Residential Ground Source Heat Pumps

Chuck_7

Any one had experience with ground source heat pumps with forced air, radiant, and domestic water heating?
Anyone had to use back up electric heaters (esp. for the water-to-water) with a horizontal ground loop?

Glenn Harrison_2

I service some houses...

that my employer did that use WaterFurnace units for forced air, radiant, and boosting hot water. We always use electric supplement due to there being a much higher heat load than cooling load.

What else would you like to know?

Mi39ke_2

An Opening of Grounded Exchange

I'm still trying to suss some of this stuff out. We've been installing geoexchange for a few years. Radiant, Standard Forced-Air, High-Velocity, Chilled Water Ductless, Etc. We haven't installed a horizontal closed loop system. All our systems (excepting one open system) have been vertical closed loop. Primarily because they have been within the city and acreage has been at a premium.

It seems the manufacturers and reps who want to sell equipment will always recommend electric resistance as part of the system. If left to their specifications, we see a huge amount of material specified, with little guarantee of actual results. No one will guarantee anything. Electric resistance rules. Oversize the cooling side, ductwork sizing is unimportant.

Ground exchanger analysis is unimportant (yeah, right). After all, this is residential, people only live in homes for a few years, so we don't have to provide actual results!!! [huge chuckle]

It would be nice to hear from more experienced installers who have actual data from past projects. It would be even nicer to hear from Reps who have real-world data from properly installed and priced projects.

We don't want to hear from the folks who have had their project installed by yippee-yimminee from glasgowee, or missnogome, who has never installed a profitable system before. A profitable system. A profitable system...should I go again!? A profitable system. [grin] So many systems have been installed without even the basics of common sense. Oh...sad I am, this poorly grounded and exchanged man.

Michael Ward

Chuck_7

The applications I might be looking at have plenty of land so horizontal might be the way.
Another question that comes to mind is whether the system should be installed with glycol in the loop water (this is a NY state application).

Ken D.

Water source heat pumps.

We have installed many WSHP's over the years. We mostly use Florida Heat Pump with good success. We have also used ECR which are unique to say the least and Waterfurnace to a lesser extent. Mostly high end users specify and many places have multiple units. One home has 10 of them. The heat loads mostly say you don't need backup heat. This depends on the winter temperature, type of water or earth source,etc. Most of ours have been spec'd with backup. It is handy when the system goes down to have another source of heat. We have some fossil fuel backup systems as the customers wanted the option and we were using a boiler for their hot water anyway. We have open and closed loops. Some verticle and some horizontal loops. Three of the jobs don't use water, they run the freon lines underground. Two are horizontal, one verticle. They worked well, but one had an underground freon leak that required excavation to repair. From what I have read the open loops are more efficient due to to the movement of the water. The horizontal closed loops are not as eff. due to the fact that soil is not a good conductor of heat and the soil around the pipe gets heated or refrigerated and does not conduct away readily unless the loop is totally submersed in ground water as would be in wetlands. Most areas to not allow any building or excavation at all. Anti freeze is a must for horizontal loops unless it is very DEEP which I have never seen probably due to the cost of excavation. Many of the local governments regulate the types of systems and materials. Some don't allow antifreeze at all while others require biodegradable. The costs of installation as well as maintenance and service makes me wonder how much you reallly save. The water quality in an open loop is a big factor for longevity. Some of the problems with open loops are the wells themselves. Sometimes you need 2-3 or even 4 wells to handle the supply and return water. If your property is big enough you could build a pond to handle the return water. Some of our rural municipalities prohibit ponds as they say it affects the aquafer. I do prefer the FHP units as they seem to be, in my opinion a better design and better to service.

Tom_35

Geo-thermal HP's

Like Ken, our company has installed WSHP's for years. I can only remember 1 open loop and this was on a home that had an Artesian well that had water within a couple of feet from the surface.

We probably had as many horizontal systems as verticals. Also some lake loops, which totally cuts out the drilling and/or trenching. In Arkansas, we have to have the horizontal trenches 6' deep, and wells are around 200' per ton. This is not cast in granite though. We had a commercial project where the electric utility company had a consultant come in with a drilling rig that would analize the soil, put "artificial" load on the bore with the hope that the soil will allow the installation to use less bore per ton. This particular job ended up needing 240'/ton due to the poor heat transfer of the soil.

We always use an anti-freeze. Started with propylene glycol, used methanol as per WaterFurnace guidelines (had lot of rusting problems with the pumps), and have gone back to the glycol. It is much more expensive, but we just don't have the rusting problems with it.

We like the Florida Heat Pump also. Have installed WaterFurnace, Carrier, and Climate Master as well. The August 23rd issue of The News has a series of articles on WSHP's with an article also on the new Climate Master that has an EER of 26-27.

