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Old 07-13-15, 01:05 AM   #1
Redmohawk
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Default Red's down under heatpump hotwater

Ok I've moved this post here to avoid a Thread hijack, and will continue my build thread from here.

Quote: I've spent approx 12 hours over the last two days skimming info from this forum. I'm very DIY orientated, with a strong fabrication background , I'm familiar with a rudimentary understanding of Gas dynamics in this sort of environment.

Have a electronics background , I'll muse over the info for a day or two before deciding on the eventual initial design. I was initially thinking something very similar to your own design but I see the long term heat transference of a single bore to be an issue for large water heating use.

So I'm leaning more to a water loop purely on a cost to benefit ratio, The entire unit will be 100% solar powered. And need to supply enough water for a 5 person household and medium water consumption levels for around here. Being on rain water alone limits our consumption a little but not that I can convince the females of the house so far.

I would factor around 50 to 60L per person per day, Here in Aust a hot water storage unit MUST heat stored water to 60 deg c every heating cycle , unless the water is NOT in circulation (IE sealed heat bank).

Obviously without going to a CO2 based system this is not feasible , and Though I believe I could source the correct components to achieve this it would be at close to commercial off the shelf units anyway . Negation the whole point of DIY for me (Lower COST).

Desired consumed water temp would not exceed 45 deg c as all clothes washing is done in cold water and dishes will be washed in a dishwasher that heats the water to correct operating temp with electricity. So I'm thinking a extremely well insulated 600L heat bank with a copper coil inside as a heat exchanger for consumed water.

Heated by window mount type unit in a compressor sized to consume around 1.5kw would be about right I hope. Removing the fan completely. Now that I think about it , its probably quicker to fabricate water boxes around the existing air con condenser and evap avoiding opening up the sealed system at all.

Ground is a sand/clay type with a water table around the 5m mark average year round ground temp below 1m is 15.5 deg c . Climate is Mediterranean like , summers are 25 deg nights 36 deg days with peaks of 8 to 10 days over 40 deg c 44 deg 2 to 3 times a year. Winters -8 early mornings frosts day temps around 12 to 13 deg c but ground temp remains 15 deg c below 1m.

I will rummage through my dwindling brain cells for a day or to and nut out a idea. For now I'll get out of your thread and stop this diversion. If all Goes well I'll start a thread and post up some constructions of my own.:

Ac retorted with

Quote:
Originally Posted by Redmohawk View Post
I would factor around 50 to 60L per person per day, Here in Aust a hot water storage unit MUST heat stored water to 60 deg c every heating cycle , unless the water is NOT in circulation (IE sealed heat bank).

Obviously without going to a CO2 based system this is not feasible , and Though I believe I could source the correct components to achieve this it would be at close to commercial off the shelf units anyway . Negation the whole point of DIY for me (Lower COST).
I understand the 60C requirement, but that doesn't totally rule out 'low tech' compressors. If you looked at your heat pump as a pre-heater, you could then do the daily 60C bump-up with your heating source of choice. No need to go CO2 all the way... at least for some years hence, when scrap CO2 compressors come available.

Quote:
Originally Posted by Redmohawk View Post
Heated by window mount type unit in a compressor sized to consume around 1.5kw would be about right I hope. Removing the fan completely. Now that I think about it , its probably quicker to fabricate water boxes around the existing air con condenser and evap avoiding opening up the sealed system at all.
The air-source-HX-in-a-water-box idea is OK for someone who wants to prove that it can be done. But for long time, dependable service, you should go whole hog and get or make a good heat exchanger. (Imagine you family members and member-ettes standing in front of you wanting to know why the thing that you call your exchanger-in-a-box, has become an ugly wad of green-slime, and will not allow them to take a bath!!). Since you are doing this for domestic water consumption, a plate type HX is the wrong choice. Some form of tube-in-tube or tube-in-shell is what you want, to avoid mineral build-up from rapidly killing your system.

Quote:
Originally Posted by Redmohawk View Post
Ground is a sand/clay type with a water table around the 5m mark average year round ground temp below 1m is 15.5 deg c . Climate is Mediterranean like , summers are 25 deg nights 36 deg days with peaks of 8 to 10 days over 40 deg c 44 deg 2 to 3 times a year. Winters -8 early mornings frosts day temps around 12 to 13 deg c but ground temp remains 15 deg c below 1m.
I can not recommend this book more highly: CLGS Installation Guide (#21020). There is information in there to guide you through all the Ground Source considerations.

As far as the actual heat pump hacking... there is no better book than this forum... you are in the right place.

Do not fear breaking into the system... we are here to help.

Sincerely,

AC_Hacker]

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Old 07-13-15, 02:17 AM   #2
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AC the initial setup using water boxed unit is a temporary initial install .

Functioning hot water will be needed in under a week maximum. I have access to a free unit for initial testing hence the unit is pre chosen. I have access to a pair of 315L storage tanks , both can be retro fitted with conventional element type heaters Though I'd rather not. They may even have one already of smaller than conventional wattage for they're size .(both units are glassed steel solar storage tanks of known origin removed early in life due to converting to continuous gas heater).

