Pond Boss Forums INTRO Questions & Observations Geothermal Heat Pump

So glad you brought this up.
During my minimal research into geo HVAC, I wanted to know if there was even a prayer for it's use with an off-grid solar power system. I contacted a geo contractor to discuss power draws. Besides the normal amperage, he noted that the defrosters would be killers. Huh? Defrosters? As I understood his explanation, just like a window air conditioner that runs too cold for too long, the coils can eventually freeze up with frost on their exterior. OK, I know that occurrence. He said that a HP is exactly the same, operating in reverse. The same thing will occur and some killer amperage defrosters can/will kick in for about 5 minutes to melt it off.
Correct?

Sounds like he was describing an air source system. Geo does not require defrost. Antifreeze is circulated in the ground loop and the system simply shuts down if it gets too cold. It souldn't shut down if the loop is sized properly and the flow across the heat exchanger is correct.

You might want to consider using a Solar collector to heat water to supliment this system.

Oh, goody, so I can play?? LOL I'll do that, and start a thread soon as we get started on the pond. We are lucky in that my husband works for a roadway contractor(project engineer) so they are going to come with all the equipment and do some digging. (trackhoe?)Since they are doing this instead of us having it hired, we can make it larger than originally intended. We both love to fish and I can't wait to see this pond take shape! Been in the planning stage for years and years. We cut the timber last fall and now we have the funds to proceed. We are going to build a nice pier, and even a pavillion on the other side for tables, etc. I have friends that did this and decided I HAD to have one too! They have a little kitchen and bathroom (with used appliances). I even thought maybe to include a set of bunkbeds for hunters and fishers. Of course,plenty of hammocks outside, grills, fish cleaning station, fish fryer....oh, I can just see it now :~)Ya'll come!

Our heat pump runs nonstop only at very low ambient temperatures and windy nights. I am guessing only for few days in each heating season. Also our house cools down very slowly it takes about 8 hours without heating to feel noticeable discomfort even at very low ambient temperatures. So in our installation we hardly notice loss of heating due to heating of hot water.

We have installed 9 kW electric heaters in the heat accumulator but the breaker was never turned ON. We might use it only in emergency when the heat pump fails completely or we might never use it because we also have two propane fireplaces located strategically in the house.

We know people who have floating bedroom on their pond. How romantic and original. We are going to build one too but only after we find and fix the leak in our pond.

It all depends on how much money you want pay for increased comfort. If money isn't object I would add whole house filter integrated to the AC ducting. The difference between recirculation and separate filter is that the filter draws certain percentage of air from outside trough a heat exchanger (to increase the economy) and keeps the house under small positive pressure to prevent dust from outside entering the house. It also have hypoallergenic filter that is not always easy to incorporate in the AC. The reason is relatively large pressure drop at the flow rates used to cool or heat the house. The filter flow rates are much smaller.

Fan coils for geo are usually two speed. High speed is used for AC and the low speed is used for circulation.

The efficiency of heat pump in general depends on the temperature differential between outside and inside of the house. The smaller is the differential the better is the efficiency and vice versa. In other words the greater are the temperature extremes and longer is their duration the more advantages is geothermal system. So in some climate such as NC, SC, VA or OR air heat pump would work quite efficiently but further south or north geo is the winner.

Here is a sneak peek of the cabin -to- be by the pond-to-be..

http://ourdreamgreenhouse.blogspot.com/

oh, do tell all! A floating bedroom....never heard of that. Good place to put the hubby when he snores. I'll even tuck a fishing pole under the sheets so he doesn't wake up complaining.

Well, I have to correct my statement. I thought that those people were my wife's clients but I just talked to her while ago and she said that I am confusing it with a show in TV she told me about many years back. In any case I think it is great idea regardless of the source. We definitely plan to build one and use it.

I love your project. But it is a lot of work. More than building from scratch.
We have the shell of our barn built by a contractor and finished it all inside by ourselves so we can apperciate it.

