Home built geothermal

[pghdave]

Just found this site tonight. I started thinking about Geothermal about 14 years ago when I acquired 3 Mcquay water source heat pumps two are 3 ton 1 is 2 ton although they are not rated for geothermal. These pumps sat in my basement until 3 years ago. At that time I decided to try utilizing 1 of the that summer I built a manifold off the swimming pool ran garden hoses to the house through a window and set up the heat pump. The heat pump worked very well at cooling the 1st floor even though no duct work was installed. When fall came I switched to heating mode and used the pool to heat my house all the way up to November. The second year I did the exact same thing. During the fall of last year I expanded my system using a 100 year old hand dug well in yard. The well is about 3.5 feet wide and 50 foot deep to the water. I installed a submersible pump and water line into basement. My first attempt was a partial success the heat pump worked for about 4 days then the well went dry. It took about 2 months for the well to recover. With the well running dry I had to try a different approach which consisted of a hose from the basement back to the well not knowing how long the water could sustain the system before loosing too much heat.I built a homeaid pressure tank from an old air compressor tank not wanting to spend to much until I could see if this would work. Long story short the water stayed above 45 degrees almost all winter. I did have the water drop below 40 in January which involved some more deep thought to keep it running. I had a 10 gallon water heater I installed on the water inlet found this would raise the water temp several degrees which was just enough to keep the system running. After my good luck I bought a proper pressure tank and installed i1 inch pvc supply and return lines. I have been able to run 2 heat pumps with this system 1 in the basement and 1 on the 1st floor. This system almost cut my electric bill in half. At this time I do not have duct work installed. I installed an automatic temperature control on the water heater that comes on at 43 degrees off at about 45. I plan to install permanent lines to the pool and valves to switch between pool and well depending on temp in pool. Still working on improving this system but has worked better than expected.

[jeff5may]

Welcome to the forums! Sounds like you've put a considerable amount of effort into the system.

[pghdave]

Thank you Jeff

I have several questions I was hopeful someone could help me with?

I have a sediment filter coming in from the well pump which works fine but I have a whole hose filter with a 10 inch cartridge. This filter clogs up in about a week. Would there be a mesh filter cartridge filter available or a filter cartridge with a much lower micron rating?

I have looked at Arduino controllers although I know nothing about these also I have found a solar controller that seems it could monitor water temperatures called the sp3 and wondered if anyone has used these any input would be appreciated.

I have seen where someone used 1 inch sprinkler valves to control water flow would this work as a cheap alternative to expensive valves?

When I need to temper the incoming water to raise the temperature is the small water heater better than say a smaller tube with a heating element inside?

Is there a low cost way to separate the pool water from the heat exchanger in the heat pump without loosing efficiency?

Any help that could be provided would be greatly appreciated.

Dave Lux

[jeff5may]

Ok, I will answer a question at a time for you. These answers are not going to be thorough or exhaustive.

First, the water heater idea is not an especially good idea. Yes, it will keep your heat pump from freezing its water loop, but it is blatantly inefficient unless it is running off solar power. You are basically warming water just to cool it back off. Find another backup heat source below the balance point.

Second, there is an endless supply of flow control valves on the internet. The main idea is you usually get what you pay for. The cheap plastic fleabay items are ok to experiment or prototype with, but for a final version it is much wiser to install a piece you know will be durable. I like the ASCO "red hat" valves and their copiess. Check out surplus city liquidators for some awesome prices and customer service. They have a massive selection if items, so do a little research to figure out exactly what you're after. It is easy to get lost in their site, and the descriptions are fairly vague on purpose. When in doubt, call the store. Their phone people are expensive at other places.

[pghdave]

I appreciate all suggestions offered.

The water heater idea was to make what I had to work with keep running when water temperatures began to get to low. I believe it draws about 1500 watts same as a small space heater. The sacrifice in efficiency was worth keeping the larger system operational to see if it could support heating the whole house for the winter.

I agree I need a better system and have thought about a small solar collector above the well problem being there is no glycol in this system. I thought about a temp sensor in the solar collector to only allow water to be diverted when temp is above a certain level and gravity would drain collector when heat pumps are off there by eliminating any water freezing in collector. I have never done anything with solar but I have never done any Geothermal before this either.

