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Old 02-01-13, 04:32 PM   #1
randen
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Default 5 Ton GSHP Build

I made an error infusing my ground loop with Propylene Glycol. The infusing part went well but the purging air completely out of the loop didn't. The circulation pump ingested that illusive bubble, cavitated and my evaporator began to freeze as the water/glycol hadn't had enough time to mix.
I know what your thinking, where was I.? I had watched that 3.5 ton for an hour. It was 6:00 o'clock and I decided to go home and come back to see how warm the shop got.
When I returned, the shop was getting chilly and there was a huge block of ice were my HX should be.

Long and short I wasn't carefull enough to ensure the air had left and my homemade 3.5 Ton GSHP suffered a terrible fate.

It made me grumpy. I didn't really want to do a rebuild when outside temps were dropping to -15 Deg C. I re-installed my old GSHP the 2.0 Ton. My first GSHP attempt. It keeps the shop +12 Deg C min.

The unit was ripped out and torn apart to rebuild the HX.

Well since its apart maybe we should think of improving the Heat Pump (put in TIM ALLEN'S "lets rewire that bad boy")

As BradC had been thinking of the advantages of a 3 phase compressor I had as well. So on the bench as I write there is a 5 Ton 3 phase 208 V scroll compressor (new surplus) (insert Tim Allen "Grunt") Taking the place of the old 3.5 Ton recip. The 5T is smaller dia but 2 in. taller

The 3 phase scroll is more efficient than the recip and can be controlled with a varible frequency drive. This will allow the heat/cooling output to be modulated with speed control. With this the compressor can be started with a ramping to speed and programmed to ramp in the early morn. hrs. and after my work is completed slow to keep the shop warm. There are a lot of possibilities. The VFD has relay out-puts to run the circ. pumps. The VFD should be here this coming week. But as we have 3 phase in the shop we can run it without the VFD.

This weekend a little more brazing and should be running in place early next-week

Randen

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Old 02-01-13, 04:37 PM   #2
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What a great looking compressor.

Looks like you're off to a great start!

Best,

-AC
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Old 02-09-13, 09:58 PM   #3
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Default 5 Ton GSHP Build

Most of the components have arrived and are being assembled. A few alterations have been nessisary. The height of the new compressor is about an inch taller and its having a bit of a snowball effect with now the case not being tall enough and the reversing valve position. In true Ecorenovator fashion the new build is also sporting a suction tube heat exchanger. Mikesolar and Jeff have done some work showing some efficiency gain but we'll have to see what happens
The varible frequency drive VFD is taking its time arriving. But until the final strokes are completed on the 5 Ton the little 2 Ton will keep the shop almost warm.

Up grades to the 5 Ton:
scroll type compressor
VFD
Liquid sight glass
new filter/dryer
Suction line HX.

Randen
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Old 02-10-13, 10:46 AM   #4
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Quote:
Originally Posted by randen View Post
Most of the components have arrived and are being assembled. A few alterations have been nessisary. The height of the new compressor is about an inch taller and its having a bit of a snowball effect with now the case not being tall enough and the reversing valve position. In true Ecorenovator fashion the new build is also sporting a suction tube heat exchanger. Mikesolar and Jeff have done some work showing some efficiency gain but we'll have to see what happens
The varible frequency drive VFD is taking its time arriving. But until the final strokes are completed on the 5 Ton the little 2 Ton will keep the shop almost warm.

Up grades to the 5 Ton:
scroll type compressor
VFD
Liquid sight glass
new filter/dryer
Suction line HX.

Randen
randen,

Great pix on an awesome project. I attended a solar installer's training conference some years back, and they strongly recommended a different type of pipe insulation for solar installations. Seems the type that is least expensive and most available (the type you have) does not handle the temperature cycling that solar installations are subject to. Their life is short and they become brittle and crumbly after a few years.

The type that was recommended was a black, closed cell, sponge rubber type of insulation. And their primo choice was the rigid fiberglass stuff that is so difficult to install.

I don't know if your application will have the large range of temperature cycling that a solar system would have, but you might keep it in mind. Shouldn't be too hard to change out, if required.

Also, on your suction tube heat exchanger, did you do any kind of quantitative sizing, or was it more of an inventor's intuition?

Lastly, what dimensions (lengths, diameters, etc) did you use on your tubes-in-tube HX?

By the way, I think your copper-in-plastic HX is just brilliant!

(* in pic #2, I see a panel with many buttons... that explains a lot! *)

Best,

-AC
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Old 02-10-13, 01:46 PM   #5
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AC Hacker
You are correct That is the cheap foam insulation. For the temps involved it should be just fine. But for exterior applications (solar) it would not do the suns exposure turns it to dust and it could melt. The foam for the GSHP will tolerate the -20 Deg C to 60 Deg C enclosed away from light. I did use the rubber foam for the 2 ton unit.

The suction tube HX is just a guess. I wasn't going to put one in. Thought I would give it a little try.

The lengths of tube are about 26 ft three pcs of 3/8 copper tube twisted for turbulance inside 1.5" dia outer tube.

I had a thought for a tube in tube HX if anyone would like to try. It should be easy with ABS drain tube for the outer shell and 1/2 copper for the refrigerant. All the fittings you require can be purchased at the hardware store. You could fasten these to wall or up in the floor joists any length you want for minimal dollars.

The buttons belong to the CNC lathe. I've been operating machine tools for 35 yrs. Although the learning curve is steep and long for these things. I don't touch the manual stuff anymore. The new machines with their on screen programming are fabulous.

