"It's generally thought to be a good thing". I would expect (I'm no engineer, so be prepared to hear better views) that the pond would carry off a lot of heat from your AC needs- but whether it was enough for all of it, I just don't know. It depends on how well the house is insulated, its exposure, the windows, the habits of the owners, how humid the summer is -just everything. But certainly it's going to be much cheaper to lay coils in the bottom of the pond than to drill a well or dig deep trenches. Climatemaster endorses the procedure on their website. In my mind it would most likely be worth trying it at your location, with the understanding that you might end up digging trenches to increase the capacity later. Perhaps it would be worth digging the wide trench to and from the pond, and then laying the coils out, into the pond, and back. It might be enough to lay coils out through the pond and then bring the return back in the same trench. I imagine your contractor has ideas about this. Any way to increase the volume or retention of the pond? Is it spring fed or does it depend on rain? I take it your pond, if a square, would be about 180 feet on a side. If you "slinkied" coils four feet wide back and forth through that entire area you'd have the equivalent of 45 trenches each 180 feet long. I don't even want to think about how much pipe that would take! But seat of my pants thinking tells me it's a lot of capacity. Should observe, although you probably already know it, that water and wet soil are many times better at carrying off heat than dry soil, even clay. That makes me imagine that you would not need as much pipe in the pond as you would in the soil. Overall, I think you should give it careful consideration. Good luck, M

Sorry to hear youÂre having trouble with your system. First of all, we need to know more about your installation. How do you know your installer is competent? His explanation doesnÂt seem plausible. Did your installer document everything that was done to install and start-up your system? Do you have such a document in your possession? Was a proper (Manual J) heat gain/heat loss analysis done to determine which HP to install? What type of Ground Heat Exchanger do you have (vertical, horizontal, pond loop etc.)? The devilÂs in the details; we need more of them. SR

Re Mike: You might be mixing me up with âÂÂTigerâÂÂ; IâÂÂll take that as a compliment. âÂÂThis an elaborate system to heat water.â An elaborate system to inexpensively heat water and heat/air-condition your home. This will be about the most expensive way to go up front but the life cycle and operating costs are extremely low by comparison when executed properly. Think about it this way, per equal volume, water delivery is 3,500 times more efficient than force air delivery and the HP will have a COP of about 4 irrespective of outdoor conditions. In the case of the OP, their entire distribution system can be kept as is if in good repair, no money spent on tearing it out and replacement. Given the size of the property, perhaps a horizontal ground loop might be possible for less than the cost of vertical drilling. When they complete their new addition another zone can be added to the existing geo HP system for VERY little money. It would hardly be more than another manifold and either a pump or zone valve plumbed into the existing buffer tank (see linked manual again). Water heated to about 120F instead of 140F with free DHW when in A/C mode. You always have to look at the total cost differential between conventional and geo, including rebates & tax credits, along with life cycle and energy costs. If gas isnâÂÂt used as an alternate backup fuel, the cost of installing the gas line could be put into the ground loop. In the end everyone does what they perceive is best for them. Were the installation manual plumbing schematics clear and helpful? IMO SR

It boggles my mind that people think 10 years is a long time. After installation, you pay each month (including financing) about what you were already paying anyway (probably less). You do it for 10 years, (especially with all the new government incentives, rebates, and low-interest financing now available) and after 10 years you're paying a ridiculously paltry amount for heat. Of course it makes sense. Think of the payback over 20 years once that loan is paid off! Even if you only end up paying even 1/2 of the normal cost over that period (including the cost of your system and electric), you're still saving substantially. I know not everyone lives in a home for that long, but seeing low energy bills does increase home values. I've seen homes sold almost immediately with their main advertising point being their geothermal system even in our horrible present climate while others still linger on the market. Not only that, but why not decrease your monthly bills slightly (before the loan is paid off)? Slightly lower bills, a higher sales price which will pay off the rest of that loan - still makes sense. We had someone come out to our house and they specifically calculated everything from current estimated heating costs, heating/cooling with geo, then savings/payback period. This was a full service option, including thermostats, etc. Finding that should not be difficult. One argument I saw above made no sense. If it really is worth insulating your home to use a normal system, it is a no-brainer to insulate your home using geo. Whether you decide to use geo or not, you can't say, "Well, normal is better, because we insulated, too." That makes no sense. Insulate either way. Then compare. The financial analysis does not make much sense, either. Yes, it would be wonderful if we could just stop paying the oil company, live without heat, and invest that money! Realistically, while you could want to put away the whole $25,000, you really are still using it for heat either way over those 14 years as projected. Geo, with the loan, electric, etc, will cost about the same each month as heat before the loan is paid off, so you can't just pretend that money could be invested elsewhere. Use it upfront with geo, use it over several years with oil, it makes no difference. That money is being spent on heat. Should it be spent on something worthwhile, or just, at the end of 10 years, have you still spending the same amount on more heat with oil? Geo will typically initially cost you a little less (including the loan and electricity) per month than you would be paying otherwise, then suddenly drop dramatically to only the cost of using the system as soon as that loan is paid off. That's money you would have spent anyway each month with your normal system (even though some of it went to financing, it is still less that what you would have paid for oil). Then suddenly, once the loan is gone, you actually DO have perhaps $1,000 a year in money saved that you can invest if you wish over 10 years. If, with financing costs, it does cost more per month than your normal heating system, that's one thing; but if not, the argument that it is wasting money is not valid. You're spending it anyway. Might as well spend it on something that will, in the future, save you tons of money. (Not just a little, a lot.)