The Homemade Heat Pump Manifesto

[AC_Hacker]

Originally Posted by Jazzoo

Some of your purchases and reference to Strider3700’s thread seem to be going in two different directions. Strider3700’s thread and your purchase of “one-wire” temperature sensors (DS18 series?) indicate a desire to use “digital” sensors.

I have (at least) four data logging/control projects in mind.

• GROUND MEASUREMENT - One would be to dig a hole as deep as my boreholes and bury a vertical measurement array, with temperature sensors every two feet. The frequency of the measurements would be about data reading one every two hours. It might be well to make ten readings within the two hour period and sum the result for subsequent division, to get a smoothed average. This would need to run for several years, and not lose data if house power was lost.
• WHOLE HOUSE - Another would be very similar to the whole house energy logging, pretty much as Strider is going about it. It would be nice if it could survive power loss, but not critical.
• HEAT PUMP TESTING - Another would be a data logger for the heat pump for the purpose of learning about how it works, and tweaking it for optimum efficiency. The expected run times would probably be pretty short, maybe a few days at the most.
• MACHINE CONTROL - The last, but most important, is a heat pump protection controller to minitor its performance and to shut it down if certain danger-points are reached. (If this controler could also monitor performance and envorinmental data and change certain settings, refrigerant flow to the evaporator, or circulation pump speed, or switching water flow from heating mode to cooling mode, for instance would be really cool, but that's in the future.)
  
  [* EDIT (11-11-11): Since this post, an inexpensive controller with a web interface has been found. Xringer has posted a thread where he gives a pretty good introduction to the controller including sources of interface devices that make it very useful. *]
  

I bought a Sparkfun Log-o-Matic that I used for a DIY data logger. It does analog or digital reading, but not both. Then somebody named Kwan wrote a new firmware for it, and I believe that it will allow both. I've downloaded the Kwan firmware but haven't gotten around to trying it yet. I like it that I can use analog (which is good enough) or 1-wire which would give me extra sensors.

Originally Posted by Jazzoo

My suggestion for using Automotive sensors is they are designed to work on a low system voltage in a very harsh environment. This works to our advantage two fold. One, they will likely interact with Micros’ such as the Atmel processor in your Arduino. Two, they should function reliably over the 20-25yr system life expectancy.

Great thinking, just great.

Originally Posted by Jazzoo

An area of concern, repurposing devices, are the chemical interactions at the physical contacts. I.E. Will the membrane in the Oil-Sensor react with the Refrigerant? This may not be the case, I don’t know. I’d be willing to wager that the Hi and Lo sensors from the AC would be a good match for the Evaporator, Condenser, and Compressor.

I think that if mineral oil compatible refrigerants were used (R-22, R12, R-290), you would be correct.

Originally Posted by Jazzoo

If it were my time and money I would get a PC to dedicate to the project. An older model with a serial port (DB9 or DB25). Can be had for free or nearly free.

This would be really great for Heat Pump Testing, but not so good for machine control.

Thanks, James for all the good ideas and links!

Best Regards,

-AC_Hacker

[morphector]

I tough a bit after reading a bit all pages of this thread.

You could easily add a big tank of water to get some storage so when it's really cold you're not using any back-up heater.

There could be better savings with a big tank here as there's some bi-energy discount (electric heat when temp is more than 5f,fuel heat when below 5f) ie you're paying around half price for electricity when it's more than 5f outside but you're paying 4x when it's below that.

So someone could heat a massive tank say 1000gal when it's more than 5f and shut down the pump when it's too cold to get more savings...Maybe I'll try something like that when I'll buy a house this year....

A big question for you, I really like the way your condenser is set-up, would there be a lot of losses by running glycol in a radiator outside instead of having real condenser outside?

[AC_Hacker]

"Insulate, insulate, insulate"

Originally Posted by morphector

A big question for you, I really like the way your condenser is set-up, would there be a lot of losses by running glycol in a radiator outside instead of having real condenser outside?

You mean to make it a ASHP instead of a GSHP? It would work but I don't have any information on expected performance of one over the other, with the exception that the rule of thumb is 10% loss per HX.

I've been thinking about something similar myself... being able to switch from a ground loop HX to a air-radiator HX... depending on if the air is warmer than the ground. If you had the same water-glycol mix in both loops, it would pretty much just be a plumbing issue.

