posts: 1343
Posted: 09:28am 07 Sep 2009
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Eh MacGyver,
That suggestion of the fire tube hot water system is a bloody beauty... I do have about 50 years worth of the Model Engineering Mag here which is full of stuff on steam. I also have a heap of brass tube so when my missus lets me have some shed time I reckon a scaled down version only a metre(3') long and make it into a little steam generator not hot water. Then I can see another project of a small steam engine maybe driving a F&P.....

All in fun of course and everything will be made using RE power.

Cheers Bryan
 
MacGyver

Guru

Joined: 12/05/2009
Location: United States
Posts: 1329
Posted: 01:45am 08 Sep 2009
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Bryan1:

I've built model steam engines for 40 years! If you need any help or have
any questions, fire away. I'm glad to assist in any way I can.

I stopped using live "steam" years ago in favor of using compressed air.
My windmills all pump air into a common receiver system to that end. I'm
currently building a single-cylinder, reciprocating, double-acting air
engine, but have designed it as not to need a "cross-head". Actually the
cross head is built in.

The reason I made the switch was "lubrication", which is a nightmare
using live steam. Air engines use either graphite or nylon or delrin
bushings that don't need oil.

If you do end up building an engine, remember to build it "loose". Tight
design "looks" great, but won't work. It's fine for very large engines, but
the smaller you build, the more aware you have to be of internal friction,
which must be overcome for the thing to even run at all, let alone run
something else as well (like a generator).

MEdited by MacGyver 2009-09-09
Nothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
 
Dunks

Newbie

Joined: 20/09/2009
Location: Australia
Posts: 7
Posted: 03:04am 22 Sep 2009
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Hi Guys,

back to the heat pump not being on off peak power. I was thinking if you had one of the new electronic meters with different tarrifs at different times of the day you could set your heat pump on a timer for the cheaper time.
Personally I plan to run evac tubes on the roof to an electric back up tank and just us a timer for this. Hopefully never really need the back up anyhow.
Any idea what the different tarrifs are?

Cheers
Dunks
 
AMACK

Senior Member

Joined: 31/05/2009
Location: Australia
Posts: 184
Posted: 10:21am 22 Sep 2009
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Dunks..
With the heat pumps from what I have been told and read in the instruction book it needs to be conected 18-20 hours per day. If you live alone or have a family that has short showers then you may get away with 11 pm to 7 am. I would be looking into it a bit more before you set the timer up..

Andy

Macgyver

I would love to know more about steam power and water. Like I have mentioned in post before i have a small creek that flows past the house (200-250 mt away ) that runs all year round. I have still not been able to find a cheap system to get the power from the creek to the house..??..

The system I was looking at is a low head as this would make the pipeing required cheap and to use a draft tube system. I like this system as it uses the power of the water twice.. Let me know if you have any advice Thanks..

Andy.
*Note to self

1. Make it thick

2.Make it heavy.

3.Make it stronger than it should be.

4. Don't rush the first job as the second job will cost more and take mor
 
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