I have just had and Earthlinked DX system installed in my home, but I don't think it will do what I wanted. I was very clear with the saleman, who also turned out to be the company owner and foreman.

I told him I wanted a system that would provide me with heating and cooling and that would make hot water all year round, spring and fall, even when the system is not heating or cooling.

I had a quote from a Waterfurnace contractor, who was prepared to install a system like this for me.

I chose the Earthlinked DX system because the guy told me that with the Earthlinked system he could add a desuperheater for $400, and that would give me what I wanted.

The Waterfurnace guy was close in price to the Earthlinked guy for climate control, but was $8000 extra for the hot water, because he had to install a separate box dedicated to hot water.

That made my choice easy, except  my furnace is almost never on this time of year and I find my system is not preheating my hot water. They say they are finished and everything is working. I looked online to see if I could find out why this might be, and learned that the desuperheater does not preheat the hot water all year round. It only works when the air handler is running.

The waterfurnace guy could have added a desuperheater too.

So, now I find myself apparently with the wrong equipment supplied to me, according to my design specifications.

Can this be rectified? Is there any way I can get some sort of add-on to my residential Earthlinked DX system to pre-heat my hot water all year round even when the air handler is not running? 

The Earthlinked web site is not clear about this at all.

Here is what the web site says:

The Earthlinked system has three major components:

1. An earth loop system that circulates a heat transfer refrigerant to exchange heat with the earth.

2. A heat pump that moves heat or cool between the building and the earth via the earth loops.

3. A distribution system to distribute comfort throughout the building.

And two options for water heating:

1. A desuperheater to capture waste heat from the air conditioning cycle and move it to the water heater.

2. A full-demand water heater, where the Earthlinked system supplies all of your hot water needs year-around.


#2 . What does that mean?

Does that mean the whole unit is dedidcated to hot water and does no air handling?

Does it mean, with option 2, I get air handling and year-round hot water?

You would think they would provide more details.

------

update:

The guy is in this morning and he is saying it would cost more in electricity to heat hot water year round using the DX system than using the electric hot water tank, because the DX draws 40 AMPS, and the hot water tank only draws 20 AMPS. He says it only saves money on hot water when you make hot water when the air handler is running. Otherwise it costs more.

Is this correct?





 

Posted By cnygeo on 17 Nov 2010 12:24 PM
I wouldn'y listen to anything else this guy says - most of this is completely wrong. It is entirely possible to make 100% of your DHW year round with geo, and unless something is really badly screwed up, it will use 60-80% less electricity than a straight electric heater, depending on the system, loop temps, and DHW temp required.

As Joe said, in many cases it does not make financial sense to do this in terms of capital cost, especially when starting with a forced air system, but the energy to run the system will absolutely be significantly lower.

Out of curiosity, what are you using to generate your power? If you are considering PV, keep in mind that for an off-grid application, you would probably come out ahead efficiency wise by using a solar water heater - even if you get an average COP of 3 for the heat pump, the PV is probably only 15% efficient, so you'd only be using 45% of the available solar energy. Most solar water heaters should beat this pretty easily.

Second I am being told that using my geo-system to make hot water year-around would cost more than just running the electric water heater in the pre-existing hot water tank, because the unit draws 40 AMPS and the hot water tank electric element only draws 20 AMPS.

Even with a $7000 add on unit dedicated to making hot water, I am being told it would cost more for electricity to make all my hotwater that way, than just using my electric water heater. More importantly for off grid, the electrical power consumption would be higher, not lower.

I am being told that many commercial places are installing geothermal hot water systems to go green, but they are actually using more electricity to make the hot water than before, and are not really doing anything green.

Posted By foaf on 17 Nov 2010 12:48 PM

So, I am being told that the Earthlinked DX system can easily be made to do this with the existing equipment, by reconfiguring something in the compressor box. Is that also wrong?

I have been investigating using HVAC technology to generate say 3kw 24/7, for 72kWh a day, with batteries to handle surge demand, and startup. Endless Energy Inc has a system that looks interesting. 

Yes, it would be nice if there were someone on the board who does Earthlinked Geosystems who could provide some answers.

The WEB site has no contact us section that I can find.

WRT Endless Energy, I'm using their system as an example. The concept is fairly flexible and uses HVAC equipment, with a generator that you should be able to purchase separately. I'm sure there are various ways to use heat pumps to create a suitable temperature gradiant to support power generation. They are claiming a realistic 80 F temperature differential which does not allow for very efficient operation, but even low effieciency can be enough for continuous micro generation.

