Freeze Dryers and Freeze Dried Food (Part 2)

[dscheidt]

The one "gotcha" I encountered in making this is that a typical car oil filter attaches with a 3/4x16tpi threaded pipe.  I could find no such pipe anywhere.  My solution was to use instead a 3/4x16tpi bolt, and then drill a hole through it.  Fortunately, I have the equipment to do that, but most probably wouldn't.  Even then, bolts are hard material, and I dulled two drill bits getting it done.  If someone can find a source of 3/4x16tpi pipe – be it steel, aluminum, or even plastic -- making this filter would be a pretty simple task for just about anyone. 

 

A couple of other points:  There are obvious and easy improvements that could be made, such as using a container with a dispensing faucet (think of a lemonade jar, for example).  Also, for the technically savvy, auto-mechanic-type person who may be wondering about it, there is an anti-backflow seal that has to be removed from the oil filter, but that can be removed by cutting through it and pulling it out with needle nose pliers, which is easily done.

 

 

AN8 male fittings are 3/4 X 16tpi.  Should be able to get one that will work in this application.  Also, there filters that use metric threads, might be easier to deal with.

 

Not all fiters are equipped with anti-drainback valve, so you might pick one of those.  (They're not required in applications where the filter is pointed down, like yours, since it can't drain when the engine is off.) 

[Gypsyman]

You've given me an idea. I have the parts at the shop to use an actual filter head and a spin on filter. I could have a bracket laser cut and powder-coated that would hold the filter/head assembly horizontal which would allow it to completely drain and the outside of the filter would stay clean. You would simply pour the used oil in one side of the head and it would pass thru the filter, come out the other side of the head and drain into your catch container. Hmmmmm........

[Brent]

Thanks dsheidt.  I was afraid that the AN8 fittings I could find might not be long enough to provide the space needed so that the oil could flow over the top of the filter, especially given my "disk" method of holding up the can.  Of course, if someone used a larger can, say a #10, that is bigger than the top of the container that surrounds the filter and captures the oil, then the "disk" wouldn't be needed at all.  In that case, an AN8 fitting might work -- or maybe there are longer ones out there somewhere. 

 

I found out the hard way about the anti-drainback seal when I first tried the filter and got... nothing.  I did do some research afterward and learned, as you point out, that there are some filters than don't use the seal but by then I was committed. Fortunately, it wasn't all that hard to remove it, but definitely better not to have to.  

[Brent]

Gypsyman:  Proof again that "great minds think alike".  In my initial pondering, I thought using an oil filter base would be a logical approach -- but I didn't have one handy and figured my car might miss it.    Besides, one of my goals was to keep this affordable, and they tend to be a little pricey.  

 

I did wonder though, since this is gravity flow and not pressure driven as on a car, if having the filter mounted horizontally might result in using only "half" the filter, as the oil would tend to travel through the low side of the filter -- although in practice, I suppose, as the filter material gets plugged it would force the fluid level higher.   

 

If you make one, let us know how it works out! 

Edited September 16, 2015 by Brent (log)

[Gypsyman]

Let me see what I can throw together with existing parts off the shelf in the morning. =)

[TonyC]

This is going to be a long post...  so sit back and take your time reading...or skip over it if you like!

 

We purchased our FDer January 2015 and it has been running 24/7 with 30 minute defrost cycles since that time until a few weeks ago when we had to travel for 5 days.  We live in central NC and the summer is full of dog days with 95%-100% humidity and +90F days.  Our FDer is located in our garage and with outside temps in the high 90's the garage temps soared to 100F on many days.  We have two freezers in the garage as well. All of these machines generate heat and humidity.  Our FDer front regularly sweats up an storm and water drips off the door and from around the entire chamber perimeter down the front of the unit.  It got so bad that I taped a plastic shield above the display to route the water around it.  You can see the water on the door and on the stainless steel front past the 4 screws on the unit.

 

Now that you understand the conditions, you can better understand what happened when we finally turned off our FDer after an extended use in these conditions.

