i don't know how to pick a circulation pump. if i go for a positive displacement pump, i'll absolutely need that second interlock; if i go for a centrifugal pump, those can operate with the output plugged though i don't think they like it very much
do any of you have experience here?
now that i think about it, "overflow valve" is a product that probably only exists in factorio. but what i can use instead is a flow restriction or a metering device. if the jacket is connected, there is a low-resistance path through it. if the jacket is disconnected, that path is broken and water is forced to flow through the restriction. i think that's good enough?
Jul 9, 2026, 12:50 PM@whitequark thats just a pressure relief valve with a connection to the reservoir. This is how it done on on my autoclave for example
@4censord oh makes sense
@4censord not sure if i can find like, a plastic one for hose barb >.>
Jul 9, 2026, 12:54 PM@whitequark hmm yeah that might be harder
Also the pressures there might be quite low (as in the difference between working and jacket disconnected)
So a thing that turns the pump off when the pressure rises to far might be better
@4censord wouldn't that just cause cycling
Jul 9, 2026, 1:02 PM@whitequark hmm true
That could be a feature ala "retry every 30s whether the jacket is connected yet"
Or just have it enter a failure condition that needs to be reset with a button or such?
@4censord hm I guess, then it just needs a flow sensor
@whitequark @4censord Current sensor on the motor. If it’s bunged up the current will go too high; if it’s sprung a leak, too low; detection of a dead motor and motor on fire are bonus features you get for free.
@4censord @whitequark Often called an automatic bypass in the plumbing world. Essentially an adjustable pressure relief valve designed for repeated cycling.
Depending on the pressure differential a non-return valve can serve the same purpose. It will take some trial and error to find one that opens at the right pressure. Try aquarium supply stores.
@whitequark this is for central heating, but might be what you're looking for https://www.screwfix.com/p/straight-auto-bypass-valve-22mm/4747v
@derryh way too big
@whitequark if it’s just water simply point a pressure relief valve at operator’s face and rely on pavlovian conditioning
Jul 9, 2026, 1:17 PM@whitequark If it's just a restriction then there'll always be some flow, and there's some efficiency loss from entropic mixing of cold bypass and hot return.
Idk if that really matters given the temperature rise through the jacket is quite small, but putting a relief valve on the bypass would avoid it.
@whitequark this whole project is cool as hell
@bunny_jane thank u
Jul 9, 2026, 11:25 PM@bunny_jane @whitequark … I see what you did there
@jpm @whitequark :meow3cSmirk:
Jul 9, 2026, 11:22 PM@whitequark in .au they’re called “pressure over release valve” and found on tank storage style hot water systems to prevent the tank turning into a pressure vessel due to over-heating. Completely passive device, just works on pressure differential, and available in wide range of activation pressures.
If you do this, you’ll need a different interlock to stop the pump from running if the reservoir runs dry (which you probably should add anyway)
Jul 9, 2026, 11:32 PM@whitequark oh, and for quality of life, you want a pair of series stop valves with a quick-disconnect in between them between the jacket and the refrigeration system, and put the pair on both the supply and return lines. Close both valves, disconnect, almost zero coolant comes out.
Jacket —— x || x —— system
@whitequark only pumps I know a little about for wearables are peristaltic and maybe that would have insufficient flow rates.
@whitequark I have a couple of nice little 24V centrifugal pumps with BLDC motors with a little speed controller in a box with a pot to adjust it. A Chinese friend ordered them, about 12 years ago. It won't self-prime, so it should be located below the water level (or below any possible air bubbles, even if there isn't supposed to be air).
They are about fist-sized, and waaay too powerful for what you want, I think. They make a fountain comparable to a garden hose at full power.
@whitequark In open-center hydraulics, they solve this by using 3-way valves for all the actuators, with the normal positions going to the next actuator and then the last actuator goes back to the tank with no restriction or further valves. With no actuators engaged, no pressure gets built, and a fixed-displacement pump will run fine into zero load (and the prime mover will basically idle). Not sure if they make "3-way quick connects" or something though
@whitequark If I were making this I'd be tempted to use metal quick-connects, add a bonding wire between the jacket-side quick-connects, and then wire the pack-side connects to the power supply and enable input such that plugging in the quick-connects starts the pump after a few second's delay. You'd want a plastic bracket for the pack-side connects to ensure they can't complete the circuit by touching each other
@whitequark alternately a pressure switch with an activation point below the maximum pressure of your pump would work (I think the ones sold for reverse osmosis units would be a good match for your system). If your pump doesn't have check valves you could add one before the switch to keep pump backflow from causing constant short-cycling
@multioculate oooh, the check valve idea is really good
Jul 9, 2026, 5:12 PM@whitequark
I've experience with centrifugal - they're fine with a blocked output but suffer badly if there's any restrictions on the input.
However I was using them for boiling liquids so YMMV.
@jamesb yeah the input is directly connected to the tank so that's not a problem