Free Hot Water?

[DCRC]

Has anyone seen this system before?

It's a simple idea. A system that uses the heat from your air conditioning systems freon to assist your hot water tank.

http://www.trevormartincorp.com/hru.asp

check it out and let me know what you think.

Since we run are A/C 9-10 months out of the year it sounds like a neat idea.

 

[GRUMPA]

That is curious indeed, if theres water touching the condenser coil it will eat thru it in time. I wish they had some sort of diagram as to the mechanics behind it. Living where you do solar I would think would work better, theres 2 types open and closed loop systems. Closed loop are pricier and have more parts. Open loop uses the solar to pre-heat the water before it goes into the water heater and is alot cheaper.

In this house I had the condenser in a pool of water eliminating the condenser motor altogether. Worked like a champ for 5 years (lower bills much colder air). Then the water ate right thru the metal and I just went back to the original design.

 

[Birdhunter1]

Grumpa, the water doesn't exactly touch the coil as I thin you described or are thinking. What it does is the water (for hot water generation) is run through a tube that is wrapped around the discharge line of the compressor, heat is transferred from freon-copper tube-copper tube-water. It's kind of hard to explain without a picture but it works real well. I use to be a sheetmetal worker and the company I worked for for several years installed a lot of geothermal equipment and this was standard on all of our stuff. It is very neat and you would wonder if it worked well enough to justify it. One house in particular that we did the electrician ran the wire to the hot water heater and left it hanging for the plumber to hook up, the plumber didn't hook it up because he thought the electrician would do it. We had hooked up the hot water generation to our unit and it was like this for 4 months. we went back to pressurize the loop and I noticed it and the plumber happened to be there hooking up a sink in the basement bathroom so we discussed it. The homeowner happened to be there and we asked him if his hot water ever ran out. He said (with two teenage girsl and a wife) he was the last to get in the shower every morning and about halfway through it ran out. He just thoguth it was because of the woman factor, we hooked it up for him and he never noticed it runnig out again and never noticed his bill being any different from then on. For 4 months the only thing heating his hot water was his a/c unit.

 

[MicroPilot]

I have a geotherm unit in my house and have the water heater turned all the way down. Never have a problem running out of hot water.

A buddy of mine is an HVAC installer for one of the bigger local contractors, and was telling me about this demo they had recently showing this new thing for using the heat from the AC to help the water heater. I said, "Wow, just like my geotherm unit has been doing for years."

BTW, this is only supposed work in the summertime when running the AC, but I don't change the temp setting of the water heater in the winter and don't really notice any difference in amount or temp of the hot water.

 

[SPIKER]

I under stand what you are saying I THINK: you have the AC cooling loop of copper/aluminum coils, for the HOT freon, and then a COLD water copper/aluminum tube is attached to the freon tube side by side. the cold water circulates through one tube and into the hot water tank. the hot AC freon actually pre-heats the cold water into WARM/hot water before the water gets to the tank correct?

this would probably work well in WARM places, but up here it gets way cold, you need water lines burried 4' deep many cases to stay below frost line... anything attached to a non-functioning AC would mean it is setting outside in the ice cold temps... it probably would be OK as long as you had a SUMMER/WINTER setup and drtained the coldwater line after the summer heat was over... WE only used AC a few days this year, so it would be worthless as far as re-capturing MUCH from the install date to the tear out date.

for you southe & west boys though it sounds like a plan...

MarkM /forums/images/graemlins/smile.gif

 

[boustany]

I don't doubt that there would be a savings, but (to put it mildly) the company's hot water savings are a tad optimistic.

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.

So they claim to save more than the cost to heat the water (I wonder where the money comes out?). In fact, if you look closely, the table on the left is the cost of heating the water and their calculation supposes you save all of it with this magic gizmo. (They seem to ignore the operating costs of the heat exchanger, which is cute as well).

I would be surprised if they could save more than 10% of the heating cost by preheating the water a few degrees. The A/C savings is immaterial, and probably overstated as well.

It sounds very suspicios to me. /forums/images/graemlins/mad.gif

I'd ask for an independant engineer's report and a guarantee. That usually scares 'em away.

 

[BIGUN]

Remember the difference in A/C load between Canada and somewhere like say south Texas is like night and day.

I remember reading in a Popular Science type magazines a few years back about this revolutionary new type of A/C developed by some guy up north. He was so proud of it and said the only time it wouldn’t work is if the temp got over 90 deg F or when the humidity exceeded 80%. This is laughable to anyone living in Houston or anywhere around that area where it exceeds both of those figures almost every day during the summer.