 

Over night the FDer warmed up and the next morning we had a massive puddle under it - running off the counter onto the floor.  I cleaned up the mess, but the next day the puddle was even bigger.  On the 3rd day it was back again just as large even though I left a large towel under the FDer.

 

I removed the side covers and found the water dripping from the chamber insulation.  I called up HarvestRight to ask for ideas on how to avoid this in the future.  They sent me a roughly 2' length of 1/2" or 3/4" foam rope to place in the gap between the bottom of the insulation and the front panel.  The only problem is that I had tried this earlier and it simply backed up the water and it leaked out.  

 

What I presume was happening was that condensation was building up on the cooling coils between the insulation and the chamber and freezing.  When I finally turned the FDer off it took 3 days for the ice buildup to melt and slowly soak through the insulation and drip onto the counter.  Looking at the picture you can see the water drops on the insulation and where the water had flowed down the back of the front panel.

 

 

Back from our trip I turned the unit on and to my dismay found that the display was missing the middle two lines. 

 

 

I sent Harvest Right a note with a picture and they immediately shipped me a new display.  Great Service again from the support team there!  I think water had dripped down the front and the back of the unit and onto the display card shorting it out.   

 

While I had the unit apart to replace the display I decided to correct the water condensation problem.  If you find yourself using your FDer in the same conditons as we do you may want to consider modifying your FDer to keep the condensation from your FDer control circuit and display cards.  Here are the steps that I followed to minimize what the NC high humidity climate does to my FDer.

 

1) I installed a 3/4" wide high density closed cell foam in the gap between the front of the chamber and the back of the front panel - just what Harvest Right suggested except all the way around (the first picture shows the gap).  Use your fingers to push it into place.  It needs to be tight against the inside panel.  I then installed a vapor barrier around the entire FDer chamber.  I used 7mil plastic and clear packing tape.  There are 3 ports on the chamber that I made slits in the plastic to get around and taped them up once around them.  Do not tape to the insulation.  Tape only to the vapor barrier plastic.  It doesn't take long, just be careful.  After the plastic is in place and secure around the chamber I sealed the plastic to the back of the front and back panels using the packing tape. All the way around the front and back of the chamber to completely seal the chamber from outside air and humidity.

 

2) I placed an 5/8" auto rain guard 2.75" below the door opening seal to route the external condensation away from the display and into a pan beneath the FDer.  At the lowest point of the rain guard I drilled a small hole through the guard and the SS panel (I hated to do this!) that allows the collected water to drain to the inside of the FDer.  The alternative was to simpIy cut a small section from the guard at the lowest point and allow the water to run down the front of the panel in a single stream. I am not crazy about the look, but it is absolutely necessary to protect my investment and the electronics.  If you look carefully you can see the hole in the gutter beneath the center screw.

 

3) Inside the front panel I installed a plastic shield over the display card and a water deflector just below the hole to route the exterior condensation to an 11x17 pan beneath the FDer.   I cut up a thin flexible cutting board to make the shields and secured them with clear high grade packing tape.  The cutting board is stiff but it will fold and hold a 90 degree crease.  The shields are not going anywhere, but are easy to remove if necessary. 

 

4) I made a plastic shield to protect the main circuit board of the FDer.  it simply slides into place and protects the top and both sides of the board from condensation.

 

5) Next up I insulated the pipes where condensation forms directly from the compressor.  I used inexpensive water pipe insulation from Lowes or Home Depot to wrap all exposed parts that had potential for condensation.

 

6) The first place was the cold return line into the compressor. It had insulation, but a second layer helped stop the constant drips.  I used black electrical tape to secure the foam.

 

7) Next up the drain line.  This not only deminishes condensation but also eliminates an unnecessary hot spot into the chamber. 

 

8) The vacuum port was up next.  You can see the condensation on the brass fitting.  That means cold is escaping and heat is getting into the chamber.  This small section was placed inside the panel.

 

and this piece was placed on the vacuum hose fitting.  I can still remove the panel without removing the hose to clean the coils. Simply remove the screws and slide the panel down the vacuum hose a few inches.