I think the energy to drive a fan would be greater than the energy to drive a pump, by how much I don't know.

I think the 1000 gallon tank idea is a good one. You'd need to figure how many pounds of water you'd have, and figure how much heat you'd put into it (@ 120F max), and how much heat you'd take out (@ 34F min) and calculate the BTUs you'd get out, and then knowing the heat loss/hour of your house that you'd likely suffer during a cold snap, you could calculate how much good the tank would do you.

You really need to know the heat load of your house to make any informed decisions about tank sizing, though. It is a very important piece of information.

And don't forget, "Insulate, insulate, insulate".

-AC_Hacker

[Piwoslaw]

Originally Posted by AC_Hacker

I think the energy to drive a fan would be greater than the energy to drive a pump, by how much I don't know.

My car's radiator fan is something like 180-200 watts. Our small desktop fan is 35-45 watts. It all depends on how much air you need to move...

[Jay-Cee]

Hey all,
Just wanted to drop a link in for those of you who are in the "doing stage" of things. I have been glued to this guys' website this morning, and really like what I see. I posted his link yesterday in the Radian Heat section, but it seems it may be appropriate here as well.

This person seems to have a heart and willingness for the questions/concerns of the DIY'er and claims to offer his experience to anyone with a DIY challenge: "Please feel free to contact me regarding anything to do with radiant panel heating, snowmelt, Solar thermal, Geothermal and PEX based plumbing systems." ~ Tom Tesmar

That said, he may be a great resource for some of you to reach out to. Disclaimer: This is not a plug for his business, I do not know this person whatsoever. I just really liked some of the info he gives on his website and the appearance of his willingness to help the DIY guy.

Here is the link
Radiant Heat

[Jazzoo]

Stopped by my local pick-a-part yard and scored 8 hi and lo side sensors off late-model car AC units. I was in luck as the dealer was just starting to crush about 1000 cars and told me I could have what I wanted, as far as sensors go.

My shop air-compressor will do up to 250 PSIg so soon as I can make a jig to fit the sensors, I'll start testing. As a side note, all of the cars were using 135a.

Looking at my Water-Furnace, sitting in the middle of the control board is a Pic-Micro. I don't see why you could not use an AVR.

As far as the multiple sensor "branches" you want to run. There is a HUGE amount of 1-wire source for the AVR. Multiple branches could easily be handled by a single AVR acting as Master.

I plan on implementing either a AtTiny13 or an MSP430 as a combo Pressure and Temperature 1-wire slave; as an initial trial. This is assuming the sensors I picked up today show to be of practical use.

In closing, I was wondering if you had thought of the start-up and shutdown procedures for your GSHP. For instance, you have ~200 feet of loop containing ~190 gallons (3/4" pipe) of water/solution (~8.3 lb/gal) traveling at 3 ft/sec. I could be way off here, but if M*V=I then (190*8.3) * 3 = 4731ft/lb. again I could be way out. If you were to instantly shut off the pump, would this not cause undue wear on the pump? In addition if you shut off the pump at the same time you shut off the compressor, do you not also have heat that would go "unused". My unit both gradually reduces the speed of the loop (over ~30 seconds) and has a "cool down" period (~2 min.).

Best wishes,
James

[AC_Hacker]

Originally Posted by Jazzoo

Stopped by my local pick-a-part yard and scored 8 hi and lo side sensors off late-model car AC units. I was in luck as the dealer was just starting to crush about 1000 cars and told me I could have what I wanted, as far as sensors go.

Jazoo,

Great work. There may be a problem with sensors built for R-134a, but we won't know until we try.

Can you spost some photos of the sensors? Where in the car are they located? Did they just come off with a wrench?

Originally Posted by Jazzoo

As far as the multiple sensor "branches" you want to run. There is a HUGE amount of 1-wire source for the AVR. Multiple branches could easily be handled by a single AVR acting as Master.

This is very good news...

Originally Posted by Jazzoo

I plan on implementing either a AtTiny13 or an MSP430 as a combo Pressure and Temperature 1-wire slave; as an initial trial. This is assuming the sensors I picked up today show to be of practical use.

I checked out the ATTiny13, looks good. Have you looked into the Teensy Development Board?

You can use it with the Arduino environment or WinAVR.

