Free Hot Water?

[MicroPilot]

Birdhunter, I was told that on my unit (a WaterFurnace) that the superheater turned itself off when in heating mode.

Is there any periodic maintenance that needs to be performed on the ground loop part of a geotherm system? I have a vertical loop, 2 - 200' holes.

 

[boustany]

I wasn't arguning whether you could pull heat from an airconditioner, what I was pointing out was the payback calculations are almost certainly bogus.

Cooling a heat exchanger with cold water works well, so long as you've got lots of cold water. As the water warms up, the transfer of heat slows down. So, works real good with 50 degree water, but 60 degree? 90 degree? 110 degree?

You see, unless the heat exchanger core is much hotter that the water, the A/C would probably be less efficient than one using air.

Now, (remember, I'm talking the payback calculation here) think of hot water use. If you take a shower and you need to heat 5 gallons of water to 110 degrees. You'll need so and so many BTUs right then and there. Not over 24 hours, right then. Otherwise, the electric cuts in and starts heating the water (the hotter the water gets the less efficient the heat transfer is, etc).

Unless the waste heat from the exchanger is at a really high temperature (which would be unlike any A/C unit I've ever seen) it wouldn't be anywhere near as efficient as they claim. And the physics work the same in Canada or the US, although I'm willing to admit we are all pretty stupid up here.

So, in principal, you can recycle the heat from a heat exchanger to heat water. Not the point. The point is, they give a bogus payback example. Ask them to prove it.

Now, honestly, just because somebody posts on a website that you can get 'free' hot water from a gizmo, without any proof, theory of operation, etc., why would you believe it?

I've seen all kinds of magic claims like gizmos that convert hard water to soft by magnetic fields and so on.

Please

 

[SPIKER]

BIRD:

while I agree a geothermal unit does run more often than our AC, I belive he asked about AC only not geothermal, which works well in the moderate temps, but we get too much COLD temps with high humidity and those things are not GOOD for AC or geothermal... I would like a geothermal system but I would be much farther off installing a solar system, even though we only get 110 days of sun where there are more than 4 hrs of sun a day. bump that to 6 hrs a day and it is somwhere around 80 days a year. getting nearly all the hot water for that 80+ days a year vs getting a BIT of warm up for a few days when the AC is on, (as mentioned not geothermal) then the invest ment for a solar warmer is way more cost effective!... ( I DO understand there are people who are after every bit of wasted energy they can re-coup.) some cases it is more of a gimick than an actually savings for the person...


anyhow if there was a LARGE building running LOTS of AC (even in winter where AC is on in the center of the building and HEAT on the outside) then it makes since. watching discovery again the other day, (Engineering of BIG buildings) they are actually using AC to make large tanks of ICE durring the night (when electricity is cheap) then the use the ICE to cool the building (durring PEAK DAYLIGHT hrs.)

this takes a lot of dedicated space but their returns were some where like only a few years the equipment pays for it's self in savings & also helps the grid! I'm on the Ohio state list for funding for solar & wind resources so I get updates on NEW things, (I don't contrubute anything now or ever) but simply asked for more INFO. this was about 6 onths prior to last summers grid debockel! all of a sudden I get stuff about every other month now... I orriginally wanted to look into using the "Solar Shingles" for my barn roof. I figured a grant may pay for it, but unfortuneatly they will only reinburse up to 50% of costs up to $10K max. and only AFTER the system was running & proven for 2 yeras /forums/images/graemlins/blush.gif /forums/images/graemlins/frown.gif (running and proven means making a return through the utility buy back program!) : /forums/images/graemlins/crazy.gif /forums/images/graemlins/tongue.gif

so I pretty much gave up on it SO FAR, then they anounced a change in the guidelines as NO-ONE really aws up to the OLD ones. but now the TAX crunch has even stopped the agency form operating so the $ for grants & stuff has dried up... I belive a few commercial units did get it into production but I wasx no where the roof space of a large industrial building...