 

9) The last port to insulate required the top be removed.  Before I removed the top cover I replaced the side covers.  This keeps the back and front panels structurally rigid.  Do not remove both the side panels and top or you will have problems reassembling as things get very loose.

Here is the fitting before insulation is applied.

 

 

After the bottom of the sensor port is insulated.

 

And the top is of the sensor port insulated.

 

I have used the FDer 3 times since these mods, and have found it is much faster drying foods.  Nothing has taken over 26 hours so far, and we were routinely running 36 hours on some foods. 4 trays of mashed potatoes used to take 36 hours, now only 26 hours.   4 trays of corn takes only 16 hours,  I would estimate that we have cut our FD times by 30% or more!  Condensation has been decreased by 90% - no more dripping down the interior front panel and collecting on the aluminum base.  There is still condensation around the front door seal, but it no longer drips down the front onto the floor. 

 

FDer cooling times are (from ambient temps of 70-85F) 30 minutes to -15F, 1 hour to -30F, and under two hours to -40F.

 

The only downside is that the interior is now so cold that defrost time has doubled! I use a large high volume fan to defrost the unit, not the heat trays. It used to be a 15 minute job, now it is closer to 30 minutes.

 

After the 3rd cycle I had hit my 20 cycle oil limit so it was time to change the oil.  This time I took the time to add a flush port to my pump.  When I replaced the plumbing with larger diameter brass and a cutoff valve I did not think to add the oil flush out port.  So I corrected the oversight - I drilled and tapped the elbow to add the port. Here is a picture.  It worked great today when I flushed the pump to clear out the gunk.

 

BTW, I have found that defrosting the unit every 8-10 hours of drying time results in less water in the oil and faster drying times.  It appears that the ice build up inside the chamber sublimates as well as the ice in the food.  Eliminate the ice and the process is faster, and less water ends up in your oil. 

 

Forgive me for the extremely long post but I thought other southerners may also face this problem and could use this information.

 

Tony

[Brent]

Tony: 

 

Very interesting!  Makes me glad I live in a dry climate.   

 

Question for you:  I'm impressed by the shortening of cycle times.  Obviously some of that is from the improvement in insulation on the lines, etc., but I'm wondering how much of it might be from "drying out" of the insulation and outer walls of the freeze drying chamber.  Perhaps the ice buildup reduced the efficiency of the insulation(?)  It would be interesting to know.  Have you noticed any differences in your internal temperatures since your changes?  (By the way, I liked your idea for monitoring the temperature, so bought the thermometer from Walmart you previously suggested.)  

 

I, too, have noticed a significant difference when I defrost mid-cycle.  I do that routinely now.  I carefully use a heat gun to "shock" the surface of the ice, moving back and forth across it fairly swiftly, which causes it to crack and separate somewhat from the cylinder.   I can then usually remove it while still in the ice stage, producing very little actual water.  Doing that I can remove the ice, reload the system, and be back up and running again in about 5 minutes.  

Edited October 15, 2015 by Brent (log)

[TonyC]

Hi Brent

 

Re: Shortening Cycle Times

 

I think that we are on the same page... The temps didn't get any colder, just peaked faster.

 

Drying things out played a roll as well as the added insulation.  We had 3.5 weeks of constant rain here in central NC with humidity over 95% and temps near 95F in the beginning and tapering down to 80F by the end of the rain.  The condensation on the front panel around the seal had water running down the front of the Freeze Dryer constantly during the entire cycle, not just the freeze cycle. I initially went into the FDer to simply stop the humdity from reaching the outer chamber shell and freezing...  Hence the vapor barrier.  But once I opened it up I figured I may as well insulate the bare ports as well, and insure that the water was diverted away from the electrics of the system.  Once I sealed up the insides I noticed that the condensation on the front panel increased dramatically as the air was trapped between the plastic vapor barrier and the back of the front panel.  That was when the drip rail was installed on the front of the unit.