My other thought was a smaller ground loop in conjunction with the well loop. I have not seen anyone with this approach seems like it would work though. I know I need at least 43 degree water for the system to operate.

It's refreshing to find a site with so much knowledge and others interested in helping find solutions.

Thank you Jeff Seems I'm going to learn a lot from this site

[Kramer]

Here's and idea from someone with no experience. On a separate line from your current system, have a small solar powered pump move the well water up to a drainback system. The pump would only operate in sunlight, so freezing would not be a problem. You could operate this system all year long and pre-heat your well during the summer. This all assumes the well is not you domestic water supply. There are dozens of DIY drainback systems that can be made cheaply on the web. Dudadiesel sells a $500 pool heater that would also work very well. I've thought about doing the same thing you have done with your pool. If I did it, I would use the pool heater to heat the pool then use the pool water to heat the evaporator on a heat pump. Basically the pool would giant buffer for a solar heated home rather then a geothermal heat source. The solar water heaters are much cheaper then then digging trenches. Hopefully you keep getting some great ideas from someone who unlike myself has actually tried some of this stuff.

[pghdave]

I like the idea of a separate system for solar heat and have thought about that never heard of a drain back system though it sounds interesting. the only thing keeping me from a separate system is the water is 50 foot down which would require running my submersible more or a second submersible to get the water to the collector. This is why I thought I could divert some of the return water when needed through a collector. Heating the water in the summer might happen because when the pool gets above 88 degrees from being used as a heat sink for the heat pump I am going to switch back to well for a heat sink.

I have not attempted cooling the house with the well as of yet and will find out if it works as well as it did in the heat mode. If it overheats the well water I still have my pool to transfer the load to giving it a chance to recover.

I have an 18 foot round pool by 4 foot it worked pretty well although I have found when the water in the pool gets to warm the heat pump does not work as well that's what is going to make the well more useful being able to switch between the two heat sinks.

This well is strictly for the heat pumps and adding water to the pool. Really is amazing to take the cover off the well and see the amount of effort taken a 100 years ago to dig a well by hand for drinking water. Who would have thought 100 years ago that their well could be used to heat the house.

[jeff5may]

Originally Posted by pghdave

I appreciate all suggestions offered.


My other thought was a smaller ground loop in conjunction with the well loop. I have not seen anyone with this approach seems like it would work though. I know I need at least 43 degree water for the system to operate.

DING DING DING! WINNER!

With what you have described so far, the ground is your best friend in satisfying your heat pump, especially on gloomy winter days. If you read through some (or all) of the Manifesto, you will quickly learn why. There are a ton of graphs, charts and calculations contained there to help you figure out whether your concepts will actually work before you spend lots of time and money doing it the hard way. It's a lengthy read, but it is absolutely worth it.

Here's my crazy idea of the day: use your well bore as a temperature leveling, heat soaking device. A few feet below ground, the temperature stays nearly constant year-round, all the way to the bottom of your well bore. If you mist the wall of your well every so often with hot or cold water, it will naturally stick to the wall and flow downhill towards the pump, gaining or losing energy (in the neutralizing direction) along the way. This "bottom water" can then be easily routed to wherever it will achieve your needs. Since it was hand-dug, I'm assuming the borehole is larger in diameter than the typical 6 inches or less. Multiplying your circumference by 50 feet will tell you how much surface area you have. The key here is maximizing heat transfer into and out of your well bore. Not as efficient as a slinky or snake ground loop, but much less labor intensive.

Recycling your well water is also a good idea. Since you are not using this well as a potable supply, you should be able to use a sand filter (for pools) to filter out 99% of your sediment. It will have much more capacity than a cartridge filter, and when it gets clogged up, you just flush out the crud. It's about pool-opening time, and plenty of preppies will be replacing theirs this year for no obvious reason, other than trivial repairs (o-rings, gaskets, laterals, etc.) or just plain old age. You may even have one connected to your pool already...

[pghdave]

Very interesting I never thought about misting the sides of the well. I had thought about a 50 foot tube with holes to have the water fall like rain your idea seems much better. I knew the well walls had a higher temp than the water that's a great idea. The only part to work out is making sure I keep my flow rate where it needs to be. I have thought about a pool filter though just have to find one.

Again this a great site for support
Thank you to all who have helped steer me to a better system