Both tanks should have heater ports , plus they both have 5 access ports , initial inspection makes me believe both have copper heat extraction coils and have been designed to run a glycol mix in the tank (designed for steel flat plate collectors) With the tank mounted on the ground and a circulation pump.

Quote:
I understand the 60C requirement, but that doesn't totally rule out 'low tech' compressors. If you looked at your heat pump as a pre-heater, you could then do the daily 60C bump-up with your heating source of choice. No need to go CO2 all the way... at least for some years hence, when scrap CO2 compressors come available.
I see the benefit in a pre heater , BUT I also hate waste, heating water to 60 deg c to only cool it down again for bathing seems a waste to me if I do not require 60 deg c for anything else. A previous system I installed with my father years ago does just this using a wet back off a slow combustion stove with electric backup. The extra heat in that case was used for hydronic heating through UHDPE pipe in a concrete slab under mud brick house.

Long term I wish to go 100% solar as the electricity grid here is 100% privately owned , a 200% increase in charges (both per Kw and connection fees) in the last 3 years has made electricity (and Gas is the same deal) non viable long term in my opinion. Off grid is the only way forward without great stuffing about . (even grid interactive solar is at great cost due to non existent (a pittance anyway) feed in rates. Add monthly extra connection charges for the right.

Current rates are sitting at 16c off peak , 22c shoulder ,and 32c peak ! with connection fees hovering around $54 a month on top. This will continue to increase significantly due to stupid governance in Aust.

Anyhow enough bitching about politicians. I did seriously look at evacuated tube solar water , As it is currently believed to be "The ideal off grid setup" By many over here. And I a very familiar with its function and setup (installed 3 units so far for others) It has strong merit for this area's solar aspect , but cost is high for an initial install. Gov rebates will drop the price to around the $6900 mark installed. BUT it must be a brand new system installed by a certified plumber. DIY is 100% out , and plumbers are not very keen to have an "Assistant" so to speak to reduce costs.

Also a 30 tube system would provide us with hotwater unboosted almost 100% of the year, boiling the water in summer often and being a little cool (due to inclement weather) maybe twice in winter max.

I could cover tubes to prevent boiling in summer and deal with a few cooler showers every year (the girls maybe not without some serious talks to me).

The initial $7000 is a little painful , and evac tube systems are not common enough to acquire damaged or second hand. And I'm less than keen to have to make a shading system so the tanks not ready to cook lobster by 11 am in summer. Also I can't use the waste heat , its just waste.

I Have the knowledge to make/modify and inverter very cheap to run a Aircon setup directly off PV panels, PV panels are a dime a dozen so to speak ATM with access to panels under a $1 a watt in the 200 watt size and above.

There is a rebate for solar PV , it requires the same qualified deal with a solar accredited electrician to do the install for a grid connect or independent system . But the initial costs for a small system are much lower (1.5kw system of my choice , of inverter and panel type) would be around the $1600 mark after rebates.

I can use the "waste electricity" to run the house, no a 1.5kw system would struggle to power the water heater in all times of the year besides peak output summer. But once the initial install is done I could "ADD" to the system without the fear of big brother looking over my shoulder and the extra cost of paying for a "Certified installer". The initial rebate is only cost effective for a smaller system install. But I can upgrade for similar $ per watt prices to the rebate price by DIY.

Once the system is upgraded (by adding banks of extra panels and parallel linked battery backed inverters) I can go off grid 100% at my pleasure.

Quote:
The air-source-HX-in-a-water-box idea is OK for someone who wants to prove that it can be done. But for long time, dependable service, you should go whole hog and get or make a good heat exchanger. (Imagine you family members and member-ettes standing in front of you wanting to know why the thing that you call your exchanger-in-a-box, has become an ugly wad of green-slime, and will not allow them to take a bath!!). Since you are doing this for domestic water consumption, a plate type HX is the wrong choice. Some form of tube-in-tube or tube-in-shell is what you want, to avoid mineral build-up from rapidly killing your system.
Indeed the plan is to use the (OLD) in window unit as a proof of concept , with the backup of the water storage units having resistive load (just in case). The hope it to have the unit function 100% off the bat with the compressor, If the heat moved is effective and the heat sink is stable enough.

If after the initial trial is effective , I plan to implement a better more efficient setup. Using a more modern compressor, possibly a inverter based unit with variable pump drive. A "Coil in Coil" transfer to the heat storage would be a definite. As would another for heat sourcing, I think the copper cost to benefit of direct vapor in earth for a system large enough to extract regular large amounts of heat might be prohibitive.

I've worked as a plastic welder , welding HDPE pipe , this is very familiar and cheap for me. Large amounts of pressure copper tube in the ground over a wide area looks expensive. Drilling holes should be no issue to depths of 10m without issue. I have 1 ah of land to access for a heat bank.