Originally Posted by Jazzoo

In closing, I was wondering if you had thought of the start-up and shutdown procedures for your GSHP. For instance, you have ~200 feet of loop containing ~190 gallons (3/4" pipe) of water/solution (~8.3 lb/gal) traveling at 3 ft/sec. I could be way off here, but if M*V=I then (190*8.3) * 3 = 4731ft/lb. again I could be way out. If you were to instantly shut off the pump, would this not cause undue wear on the pump? In addition if you shut off the pump at the same time you shut off the compressor, do you not also have heat that would go "unused". My unit both gradually reduces the speed of the loop (over ~30 seconds) and has a "cool down" period (~2 min.).

I have thought about the 'cool down' part, I recognize the advantage of prolonged circulation of the the warm fluid.

I hadn't thought so much about having a soft stop. I may be wrong, but I think that centrifugal pumps don't have a problem with hard stops, because the fluid can continue to push on through after the pump stops.

And how would you create a soft stop?

I'll be around intil tomorrow evening, then I will be out of touch for a week and a half, retreating to a sunnier clime.

I should return and be back online by Feb 15 or 16.

Thanks for your work.

Be well,

-AC_Hacker

* * *

[Jazzoo]

Originally Posted by AC_Hacker

Jazoo,
Great work. There may be a problem with sensors built for R-134a, but we won't know until we try.

In related material to/from the "German" site(s) you've previously posted, looks like there are "custom" blends used in some applications (here I'm thinking of the paper "Building and alcohol trap." As pascal indicates "pressure is pressure."

Originally Posted by AC_Hacker

Can you spost some photos of the sensors? Where in the car are they located? Did they just come off with a wrench?

Sure, I'll take some photos of my "score" at the shop today. The Hi-side sensor is usually located on or after the Receiver Dryer and the Lo-side is near/just before the pump. With the exception of some Lo-side sensors, all just screw onto taps that contain a schrader valve. I found two Japanese models that screwed into the Receiver Dryer itself. All came off with the snip of the dykes and a trun of the wrist. The all could have used a wrench to take off but none were too tight to take of by hand (note, I live and work on my farm, do lots of physical work so; I may be a little stronger than the average bear, YMMV).

One thing I forgot to mention, several models had TXOs. Hummmm, wonder if we could re-purpose these...

Originally Posted by AC_Hacker

I checked out the ATTiny13, looks good. Have you looked into the Teensy Development Board?

No, however; I have done some limited business with Paul and can verify he is a stand-up guy. As far as development environments, this really comes down to what you prefer or have become accustomed to using. The Teensy /(++) looks like a nice solution to prototyping if you do not have the skills or time to fab your own board. With exception to their respective combination of bells and whistles; every AVR is exactly like ever-other AVR. If you work with one AVR you have worked with all AVRs. Generally they all use the same SPI header to "program (read flash)" the chip. The devil lives in the included devices (on board) take a look at the Errata sheet(s) for a fair look at the "got-chas" your chip may hold.

Regardless of the family of chip you choose to work with (AVR, MSP430, Blackfin, Atom, Geo, etc.); your starting point should be a list of what you expect the chip to accomplish with regard to your solution/project. Then take a hard look at the Data and Errata sheets for each chip you would like to use. If you check-off each item in your list and there is still functionality left in your chip you have a winner.

Originally Posted by AC_Hacker

And how would you create a soft stop?

PWM (Pulse Width Modulation) driver for the circulation pump(s). PWM would give you the ability to implement both "soft-stops" and "soft-starts". IMHO mechanical things HATE sudden change. Mass likes to start moving slowly then accelerate through a smooth curve, logarithmically. The converse is also true. On start-up we increase the "duty-cycle" until we reach the operating voltage of the loop pump. On shut-down, we walk the "duty-cycle" down until we reach 0. Most controllers implement PWM so most of the hard work has already been done. I use this for fan speed, augar, and loop pump control on my outside wood furnace.

Originally Posted by AC_Hacker

I'll be around intil tomorrow evening, then I will be out of touch for a week and a half, retreating to a sunnier clime.

Man, do you need someone to carry your bags? It's been in the teens and low 30s here for a month. Seriously though, I hope you have a great time and a safe journey.

Best regards,

James

[rkelly]

this is very cool. last up date was some time ago, where you at now a days with this?

[Geo NR Gee]

Originally Posted by rkelly

this is very cool. last up date was some time ago, where you at now a days with this?

Three posts up.......... Incognito..........