Adding a Nitrogen Bleed Valve to Vac Oven

I have a .9cf HFS vac oven and a 3 cfm 2 stage vac pump. My pump has two connections and have read that a bleed valve can be added on to the unused connection but do not understand how this valve would know when to bleed fresh air to keep my desired level of vacuum. I have also read about bleeding nitrogen directly into the oven when the vac reaches 29.5. I am trying to calibrate my system so that my pump runs continuously but never pulls deeper than 29.5 or at my elevation in Denver 24.4(24.9 is my max at this elevation).

Here are pictures of the vac oven internals and my pump. If anyone can point me in the right direction I would greatly appreciate it. I have called HFS and scoured the internet with little to no luck. I saw some of GW's notes on a forum on a different website regarding N bleed valves but only brief details were discussed. I feel this is the last step I need to make my extractions consistently amazing and I would like to sincerely thank @Fadedawg (are you GW?!) and everyone else on these forums for all of the pointers. I feel as if I have progressed immensely due to the plethora of information and trial and error.

In the internals of my oven under the metal door I find a wishbone shaped hose leading from the metal hose attached to the vacuum and the oven. The two tubes that go from this metal hose are rubber and lead to the bleed valve and the gauge. Is this where I would install my bleed valve? And if so where do I find such a device that will bleed nitrogen in and maintain the levels I am seeking?

https://www.icmag.com/ic/showthread.php?t=306739&page=2 I like what GW says on this about backfilling but can't seem to find specifics. Thanks for looking!

"If hoses, replace them with 3/8" or larger stainless fittings and tubing. Replace valve as necessary and suggest looking at one brand like Swagelok for mating parts and assemblies, rather than mix and match.

Hook the N2 hose from your bottle regulator to the oven vent/backfill line, and set pressure at 15 psi. If you wish to sometimes backfill with atmosphere, add a tee and another valve venting to atmosphere." Credit_Greywolf. This is all I can find but am a little confused by it

"my vacuum has two slots to put hoses, i only use one.... i hook up a hose to the vac, that is attached to my pressure regulators, from there, i have another hose that attaches to my vac chamber.. Vacuum has one setting, on, its goal is to reach full vac, with the regulators, i can control the hg very very precisely.. the hose from my regulator currently has a suction cup type of deal to vac my chamber.. i can simply pull the hose out of my regulator to release pressure. a bleed off valve, or something simple like this helps speed up the process" Credit Guzias1 https://www.rollitup.org/t/bho-with-vacuum-oil-wax-tutorial.624465/ Again left with no further explanation

MinnesotaHomegrown303 said:

In the internals of my oven under the metal door I find a wishbone shaped hose leading from the metal hose attached to the vacuum and the oven. The two tubes that go from this metal hose are rubber and lead to the bleed valve and the gauge. Is this where I would install my bleed valve? And if so where do I find such a device that will bleed nitrogen in and maintain the levels I am seeking?

https://www.icmag.com/ic/showthread.php?t=306739&page=2 I like what GW says on this about backfilling but can't seem to find specifics. Thanks for looking!

Click to expand...

The smaller hose running from the tee, between the pump isolation valve and the oven, looks to be your vent. You can bleed nitrogen in at that point.