I hope the "inverter system" may allow tailing off so to speak, so as target heat is achieved load sharing between the hot water unit and the other house loads can be maintained. Instead of a compressor on or off situation as temp is maintained . This should also reduce load on the end design when 100% off grid throughout the night. (no solar gain) though I have plans for a micro wind system to augment the solar. And another power generator of yet undisclosed design.
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Old 07-13-15, 07:59 AM   #3
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Sounds like you have lots of homework to do and even more real work to plan out.
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Old 07-13-15, 04:33 PM   #4
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Very much so , the house has to be re stumped with concrete stumps and lifted 6 inches , and I'm starting a small business from there at the same time. fed up with making dim witted fools money from my toil. Time to do a bit for myself.
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Old 07-14-15, 12:18 PM   #5
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My view on that: any business is good business. Even if you don't make a product or profit, you can write it off on your taxes. The more you do on your own, the less you pay. Whether it is the tax man or an individual, you keep more. Good luck to ya.

You may be able to get away with a compressor smaller than 1500 watt electrical consumption. Most units draw around 800 watts or less. If you plan on heating more than just dhw, you may need more. At this capacity level, an inverter compressor or txv is an expensive option that may not pay for itself over the life of the unit.

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Old 07-18-15, 01:12 PM   #6
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Many ecorenovators have built heat pump water heaters out of what have you.

Xringer bought a manufactured unit and installed it in an electric water heater. He uses the electric element as a power dump for his pv panels, and the heat pump does the rest. He has been ecorenovating for a while, and has replaced his oil-burning boiler for all practical purposes. He is still keeping it on standby, maybe for the imminent global collapse or zombie apocalypse.



Randen built one out of an old water heater and a 5000 btu air conditioner. He quickly whipped the unit together, made it look nice, and put it into service. Works like magic. He is a workaholic, and has many detailed projects either finished or in process in numerous threads on this forum. Much of his work ends up looking better than something you can go out and buy.

Before

After


Memphis91 just built one with a DX evaporator in a borehole. This rig has the most energy saving potential, and has less moving parts than the other two. How much potential has yet to be chronicled, but initial numbers look promising. Unlike the other two, Jake's unit doesn't dehumidify the air or cool the living space. This may or may not be important or necessary to you. He also has other projects in the works as we speak. I would put up a picture of the completed rig, but he hasn't posted one.

These units are all working today in one place or another as you read this post, quietly saving their owners energy and providing exactly what they were built for. If you ask any of them, the build process was not quite as difficult as you might think. It is easy to get stuck in the thought process, trying to visualize and optimize things and such. Once the major components are gathered, start building it. Details will pop up in the build process that you never thought of. But once you start building, the unit will come together quickly.

After you have a working unit to try out, you can run it however you want. There is nothing stopping you from revising something in place. But if all you have is ideas on paper, you are not saving any energy. The solar panels/DX loop/windmill can come later. This stuff is addictive, so once you start building something, the process becomes contagious. You end up with something that is better than you could have planned for.

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Old 07-19-15, 03:12 AM   #7
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Quote:
Originally Posted by jeff5may View Post
Many ecorenovators have built heat pump water heaters out of what have you.

Xringer bought a manufactured unit and installed it in an electric water heater. He uses the electric element as a power dump for his pv panels, and the heat pump does the rest. He has been ecorenovating for a while, and has replaced his oil-burning boiler for all practical purposes. He is still keeping it on standby, maybe for the imminent global collapse or zombie apocalypse.



Randen built one out of an old water heater and a 5000 btu air conditioner. He quickly whipped the unit together, made it look nice, and put it into service. Works like magic. He is a workaholic, and has many detailed projects either finished or in process in numerous threads on this forum. Much of his work ends up looking better than something you can go out and buy.

Before

After


Memphis91 just built one with a DX evaporator in a borehole. This rig has the most energy saving potential, and has less moving parts than the other two. How much potential has yet to be chronicled, but initial numbers look promising. Unlike the other two, Jake's unit doesn't dehumidify the air or cool the living space. This may or may not be important or necessary to you. He also has other projects in the works as we speak. I would put up a picture of the completed rig, but he hasn't posted one.

These units are all working today in one place or another as you read this post, quietly saving their owners energy and providing exactly what they were built for. If you ask any of them, the build process was not quite as difficult as you might think. It is easy to get stuck in the thought process, trying to visualize and optimize things and such. Once the major components are gathered, start building it. Details will pop up in the build process that you never thought of. But once you start building, the unit will come together quickly.

After you have a working unit to try out, you can run it however you want. There is nothing stopping you from revising something in place. But if all you have is ideas on paper, you are not saving any energy. The solar panels/DX loop/windmill can come later. This stuff is addictive, so once you start building something, the process becomes contagious. You end up with something that is better than you could have planned for.
I don't have the place for at least another month, so plan is about it for now. I've read all the treads described , As for doing , that will not be an issue.
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Old 08-11-15, 11:22 AM   #8
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Redmohawk, did you get the place? Any progression with the plans?
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Old 08-11-15, 06:13 PM   #9
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Atlas no I don't yet , handover was to be this Friday the 14th. But the legals involved have hit a snag with local council and it will be another 6 to 8 weeks ! Mad as hell at the moment but nothing I can do but sit and wait.
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Old 09-10-15, 10:03 AM   #10
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Its been a month. Any updates?

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