Where this may not be practical in Canada, it might make all kinds of hot water in Texas.
I heard Dan Rather who used to live there, say Houston is a city that runs on Freon. No way I would live there without A/C or with it for that matter. /forums/images/graemlins/ooo.gif

 

[Birdhunter1]

SPIKER and Micro: The hot water generation (HWG) will always work on your geothermal unit whether it is heating or cooling. Your HWG tubing is wrapped around the discharge line of the compressor which no matter if heating or cooling will always be hot. With a geothermal unit the outside temp is irrelevant for the most part, what matters is how well your house is sealed up. Since the ground stays the same temp all year (40-50 depedning on geographical location) and your house thermostat setting is probably close to the same the whole year the unit actually never notices any big temp swings. In fact the only swing is what your house is set at. So, if your house is sealed and insulated well and doesn't loose or gain a lot of heat then your unit runs less, since the unit doesn't operate in temp extremes and is almost at a constant operating temp it doesn't really change as far as cost to operate. What should be figured is cost to heat/cool the space which is considered by how well the house is insulated/sealed and how muchit looses or gains heat. I hope this may help.

Boustany: Not to argue the ratings they showed but: hot water generation is a waste product when running a geotheraml unit in A/C mode. In the part of this post above and my earlier post I explained that it comes from teh discharge heat of the compressor, that heat needs to be expeled somewhere so heating your hot water is simply trasfereing a waste product into something useful. Therfore Iwould look at it and say I am wanting to cool my house, I can cool my house but i have to get rid of the heat somehwere. I need to heat my water, how abuot getting rid of my heat from cooling myhouse and making a way for it to heat my hot water. The only cost involved this way is the cost to cool my house. (Actually you also have to run a small pump that circulates water from the hot water tank to the unit and back. It doesn't even draw 1/2 amp on 110 volts ac). Basicly heatig your hot water in the summer time by use of your a/c system is free because your running your ac unit anyway. Now it will also owrk on a geothermal unit in heating mode, but you are slightly robbing yourself of some heat by requiring more to heat your hot water but: the basic principle of a heat pump is it is cheaper to transfer heat than it is it generate heat. A good example is a heat pump vs. straight electric furnace, both systems run off electricity which is cheaper? A: the heat pump. Okay with this beig said would it be cheaper to transfer heat to heat your hot water or generate it electrically. You are robbing your system slightly but it still has plenty enough heat that is being transferred making it cheaper than anything else to do the same.

if all of you guys want more information i have the link below for the geothermal equipment distributor we use to deal with when I was working for the sheetmetal contractor. When i worked there we had Climatemaster equip. and they have since gone with Geo-Comfort. I have o first hand knowledge of Geo-Comfort stuff but the service tech at the shop I use to work says they are nice. The link is to Enertech Inc. http://www.enertechinc.com/

 

[MarkV]

Birdhunter, Geothermal systems depend on an exchange loop to transfer ground temperature to a heat pump. From what I have read the most common type of exchange loop is buried poly piping. I have also heard of systems that use two drilled wells to draw from one and discharge into the other. The third system I have heard of is an exchange loop of poly pipe that is laid in a body of water like the pond in my back yard. Have you ever worked on a system that was setup in water? Or, have you ever heard of any comparisons of the different types of loops?

MarkV

 

[Birdhunter1]

Correct, they do require an exchange loop but there are actually four types that could be used. The piping used is polybutylene pipe and it is all fusion welded. One type of loop system draws water from a source then discharges it to a source (drawing from a lake and returning it to the lake). I have never dealt with this type. The other three I have dealt with. One is a ground loop that is installed horizontally, one pipe is buried at say 5' the other underneath it at 8'. I don't prefer them becuase it takes a large area (roughly 500' of pipe one way per ton of refrigeration required) and the ground temp will change slightly at these depths. The good thing is they are cheaper to install than the vertical loops. The pond loop requires a given average depth and must cove so large of a surface area. There have actually been instances of the loops not being sunk far enough or the pond not being deep enough and it will literally be a block of ice in the winter. That is why I would shy away from a pond loop. Don't get me wrong they do work, one house we put a geo system in was right at the edge of an old strip mine and the pit was used as a pond with a pond loop, but not every pond is going to be as deep as a strip pit. The fourth type is the vertical loop which is in my opinion the best. The vertical loop is pipping gooing stright down in the ground, usually about 150' per ton of refrigeration is what is used thoughit can be veried for say a 3 1/2 ton system they may drill three 180' loops where a 3 ton system would be 3 150' loops. What I like about the vertical loop is that the ground temp NEVER chagnes at the depths this thing reaches so to the unit it is never seeing a change in the water returning to it whereas the pond loop, open discharge and the horizontal ground loop you will see changes. Another thing about the vert. loop is that it doesn't take up as much space and you'll be less likely to dig it up or it be in the way of new projects. Another nice thing is that when they are drilling if they hit water and run the loop through that water (water will be surrounding the closed loop) you get an AWESOME heat exchange.

 

[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.