Mid temperature also considered low temperature geothermal generation uses a binary cylce with minimum temperatures around 190 F. This gives a temperature gradient against the environment of about 120 degrees. Efficiency drops with temperature differential. They claim 500% heat transfer efficiency across the gradient between reservoirs. It is the heat differential that is used to run the generator and that is where you lose efficiency with temperature.

Endless Energy is reporting net output of 2-4 kw which is a lot when generated continuously. The generator they are using was designed for use with solar heat collectors to provide the temperature differential, but they are using heat pumps for that, and still producing enough power to run the heat pumps and produce a few kw extra.

This I am hazy on. It's like they are playing some sort of fast shuffle with heat transfer, that smells of a perpetual motion machine.

Posted By cnygeo on 17 Nov 2010 04:41 PM
The concept is analogous to using an electric motor to drive a generator - it is a perpetual motion machine the way they're using it. If you read the prototyping section, they haven't actually tested a unit that shows a net power generation, they were using an electric motor to pump refrigerant and drive their turbine. So maybe snake oil is too strong a term, it is possible that they honestly think it will work.

Low temperature differential heat engines can work, of course, and I think it's a pretty interesting field. Some of the ocean-based systems might have promise in the right locations (google "OTEC"). In this case, even if they did it right they would be looking at a temperature differential of 30-40F max (and then only in the middle of summer or dead of winter) - THEORETICAL (Carnot) efficiency would be in the 7% range, so in practical terms they might hope to capture 1-2% of the available energy. 3kW would require 1000gpm or so. That's a pretty big pipe. Again, this is best case, more than likely it wouldn't work at all.

Posted By joe.ami on 17 Nov 2010 10:18 PM
"So what I finally need a certain answer about is if I need the HWHX box, or is there some special way the system has of preheating hot water all year around without the HWDX box. Is the HWHX box just for heavy hot water demands like radiant flooring and pool heating, or is it needed for any hot water heating when the air handler is idle?"

Again we confuse "preheating" with finish heating. Most every brand/type of heat pump can "preheat" water for you, but that's not really what you say you want.
A DX to water heat exchanger is not $7000, but if you want it to heat all your DHW it may take more BTU's than your system has available after heating your home. That could require additional equipment that does cost thousands. 
I think you are inadvertantly excluding information which handicaps us in answering your questions.
Joe

Posted By joe.ami on 19 Nov 2010 09:10 AM
"This issue is whether or not the unit can preheat water when the air handler is idle, without a HWHX box, and if it can, does that save on electrical usage, and if so, how much"

No, it can't heat or preheat water when unit is otherwise idle.

I'm not sure if you were "mis-led" or if your bidders did a poor job of clarifying the differences for you. I really can't imagine anyone suggesting that on demand water "pre-heat" was available or even a good idea (in a residential DHW application).
Perhaps we can do that here....

A desuperheater which it sounds like you have, preheats water with "waste" heat from the refrigeration process. Water is generally stored in a buffer tank up stream of finish tank. A DSH will not heat water on demand, geo must be running to heat or cool home. It saves money on electrical usage when used in this configuration.
One could set up a duct zone to "dump" heating or cooling to basement, crawl or outside, to run DSH on demand, but this obviously would add electrical usage.

On demand water heating with geo can be done as well, but it would generally not be done as a "pre-heat", it would replace your finish tank. While it could be done as "pre-heat" it would be the least effective of the scenarios (why finish heating the water with a less efficient method if you've invested in the hot water heat exchanger).
On demand could save energy ($$$) over current configuration, but at what cost?

The configuration you purchased is IMO the most cost effective of your options. No it won't pre-heat water when geo isn't running, but it does save you money without further expense.

j

Posted By stuart.wyss on 19 Nov 2010 12:29 PM
The desuperheater on most units only takes a small percentage of the actual heat the unit is generating...it's a very small heat exchanger compared to the main exchanger used for ultimately heating the ducted air. I've read on the order of 5 to 15%. In cooling mode, 5% to 15% of the heat pulled out of the house can be dumped into the hot water generator (desuperheater) and rest of the heat is "sent" to the ground loops. In heating mode (when running, of course), 5% to 15% of the heat pulled out of the ground is sent to the hot water generator. The rest goes to heat the ducted air for the house. When the compressor is running, in either heating or cooling, certain other conditions have to be met in order for the actual desuperheater components to operate. The temperatures of the incoming desuperheater water, the amount of "excess" heat coming from the home (cooling mode) or loops (heating mode).

Trying to run the desuperheater exchanger system without running the actual air handler would, most likely, be highly ineffective.

Posted By engineer on 19 Nov 2010 10:52 PM
Nope - desuperheater heat exchanger is way too small to accept and transfer anywhere near the compressor's full output. This is by design.