MarkM /forums/images/graemlins/smirk.gif /forums/images/graemlins/smile.gif

 

[brad_oatley]

It is a desuperheater. As a hot water PREHEATER it is a cost effective energy saver if it is sized , piped and controlled right. Should result in approx. 3 year payback for a family of 4 if the installed cost is under $1,000.

 

[DCRC]

Boustany , </font><font color="blue" class="small">( Lets say you want to heat 40 gallons of water by 60 degrees F (from 50 F to 110 F) in one hour (their first hot water example). That takes 6.4 KWhr. (KW = Liters x Temperature Rise (°C) / 790 x Heat-up Time (hrs.) ), or $0.64 @ $0.10/KWh. x 365 = $233.60 vs their 'savings' of $299 (upper right hand table) for a family of 2 )</font>

The $299 was the estimated annual cost not the savings. Their savings was based on amount of use.

 

[Egon]

Tain't no such thing as free.

Egon /forums/images/graemlins/grin.gif

 

[boustany]

They pro-rate the cost with the number of month's use.

So, if you use the gizmo 12 month of the year, you save $299.

Their bogus payback calculation uses a pro-rated value (i.e. 6 months at $299/year), which literally implies 'free' hot water which the thing is in use.

My point is/was/remains that because the payback calculation is transparently wrong, then alarm bells should be going off.

So, demand proof and a guarantee.

If you don't I've got a magic diesle pretreater with a 3 year payback I'm trying to sell for only $199. Any takers? /forums/images/graemlins/smile.gif

 

[techman]

I think a lot of you are missing the point. Any AC unit, geo or air-to-air, moves heat from inside to outside (or ground). This heat must be dissipated, and if it can be used to heat, or preheat, domestic hot water, that's energy you would be otherwise be throwing away (compressor also adds to the heat generated, but most is "moved" heat). If your AC is running 3 tons of cooling (36,000 BTU/hr) that's also approximately the same amount of heat you are dumping into the environment. It is "wasted" heat which could be potentially used. The real question is the cost of the gizmo, and what is its payback time. If it costs a few hundred, it may be a good investment based on a couple of years payback. If it is close to a grand, forget it.

One other point, you really don't want to use it when you are in the heating mode of a heat pump, since the heat you would be extracting would be the same heat you want to warm the living area.

paul

 

[DCRC]

Well said techman.

The concepts sounds logical and the claimed savings could be questionable.

The questions then becomes will the unit outlast it's payback period without any problems?

I think the "Green" sight that referred me to the things was mentioning it more as an assistance to you hot water heater and to use the the energy for some manor other than to waste it. I havn't checked on the cost but I believe it to be around $200-$300 for the unit.

I'm about to upgrade my complete A/C unit so the labor cost would be next to nothing since I have to run a new line set while relocating my outside unit.

My main concern would be more on the build quality. Would hate to have the chance of this thing leaking water, or worse leaking freon in to my water supply.

The more I think about it. It would probably make more sense to put the money towards a tankless hot water heater.

 

[Birdhunter1]

First off I don't know how refrigerant would even remotely be able to leak into your water system. Also I think many of the people on here may be a bit misinformed, the de-superheater piping (hot water generation) does not pre-heat the water. If it were set up this way there would be no water flow except when a hot water faucet is opened somewhere, to actually pre-heat the water (as I belive many are thinking) the unit would have to be running at the same time the faucet is opened. The way it does operate, at least how our equipment was designed and how we installed it, we had to unscrew the drain valve on the hot water heater and install our adapter (also had a drain valve) that would draw water from the bottom of the tank then run through the heat exchanger co-axial tubing on the dicharge line of the compressor then deposit heated water back into the tank. If your unit was running it was heating and re-heating your hot water all the time.
MICRO: With the Climatemaster equipment we installed we always set up the de-superheater to operate in any mode. We could have done it in a/c only but we kept in mind that it is still cheaper to transfer heat than generate it. Either way would work fine and there are many arguments either way.