 

IMHO, Improvements in drying times result from:

• Removing the ice from between the chamber wall and the insulation (hopefully will never have to do this again)
• adding a vapor barrier to keep the ice out (one time thing)
• adding insulation on the 3 ports on the chamber  (One time thing - the drain and vacuum ports are very easy to get to)
• Adding insulation to the cold compressor line (one time thing and easy to do)
• Never allowing the unit to heat up to ambient temps - Quickly removing the ice from the chamber and starting the next cycle while the chamber unit is still very cold.  Remember the minimal off time is 5 minutes... compressor pressures must drop before restarting the unit...  You can blow seals starting it up too soon.  
• Prefreezing the food in FDer trays to -7F to -10F in a staging freezer
• Monitoring the FDer internal temps and once I see -40F I start the dry cycle, except for high sugar content food which I give an extra hour.  I'm still experimenting with Ice cream and a few fruits to determine optimal freeze time to get the best results. The cooling cycle ends up much shorter.
• Remove all ice every 8 hours of drying time.  It is amazing how much faster the drying time drops doing this.  A side benefit is water vapor does not contaminate the oil as fast.  I've gotten up to 20 cycle per oil change by carefully monitoring the oil and water.  

Re:Monitoring Temperatures

I honestly think putting a thermometer inside the unit is an excellent idea.  I sent the following note off to Harvest Right Support in an effort to gain a little better understanding  of the process.

 

How long after the FDer reaches -40F does HarvestRight recommend freezing the food?  I'm trying to optimize FD time.

I noticed on one of your videos where Dan Neville mentioned that the FDer "freezes the food to -40F" (15 seconds into the video).  I have also noted this on my FDer.

I'm tracking my FDer right now... and it hit -30F in the first hour, -40F somewhere between hour one and two, and has held constant since (I'm presently approaching hour 4).  The food was pre-frozen to -7F (for days so I know that the food was at -7F) before it went in the DFer.  Logic dictates that once the food freezes to -40F, cooling it any longer is a waste of time, electrical energy, and wear and tear on the FDer.  I realize that the food freeze curve follows the FDer internal temp curve, and I am asking by how much time it follows that curve.

I am looking for a more defined "heuristic" curve based upon the internal temperature.  I am sure that your engineers probably have tables for such things. I also know that different foods freeze at different rates, that is why I am asking for a heuristic answer.

I know HarvestRight states "trim two hours off frozen food from the default 9 hour freeze time", but this seems excessive... After all, I'm only dropping the food temps by 33F, not 110F ( from 70F to -40F ). 

Let's do a simple math exercise.  Non Frozen food put in freeze dryer at an ambient temp of 70F needs to be at -40F before the dry cycle begins.  <If> things go linear, each hour the temps would drop the food by 12.22F, achieved by dividing 9 hours by 110F (the difference in food temps).  We both know that the FDer doesn't do linear as the temps fall faster early on and slowly peak to max low temps, but the food freeze time might be a tad more linear than the FDer as food is denser and must be frozen throughout.

Now lets plug in the same number with the food going in at -7F... again "assuming" a linear approach, we need to drop the temp by 33F.   If we use the same 12.22F degree drop rate we get a 2.7 hour freeze time to drop to -40F.  As mentioned earlier, my FDer drops internal temps to -15F in 30 minutes, -30F in an hour, -40F in under 2 hours.  The food freeze rate is going to lag a little behind this temp drop rate curve. 

I'm asking how much is the lag in time?  Again, a heuristic is enough for me. 

Thanks for the help.

 

They replied with some good information, but didn't really directly answer the question.  I know that there is no one answer for all foods, but a rule of thumb is certainly within reason.

 

The evaporator coils that touch the surface of the stainless steel vacuum chamber reach about -42 F.  With food in the chamber and because the location of the thermister is on the middle shelf of the four shelves, the temperature it records is going to range from -25 to -30 F in the 9 hour default freeze time.  This temperature is very adequate for freeze drying the food.  In fact, some foods can be freeze dried once they reach about -10 F (corn, green beans, spinach, kale, meats of various kinds, yogurt bites, sauces and soups).  The more sugary foods like grapes, mango, papaya, pineapple, berries, cherries, and the like, require lower temperatures so reaching -25 F is important.  In the hot temperatures the freeze dryer will only reach about -25 F while in the winter it will go lower.