Well, we have a picture frame business, using only old distressed wood siding, so once we tear off the siding, we just keep going. We just get what we can use...alot of the inside tongue and groove we can use too. The rest we knock off walls with chain saws. The hard part is getting the nails out. UGH! Those old square head nails are so soft. Since we are after the beams underneath mostly, that's the prize once we get through. It is hard work, but usually free wood. Wood that can't be bought. I priced an old beam the other day, 1000.00 per beam! So I guess if we get really bad off, we can sell all the beams. How are you going to build that floating bedroom?? Like a raft?? I could see taking an afternoon nap while hubby fishes for dinner.

southernbelle,
Alot of questions here I will try to cover what I can.
I would start by trying to optimise the building envelope. There are software programs availible that you can model your building in and they will output the thermal performance. They use historical weather data to calculate the heating and cooling demand. It will calculate solar gain. Once you have the model you can optimise it by changing glass type, adding overhang, reorienting the direction, adding insulation, ect... You can see the effect of changes imeadiatly and decide what's cost effective. The one I used is called HVAC-Calc and it's ~50.00 for home-owners. HVAC-calc

The Slim Jims you refered to appear to be pretty good units. These things are installed all over place in Asia and Europe. They're duct less units so they are pretty cost effective fo retrofits. Their top of the line units use a variable speed compressor so you can try to match the output to the load. Your floorplan and lifstyle will dictate how effective a zoned system can be.
Generally speaking the geo system should cost you about .60 to the dollar, btu for btu of what a good air source HP system would cost. It depends on how mild the climate is. Up north the difference is greater and if you're on the coast it may be less. You really have to do the calculations for your specific area.


There are two types of cooling loads, sensible and latent. Sensible is dry bulb. Latent is wet bulb. The higher the humidity the higher the latent load will be. In a forced air AC system humidity is removed by passing the air across a cold heat exchanger. The water condenses on the cold surface of the heat exchanger and falls into a catch pan via gravity. It's very important that the AC system is sized correctly to deal with both type of loads.
If the system is too large it will cool the space without removing the latent load.

I don't have specific plan at this time just the idea. Our pond is leaking about 1"/day when half full. The watershed is somewhat marginal for our area so our priority is to increase the watershed by digging a draing diches cross horizontal line in the walley downstream of the pond. And obviously we have to fix the leak first.
For the floats I was considering plastic 50 gallons drums (sometimes for sale $10 each) or the floats they make boating docks from. I am thinking about 10X10 to 12X12 size.

what will be on it? Just a mattress? Hope you get your pond fixed!

Southernbelle,
My house is mostly glass facing south, and I have seen no problem with this design. There is a minimum of roof overhang, but the sun being low in the sky in winter and high in the summer is what makes all the difference.

tejasrojas is referring (I think) to a wall-pak A/C, not the Slim Jim you mean. That is, I think yu mean the radiator thing that goes in the pond rather than a few thousand feet of plastic tubing. I found that a Slim Jim casts about as much as having the tubing installed. It has to be kept clean or it doesn't work, and I just couldn't justify not going the conventional route. It might be worth doing in a small pond, but you say you will have 3 acres.

I'm heating / cooling over 7000 sq ft with a 6 ton geo system. Humidity is not a problem here in Georgia. Neither are the electric bills which are under $100/mo.

Brettski, a geo installer told you about the defrost cycle? Find a new geo installer.

Blaine, I got my shocker today, my second electric bill has come in (this is after not being able to determine if electric strips were on and also finding out that the transformer outside wasn't big enough). My previous bill was $267.00. Maybe someone can point me in the right direction. This one is or 01/23/08-02/20/08 (28 days) and says I used 5,045 KWH and my bill is $505.78. This makes me think the heat strips were kicking in full force and heating the house and geo wasn't. The geo tech never came back with an answer from the manufacturer(and yes, he's getting a call tomorrow). If the heat strips have to maintain where the geo fails, I'm in deep trouble with geo. I just need some direction in what can cause this problem, if any of you have experienced this.