We've always provided the back-up heat, but have the controls set up where it won't come on unless a toggle switch is manually turned on. That way, the homeowner can turn the stat down at night, then when they get up in the morning and turn it up 5-6 degrees, the resistance heat doesn't come on. As far as I know, we've not had a system that needed the back-up heat to keep the temperature at the desired set-point.

We are currently installing some of the ECR equipment and are very pleased with the performance. They have a patented refrigerant metering device that helps control the humidity even if the system is oversized. The ECR system does away with a lot of water piping and replaces it with refrigerant piping.

I have an ECR in my home for my radiant heating and "on-demand" domestic water heating. Works great.

Tom Atchley

Mi39ke_2

Deep, deep, shallow, shallow, protected, delivered or different.

Vertical vs. horizontal. Glycol or no.

It sounds like you are in a cold state...use the glycol. We use propylene, I believe, the foodgrade stuff. Our looper provides it. Our water in Wisconsin is so pure and valuable that messing with anything harmful is out of the question...as it should be in every state--IMO. Note: Your glycol percentage won't be what it will be for applications close to the extreme cold--above ground. It might only be 10 or 15 percent. Look into this. GSHPs don't work well with high percentages, if at all.

Here's what a Rep told me regarding the choice of ground exchanger types. His rule of thumb (beware): Dig down to your ground exchanger depth for the horizontal application. If you squeeze the dirt and water oozes out, you can probably do a slinky-loop design (the most compact, area-wise). If the dirt clings and is moist, you might be a candidate for a one or two-pipe application, wherein the tubing is laid in a big loop and long trenches so that the tube has more contact with more earth. If the dirt is dry, go vertical.

Do yourself a favor, get the full set of books from IGSHPA. If you take their 3-day course, they teach you where to look for the information you need and give you some confidence and real people connections for future reference. Nothing replaces the analysis.

Don't use any rule of thumbs regarding how many feet of tubing installed will get you how many btus of ground exchange. If you are forced to do this, convince the client to buy the biggest ground exchanger possible, without affecting the pump-size enough to screw up operating costs. When it comes to ground exchangers, bigger is better until you reach the point where the pump is using too much energy.

Horizontal and vertical loops perform differently. Imagine...the horizontal is close to the surface...close to the cold...close to the warmth of the sun. Imagine...cold winter...frost and cold penetration below...long run times.

In the best world, imagine...deep vertical loop...flowing aquifer (terms are suspect here--sorry) moving over the ground exchanger, much like a loop embedded in a spring-fed pond or lake (the best exchanger for closed loop apps.). The exchanger does not degrade in performance throughout the season due to excessive heat extraction or rejection. High COPs throughout the entire season.

Ground exchanger design is under-emphasized by salesmen in the residential market, because the exposure to financial loss is not as great as in a massive loop field on a commercial project, where test wells will be done to verify specifics. The nature of economics, I guess.

Consumers need to really check into the experience or education of the installer for residential installations. An installer with little experience but a good track record of customer service and good educational credentials might be a better choice than the fellow who has installed a hundred systems inexpensively with poor COPs delivered consistently. Obviously.

Just a learner, not an expert,

Michael Ward

Tom_35

Questions for Michael Ward

Michael, I've got some questions concerning installations in your area:

Does your driller/looper have a set fee for an exact amount of dollars per foot?

Do you have rock that you run into? If so, how much more does the driller charge, if any? (The reason I ask is that the driller I use for the ECR systems charges the same whether it is rock, shale, etc; he is only drilling a 2" hole since we are going down with small refrigerant piping rather than 3/4" PE tubing).

Does the looper bring the pipe into the pump module, flush, and purge air from the loop?

What material does the driller use to grout the well with?

How do you top the wells off at the bottom of your ditch line?

How are "warranty" issues handled if you sell the job and within your warranty period, there is a problem with the loop?

Thanks,

Tom Atchley

Mi39ke_2

Reply to Tom

Tom,

Our looper/s look at historical well records and other data and come up with a price based upon this and in some situations, they will want our heat loss analysis to integrate with their analysis. Costs for vertical loops run from $1200 to $2000 per loop in our market, which usually includes filling and purging.

Some loopers will attach to our system and test, flush and fill with glycol solution. Some loopers have us do the flush and fill. They always test and warranty their loops.

Bensonite grout is the typical product used to seal and encase the loops. Sometimes we will install a trace-wire to allow a way of figuring out where the pipes run horizontally. Pictures and drawings are always necessary, of course.

We will always specify home-run systems and try to take consumers away from fusing manifolds in the ground. Basic, common sense hydronics, in our opinion. We can then balance and control each loop and we don't have to use a high pressure pump-cart to purge; we can use the system pump.

No warranty problems as of yet. I hear that some pipe manufacturers will dig up and replace within a certain time-frame, others will not. Impress upon your looper, your desires and needs. Hope this helps.

Michael Ward