 

Let me know if you need any other information from Engineering on this matter.

 

Re: Thawing out the FDer

 

I have one of those hand held heat guns (inexpensive from HF), but I was afraid of accidently burning the insulation.  My gun gets very hot!  I do the same technique with a fan, shock the ice and listen for the cracks as it separates from the chamber wall.  Then I hit the Ice edge with a large flat blade screwdriver and the entire sheet comes loose in one piece.  I may try the gun again using your technique.

 

Tony

Edited October 19, 2015 by TonyC (log)

[DriedUpStuffs]

Hi everyone - new member to the forum, and I was drawn here by this thread.  I have been using my HR freeze dryer for a few months now and it's been great.  Reading about all your experiences shows that I'm not alone in loving this machine! .  Lately, my machine has decided to be a pain.  Wasn't drawing enough vacuum to cycle.  Flush pump, clean out pump, and all that goodness, but still no luck.  Have been working with HR to figure out what's going on, and they've been very responsive, so kudos to them.  Still chasing the problem, however, so I thought I would ask the assembled experts here.

 

A bit of background on me - I used to work in a sold state fabrication lab (university research lab) and had a lot of hands-on work with ultra-high vacuum equipment.  The pumping we do for freeze drying was what was required to just start the "real" vacuum pumps on those machines, with ultimate vacuum levels a few more demial places over.  I've chased many a leak in my time,but it was: A. Long ago. and B. I don't have the test equipment I did then. I guess what I'm saying is don't be afraid to get too technical with me in your answers. What I wouldn't give for a helium leak detector right now...

 

OK, so what have I done thus far? 

• Flush pump
• Clean pump interior and re-seat gasket
• Fill with clean oil
• Run full system test with no food in chamber (results, 630 mTorr lowest steady reading - looking through the oil level window, some bubbling seen in oil even after an hour of pumpdown - some "air" noises from pump)
• Isolated pump by capping the stack (no meter to measure pressure, but no bubbling after a very short pumpdown - pump sounded normal for a high vacuum situation)
• Reinstalled the vacuum hose and capped far end of hose to do a hose test.  (same results as pump alone)
• Reattached hose and ran another full system test (results, 750 mTorr lowest steady reading - looking through the oil level window, some bubbling seen in oil even after an hour of pumpdown - some "air" noises from pump)
• Upon turning off the pump (no isolation valve on the pump - standard setup), the chamber pressure rose quite rapidly going to 2000 mTorr and continuing up in a couple of minutes or so.

Observations:

• Oil has remained clean and clear throughout testing, so it looks like it's well flushed.
• When isolated, the pump seems to behave well. Short of putting a meter on the pump, my impression is that it is operating properly. I'm considering investing in a good meter to verify that it is reaching a good ultimate vacuum.
• The hose appears to be OK, and by implication, the gaskets at the connections are working as well.
• The bubbling of the oil even after long pumpdown indicates a leak somewhere in the system.
• The differing vacuum levels during the system tests would be consistent with either a door seal leak or an drain valve leak.
• Wherever the leak is, the pump is unable to keep up.
• Door seal appears good against the plexiglass side, even stripe of contact, nice and wide. Inside gasket groove has been checked for debris and cracks.  Looks OK, but the design seems odd to me!

That's what I have so far.  Thoughts?

[Deryn]

Welcome to eGullet, Stuffs.

Not all of us are technical experts (the 'not' category includes me) but I hope someone who can help you will come along soon. We have some really great 'techy' type guys here who are, as they have been exploring the FD mechanics and sharing that in their posts, writing what is turning out to be a 'troubleshooting manual' for us less capable folks.

And once you have resolved your issue I hope you will stay around and talk to us all about what you have been drying in your machine, etc.

