The Homemade Heat Pump Manifesto

[Spiv]

Originally Posted by AC_Hacker

From our conversation so far, I suspect that you are the kind of guy who just want to get on with it. Well, there are plenty of folks here on EcoRenovator who prefer to 'shoot from the hip', and I am quite sure that they will be willing to join in on your project.

Along that line I have just created a new thread dedicated to your project and I invite all of the talent that exists here in EcoRenovator to join in on this exciting project.

Design and Build Spiv's Solar and Geothermal House

Best of Luck!!

Sincerely,

-AC_Hacker

Thanks AC, appreciate your time!

[BillG]

Originally Posted by AC_Hacker

So, let me know if there's interest... I have loads and loads of information I'd like to share.

If we are not the people who can re-purpose pieces of junk that are now headed to the scrap yards and turn them into state-of-the-art high-efficiency home heating systems, who's going to do it?

Humbly Yours,

- AC_Hacker

Thanks for doing this, Hacker. I'm one who is very interested, and have several applications in mind.

Bill in MN

[AC_Hacker]

Originally Posted by BillG

Thanks for doing this, Hacker. I'm one who is very interested, and have several applications in mind.

Bill in MN

BillG,

Welcome aboard!

Tell us what you want to do. All the specifics, the more the better. Along with visuals (very important): drawings, diagrams, photos, charts, etc.

Always interested in new projects.

In some cases, we may have fellow EcoRenovators who have done similar projects. That might save you from re-inventing a working solution. Alternatively it could trigger to you to develop a better way to solve a problem.

And, always hoping to to find completely new challenges that will blow the dust off of our gray matter.

Let her rip BillG!

Sincerely,

-AC_Hacker

[BillG]

Originally Posted by AC_Hacker

BillG,

Welcome aboard!

Tell us what you want to do.


Let her rip BillG!

Sincerely,

-AC_Hacker

Well, I'm only about ten pages into the thread, and maybe it will answer the questions after I get further. There are a couple of projects in mind. First, I am planning to build a cabin soon, to Passivhaus specs or close, just north of the big running nose of the Wisconsin Indianhead. One thought was to string out a bunch of PEX underground, and pump glycol through it to preheat/precool the ventilation air. Then, I wondered if I could do better by doing a custom air to air heat pump made from a dehumidifier, then thought about extending the field a little more and making a ground source heat pump. The load will be too small for a big commercial unit.

I've wondered if a tiny W2W heat pump would benefit solar thermal on a marginal day, making the collectors more efficient and getting a more usable water temp out. Again, tiny load, commercial units too big.

Another project is actually a friend's, who has a great solar/geothermal source for supplementary heating, which could make good use of a tiny W2W heat pump.

Haven't done the math on any yet, and need to decide if the overhead energy makes sense to invest or not on such small loads,. or whether it is better to go passive on the preheat-precool with an earth tube.

[AC_Hacker]

Originally Posted by BillG

Well, I'm only about ten pages into the thread, and maybe it will answer the questions after I get further. There are a couple of projects in mind. First, I am planning to build a cabin soon, to Passivhaus specs or close, just north of the big running nose of the Wisconsin Indianhead. One thought was to string out a bunch of PEX underground, and pump glycol through it to preheat/precool the ventilation air. Then, I wondered if I could do better by doing a custom air to air heat pump made from a dehumidifier, then thought about extending the field a little more and making a ground source heat pump. The load will be too small for a big commercial unit.

I've wondered if a tiny W2W heat pump would benefit solar thermal on a marginal day, making the collectors more efficient and getting a more usable water temp out. Again, tiny load, commercial units too big.

Another project is actually a friend's, who has a great solar/geothermal source for supplementary heating, which could make good use of a tiny W2W heat pump.

Haven't done the math on any yet, and need to decide if the overhead energy makes sense to invest or not on such small loads,. or whether it is better to go passive on the preheat-precool with an earth tube.

I really like your thinking on this. You are correct that reducing your heat loss reduces your need for heat generation. In that regard, you are way ahead of most, who think of the heat first and the house last.

Passive house is a great idea and is significantly different from standard construction, learn all you can. If you search this site, you'll find a fair amount that some of us have gathered from around the web. But you'll need to go off-site to get some really deep understanding. There is an interesting related house design approach called Zero Energy House, with good ideas, also.

Put as much energy and thought as possible into retaining energy rather than gaining energy. Because in the end, you'll have to generate less energy, and this will open the possibility of low exergy heating (low temperature heating).

Getting too late tonight to discuss much more. You're on a good track though, keep the ideas coming.

Best,

-AC

[BillG]

Originally Posted by AC_Hacker

I really like your thinking on this. You are correct that reducing your heat loss reduces your need for heat generation. In that regard, you are way ahead of most, who think of the heat first and the house last.