Randen

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Old 02-10-13, 02:18 PM   #6
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A little clarification on pipe insulation:

The less expensive type sold at the big-box stores (frost king O/E) is polyethylene plastic foam. This stuff is ok for insulating water pipes. At higher temps than about 140 degF, it tends to shrink (up to 25%, quickly), then melt at higher temps. Since dhw rarely gets above 140 degF, it is by far the most widely used in homes. It isn't used much in commercial applications, due to the lack of industrial ratings. When exposed to the elements, it lasts up to 10 years.

The more expensive type sold at the same stores is (armaflex AP) is rubber foam. This stuff is the go-to material in industry for insulating anything where moisture is a factor. It is rated to 220 degF (105 degC), and has very minimal shrinkage properties. Long-tem durability is 15 years or more. At high temps or when exposed to the elements, it tends to harden. However, it costs about twice as much as the plastic equvalent.

Both types have close to the same r-value (about r-4 per inch thickness), so the main considerations when deciding which type to use are temperature range and exposure to the elements.

For insulating solar and steam heating systems, contractors use armaflex HT or an equivalent. It is rated for temps up to 150 degC and has UV protection built in. It is not readily available at your local home improvement warehouse. It also costs 3X as much as polyethylene.

Lots of DIY'ers stick a rubber layer inside a poly layer when superinsulating solar or boiler lines. The armaflex takes the heat, the frost king provides added r-value for less money.

Here's an article comparing the two common types:
http://www.enviro-tec.com/pdf/catalo...ns-FromNIA.pdf

Randen,

The new rig looks and sounds as if it should perform much better than your previous setup. I anxiously await your progress. That unit is much more massive than anything I would ever need. But with heat pump tech, bigger is definitely better.

The variable-speed compressor is the icing on the cake with your rig. It should be able to allow you to do whatever you want to with the new unit. At start-up, you can save power. Then you can ramp up to whatever capacity you need, then slow down to maintain a high COP near your target temp. It should save you a lot of energy and pay itself off quickly.
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Old 02-10-13, 06:08 PM   #7
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Quote:
Originally Posted by jeff5may View Post
The variable-speed compressor is the icing on the cake with your rig. It should be able to allow you to do whatever you want to with the new unit. At start-up, you can save power. Then you can ramp up to whatever capacity you need, then slow down to maintain a high COP near your target temp. It should save you a lot of energy and pay itself off quickly.
All true, but randen now has a compressor that is capable of extracting heat more rapidly from his loop field than it is able to provide.

As long as he runs the compressor below that limit, no problem... but if he goes above it, there would be problems.

randen, I think it would be advisable to regularly monitor your incoming loop temp, especially at the point where the water leaves your HX. That's the critical point. Maybe with some kind of alarm.


It's as if you now have a very large engine under the hood of your car, and you need to be more cautious when you drive.

Best,

-AC
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Old 02-11-13, 08:59 AM   #8
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Default 5 Ton GSHP Build

AC Hacker Wrote:

I think it would be advisable to regularly monitor your incoming loop temp, especially at the point where the water leaves your HX. That's the critical point. Maybe with some kind of alarm.

In deed the installed ground loop is only 4 ton but this is a continuous demand rate. The 5 ton GSHP will only require 5 Ton worth of heat on occation. Weekends and after hours temps are set back and not always do we experience -20 Deg C. temps. With the propylene glycol in the ground loop we can theoretically go <0 Deg C. But Extremly bad idea. However as we approach 0 Deg C. there is a lot of latent heat there. But I promise I'm not going there. Not to mention what could happen to our COP.

The whole idea here is to save money hacking your own heat-pump. To-date this is my third build and a lot of time invested. Hopefully now I will be able to keep the shop warm and save enough to have made it all worth-while. I have learned alot. Maybe with the money I will save I can invest in more insulation.

With the VFD I can control how much heat is being pumped. At 6:00 am I can ramp up for the 5 ton for a couple hrs till I get into the shop then drop back to 3 ton while I'm there working and then cruise through the night at 2 Ton.

AC Hacker you are right just because you have 600 HP under the hood you don't need it all the time. Periodically if you want to put the peddle down to pass or pullout its nice to have it on tap. Otherwise to cruise to work on 50 HP it still gets you from where you are to where you want to be.

Randen
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Old 02-11-13, 10:49 AM   #9
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One quick note on my build. Most items I source online and have no problems but you need to be patient. I didn't receive my filter drier and I wanted to braze it together this weekend. I called a wholesaler for a drier. NO I CAN'T SELL IT TO YOU. I wasn't asking for Freon. Had to call a HVAC guy!!!!

Good news VFD arrived this morning. Just shy of $300.00 a 4kw unit. Won't be long now.

Randen
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Old 02-12-13, 10:52 AM   #10
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Quote:
Originally Posted by randen View Post
In deed the installed ground loop is only 4 ton but this is a continuous demand rate. The 5 ton GSHP will only require 5 Ton worth of heat on occation... At 6:00 am I can ramp up for the 5 ton for a couple hrs till I get into the shop then drop back to 3 ton while I'm there working...
OK, I just want to caution you, and this is a BIG CAUTION... but your 4 Ton loop is, as you said a rate. And your compressor capacity is a rate.

So, this is my theory:

When you draw heat from your loop, you have many, many feet of pipe that go through the earth, but the earth only oozes heat, it releases it slowly. The water in your pipes can release it's heat very fast to your HX. If you try to draw heat 20% faster from your loop field than it can produce, you will quickly exhaust the heat in the water, well before you exhaust the heat in your field.

If you are actually going to do this, please be sure that you are sitting in front of your system, close to the OFF SWITCH and be sure that you are continuously monitoring...

Because, if I am right, things will change quite suddenly.

I experienced this myself on a very small scale, It was a hot day in August, I has a tiny 450 watt compressor drawing heat out of a 12 foot deep hole, and the loop froze in a matter of minutes (a very few minutes).

randen, you're my hero, I want you to stay that way.

Best,

-AC

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