[peggy w]

I have had a similar problem and had to take the right side panel off and vacuum the dust off the condenser fins. That solved my problem and put my freeze dryer back on track. I too have been running mine 24/7 since January

[DriedUpStuffs]

. We have some really great 'techy' type guys here who are, as they have been exploring the FD mechanics and sharing that in their posts, writing what is turning out to be a 'troubleshooting manual' for us less capable folks.

And once you have resolved your issue I hope you will stay around and talk to us all about what you have been drying in your machine, etc.

 

I think a community-built troubleshooting manual is a great idea.  These machines are simple in some ways, and more complex in others, and having a lot of eyes on the problem is always good.

 

You can count on me sticking around to talk about the food side of things!  My wife looked at me a little oddly when I got the freeze dryer, but now she's a fan too.  I'm discovering things that it can do that I hadn't expected, such as making low carb snacks.  It's so much easier to stay on a low carb diet when you have things to nibble on. I've been drying meatballs (cut them in half first), and they make a fantastic savory snack. I'll post to the Tried and True thread when I get a chance.

 

Thanks for the welcome!

Edited October 25, 2015 by DriedUpStuffs (log)

[TonyC]

DriedUpStuffs,

 

Based upon your work experience you probably know more about vacuum pumps than most of us.  Chasing a vacuum leak can be frustratingly difficult.

 

You seem to have narrowed down all the failure points.

 

Without an pump isolation valve I would expect some air to flow back into the chamber through the pump resulting in the steady rise you witnessed.  I saw the same phenomenon before I installed an isolation valve on my pump.

 

Do you have any vacuum gauges at all to test the pump?  ( Though I doubt that is the problem based upon your tests )

 

I did have a vacuum hose fitting leak at the FDer port once.  I had similar symptoms to yours. I found that the hose would slightly rotate even when the fitting was snug.  It allowed air into the system.  If there is any play in the brass fittings on the hose, either lateral wobble (up and down) or rotation (spin), the hose will leak.  I now only remove those lines when absolutely necessary. 

 

I would prefer those fittings to have internal O rings and knurled thread on ports (similar to R134a vacuum gauge sets) that do not require high torque compression fittings.  Finger tight and you are good to go.  You spot a leak, change the O ring and you're back in business.

 

Odds are the problem is the vacuum hose or its end connections, the drain valve, or the door gasket.  Based upon my experience I'd double check the fittings while installed on the FDer.

 

Good Luck!

 

Tony

 

 

 

[Jenipher]

Hello!  I have finally caught up on all of the reading available in these freeze drying threads.  SO MUCH INFORMATION!  It's awesome!  I don't have a freeze dryer yet but am planning to place an order tomorrow.  I am super curious how Kerry's scroll pump is holding up... eliminating the oil from the equation would make this whole thing SO much easier.  

 

Jen

[Kerry Beal]

Working well - when I was down visiting Harvest Right last week, Matt said they are hoping in the future to offer a scroll pump for around $500 more. They had at least 3 scroll pumps they were playing with.

[Jenipher]

Well I finally put in my order Thursday of last week so we'll see how long it takes to get fulfilled. My husband has been contemplating cost effective alternative ways to get oil-less vacuum happening... what would the specs needed be, since I don't have a pump to look at. Hopefully I asked that in a way that makes sense.

[Kerry Beal]

Here are the notes I have after I talked to Matt at HR.

 

Vacuum for freeze dryer

 

Below 200 mTorr (0.2  Torr) (.3millibar or .000266 bar)

adapt to 1/2 inch hose 

at least 6 cfm

 

Edwards xds would work - dry scroll

Vacuubrand mv 2 or 10 nt vario only

[Brent]

A Day in the Life of a Freeze Dryer

 

After buying our freeze dryer I was naturally curious as to how it "knew" when something was done, since batch times varied so much depending on what was being processed.   Watching the cycle times didn't seem to tell me anything at first  -- especially without a thermometer to tell me what was happening inside -- until I finally caught on that applying heat to the frozen food affected the vacuum, which provided the measure of how dry the food had become.