Does anyone know what the termperature of the incoming fluid should be coming in from the pond as we know the tech commented on how cold it was. And the second time, he talked about how cold it was again.

What are your thoughts on this one, did any of you experience any problems in the first year of your geo (especially with the heat strips? At this rate my geo is costing $100 extra electric a month and not the $40.

thanks for the good info. I'll certainly look into that calulator software. Sounds interesting.
Are you referring to the Slim Jim Lake plate that goes into the pond? http://www.awebgeo.com/ Didn't know there was another type Slim Jim...... 'cept for maybe the beef jerky

Jersey, where in Ga do you live? I'm originally from South Atlanta/East Point. You mean to tell me there's no humidity where you live in Ga? You must be in the mts. Or that you don't have a problem using the geothermal in high humidity? We will probably have a 2 ft overhang over the glass. Glad to hear somebody local say '100.00 power bill'!! That's my game plan. I have a dumb question ...when the geo people come and install everything, does that include the unit that goes inside too? I assume you have to have all the ductwork already installed. What exactly do you have to provide and what do they provide?

Oh no.....will the Geo company reimburse you? I've read several of you mention a refund if the unit doesn't work correctly. Am I right? I sure hope it's just a glitch Mark. Let us know what they say.

I would turn the heat strips off to test if it really affects the comfort level and electric bill. If you can't tell the difference in comfort leave them off. I would also look closely at the program in the controller. In my opinion there should be a delay in the algorithm turning the heat strips on. In example the temperature would have to be below the set point for more than xx minutes or dropping despite HP running or something similar. To turn the heat strips on anytime somebody opens the door makes no sense.
I would also check the temperature of coolant entering the house. Spray some black matt paint on the suction pipe and shoot it with the infrared thermometer when HP starts and then again after it runs for certain time. The first measurement is the temperature in the pond. The difference between measurements is the temperature differential. Hopefully somebody who does geo for living will read this and tell you what is the reasonable temperature differential for properly functioning pond loop. I measured 34F several years back while estimated temperature of the water in the pond was about 36 F.
I looked at the pictures of your coils you published many pages back. The coils are so called "fluffed coils" meaning that there should be spacers between each layer of the piping and the piping shouldn't be tightly wound. Your coils don't look too fluffed to me. If the fluid is way too cold they should refloat the coils and fluff them properly. There still might be air in them. I learned from my installer that the flow center migh not be able to purge it. They used quite large portable pump to get the air out. But my house is about 50 ft above pond level.

Infrared thermometer is available here:
http://www.omega.com/ppt/pptsc.asp?ref=OSXL450&Nav=temj04

http://www.omega.com/Temperature/pdf/OSXL450.pdf

Amazon also sells them.

Ladia, Will do some checking tomorrow. Pretty frustating, things were going pretty good--so I thought--had the transformer changed, last electric bill didn't look too bad so thought maybe we 'thought' the strips were on but obviously they WERE on. We're trying to look at the book now and figure how to turn the strips off. Thanks for all your sound advice.

The strips should have its own breaker.

Ladia, my hubby just turned off the heat strips (they were on a separate breaker). We shall see.

MarkECIN, Some weeks ago I thought you might have a setting problem but as I read back through the thread I noticed on 1/17 you posted "This last week it's bee minuses and low one digit and even though we have the thermostat at 72; it shows 63 and we do believe the heat strips are kicking in a lot".
I think you need to get your contractor out and go over their calculations. Does the system perfom as per design intent and if not, why not. For example, the entering water temp had to be known in order to size the unit. Does it meet the design specifications, if not, why not? Ladia made some good points about the loop and they may be spot on, but I think you really need to have your contractor take ownership of this issue. They shoud know at approxamatly what outside air temp the heat strips kick in if they did an appropriate load calc. If the numbers don't match there is a reason.

Southernbelle,
My geo installer, who is now out of business, hired a subcontractor to install the pond loops. My system was installed in new construction, so the ductwork, pond loop, and system were all part of a package deal. All I provided was the bucket of money.

I was saying that the system takes care of the humidity, not that there isn't any.