Experience with ground-source 1-stage?
I’ve been following the developments in ground-source, single stage (means the actual refrigerant goes down in coils in the ground) heat pumps; in a drilled field / array of 3″ wells.
Next big job (residential) will wind up with three heating/cooling systems, two of which will be in new spaces. Potentially, a single well field could supply all the needs to three systems. Met with my HVAC guy today – he’s game, though has only done 2-stage systems, into a nearby lake.
Does anyone have any first-hand experience with the specific type I’m considering?
Forrest – thinkin’ interesting thoughts
Replies
"Staging" generally is used in HVAC to describe the number of different levels of energy that it can supply. Two speed pumps (or some use multiple compressors) for AC & heatpumps. Modulating burners for gas fired. Stepped heating elements for electric heat.
There is another term for what you are talking about. But I forgot what it is. Maybe Direct Contact.
I first heard of this in an article on heatpumps. I think that it was in JLC about 2-3 years ago. At the time I think that there where two companies that did it.
I think the term you're after here is "Direct Exchange". JLC had an article on it in February of last year. "Ground-Source Heating & Cooling Gets Better" Supposedly, the direct exchange units are about 1/3 more efficient that the "standard" geothermal units. Ground loops seem easier to install too.
One of the companies JLC references is ECR, so you might try http://www.ecrtech.com"Listen, strange women lying in ponds distributing swords is no basis for a system of government."Jon
<JLC had an article on it in February of last year.>
I just pulled out and reread the JLC article, and called one of the sources listed, American Geothermal. Earlier this year they sold their geothermal stuff to Earth Source Energy Solutions, in Boston.
So, I spoke at some length today with Earth Source CEO, Jim Smith, and learned a lot. ESES also bought the equipment manufacturer, located in Murfreesboro, TN. They do push the "direct exchange" method, where the actual refrigerant goes through copper coils in the ground - two 55' long coils in 3" boreholes per ton, then filled with grout.
For a residential well field, a ~8-12' diameter circular pit is dug below the frost line. The appropriate # of wells is drilled around the periphery; all lines are ganged at a manifold at the center; then a single pair of lines passes to the inside equipment. Pit is then refilled with earth. Inside equipment is conventional; refrigerant pump is special.
Water loop (two-stage) flexible PVC coil systems claim 250-350% "efficiency" (really coefficient of performance), and the direct exchange copper coil claims 400% and up, as well as less maintenance, and 3" vs 6" bore holes.
ESES offers HVAC contractor certification classes (weekend). Two sessions in Nov, one in Dec are scheduled now. I'm going to see if I can talk my HVAC guy into going - he's had some exposure to water-loop systems
I'm going to investigate this to the point of getting a ballpark price for a 4-8 ton system, and present it to the client.
General rule-of-thumb I keep hearing is, "50% more for full system installation relative to conventional 12 SEER; 2-4 year payback"
Forrest - learnin' some stuff!
You might want to ask over here.http://hvac-talk.com/vbb/index.phpIIRC there where a few that at least heard of the systems. I ask when tht article first came out and severl of them did know what it was. Don't know if any had any experience or not.
Go to this web site: http://www.waterfurnace.com/
Lots of good info there. I'm considering getting one. I have access to a rear round spring that flow water at 65°.
I had a quote of $11K to have a 3 ton (36,000 BTU) unit installed, including all duct work (new 1800 sq ft home). With a 10 year parts AND labor guarantee.
I'm right now trying to figure out the water supply situation.
PlaneWood by Mike_in_Katy (maker of fine sawdust!)
PlaneWood
Oops, I missed the part about the refrigerant going down the hole. That would certainly take LOTS of refrigerant!
The ground source loop (2 stage) says 3 holes each 150' deep & 6" diameter. Use 1" Polyethelyne line and backfill the hole with something (baroid??).
I'm thinking about running my spring into a 1000 gallon underground tank and putting copper coils on the bottom of the tank. The line from the spring would discharge at the bottom of the tank and the overflow water (warm) would overflow into another line at the top of the tank for discharge into a creek. This would be a closed loop. Cost for tank and lines would be about $1000. Cost to drill 3 holes 150' feet deep would be about $3000.
PlaneWood by Mike_in_Katy (maker of fine sawdust!)
PlaneWood
Google on SCW (Standing Column Well) ground-based heat pump systems for typical plumbing. Your 65 F spring source makes me drool. In the northeast, well water typically is mid to upper 40s. Pumping heat up from 65 F allows considerably higher COP. Rather than running refrigerant coils into the tank, put a well pump in there and pump through a buried line into a heat pump unit designed for water source. Return line goes to wherever the spring otherwise goes. The tank need not be that large, either, just enough to provide surge capacity, so spring can refill it between heat pump cycles. It would serve as the "well" in a typical SCW system, except that the cooled water would not return to the well. With 65 degree water, you can easily take 20 degrees of heat out of it. Assuming a COP of 4.0, then a three ton (36,000 BTU/hr) delivered load will take 27,000 of it from water. At a 20 F temperature drop, that is only 1350 lb/hr or 2.7 GPM of water. A 10 degree drop will require 5.4 GPM but allow for slightly higher COP. If the spring flow is better than that, then you need just enough tank to provide suction head for the pump, buried deep enough, of course, to avoid frost. All of this assumes the spring doesn't dry up at times.
Generally accepted advice is to have an experienced GSHP contractor do a heat load calc on the home for proper sizing of the system. They can consider all the details of the water source and spec out a good system for you.
Double check the operation of the system you are considering. Running refrigerant through several hundred feet of buried piping seems a very poor idea. I have never heard of such a system. Personally, even if a manufacturer produced one, I wouldn't consider it. I would also doubt that many states/municipalities would allow this type of system to be installed. The potential for refrigerant system leak is 100 times that of a "standard" system. The refrigerant, especially if your going with a newer type, like R410A, will cost several times that of the equipment.
I need to reread the FH article - their point was that the cost of a system was almost a wash, and payback fro the rest was quick. Also, heat pump equipment was guaranteed for 20 years, not 8, because it was a more stable, durable environment.
Forrest
Here is one.http://www.hitechconstructionproducts.com/earthloopoptions.htmlhttp://www.hitechconstructionproducts.com/earthlinked.htmlhttp://www.ecrtech.com/content/
You learn something new every day. With refrigerant (R410a) at $10/lb and 6lb/ton, not nearly as bad as I would have guessed.