 

I thought an easier way to see what was happening would be to make a time lapse video of an entire freeze drying cycle.  As I was about to prepare some apples for freeze drying yesterday, I thought it would be a good time to do that -- so out came the GoPro. 

 

It's hardly the most exciting GoPro video for sure, and some may think it's about as interesting as watching a tree grow, but if you really want to see the Harvest Right "in action" in order to understand what's happening (not that there's much to see), this provides a "speeded-up" way to do that!

 

In any case, maybe it will help some newbie HR Freeze Dryer owners to answer some of the questions I once had. 

 

Here's the link to the video:

Edited November 27, 2015 by Brent (log)

[Jenipher]

I've also added an oil catch can that does a wonderful job of trapping oil vapor exiting the exhaust of the pump.  Now instead of coating the area in a fine oil mist, the oil settles into the can.  The clear tube on the side of the can lets you know how full the can is.  I routed the exhaust from the catch can to a home made catch can that consisted of a jar with two ports with steel wool inside.  I wanted to see just how much oil would escape the newly install catch can and collect in the jar. 

I've run the system in countless tests including over filling the pump and running the pump without a load (both result in lots of oil spitting out the exhaust port of the pump).  I've drained the catch can twice, once with over 5 oz  of oil in it, but have not collected any oil downstream in the jar so the system is performing well.  I bought the catch can on eBay for $15.89 including shipping! It included all mounting hardware, gaskets, hoses, and clamps. I did put rust resistant steel wool in the can (though the drain plug) to add surface area for the oil vapors to attach to.

 

Tony

 

Tony, if you see this, I went ahead and purchased the catch can.  Do you think it's okay to just purchase a reducer to go from the size of the exhaust to the size of the hose that came with the can?  Hopefully I said that in a way that makes sense!  As well, does it matter which port is used as "in" and which as "out"? 

 

Thanks so much,

Jen

Edited December 1, 2015 by Jenipher (log)

[DriedUpStuffs]

I would prefer those fittings to have internal O rings and knurled thread on ports (similar to R134a vacuum gauge sets) that do not require high torque compression fittings.  Finger tight and you are good to go.  You spot a leak, change the O ring and you're back in business.

 

Odds are the problem is the vacuum hose or its end connections, the drain valve, or the door gasket.  Based upon my experience I'd double check the fittings while installed on the FDer.

 

Agree entirely on the fittings! After many emails and phone calls to HR, some advice that didn't pan out, and some parts replacement, the unit is back in business!  Turns out it was the wire passthrough for the heater wires. (had to replace the whole galvanized T piece with new wires in it) Seems they are epoxied in there, and in my experience passthroughs are a problem spot, so it's not at all surprizing that there was a slight leak there.  In any case, I thanks the folks at HR for sending parts and sticking with me throughout. 

 

I did a couple of batches (peas and carrots, and another load of precooked chicken meatballs cut in half) and it all worked perfectly. Looking forward to trying out some new things and sharing the results.

[Pipsqueak]

On 7/31/2015 at 11:12 PM, TonyC said:

 

Here is my first pass on a Vapor Trap... it is an old whole house water filter that I modified.  It failed to reduce the moisture in the oil...  I'm in the process of modifying it to catch and suspend the moisture in the container long enough for desiccant beads to absorb the water.  The air flow comes into the inlet, down the central pipe to the bottom of the screen and filters up through the beads and out the top.

 

I know this was like forever ago, but I thought I would respond anyway.  I haven't been on much in a while, I only run my freeze dryer in the winter.  

