Geo-Thermal heat pumps

[Redneck in training]

I can't give much perspective on unit costs, our was budgeted for a complete new install including the ground and floor loops.

The only downside I've seen to the system we have is the compressor noise, it's louder than I'd like. Not a fatal flaw, but irritating.

Ladia, have you considered adding an outside temperature sensor? Our control (Tekmar) uses a remote sensor on our north outside wall to tell the boiler control what temperature to aim for depending on how cold it is outside. On a warmer day it adjusts the target temperature lower, and hotter on a cold day. This time of year it's looking for approx. 75 F water temp, and up to 90 F in cold weather. The cooler water temp allows for shorter run times for the heat pump, since it doesn't need the hotter water to keep the house warm.

We also added slab sensors to allow the system to keep the floor warm on a sunny winter day when the house air temperature is boosted by the sun.

Sean

I wish the guy who sold it to me supplied Tekmar controller. I was not happy with the control system they delivered so I bought a PLC for $80 on ebay and made my own system. I have one "smart" Tekmar thermostat in the kitchen that decides if heating or cooling is required. Since it takes about 2 hours to drop or rise one F in the house the PLC doesn't switch between AC/Heat right away but delays the switch by about 6 hours. It prevents running AC during the day and heat at night. I also found that at very cold and windy days the HP runs about 90% of the time and when it is running it is able to keep about 90F in the heat accumulator. Therefore I set the heat accumulator temperature to 90F. The PLC enables the HP only if there is a demand from at least one zone thermostat. It doesn稚 keep the accumulator hot or cold all the time. In other words there are days or even weeks when the HP will not start at all. Therefore I don't see the need for outside sensor for my installation.

In order to prevent pumps sticking the PLC runs all the pumps for one minute every day.

The PLC also controls water heater temperature and disables the electric heaters when HP starts. One of the reason I designed it that way is that we have several days long outage every few years and I want to get by with about 15 kW generator. That way the maximum house power consumption will not go over 10kW even when my wife is cooking.

I wanted to heat DHW by the HP year around but couldn't justify the cost due to cost of heat exchanger and additional pump. I might do it just for the fun of it though.

Our AC unit is high pressure high velocity system. Main advantage is low noise and DIY. The "main plenum" ducts are made of 1" thick fiberglass mat that can be cut by knife and taped together by aluminum tape. The vents are connected to plenum by flexible "snakes" about 2" in diameter. The snakes have noise attenuating lining inside. My wife and I installed the whole system in one day.

I didn't install slab sensor even though the thermostat has input for it. My experience is that it is not needed in our house.

The noise level of the HP is also higher than I would like. But it is noticeable only in the guest room and the garage. If I would do it again I would place the HP to a corner of the garage adjacent to hallway. I am considering purchasing several of those mats they put under the HP and cover the enclosure. I am hoping it will cut on noise level and also on condensation on the enclosure.

 

[whistlepig]

I think we may be scaring people here. I set the temperature on the thermostat and go to bed. Just like any other heating system.

 

[Chilly807]

I think we may be scaring people here. I set the temperature on the thermostat and go to bed. Just like any other heating system.

True enough, I actually don't even do that.. once it's set, it's pretty much good to go year round.

Sean

 

[Redneck in training]

I think we may be scaring people here. I set the temperature on the thermostat and go to bed. Just like any other heating system.

The original system was simple and worked well but was not perfect and lacked few features specific to my situation. Tekmar off the shelf controller does all that I described, is probably cheaper and straightforward to install. I spent over $500 on all parts such as two temperature controllers, RTD sensors, PLC, relays, power supply, cabinet and terminals. Then why did I do it? It was fun project to do.
The problem with my system is that if it goes bad I am the only one able to fix it. Therefore I would strongly recommend implementation of off the shelf system.
I forgot to mention that I have a thermostat for heating in every room. Bathrooms are kept quite toasty while bedrooms quite cold etc. All have single setting all day. AC is controlled by single thermostat in the kitchen/living room and has programmed different temperatures for different times of the day and/or week.
Don't know exactly how much we spent for all of it but it will be something around 30000.
The HP itself cost around $5000.

 

[eepete]

Redneck, that's a great control system. Sounds like it was a blast to put in .

As for scaring people, Rednecks system illustrates the typical challenges of our modern world. In order to get greater efficiency, lower costs, better reliability, and better comfort the complexity of the systems is growing. When done right all technology is pervasive and invisible. When done wrong, it's called Windows 7 or Vista.
I get a kick out of people who shun the Deere e-Hydro because they don't like all that electronics stuff and want a simple tractor even though the engine still has a computer module in it. Similarly, HVAC systems with lots of sensors and features are going to become more common. Our house is set up for per room zone control. Each room has humidity and temperature sensors, and the system will not let the humidity in an unoccupied room get too high. Cut out relays for water heaters and the HVAC's 3rd stage resistive electric backups will be common place. This could let you have a smaller generator, and also comes into play if you are in a region where there is peak demand billing and the electricity is more expensive in the day. Occupancy sensing can be used to let idle rooms be hotter or colder. Running pumps and fans periodically also help keep things working. Some units might have LEDs on them to give you some idea when there is a problem. I'm still waiting for a heat pump with Ethernet and a web interface for configuration and diagnostics. Given how much the systems cost it's not an outrageous thing to do. Lots more examples here, but you get the picture.

I've been working for 10 years on home automation, and while the technical and control side is fascinating, the real hidden problem with this "complexity creep" the world is seeing is this:

The _real_ problem is behavior specification by the end user.

Using HVAC as an example, some users just want to specify a temperature that the house should be year round. Others might want a range of temperatures (such as 68 to 75 degrees) that's OK. When the system is new, since the user has spent money to purchase it they are willing to invest time to figure out how to set it up. As time goes on, they forget about it. So all the things you can configure about the system has to be well organized and something a user can come back to years later and make changes. I believe this will all eventually be via a computer screen. If you you say "Oh no, not me" then your installer will use the computer screen to get you set up and install a little computer and screen she'll call a "thermostat" so you are happy.

Finally, there is an age/generation difference situation. If you grew up on the classic round Honeywell thermostat, that's your idea of how a HVAC system should be controlled. If you're a young pup that can figure out a smart phone without cracking the manual you're more likely to be comfortable spending time on a computer doing a more complex set up. This is not much different from a tractor user that just changes the oil on their own but has all other work done by the dealer verses the mechanic warriors that do everything themselves. We are all masters in at least one domain, and neophytes in most others. Yeah, Ok, I know a few people who are masters of No domains :laughing:.

So what's my point . Be sure the complexity gets you something you want (more comfort, savings, etc). Figure out how much time you're willing to spend learning the system so you don't buy features you won't use. If the complexity of a modern HVAC system is too much for you, get a wood stove. Just like a tractor engine, these modern HVAC systems have little microprocessors in them and they are not going away. Since your kids will be embracing more complex behavior specification that's not going away either (but the simple "one temperature" setting control will be around for a few more decades, hope I am too!).

You bought a tractor and had no idea about all the different things the engine controller does, treat the HVAC the same way and get a user interface (thermostat) that works for you.

Pete