-AC

Just an engineer here, AC. When others argue over whether a glass is half full or half empty, we engineers just figure that the glass was made twice as big as it needed to be.

There are unintended consequences to using more energy, and unintended consequences for creating it even with solar and wind. But there are no consequences to using less. It is something that we can do right now. That is why I was excited to see this thread. I was hoping to be able to heat on a design day with a couple of 1500 watt floor pads, but if I can get the same heat with 1000 watts of compressor and pump energy, that is even better. I just don't know if the electrical overhead will be that low. Need to do the math, I guess.

[mejunkhound]

Need to do the math, I guess.

Own approach is to do the math first.
Bone up on yu enthalpy charts and Mollier diagram equations.

COP of 5 to 6 is easily doable for a small system if your ground temp in winter is > 50F if you oversize the condenser toa ct a s a receiver also (sub-cool) and have enough evaporator for your compressor flow.

Compressor inside heated area (sound suppressed naturally) and you can get 5 kW heat from 1 kW compressor and fan inputs.

[jeff5may]

you can get 3 kw worth of heat out of a good air source unit in chilly conditions without much trouble. That's about 10k btu per hour. There are many mini-splits in the 9 to 12 kbtu range that beat the 1kw power draw cited. The new, variable speed inverter units are more efficient than that during not so frigid weather, but carry added complexity and risk of failure.

Throwing together an experimental water or ground source unit (or air source for that matter) is an extremely worthwhile endeavor if you may want to assemble something more permanent in the future (or not). Yes, you can go out and buy prefab, pretested equipment, but it is expensive. The trial and error process on smaller rigs is pretty forgiving. The initial investment is low, since small window air conditioning units and dehumidifiers can be had second-hand for next to nothing. The main investment will be labor for your ground source.

Again, as AC has stated, read through some of the build threads in this forum. There are lots of systems detailed from start til present day, operating now, that started where you stand now. Some are finished, most are works in progress. When you design and buid your own rig, it's difficult not to tinker with it. Especially when you live in it.

Welcome to the forums. I hope you find at least some of what you are looking for here.

[AC_Hacker]

BillG,

Yes, by all mean do the math.

But I don't know of any of our members who got less than COP 3. If you are able to have your evaporator in the ground or water expect more, if your condenser is in water or radiant floor, also good.

All assuming you did the numbers.

Please share pix.

Best,

-AC

[jdom]

Hi AC_Hacker, I have been reading your awesome thread while doing the research for building my own heat-pump.

Here is a bit of history on why I choose to build my heat pump. For the last 2 years I have been in the process of remolding my 1958 - 2800 sq ft house. In the process of doing so, I decided to rip out all the hydronic baseboards which was 1 zone for all rooms of the house and put in sub-floor heating (pex). I went from 2 zones ( second zone is basement slab) in the entire house to 7 zones on a 10 port manifold. Because sub-floor heating takes a while to increase the heat of the room, I installed a turbonics MVB 8-DHC for those days and nights when you want it to be warmer then what you have actually set the room temp at. I run the entire system off a raspberry pi with D18B20+ sensors in each room and instead of thermostats ive written a webapp which is accessible on any device. This all runs on an ancient 180k BTU American Standard boiler. This all works fine for heating except for the fact that the boiler is horribly inefficient (thinking about replacing with Takagi T-H3-DV-N - another story for another day...)

Now for the reason for the heat pump. because I live in a high desert the winters are brutal and the summers are hot. Yesterday it was over 100 degrees F. On days like this, the house gets to 85 and 90 degrees F, sometimes hotter depending on the previous days heat and if the night was cool enough to bleed off some of the thermal heat. the basement stays in the 70's but its 8" of cement with 2" of foam on either side (light forms built in 2003... old house moved to new basement) the top floor is 5" of spray foam but it still gets hot. So... I built the heat pump to chill water to run through the turboics MVB units, I also want to save the heat in a hot water tank or boiler mate because I run a tank-less water heater and my ground temp is 50 degrees F. If the tank gets saturated with heat, it will dump to a sprinkler line, for now... figure out something better later.

The pump is (free) 2 ton compressor and the heat exchangers are 5"x12"x3" (30 plates 120kbtu). the rest of the parts (valves and tubes) are also free from the recycling of hotel air conditions (they are 12kbtu 265-270v and even though I've tested them on my 220-240v. I read that its not good to do so.) Although I have done a lot of research, I found it to be a bit difficult to properly charge this thing based on what I've read about superheat and subcool. (could be because I'm am fairly new to the awesome world of refrigeration and heat-pumps or my exchangers might be oversize for this pump.).

Right now everything seems to be working as it should but I only have a couple days of operation. I was hoping to use some of the reversing valves I've acquired for making this a more versatile machine but haven't quite figured out how I'm going to do it yet.

Anyways, just thought I would stop in and share my heat-pump, which was mostly inspired by what you have accomplished.