So I think you'll find it's a lot harder to remove water vapor from a vacuum than just using desiccant, as the vacuum will just pull the water out of the desiccant.  The only way I know to filter the water vapor out would be a cold trap.  They usually use liquid nitrogen or dry ice to keep the temperature low enough that all the water condenses out.  Obviously you would need a supply of the liquid nitrogen or dry ice that would probably not be cost effective for most of us.  

http://www.bestvaluevacs.com/coldtrap.html

The other option to get that cold would be to use a cryocooler and build a cold trap around it.  It could be done, but would be pretty expensive.  I've been watching some electronics on ebay that have cryocoolers in them, but the cheapest I've seen is around $600.  Still not a cheap option, but you wouldn't need dry ice or liquid nitrogen to feed it.

http://www.ebay.com/sch/i.html?_odkw=superfilter&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H1.Xsuperconductor+superfilter.TRS1&_nkw=superconductor+superfilter&_sacat=0

[Pipsqueak]

On 7/31/2015 at 11:12 PM, TonyC said:

 

 

Somehow this post got posted twice so I'll edit the second one with some more useful information.  

 

I remember reading somewhere in this thread where somebody was asking how long you run the freeze cycle with pre-frozen food.  

 

I have my chest freezer set to -12F, and I usually let the freeze dryer cool for an hour before I put the frozen food in.  After I load the food in I wait another half hour to start the drying process. I've had a lot of cycles that the total time between pulling one batch out and starting the drying cycle on the next is around 2 hours.  I'm running mine in a cold garage, so it cools down pretty quickly.  If you have yours in a warm room it would probably take a little longer.  Obviously things like ice cream and marshmallows you would want to let the freeze cycle run longer.  

 

When I'm ready to start the drying cycle, I open the door, remove the insulator, and check the temperature of the food on the trays with an infrared thermometer.  As long as it's below -10F I start the dry cycle.

 

A side note for TonyC, have you ever thought about attaching a mirror to each side of the tray rack to reflect the radiant heat back in to the trays?  I've looked at some mirror finish stainless on ebay, and it looks like you could do it for about $40.   Not sure if it's worth a try or not.  I would think it would let you get more water out in a cycle because the radiant heat wouldn't be warming the ice on the chamber walls.  Just a thought....

Edited December 16, 2015 by Pipsqueak
duplicate post (log)

[TonyC]

On 12/1/2015 at 0:16 PM, Jenipher said:

 

Tony, if you see this, I went ahead and purchased the catch can.  Do you think it's okay to just purchase a reducer to go from the size of the exhaust to the size of the hose that came with the can?  Hopefully I said that in a way that makes sense!  As well, does it matter which port is used as "in" and which as "out"? 

 

Thanks so much,

Jen

 

 

Hi Jen,

 

Sorry to be gone so long.  I did exactly as you proposed.  I purchased a brass reducer and pushed the blue hose over it.  I have no adverse vacuum performance change with the catch can in place.  It just catches any oil. I still smell oil vapor when the pump first starts up, but not nearly as much.  I've only emptied the can once or twice since I've had it installed.  I slightly over filled the pump and it blew out into the can, then ran it with the FDer valve open for a few minutes.  Nothing got past the can.

 

I used the outside port as IN and the middle one as out.   I did take the port off and the longer one should be the inlet port.   It's not a great deal longer.

 

Tony 

 

Edited January 22, 2016 by TonyC
updated (log)

[Kerry Beal]

So a couple of months ago (when the weather was still warm) Alleguede has his assistant drop off some raspberries that he wanted me to freeze dry for him. Since they were IQF raspberries I assumed that they would be individual - but apparently when you leave them in the trunk of your car long enough to thaw, then put them back in the freezer - then take a couple of days to get them over to me - they are no longer going to resemble individual raspberries. 

 

So they have been sitting in my freezer awaiting a time when I was prepared to deal with them - I've told him several times that he isn't going to get usable raspberries out of this - just raspberry powder. I don't think he believes me!

 

 

I started by removing the 3 grocery bags that were holding the 2 thick bags that had at one time held the berries. Struck by how much it looked like a placenta - bag and all!

 

 

Of course the bags were frozen right in to the mass of berries so it was quite a painful struggle to get the mess to the point where I could hack off slices of the berries to put on the trays.  

 

 

So divided into 4 trays - couple of days from now we'll see what we get.

 

Raspberry juice everywhere! 

[Tri2Cook]

It does look decidedly un-raspberry like... probably still gonna be tasty though.