Article - Freeze Dried Friday

[TWP]

This is short, but it gives some good and useful information about using a freeze dryer, specifically the Harvest Right model.

If you are considering buying a freeze dryer (or even already have one), this gives some explanation about maintenance to be expected and WHY that maintenance is needed.

https://survivalblog.com/freeze-dried-friday-14/

While I would certainly like to own one of these units, they are NOT cheap and you have significant operating an maintenance costs to be factored into usage.  Remember that you will need to stock the vacuum pump oil and spare parts plus have a reliable, long term generator system to keep the unit running.

Nice, but high maintenance...

[WolfBrother]

From what I have read, at a minimum this may be needed for longer life.

Re-route the line from the vacuum pump thru a T.

The line from the FDry chamber will have a valve at the T
The line from the vacuum pump will NOT have a valve
The remaining leg of the T will have a valve.

Normal operation - Chamber valve open - Remaining leg closed.
At end of vacuum cycle - shut chamber valve - slowly open remaining leg
This allows the intake side of the pump to equal the output side of the pump.
There have been reports that at shutdown, some oil is sucked towards the chamber.

[TWP]

WolfBrother,  I would think this calls for a trap on the pump leg of the T.  Oil pulled toward the chamber would be held in the trap and not make it near the food chamber.

We did this in the lab, both in school and when I worked in a refinery.  While the Silicone oil used was not notably toxic, I wold not want it in my dehydration chamber.  It is a PITA to clean off surfaces.

I don't know what the commercial food freeze driers use in their configurations, but I'd place a bet on there being traps in use.